Thanks, Jay. *(1) *The rename from *request.time*.percent to* io.thread*.units for the quota configuration was based on the change from percent to thread-units, since we will need different quota configuration for I/O threads and network threads if we use units. If we agree that *(2)* percent (or ratio) is a better configuration, then the name can be request,time.percent, with the same config applying to both request thread utilization and network thread utilization. Metrics and sensors on the brokers-side will probably need to be separate for I/O and network threads so that these can be accounted separately (5% request.time.percent would mean maximum 5% of request thread utilization and maximum 5% of network thread utilization with either violation leading to throttling).
*(3)* Agree - KIP reflects combined throttling time in a single field in the response. On Fri, Feb 24, 2017 at 4:10 PM, Jay Kreps <j...@confluent.io> wrote: > A couple of quick points: > > 1. Even though the implementation of this quota is only using io thread > time, i think we should call it something like "request-time". This will > give us flexibility to improve the implementation to cover network threads > in the future and will avoid exposing internal details like our thread > pools on the server. > > 2. Jun/Roger, I get what you are trying to fix but the idea of thread/units > is super unintuitive as a user-facing knob. I had to read the KIP like > eight times to understand this. I'm not sure that your point that > increasing the number of threads is a problem with a percentage-based > value, it really depends on whether the user thinks about the "percentage > of request processing time" or "thread units". If they think "I have > allocated 10% of my request processing time to user x" then it is a bug > that increasing the thread count decreases that percent as it does in the > current proposal. As a practical matter I think the only way to actually > reason about this is as a percent---I just don't believe people are going > to think, "ah, 4.3 thread units, that is the right amount!". Instead I > think they have to understand this thread unit concept, figure out what > they have set in number of threads, compute a percent and then come up with > the number of thread units, and these will all be wrong if that thread > count changes. I also think this ties us to throttling the I/O thread pool, > which may not be where we want to end up. > > 3. For what it's worth I do think having a single throttle_ms field in all > the responses that combines all throttling from all quotas is probably the > simplest. There could be a use case for having separate fields for each, > but I think that is actually harder to use/monitor in the common case so > unless someone has a use case I think just one should be fine. > > -Jay > > On Fri, Feb 24, 2017 at 4:21 AM, Rajini Sivaram <rajinisiva...@gmail.com> > wrote: > > > I have updated the KIP based on the discussions so far. > > > > > > Regards, > > > > Rajini > > > > On Thu, Feb 23, 2017 at 11:29 PM, Rajini Sivaram < > rajinisiva...@gmail.com> > > wrote: > > > > > Thank you all for the feedback. > > > > > > Ismael #1. It makes sense not to throttle inter-broker requests like > > > LeaderAndIsr etc. The simplest way to ensure that clients cannot use > > these > > > requests to bypass quotas for DoS attacks is to ensure that ACLs > prevent > > > clients from using these requests and unauthorized requests are > included > > > towards quotas. > > > > > > Ismael #2, Jay #1 : I was thinking that these quotas can return a > > separate > > > throttle time, and all utilization based quotas could use the same > field > > > (we won't add another one for network thread utilization for instance). > > But > > > perhaps it makes sense to keep byte rate quotas separate in > produce/fetch > > > responses to provide separate metrics? Agree with Ismael that the name > of > > > the existing field should be changed if we have two. Happy to switch > to a > > > single combined throttle time if that is sufficient. > > > > > > Ismael #4, #5, #6: Will update KIP. Will use dot separated name for new > > > property. Replication quotas use dot separated, so it will be > consistent > > > with all properties except byte rate quotas. > > > > > > Radai: #1 Request processing time rather than request rate were chosen > > > because the time per request can vary significantly between requests as > > > mentioned in the discussion and KIP. > > > #2 Two separate quotas for heartbeats/regular requests feel like more > > > configuration and more metrics. Since most users would set quotas > higher > > > than the expected usage and quotas are more of a safety net, a single > > quota > > > should work in most cases. > > > #3 The number of requests in purgatory is limited by the number of > > active > > > connections since only one request per connection will be throttled at > a > > > time. > > > #4 As with byte rate quotas, to use the full allocated quotas, > > > clients/users would need to use partitions that are distributed across > > the > > > cluster. The alternative of using cluster-wide quotas instead of > > per-broker > > > quotas would be far too complex to implement. > > > > > > Dong : We currently have two ClientQuotaManagers for quota types Fetch > > and > > > Produce. A new one will be added for IOThread, which manages quotas for > > I/O > > > thread utilization. This will not update the Fetch or Produce > queue-size, > > > but will have a separate metric for the queue-size. I wasn't planning > to > > > add any additional metrics apart from the equivalent ones for existing > > > quotas as part of this KIP. Ratio of byte-rate to I/O thread > utilization > > > could be slightly misleading since it depends on the sequence of > > requests. > > > But we can look into more metrics after the KIP is implemented if > > required. > > > > > > I think we need to limit the maximum delay since all requests are > > > throttled. If a client has a quota of 0.001 units and a single request > > used > > > 50ms, we don't want to delay all requests from the client by 50 > seconds, > > > throwing the client out of all its consumer groups. The issue is only > if > > a > > > user is allocated a quota that is insufficient to process one large > > > request. The expectation is that the units allocated per user will be > > much > > > higher than the time taken to process one request and the limit should > > > seldom be applied. Agree this needs proper documentation. > > > > > > Regards, > > > > > > Rajini > > > > > > > > > On Thu, Feb 23, 2017 at 8:04 PM, radai <radai.rosenbl...@gmail.com> > > wrote: > > > > > >> @jun: i wasnt concerned about tying up a request processing thread, > but > > >> IIUC the code does still read the entire request out, which might > add-up > > >> to > > >> a non-negligible amount of memory. > > >> > > >> On Thu, Feb 23, 2017 at 11:55 AM, Dong Lin <lindon...@gmail.com> > wrote: > > >> > > >> > Hey Rajini, > > >> > > > >> > The current KIP says that the maximum delay will be reduced to > window > > >> size > > >> > if it is larger than the window size. I have a concern with this: > > >> > > > >> > 1) This essentially means that the user is allowed to exceed their > > quota > > >> > over a long period of time. Can you provide an upper bound on this > > >> > deviation? > > >> > > > >> > 2) What is the motivation for cap the maximum delay by the window > > size? > > >> I > > >> > am wondering if there is better alternative to address the problem. > > >> > > > >> > 3) It means that the existing metric-related config will have a more > > >> > directly impact on the mechanism of this io-thread-unit-based quota. > > The > > >> > may be an important change depending on the answer to 1) above. We > > >> probably > > >> > need to document this more explicitly. > > >> > > > >> > Dong > > >> > > > >> > > > >> > On Thu, Feb 23, 2017 at 10:56 AM, Dong Lin <lindon...@gmail.com> > > wrote: > > >> > > > >> > > Hey Jun, > > >> > > > > >> > > Yeah you are right. I thought it wasn't because at LinkedIn it > will > > be > > >> > too > > >> > > much pressure on inGraph to expose those per-clientId metrics so > we > > >> ended > > >> > > up printing them periodically to local log. Never mind if it is > not > > a > > >> > > general problem. > > >> > > > > >> > > Hey Rajini, > > >> > > > > >> > > - I agree with Jay that we probably don't want to add a new field > > for > > >> > > every quota ProduceResponse or FetchResponse. Is there any > use-case > > >> for > > >> > > having separate throttle-time fields for byte-rate-quota and > > >> > > io-thread-unit-quota? You probably need to document this as > > interface > > >> > > change if you plan to add new field in any request. > > >> > > > > >> > > - I don't think IOThread belongs to quotaType. The existing quota > > >> types > > >> > > (i.e. Produce/Fetch/LeaderReplication/FollowerReplication) > identify > > >> the > > >> > > type of request that are throttled, not the quota mechanism that > is > > >> > applied. > > >> > > > > >> > > - If a request is throttled due to this io-thread-unit-based > quota, > > is > > >> > the > > >> > > existing queue-size metric in ClientQuotaManager incremented? > > >> > > > > >> > > - In the interest of providing guide line for admin to decide > > >> > > io-thread-unit-based quota and for user to understand its impact > on > > >> their > > >> > > traffic, would it be useful to have a metric that shows the > overall > > >> > > byte-rate per io-thread-unit? Can we also show this a per-clientId > > >> > metric? > > >> > > > > >> > > Thanks, > > >> > > Dong > > >> > > > > >> > > > > >> > > On Thu, Feb 23, 2017 at 9:25 AM, Jun Rao <j...@confluent.io> > wrote: > > >> > > > > >> > >> Hi, Ismael, > > >> > >> > > >> > >> For #3, typically, an admin won't configure more io threads than > > CPU > > >> > >> cores, > > >> > >> but it's possible for an admin to start with fewer io threads > than > > >> cores > > >> > >> and grow that later on. > > >> > >> > > >> > >> Hi, Dong, > > >> > >> > > >> > >> I think the throttleTime sensor on the broker tells the admin > > >> whether a > > >> > >> user/clentId is throttled or not. > > >> > >> > > >> > >> Hi, Radi, > > >> > >> > > >> > >> The reasoning for delaying the throttled requests on the broker > > >> instead > > >> > of > > >> > >> returning an error immediately is that the latter has no way to > > >> prevent > > >> > >> the > > >> > >> client from retrying immediately, which will make things worse. > The > > >> > >> delaying logic is based off a delay queue. A separate expiration > > >> thread > > >> > >> just waits on the next to be expired request. So, it doesn't tie > > up a > > >> > >> request handler thread. > > >> > >> > > >> > >> Thanks, > > >> > >> > > >> > >> Jun > > >> > >> > > >> > >> On Thu, Feb 23, 2017 at 9:07 AM, Ismael Juma <ism...@juma.me.uk> > > >> wrote: > > >> > >> > > >> > >> > Hi Jay, > > >> > >> > > > >> > >> > Regarding 1, I definitely like the simplicity of keeping a > single > > >> > >> throttle > > >> > >> > time field in the response. The downside is that the client > > metrics > > >> > >> will be > > >> > >> > more coarse grained. > > >> > >> > > > >> > >> > Regarding 3, we have `leader.imbalance.per.broker.percentage` > > and > > >> > >> > `log.cleaner.min.cleanable.ratio`. > > >> > >> > > > >> > >> > Ismael > > >> > >> > > > >> > >> > On Thu, Feb 23, 2017 at 4:43 PM, Jay Kreps <j...@confluent.io> > > >> wrote: > > >> > >> > > > >> > >> > > A few minor comments: > > >> > >> > > > > >> > >> > > 1. Isn't it the case that the throttling time response > field > > >> > should > > >> > >> > have > > >> > >> > > the total time your request was throttled irrespective of > > the > > >> > >> quotas > > >> > >> > > that > > >> > >> > > caused that. Limiting it to byte rate quota doesn't make > > >> sense, > > >> > >> but I > > >> > >> > > also > > >> > >> > > I don't think we want to end up adding new fields in the > > >> response > > >> > >> for > > >> > >> > > every > > >> > >> > > single thing we quota, right? > > >> > >> > > 2. I don't think we should make this quota specifically > > about > > >> io > > >> > >> > > threads. Once we introduce these quotas people set them > and > > >> > expect > > >> > >> > them > > >> > >> > > to > > >> > >> > > be enforced (and if they aren't it may cause an outage). > As > > a > > >> > >> result > > >> > >> > > they > > >> > >> > > are a bit more sensitive than normal configs, I think. The > > >> > current > > >> > >> > > thread > > >> > >> > > pools seem like something of an implementation detail and > > not > > >> the > > >> > >> > level > > >> > >> > > the > > >> > >> > > user-facing quotas should be involved with. I think it > might > > >> be > > >> > >> better > > >> > >> > > to > > >> > >> > > make this a general request-time throttle with no mention > in > > >> the > > >> > >> > naming > > >> > >> > > about I/O threads and simply acknowledge the current > > >> limitation > > >> > >> (which > > >> > >> > > we > > >> > >> > > may someday fix) in the docs that this covers only the > time > > >> after > > >> > >> the > > >> > >> > > thread is read off the network. > > >> > >> > > 3. As such I think the right interface to the user would > be > > >> > >> something > > >> > >> > > like percent_request_time and be in {0,...100} or > > >> > >> request_time_ratio > > >> > >> > > and be > > >> > >> > > in {0.0,...,1.0} (I think "ratio" is the terminology we > used > > >> if > > >> > the > > >> > >> > > scale > > >> > >> > > is between 0 and 1 in the other metrics, right?) > > >> > >> > > > > >> > >> > > -Jay > > >> > >> > > > > >> > >> > > On Thu, Feb 23, 2017 at 3:45 AM, Rajini Sivaram < > > >> > >> rajinisiva...@gmail.com > > >> > >> > > > > >> > >> > > wrote: > > >> > >> > > > > >> > >> > > > Guozhang/Dong, > > >> > >> > > > > > >> > >> > > > Thank you for the feedback. > > >> > >> > > > > > >> > >> > > > Guozhang : I have updated the section on co-existence of > byte > > >> rate > > >> > >> and > > >> > >> > > > request time quotas. > > >> > >> > > > > > >> > >> > > > Dong: I hadn't added much detail to the metrics and sensors > > >> since > > >> > >> they > > >> > >> > > are > > >> > >> > > > going to be very similar to the existing metrics and > sensors. > > >> To > > >> > >> avoid > > >> > >> > > > confusion, I have now added more detail. All metrics are in > > the > > >> > >> group > > >> > >> > > > "quotaType" and all sensors have names starting with > > >> "quotaType" > > >> > >> (where > > >> > >> > > > quotaType is Produce/Fetch/LeaderReplication/ > > >> > >> > > > FollowerReplication/*IOThread*). > > >> > >> > > > So there will be no reuse of existing metrics/sensors. The > > new > > >> > ones > > >> > >> for > > >> > >> > > > request processing time based throttling will be completely > > >> > >> independent > > >> > >> > > of > > >> > >> > > > existing metrics/sensors, but will be consistent in format. > > >> > >> > > > > > >> > >> > > > The existing throttle_time_ms field in produce/fetch > > responses > > >> > will > > >> > >> not > > >> > >> > > be > > >> > >> > > > impacted by this KIP. That will continue to return > byte-rate > > >> based > > >> > >> > > > throttling times. In addition, a new field > > >> > request_throttle_time_ms > > >> > >> > will > > >> > >> > > be > > >> > >> > > > added to return request quota based throttling times. These > > >> will > > >> > be > > >> > >> > > exposed > > >> > >> > > > as new metrics on the client-side. > > >> > >> > > > > > >> > >> > > > Since all metrics and sensors are different for each type > of > > >> > quota, > > >> > >> I > > >> > >> > > > believe there is already sufficient metrics to monitor > > >> throttling > > >> > on > > >> > >> > both > > >> > >> > > > client and broker side for each type of throttling. > > >> > >> > > > > > >> > >> > > > Regards, > > >> > >> > > > > > >> > >> > > > Rajini > > >> > >> > > > > > >> > >> > > > > > >> > >> > > > On Thu, Feb 23, 2017 at 4:32 AM, Dong Lin < > > lindon...@gmail.com > > >> > > > >> > >> wrote: > > >> > >> > > > > > >> > >> > > > > Hey Rajini, > > >> > >> > > > > > > >> > >> > > > > I think it makes a lot of sense to use io_thread_units as > > >> metric > > >> > >> to > > >> > >> > > quota > > >> > >> > > > > user's traffic here. LGTM overall. I have some questions > > >> > regarding > > >> > >> > > > sensors. > > >> > >> > > > > > > >> > >> > > > > - Can you be more specific in the KIP what sensors will > be > > >> > added? > > >> > >> For > > >> > >> > > > > example, it will be useful to specify the name and > > >> attributes of > > >> > >> > these > > >> > >> > > > new > > >> > >> > > > > sensors. > > >> > >> > > > > > > >> > >> > > > > - We currently have throttle-time and queue-size for > > >> byte-rate > > >> > >> based > > >> > >> > > > quota. > > >> > >> > > > > Are you going to have separate throttle-time and > queue-size > > >> for > > >> > >> > > requests > > >> > >> > > > > throttled by io_thread_unit-based quota, or will they > share > > >> the > > >> > >> same > > >> > >> > > > > sensor? > > >> > >> > > > > > > >> > >> > > > > - Does the throttle-time in the ProduceResponse and > > >> > FetchResponse > > >> > >> > > > contains > > >> > >> > > > > time due to io_thread_unit-based quota? > > >> > >> > > > > > > >> > >> > > > > - Currently kafka server doesn't not provide any log or > > >> metrics > > >> > >> that > > >> > >> > > > tells > > >> > >> > > > > whether any given clientId (or user) is throttled. This > is > > >> not > > >> > too > > >> > >> > bad > > >> > >> > > > > because we can still check the client-side byte-rate > metric > > >> to > > >> > >> > validate > > >> > >> > > > > whether a given client is throttled. But with this > > >> > io_thread_unit, > > >> > >> > > there > > >> > >> > > > > will be no way to validate whether a given client is slow > > >> > because > > >> > >> it > > >> > >> > > has > > >> > >> > > > > exceeded its io_thread_unit limit. It is necessary for > user > > >> to > > >> > be > > >> > >> > able > > >> > >> > > to > > >> > >> > > > > know this information to figure how whether they have > > reached > > >> > >> there > > >> > >> > > quota > > >> > >> > > > > limit. How about we add log4j log on the server side to > > >> > >> periodically > > >> > >> > > > print > > >> > >> > > > > the (client_id, byte-rate-throttle-time, > > >> > >> > io-thread-unit-throttle-time) > > >> > >> > > so > > >> > >> > > > > that kafka administrator can figure those users that have > > >> > reached > > >> > >> > their > > >> > >> > > > > limit and act accordingly? > > >> > >> > > > > > > >> > >> > > > > Thanks, > > >> > >> > > > > Dong > > >> > >> > > > > > > >> > >> > > > > > > >> > >> > > > > > > >> > >> > > > > > > >> > >> > > > > > > >> > >> > > > > On Wed, Feb 22, 2017 at 4:46 PM, Guozhang Wang < > > >> > >> wangg...@gmail.com> > > >> > >> > > > wrote: > > >> > >> > > > > > > >> > >> > > > > > Made a pass over the doc, overall LGTM except a minor > > >> comment > > >> > on > > >> > >> > the > > >> > >> > > > > > throttling implementation: > > >> > >> > > > > > > > >> > >> > > > > > Stated as "Request processing time throttling will be > > >> applied > > >> > on > > >> > >> > top > > >> > >> > > if > > >> > >> > > > > > necessary." I thought that it meant the request > > processing > > >> > time > > >> > >> > > > > throttling > > >> > >> > > > > > is applied first, but continue reading I found it > > actually > > >> > >> meant to > > >> > >> > > > apply > > >> > >> > > > > > produce / fetch byte rate throttling first. > > >> > >> > > > > > > > >> > >> > > > > > Also the last sentence "The remaining delay if any is > > >> applied > > >> > to > > >> > >> > the > > >> > >> > > > > > response." is a bit confusing to me. Maybe rewording > it a > > >> bit? > > >> > >> > > > > > > > >> > >> > > > > > > > >> > >> > > > > > Guozhang > > >> > >> > > > > > > > >> > >> > > > > > > > >> > >> > > > > > On Wed, Feb 22, 2017 at 3:24 PM, Jun Rao < > > j...@confluent.io > > >> > > > >> > >> wrote: > > >> > >> > > > > > > > >> > >> > > > > > > Hi, Rajini, > > >> > >> > > > > > > > > >> > >> > > > > > > Thanks for the updated KIP. The latest proposal looks > > >> good > > >> > to > > >> > >> me. > > >> > >> > > > > > > > > >> > >> > > > > > > Jun > > >> > >> > > > > > > > > >> > >> > > > > > > On Wed, Feb 22, 2017 at 2:19 PM, Rajini Sivaram < > > >> > >> > > > > rajinisiva...@gmail.com > > >> > >> > > > > > > > > >> > >> > > > > > > wrote: > > >> > >> > > > > > > > > >> > >> > > > > > > > Jun/Roger, > > >> > >> > > > > > > > > > >> > >> > > > > > > > Thank you for the feedback. > > >> > >> > > > > > > > > > >> > >> > > > > > > > 1. I have updated the KIP to use absolute units > > >> instead of > > >> > >> > > > > percentage. > > >> > >> > > > > > > The > > >> > >> > > > > > > > property is called* io_thread_units* to align with > > the > > >> > >> thread > > >> > >> > > count > > >> > >> > > > > > > > property *num.io.threads*. When we implement > network > > >> > thread > > >> > >> > > > > utilization > > >> > >> > > > > > > > quotas, we can add another property > > >> > *network_thread_units.* > > >> > >> > > > > > > > > > >> > >> > > > > > > > 2. ControlledShutdown is already listed under the > > >> exempt > > >> > >> > > requests. > > >> > >> > > > > Jun, > > >> > >> > > > > > > did > > >> > >> > > > > > > > you mean a different request that needs to be > added? > > >> The > > >> > >> four > > >> > >> > > > > requests > > >> > >> > > > > > > > currently exempt in the KIP are StopReplica, > > >> > >> > ControlledShutdown, > > >> > >> > > > > > > > LeaderAndIsr and UpdateMetadata. These are > controlled > > >> > using > > >> > >> > > > > > ClusterAction > > >> > >> > > > > > > > ACL, so it is easy to exclude and only throttle if > > >> > >> > unauthorized. > > >> > >> > > I > > >> > >> > > > > > wasn't > > >> > >> > > > > > > > sure if there are other requests used only for > > >> > inter-broker > > >> > >> > that > > >> > >> > > > > needed > > >> > >> > > > > > > to > > >> > >> > > > > > > > be excluded. > > >> > >> > > > > > > > > > >> > >> > > > > > > > 3. I was thinking the smallest change would be to > > >> replace > > >> > >> all > > >> > >> > > > > > references > > >> > >> > > > > > > to > > >> > >> > > > > > > > *requestChannel.sendResponse()* with a local > method > > >> > >> > > > > > > > *sendResponseMaybeThrottle()* that does the > > throttling > > >> if > > >> > >> any > > >> > >> > > plus > > >> > >> > > > > send > > >> > >> > > > > > > > response. If we throttle first in > > *KafkaApis.handle()*, > > >> > the > > >> > >> > time > > >> > >> > > > > spent > > >> > >> > > > > > > > within the method handling the request will not be > > >> > recorded > > >> > >> or > > >> > >> > > used > > >> > >> > > > > in > > >> > >> > > > > > > > throttling. We can look into this again when the PR > > is > > >> > ready > > >> > >> > for > > >> > >> > > > > > review. > > >> > >> > > > > > > > > > >> > >> > > > > > > > Regards, > > >> > >> > > > > > > > > > >> > >> > > > > > > > Rajini > > >> > >> > > > > > > > > > >> > >> > > > > > > > > > >> > >> > > > > > > > > > >> > >> > > > > > > > On Wed, Feb 22, 2017 at 5:55 PM, Roger Hoover < > > >> > >> > > > > roger.hoo...@gmail.com> > > >> > >> > > > > > > > wrote: > > >> > >> > > > > > > > > > >> > >> > > > > > > > > Great to see this KIP and the excellent > discussion. > > >> > >> > > > > > > > > > > >> > >> > > > > > > > > To me, Jun's suggestion makes sense. If my > > >> application > > >> > is > > >> > >> > > > > allocated > > >> > >> > > > > > 1 > > >> > >> > > > > > > > > request handler unit, then it's as if I have a > > Kafka > > >> > >> broker > > >> > >> > > with > > >> > >> > > > a > > >> > >> > > > > > > single > > >> > >> > > > > > > > > request handler thread dedicated to me. That's > the > > >> > most I > > >> > >> > can > > >> > >> > > > use, > > >> > >> > > > > > at > > >> > >> > > > > > > > > least. That allocation doesn't change even if an > > >> admin > > >> > >> later > > >> > >> > > > > > increases > > >> > >> > > > > > > > the > > >> > >> > > > > > > > > size of the request thread pool on the broker. > > It's > > >> > >> similar > > >> > >> > to > > >> > >> > > > the > > >> > >> > > > > > CPU > > >> > >> > > > > > > > > abstraction that VMs and containers get from > > >> hypervisors > > >> > >> or > > >> > >> > OS > > >> > >> > > > > > > > schedulers. > > >> > >> > > > > > > > > While different client access patterns can use > > wildly > > >> > >> > different > > >> > >> > > > > > amounts > > >> > >> > > > > > > > of > > >> > >> > > > > > > > > request thread resources per request, a given > > >> > application > > >> > >> > will > > >> > >> > > > > > > generally > > >> > >> > > > > > > > > have a stable access pattern and can figure out > > >> > >> empirically > > >> > >> > how > > >> > >> > > > > many > > >> > >> > > > > > > > > "request thread units" it needs to meet it's > > >> > >> > throughput/latency > > >> > >> > > > > > goals. > > >> > >> > > > > > > > > > > >> > >> > > > > > > > > Cheers, > > >> > >> > > > > > > > > > > >> > >> > > > > > > > > Roger > > >> > >> > > > > > > > > > > >> > >> > > > > > > > > On Wed, Feb 22, 2017 at 8:53 AM, Jun Rao < > > >> > >> j...@confluent.io> > > >> > >> > > > wrote: > > >> > >> > > > > > > > > > > >> > >> > > > > > > > > > Hi, Rajini, > > >> > >> > > > > > > > > > > > >> > >> > > > > > > > > > Thanks for the updated KIP. A few more > comments. > > >> > >> > > > > > > > > > > > >> > >> > > > > > > > > > 1. A concern of request_time_percent is that > it's > > >> not > > >> > an > > >> > >> > > > absolute > > >> > >> > > > > > > > value. > > >> > >> > > > > > > > > > Let's say you give a user a 10% limit. If the > > admin > > >> > >> doubles > > >> > >> > > the > > >> > >> > > > > > > number > > >> > >> > > > > > > > of > > >> > >> > > > > > > > > > request handler threads, that user now actually > > has > > >> > >> twice > > >> > >> > the > > >> > >> > > > > > > absolute > > >> > >> > > > > > > > > > capacity. This may confuse people a bit. So, > > >> perhaps > > >> > >> > setting > > >> > >> > > > the > > >> > >> > > > > > > quota > > >> > >> > > > > > > > > > based on an absolute request thread unit is > > better. > > >> > >> > > > > > > > > > > > >> > >> > > > > > > > > > 2. ControlledShutdownRequest is also an > > >> inter-broker > > >> > >> > request > > >> > >> > > > and > > >> > >> > > > > > > needs > > >> > >> > > > > > > > to > > >> > >> > > > > > > > > > be excluded from throttling. > > >> > >> > > > > > > > > > > > >> > >> > > > > > > > > > 3. Implementation wise, I am wondering if it's > > >> simpler > > >> > >> to > > >> > >> > > apply > > >> > >> > > > > the > > >> > >> > > > > > > > > request > > >> > >> > > > > > > > > > time throttling first in KafkaApis.handle(). > > >> > Otherwise, > > >> > >> we > > >> > >> > > will > > >> > >> > > > > > need > > >> > >> > > > > > > to > > >> > >> > > > > > > > > add > > >> > >> > > > > > > > > > the throttling logic in each type of request. > > >> > >> > > > > > > > > > > > >> > >> > > > > > > > > > Thanks, > > >> > >> > > > > > > > > > > > >> > >> > > > > > > > > > Jun > > >> > >> > > > > > > > > > > > >> > >> > > > > > > > > > On Wed, Feb 22, 2017 at 5:58 AM, Rajini > Sivaram < > > >> > >> > > > > > > > rajinisiva...@gmail.com > > >> > >> > > > > > > > > > > > >> > >> > > > > > > > > > wrote: > > >> > >> > > > > > > > > > > > >> > >> > > > > > > > > > > Jun, > > >> > >> > > > > > > > > > > > > >> > >> > > > > > > > > > > Thank you for the review. > > >> > >> > > > > > > > > > > > > >> > >> > > > > > > > > > > I have reverted to the original KIP that > > >> throttles > > >> > >> based > > >> > >> > on > > >> > >> > > > > > request > > >> > >> > > > > > > > > > handler > > >> > >> > > > > > > > > > > utilization. At the moment, it uses > percentage, > > >> but > > >> > I > > >> > >> am > > >> > >> > > > happy > > >> > >> > > > > to > > >> > >> > > > > > > > > change > > >> > >> > > > > > > > > > to > > >> > >> > > > > > > > > > > a fraction (out of 1 instead of 100) if > > >> required. I > > >> > >> have > > >> > >> > > > added > > >> > >> > > > > > the > > >> > >> > > > > > > > > > examples > > >> > >> > > > > > > > > > > from this discussion to the KIP. Also added a > > >> > "Future > > >> > >> > Work" > > >> > >> > > > > > section > > >> > >> > > > > > > > to > > >> > >> > > > > > > > > > > address network thread utilization. The > > >> > configuration > > >> > >> is > > >> > >> > > > named > > >> > >> > > > > > > > > > > "request_time_percent" with the expectation > > that > > >> it > > >> > >> can > > >> > >> > > also > > >> > >> > > > be > > >> > >> > > > > > > used > > >> > >> > > > > > > > as > > >> > >> > > > > > > > > > the > > >> > >> > > > > > > > > > > limit for network thread utilization when > that > > is > > >> > >> > > > implemented, > > >> > >> > > > > so > > >> > >> > > > > > > > that > > >> > >> > > > > > > > > > > users have to set only one config for the two > > and > > >> > not > > >> > >> > have > > >> > >> > > to > > >> > >> > > > > > worry > > >> > >> > > > > > > > > about > > >> > >> > > > > > > > > > > the internal distribution of the work between > > the > > >> > two > > >> > >> > > thread > > >> > >> > > > > > pools > > >> > >> > > > > > > in > > >> > >> > > > > > > > > > > Kafka. > > >> > >> > > > > > > > > > > > > >> > >> > > > > > > > > > > > > >> > >> > > > > > > > > > > Regards, > > >> > >> > > > > > > > > > > > > >> > >> > > > > > > > > > > Rajini > > >> > >> > > > > > > > > > > > > >> > >> > > > > > > > > > > > > >> > >> > > > > > > > > > > On Wed, Feb 22, 2017 at 12:23 AM, Jun Rao < > > >> > >> > > j...@confluent.io> > > >> > >> > > > > > > wrote: > > >> > >> > > > > > > > > > > > > >> > >> > > > > > > > > > > > Hi, Rajini, > > >> > >> > > > > > > > > > > > > > >> > >> > > > > > > > > > > > Thanks for the proposal. > > >> > >> > > > > > > > > > > > > > >> > >> > > > > > > > > > > > The benefit of using the request processing > > >> time > > >> > >> over > > >> > >> > the > > >> > >> > > > > > request > > >> > >> > > > > > > > > rate > > >> > >> > > > > > > > > > is > > >> > >> > > > > > > > > > > > exactly what people have said. I will just > > >> expand > > >> > >> that > > >> > >> > a > > >> > >> > > > bit. > > >> > >> > > > > > > > > Consider > > >> > >> > > > > > > > > > > the > > >> > >> > > > > > > > > > > > following case. The producer sends a > produce > > >> > request > > >> > >> > > with a > > >> > >> > > > > > 10MB > > >> > >> > > > > > > > > > message > > >> > >> > > > > > > > > > > > but compressed to 100KB with gzip. The > > >> > >> decompression of > > >> > >> > > the > > >> > >> > > > > > > message > > >> > >> > > > > > > > > on > > >> > >> > > > > > > > > > > the > > >> > >> > > > > > > > > > > > broker could take 10-15 seconds, during > which > > >> > time, > > >> > >> a > > >> > >> > > > request > > >> > >> > > > > > > > handler > > >> > >> > > > > > > > > > > > thread is completely blocked. In this case, > > >> > neither > > >> > >> the > > >> > >> > > > > byte-in > > >> > >> > > > > > > > quota > > >> > >> > > > > > > > > > nor > > >> > >> > > > > > > > > > > > the request rate quota may be effective in > > >> > >> protecting > > >> > >> > the > > >> > >> > > > > > broker. > > >> > >> > > > > > > > > > > Consider > > >> > >> > > > > > > > > > > > another case. A consumer group starts with > 10 > > >> > >> instances > > >> > >> > > and > > >> > >> > > > > > later > > >> > >> > > > > > > > on > > >> > >> > > > > > > > > > > > switches to 20 instances. The request rate > > will > > >> > >> likely > > >> > >> > > > > double, > > >> > >> > > > > > > but > > >> > >> > > > > > > > > the > > >> > >> > > > > > > > > > > > actually load on the broker may not double > > >> since > > >> > >> each > > >> > >> > > fetch > > >> > >> > > > > > > request > > >> > >> > > > > > > > > > only > > >> > >> > > > > > > > > > > > contains half of the partitions. Request > rate > > >> > quota > > >> > >> may > > >> > >> > > not > > >> > >> > > > > be > > >> > >> > > > > > > easy > > >> > >> > > > > > > > > to > > >> > >> > > > > > > > > > > > configure in this case. > > >> > >> > > > > > > > > > > > > > >> > >> > > > > > > > > > > > What we really want is to be able to > prevent > > a > > >> > >> client > > >> > >> > > from > > >> > >> > > > > > using > > >> > >> > > > > > > > too > > >> > >> > > > > > > > > > much > > >> > >> > > > > > > > > > > > of the server side resources. In this > > >> particular > > >> > >> KIP, > > >> > >> > > this > > >> > >> > > > > > > resource > > >> > >> > > > > > > > > is > > >> > >> > > > > > > > > > > the > > >> > >> > > > > > > > > > > > capacity of the request handler threads. I > > >> agree > > >> > >> that > > >> > >> > it > > >> > >> > > > may > > >> > >> > > > > > not > > >> > >> > > > > > > be > > >> > >> > > > > > > > > > > > intuitive for the users to determine how to > > set > > >> > the > > >> > >> > right > > >> > >> > > > > > limit. > > >> > >> > > > > > > > > > However, > > >> > >> > > > > > > > > > > > this is not completely new and has been > done > > in > > >> > the > > >> > >> > > > container > > >> > >> > > > > > > world > > >> > >> > > > > > > > > > > > already. For example, Linux cgroup ( > > >> > >> > > > > https://access.redhat.com/ > > >> > >> > > > > > > > > > > > documentation/en-US/Red_Hat_En > > >> > >> terprise_Linux/6/html/ > > >> > >> > > > > > > > > > > > Resource_Management_Guide/sec-cpu.html) > has > > >> the > > >> > >> > concept > > >> > >> > > of > > >> > >> > > > > > > > > > > > cpu.cfs_quota_us, > > >> > >> > > > > > > > > > > > which specifies the total amount of time in > > >> > >> > microseconds > > >> > >> > > > for > > >> > >> > > > > > > which > > >> > >> > > > > > > > > all > > >> > >> > > > > > > > > > > > tasks in a cgroup can run during a one > second > > >> > >> period. > > >> > >> > We > > >> > >> > > > can > > >> > >> > > > > > > > > > potentially > > >> > >> > > > > > > > > > > > model the request handler threads in a > > similar > > >> > way. > > >> > >> For > > >> > >> > > > > > example, > > >> > >> > > > > > > > each > > >> > >> > > > > > > > > > > > request handler thread can be 1 request > > handler > > >> > unit > > >> > >> > and > > >> > >> > > > the > > >> > >> > > > > > > admin > > >> > >> > > > > > > > > can > > >> > >> > > > > > > > > > > > configure a limit on how many units (say > > 0.01) > > >> a > > >> > >> client > > >> > >> > > can > > >> > >> > > > > > have. > > >> > >> > > > > > > > > > > > > > >> > >> > > > > > > > > > > > Regarding not throttling the internal > broker > > to > > >> > >> broker > > >> > >> > > > > > requests. > > >> > >> > > > > > > We > > >> > >> > > > > > > > > > could > > >> > >> > > > > > > > > > > > do that. Alternatively, we could just let > the > > >> > admin > > >> > >> > > > > configure a > > >> > >> > > > > > > > high > > >> > >> > > > > > > > > > > limit > > >> > >> > > > > > > > > > > > for the kafka user (it may not be able to > do > > >> that > > >> > >> > easily > > >> > >> > > > > based > > >> > >> > > > > > on > > >> > >> > > > > > > > > > > clientId > > >> > >> > > > > > > > > > > > though). > > >> > >> > > > > > > > > > > > > > >> > >> > > > > > > > > > > > Ideally we want to be able to protect the > > >> > >> utilization > > >> > >> > of > > >> > >> > > > the > > >> > >> > > > > > > > network > > >> > >> > > > > > > > > > > thread > > >> > >> > > > > > > > > > > > pool too. The difficult is mostly what > Rajini > > >> > said: > > >> > >> (1) > > >> > >> > > The > > >> > >> > > > > > > > mechanism > > >> > >> > > > > > > > > > for > > >> > >> > > > > > > > > > > > throttling the requests is through > Purgatory > > >> and > > >> > we > > >> > >> > will > > >> > >> > > > have > > >> > >> > > > > > to > > >> > >> > > > > > > > > think > > >> > >> > > > > > > > > > > > through how to integrate that into the > > network > > >> > >> layer. > > >> > >> > > (2) > > >> > >> > > > In > > >> > >> > > > > > the > > >> > >> > > > > > > > > > network > > >> > >> > > > > > > > > > > > layer, currently we know the user, but not > > the > > >> > >> clientId > > >> > >> > > of > > >> > >> > > > > the > > >> > >> > > > > > > > > request. > > >> > >> > > > > > > > > > > So, > > >> > >> > > > > > > > > > > > it's a bit tricky to throttle based on > > clientId > > >> > >> there. > > >> > >> > > > Plus, > > >> > >> > > > > > the > > >> > >> > > > > > > > > > byteOut > > >> > >> > > > > > > > > > > > quota can already protect the network > thread > > >> > >> > utilization > > >> > >> > > > for > > >> > >> > > > > > > fetch > > >> > >> > > > > > > > > > > > requests. So, if we can't figure out this > > part > > >> > right > > >> > >> > now, > > >> > >> > > > > just > > >> > >> > > > > > > > > focusing > > >> > >> > > > > > > > > > > on > > >> > >> > > > > > > > > > > > the request handling threads for this KIP > is > > >> > still a > > >> > >> > > useful > > >> > >> > > > > > > > feature. > > >> > >> > > > > > > > > > > > > > >> > >> > > > > > > > > > > > Thanks, > > >> > >> > > > > > > > > > > > > > >> > >> > > > > > > > > > > > Jun > > >> > >> > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > >> > >> > > > > > > > > > > > On Tue, Feb 21, 2017 at 4:27 AM, Rajini > > >> Sivaram < > > >> > >> > > > > > > > > > rajinisiva...@gmail.com > > >> > >> > > > > > > > > > > > > > >> > >> > > > > > > > > > > > wrote: > > >> > >> > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > Thank you all for the feedback. > > >> > >> > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > Jay: I have removed exemption for > consumer > > >> > >> heartbeat > > >> > >> > > etc. > > >> > >> > > > > > Agree > > >> > >> > > > > > > > > that > > >> > >> > > > > > > > > > > > > protecting the cluster is more important > > than > > >> > >> > > protecting > > >> > >> > > > > > > > individual > > >> > >> > > > > > > > > > > apps. > > >> > >> > > > > > > > > > > > > Have retained the exemption for > > >> > >> > > StopReplicat/LeaderAndIsr > > >> > >> > > > > > etc, > > >> > >> > > > > > > > > these > > >> > >> > > > > > > > > > > are > > >> > >> > > > > > > > > > > > > throttled only if authorization fails (so > > >> can't > > >> > be > > >> > >> > used > > >> > >> > > > for > > >> > >> > > > > > DoS > > >> > >> > > > > > > > > > attacks > > >> > >> > > > > > > > > > > > in > > >> > >> > > > > > > > > > > > > a secure cluster, but allows inter-broker > > >> > >> requests to > > >> > >> > > > > > complete > > >> > >> > > > > > > > > > without > > >> > >> > > > > > > > > > > > > delays). > > >> > >> > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > I will wait another day to see if these > is > > >> any > > >> > >> > > objection > > >> > >> > > > to > > >> > >> > > > > > > > quotas > > >> > >> > > > > > > > > > > based > > >> > >> > > > > > > > > > > > on > > >> > >> > > > > > > > > > > > > request processing time (as opposed to > > >> request > > >> > >> rate) > > >> > >> > > and > > >> > >> > > > if > > >> > >> > > > > > > there > > >> > >> > > > > > > > > are > > >> > >> > > > > > > > > > > no > > >> > >> > > > > > > > > > > > > objections, I will revert to the original > > >> > proposal > > >> > >> > with > > >> > >> > > > > some > > >> > >> > > > > > > > > changes. > > >> > >> > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > The original proposal was only including > > the > > >> > time > > >> > >> > used > > >> > >> > > by > > >> > >> > > > > the > > >> > >> > > > > > > > > request > > >> > >> > > > > > > > > > > > > handler threads (that made calculation > > >> easy). I > > >> > >> think > > >> > >> > > the > > >> > >> > > > > > > > > suggestion > > >> > >> > > > > > > > > > is > > >> > >> > > > > > > > > > > > to > > >> > >> > > > > > > > > > > > > include the time spent in the network > > >> threads as > > >> > >> well > > >> > >> > > > since > > >> > >> > > > > > > that > > >> > >> > > > > > > > > may > > >> > >> > > > > > > > > > be > > >> > >> > > > > > > > > > > > > significant. As Jay pointed out, it is > more > > >> > >> > complicated > > >> > >> > > > to > > >> > >> > > > > > > > > calculate > > >> > >> > > > > > > > > > > the > > >> > >> > > > > > > > > > > > > total available CPU time and convert to a > > >> ratio > > >> > >> when > > >> > >> > > > there > > >> > >> > > > > > *m* > > >> > >> > > > > > > > I/O > > >> > >> > > > > > > > > > > > threads > > >> > >> > > > > > > > > > > > > and *n* network threads. > > >> > >> > ThreadMXBean#getThreadCPUTime( > > >> > >> > > ) > > >> > >> > > > > may > > >> > >> > > > > > > > give > > >> > >> > > > > > > > > us > > >> > >> > > > > > > > > > > > what > > >> > >> > > > > > > > > > > > > we want, but it can be very expensive on > > some > > >> > >> > > platforms. > > >> > >> > > > As > > >> > >> > > > > > > > Becket > > >> > >> > > > > > > > > > and > > >> > >> > > > > > > > > > > > > Guozhang have pointed out, we do have > > several > > >> > time > > >> > >> > > > > > measurements > > >> > >> > > > > > > > > > already > > >> > >> > > > > > > > > > > > for > > >> > >> > > > > > > > > > > > > generating metrics that we could use, > > though > > >> we > > >> > >> might > > >> > >> > > > want > > >> > >> > > > > to > > >> > >> > > > > > > > > switch > > >> > >> > > > > > > > > > to > > >> > >> > > > > > > > > > > > > nanoTime() instead of currentTimeMillis() > > >> since > > >> > >> some > > >> > >> > of > > >> > >> > > > the > > >> > >> > > > > > > > values > > >> > >> > > > > > > > > > for > > >> > >> > > > > > > > > > > > > small requests may be < 1ms. But rather > > than > > >> add > > >> > >> up > > >> > >> > the > > >> > >> > > > > time > > >> > >> > > > > > > > spent > > >> > >> > > > > > > > > in > > >> > >> > > > > > > > > > > I/O > > >> > >> > > > > > > > > > > > > thread and network thread, wouldn't it be > > >> better > > >> > >> to > > >> > >> > > > convert > > >> > >> > > > > > the > > >> > >> > > > > > > > > time > > >> > >> > > > > > > > > > > > spent > > >> > >> > > > > > > > > > > > > on each thread into a separate ratio? > UserA > > >> has > > >> > a > > >> > >> > > request > > >> > >> > > > > > quota > > >> > >> > > > > > > > of > > >> > >> > > > > > > > > > 5%. > > >> > >> > > > > > > > > > > > Can > > >> > >> > > > > > > > > > > > > we take that to mean that UserA can use > 5% > > of > > >> > the > > >> > >> > time > > >> > >> > > on > > >> > >> > > > > > > network > > >> > >> > > > > > > > > > > threads > > >> > >> > > > > > > > > > > > > and 5% of the time on I/O threads? If > > either > > >> is > > >> > >> > > exceeded, > > >> > >> > > > > the > > >> > >> > > > > > > > > > response > > >> > >> > > > > > > > > > > is > > >> > >> > > > > > > > > > > > > throttled - it would mean maintaining two > > >> sets > > >> > of > > >> > >> > > metrics > > >> > >> > > > > for > > >> > >> > > > > > > the > > >> > >> > > > > > > > > two > > >> > >> > > > > > > > > > > > > durations, but would result in more > > >> meaningful > > >> > >> > ratios. > > >> > >> > > We > > >> > >> > > > > > could > > >> > >> > > > > > > > > > define > > >> > >> > > > > > > > > > > > two > > >> > >> > > > > > > > > > > > > quota limits (UserA has 5% of request > > threads > > >> > and > > >> > >> 10% > > >> > >> > > of > > >> > >> > > > > > > network > > >> > >> > > > > > > > > > > > threads), > > >> > >> > > > > > > > > > > > > but that seems unnecessary and harder to > > >> explain > > >> > >> to > > >> > >> > > > users. > > >> > >> > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > Back to why and how quotas are applied to > > >> > network > > >> > >> > > thread > > >> > >> > > > > > > > > utilization: > > >> > >> > > > > > > > > > > > > a) In the case of fetch, the time spent > in > > >> the > > >> > >> > network > > >> > >> > > > > > thread > > >> > >> > > > > > > > may > > >> > >> > > > > > > > > be > > >> > >> > > > > > > > > > > > > significant and I can see the need to > > include > > >> > >> this. > > >> > >> > Are > > >> > >> > > > > there > > >> > >> > > > > > > > other > > >> > >> > > > > > > > > > > > > requests where the network thread > > >> utilization is > > >> > >> > > > > significant? > > >> > >> > > > > > > In > > >> > >> > > > > > > > > the > > >> > >> > > > > > > > > > > case > > >> > >> > > > > > > > > > > > > of fetch, request handler thread > > utilization > > >> > would > > >> > >> > > > throttle > > >> > >> > > > > > > > clients > > >> > >> > > > > > > > > > > with > > >> > >> > > > > > > > > > > > > high request rate, low data volume and > > fetch > > >> > byte > > >> > >> > rate > > >> > >> > > > > quota > > >> > >> > > > > > > will > > >> > >> > > > > > > > > > > > throttle > > >> > >> > > > > > > > > > > > > clients with high data volume. Network > > thread > > >> > >> > > utilization > > >> > >> > > > > is > > >> > >> > > > > > > > > perhaps > > >> > >> > > > > > > > > > > > > proportional to the data volume. I am > > >> wondering > > >> > >> if we > > >> > >> > > > even > > >> > >> > > > > > need > > >> > >> > > > > > > > to > > >> > >> > > > > > > > > > > > throttle > > >> > >> > > > > > > > > > > > > based on network thread utilization or > > >> whether > > >> > the > > >> > >> > data > > >> > >> > > > > > volume > > >> > >> > > > > > > > > quota > > >> > >> > > > > > > > > > > > covers > > >> > >> > > > > > > > > > > > > this case. > > >> > >> > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > b) At the moment, we record and check for > > >> quota > > >> > >> > > violation > > >> > >> > > > > at > > >> > >> > > > > > > the > > >> > >> > > > > > > > > same > > >> > >> > > > > > > > > > > > time. > > >> > >> > > > > > > > > > > > > If a quota is violated, the response is > > >> delayed. > > >> > >> > Using > > >> > >> > > > > Jay'e > > >> > >> > > > > > > > > example > > >> > >> > > > > > > > > > of > > >> > >> > > > > > > > > > > > > disk reads for fetches happening in the > > >> network > > >> > >> > thread, > > >> > >> > > > We > > >> > >> > > > > > > can't > > >> > >> > > > > > > > > > record > > >> > >> > > > > > > > > > > > and > > >> > >> > > > > > > > > > > > > delay a response after the disk reads. We > > >> could > > >> > >> > record > > >> > >> > > > the > > >> > >> > > > > > time > > >> > >> > > > > > > > > spent > > >> > >> > > > > > > > > > > on > > >> > >> > > > > > > > > > > > > the network thread when the response is > > >> complete > > >> > >> and > > >> > >> > > > > > introduce > > >> > >> > > > > > > a > > >> > >> > > > > > > > > > delay > > >> > >> > > > > > > > > > > > for > > >> > >> > > > > > > > > > > > > handling a subsequent request (separate > out > > >> > >> recording > > >> > >> > > and > > >> > >> > > > > > quota > > >> > >> > > > > > > > > > > violation > > >> > >> > > > > > > > > > > > > handling in the case of network thread > > >> > overload). > > >> > >> > Does > > >> > >> > > > that > > >> > >> > > > > > > make > > >> > >> > > > > > > > > > sense? > > >> > >> > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > Regards, > > >> > >> > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > Rajini > > >> > >> > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > On Tue, Feb 21, 2017 at 2:58 AM, Becket > > Qin < > > >> > >> > > > > > > > becket....@gmail.com> > > >> > >> > > > > > > > > > > > wrote: > > >> > >> > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > Hey Jay, > > >> > >> > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > Yeah, I agree that enforcing the CPU > time > > >> is a > > >> > >> > little > > >> > >> > > > > > > tricky. I > > >> > >> > > > > > > > > am > > >> > >> > > > > > > > > > > > > thinking > > >> > >> > > > > > > > > > > > > > that maybe we can use the existing > > request > > >> > >> > > statistics. > > >> > >> > > > > They > > >> > >> > > > > > > are > > >> > >> > > > > > > > > > > already > > >> > >> > > > > > > > > > > > > > very detailed so we can probably see > the > > >> > >> > approximate > > >> > >> > > > CPU > > >> > >> > > > > > time > > >> > >> > > > > > > > > from > > >> > >> > > > > > > > > > > it, > > >> > >> > > > > > > > > > > > > e.g. > > >> > >> > > > > > > > > > > > > > something like (total_time - > > >> > >> > > > request/response_queue_time > > >> > >> > > > > - > > >> > >> > > > > > > > > > > > remote_time). > > >> > >> > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > I agree with Guozhang that when a user > is > > >> > >> throttled > > >> > >> > > it > > >> > >> > > > is > > >> > >> > > > > > > > likely > > >> > >> > > > > > > > > > that > > >> > >> > > > > > > > > > > > we > > >> > >> > > > > > > > > > > > > > need to see if anything has went wrong > > >> first, > > >> > >> and > > >> > >> > if > > >> > >> > > > the > > >> > >> > > > > > > users > > >> > >> > > > > > > > > are > > >> > >> > > > > > > > > > > well > > >> > >> > > > > > > > > > > > > > behaving and just need more resources, > we > > >> will > > >> > >> have > > >> > >> > > to > > >> > >> > > > > bump > > >> > >> > > > > > > up > > >> > >> > > > > > > > > the > > >> > >> > > > > > > > > > > > quota > > >> > >> > > > > > > > > > > > > > for them. It is true that > pre-allocating > > >> CPU > > >> > >> time > > >> > >> > > quota > > >> > >> > > > > > > > precisely > > >> > >> > > > > > > > > > for > > >> > >> > > > > > > > > > > > the > > >> > >> > > > > > > > > > > > > > users is difficult. So in practice it > > would > > >> > >> > probably > > >> > >> > > be > > >> > >> > > > > > more > > >> > >> > > > > > > > like > > >> > >> > > > > > > > > > > first > > >> > >> > > > > > > > > > > > > set > > >> > >> > > > > > > > > > > > > > a relative high protective CPU time > quota > > >> for > > >> > >> > > everyone > > >> > >> > > > > and > > >> > >> > > > > > > > > increase > > >> > >> > > > > > > > > > > > that > > >> > >> > > > > > > > > > > > > > for some individual clients on demand. > > >> > >> > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > Thanks, > > >> > >> > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > Jiangjie (Becket) Qin > > >> > >> > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > On Mon, Feb 20, 2017 at 5:48 PM, > Guozhang > > >> > Wang < > > >> > >> > > > > > > > > wangg...@gmail.com > > >> > >> > > > > > > > > > > > > >> > >> > > > > > > > > > > > > wrote: > > >> > >> > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > This is a great proposal, glad to see > > it > > >> > >> > happening. > > >> > >> > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > I am inclined to the CPU throttling, > or > > >> more > > >> > >> > > > > specifically > > >> > >> > > > > > > > > > > processing > > >> > >> > > > > > > > > > > > > time > > >> > >> > > > > > > > > > > > > > > ratio instead of the request rate > > >> throttling > > >> > >> as > > >> > >> > > well. > > >> > >> > > > > > > Becket > > >> > >> > > > > > > > > has > > >> > >> > > > > > > > > > > very > > >> > >> > > > > > > > > > > > > > well > > >> > >> > > > > > > > > > > > > > > summed my rationales above, and one > > >> thing to > > >> > >> add > > >> > >> > > here > > >> > >> > > > > is > > >> > >> > > > > > > that > > >> > >> > > > > > > > > the > > >> > >> > > > > > > > > > > > > former > > >> > >> > > > > > > > > > > > > > > has a good support for both > "protecting > > >> > >> against > > >> > >> > > rogue > > >> > >> > > > > > > > clients" > > >> > >> > > > > > > > > as > > >> > >> > > > > > > > > > > > well > > >> > >> > > > > > > > > > > > > as > > >> > >> > > > > > > > > > > > > > > "utilizing a cluster for > multi-tenancy > > >> > usage": > > >> > >> > when > > >> > >> > > > > > > thinking > > >> > >> > > > > > > > > > about > > >> > >> > > > > > > > > > > > how > > >> > >> > > > > > > > > > > > > to > > >> > >> > > > > > > > > > > > > > > explain this to the end users, I find > > it > > >> > >> actually > > >> > >> > > > more > > >> > >> > > > > > > > natural > > >> > >> > > > > > > > > > than > > >> > >> > > > > > > > > > > > the > > >> > >> > > > > > > > > > > > > > > request rate since as mentioned > above, > > >> > >> different > > >> > >> > > > > requests > > >> > >> > > > > > > > will > > >> > >> > > > > > > > > > have > > >> > >> > > > > > > > > > > > > quite > > >> > >> > > > > > > > > > > > > > > different "cost", and Kafka today > > already > > >> > have > > >> > >> > > > various > > >> > >> > > > > > > > request > > >> > >> > > > > > > > > > > types > > >> > >> > > > > > > > > > > > > > > (produce, fetch, admin, metadata, > etc), > > >> > >> because > > >> > >> > of > > >> > >> > > > that > > >> > >> > > > > > the > > >> > >> > > > > > > > > > request > > >> > >> > > > > > > > > > > > > rate > > >> > >> > > > > > > > > > > > > > > throttling may not be as effective > > >> unless it > > >> > >> is > > >> > >> > set > > >> > >> > > > > very > > >> > >> > > > > > > > > > > > > conservatively. > > >> > >> > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > Regarding to user reactions when they > > are > > >> > >> > > throttled, > > >> > >> > > > I > > >> > >> > > > > > > think > > >> > >> > > > > > > > it > > >> > >> > > > > > > > > > may > > >> > >> > > > > > > > > > > > > > differ > > >> > >> > > > > > > > > > > > > > > case-by-case, and need to be > > discovered / > > >> > >> guided > > >> > >> > by > > >> > >> > > > > > looking > > >> > >> > > > > > > > at > > >> > >> > > > > > > > > > > > relative > > >> > >> > > > > > > > > > > > > > > metrics. So in other words users > would > > >> not > > >> > >> expect > > >> > >> > > to > > >> > >> > > > > get > > >> > >> > > > > > > > > > additional > > >> > >> > > > > > > > > > > > > > > information by simply being told > "hey, > > >> you > > >> > are > > >> > >> > > > > > throttled", > > >> > >> > > > > > > > > which > > >> > >> > > > > > > > > > is > > >> > >> > > > > > > > > > > > all > > >> > >> > > > > > > > > > > > > > > what throttling does; they need to > > take a > > >> > >> > follow-up > > >> > >> > > > > step > > >> > >> > > > > > > and > > >> > >> > > > > > > > > see > > >> > >> > > > > > > > > > > > "hmm, > > >> > >> > > > > > > > > > > > > > I'm > > >> > >> > > > > > > > > > > > > > > throttled probably because of ..", > > which > > >> is > > >> > by > > >> > >> > > > looking > > >> > >> > > > > at > > >> > >> > > > > > > > other > > >> > >> > > > > > > > > > > > metric > > >> > >> > > > > > > > > > > > > > > values: e.g. whether I'm bombarding > the > > >> > >> brokers > > >> > >> > > with > > >> > >> > > > > > > metadata > > >> > >> > > > > > > > > > > > request, > > >> > >> > > > > > > > > > > > > > > which are usually cheap to handle but > > I'm > > >> > >> sending > > >> > >> > > > > > thousands > > >> > >> > > > > > > > per > > >> > >> > > > > > > > > > > > second; > > >> > >> > > > > > > > > > > > > > or > > >> > >> > > > > > > > > > > > > > > is it because I'm catching up and > hence > > >> > >> sending > > >> > >> > > very > > >> > >> > > > > > heavy > > >> > >> > > > > > > > > > fetching > > >> > >> > > > > > > > > > > > > > request > > >> > >> > > > > > > > > > > > > > > with large min.bytes, etc. > > >> > >> > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > Regarding to the implementation, as > > once > > >> > >> > discussed > > >> > >> > > > with > > >> > >> > > > > > > Jun, > > >> > >> > > > > > > > > this > > >> > >> > > > > > > > > > > > seems > > >> > >> > > > > > > > > > > > > > not > > >> > >> > > > > > > > > > > > > > > very difficult since today we are > > already > > >> > >> > > collecting > > >> > >> > > > > the > > >> > >> > > > > > > > > "thread > > >> > >> > > > > > > > > > > pool > > >> > >> > > > > > > > > > > > > > > utilization" metrics, which is a > single > > >> > >> > percentage > > >> > >> > > > > > > > > > > > "aggregateIdleMeter" > > >> > >> > > > > > > > > > > > > > > value; but we are already effectively > > >> > >> aggregating > > >> > >> > > it > > >> > >> > > > > for > > >> > >> > > > > > > each > > >> > >> > > > > > > > > > > > requests > > >> > >> > > > > > > > > > > > > in > > >> > >> > > > > > > > > > > > > > > KafkaRequestHandler, and we can just > > >> extend > > >> > >> it by > > >> > >> > > > > > recording > > >> > >> > > > > > > > the > > >> > >> > > > > > > > > > > > source > > >> > >> > > > > > > > > > > > > > > client id when handling them and > > >> aggregating > > >> > >> by > > >> > >> > > > > clientId > > >> > >> > > > > > as > > >> > >> > > > > > > > > well > > >> > >> > > > > > > > > > as > > >> > >> > > > > > > > > > > > the > > >> > >> > > > > > > > > > > > > > > total aggregate. > > >> > >> > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > Guozhang > > >> > >> > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > On Mon, Feb 20, 2017 at 4:27 PM, Jay > > >> Kreps < > > >> > >> > > > > > > j...@confluent.io > > >> > >> > > > > > > > > > > >> > >> > > > > > > > > > > wrote: > > >> > >> > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > Hey Becket/Rajini, > > >> > >> > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > When I thought about it more > deeply I > > >> came > > >> > >> > around > > >> > >> > > > to > > >> > >> > > > > > the > > >> > >> > > > > > > > > > "percent > > >> > >> > > > > > > > > > > > of > > >> > >> > > > > > > > > > > > > > > > processing time" metric too. It > > seems a > > >> > lot > > >> > >> > > closer > > >> > >> > > > to > > >> > >> > > > > > the > > >> > >> > > > > > > > > thing > > >> > >> > > > > > > > > > > we > > >> > >> > > > > > > > > > > > > > > actually > > >> > >> > > > > > > > > > > > > > > > care about and need to protect. I > > also > > >> > think > > >> > >> > this > > >> > >> > > > > would > > >> > >> > > > > > > be > > >> > >> > > > > > > > a > > >> > >> > > > > > > > > > very > > >> > >> > > > > > > > > > > > > > useful > > >> > >> > > > > > > > > > > > > > > > metric even in the absence of > > >> throttling > > >> > >> just > > >> > >> > to > > >> > >> > > > > debug > > >> > >> > > > > > > > whose > > >> > >> > > > > > > > > > > using > > >> > >> > > > > > > > > > > > > > > > capacity. > > >> > >> > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > Two problems to consider: > > >> > >> > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > 1. I agree that for the user it > is > > >> > >> > > > understandable > > >> > >> > > > > > what > > >> > >> > > > > > > > > lead > > >> > >> > > > > > > > > > to > > >> > >> > > > > > > > > > > > > their > > >> > >> > > > > > > > > > > > > > > > being throttled, but it is a bit > > >> hard > > >> > to > > >> > >> > > figure > > >> > >> > > > > out > > >> > >> > > > > > > the > > >> > >> > > > > > > > > safe > > >> > >> > > > > > > > > > > > range > > >> > >> > > > > > > > > > > > > > for > > >> > >> > > > > > > > > > > > > > > > them. i.e. if I have a new app > > that > > >> > will > > >> > >> > send > > >> > >> > > > 200 > > >> > >> > > > > > > > > > > messages/sec I > > >> > >> > > > > > > > > > > > > can > > >> > >> > > > > > > > > > > > > > > > probably reason that I'll be > under > > >> the > > >> > >> > > > throttling > > >> > >> > > > > > > limit > > >> > >> > > > > > > > of > > >> > >> > > > > > > > > > 300 > > >> > >> > > > > > > > > > > > > > > req/sec. > > >> > >> > > > > > > > > > > > > > > > However if I need to be under a > > 10% > > >> CPU > > >> > >> > > > resources > > >> > >> > > > > > > limit > > >> > >> > > > > > > > it > > >> > >> > > > > > > > > > may > > >> > >> > > > > > > > > > > > be > > >> > >> > > > > > > > > > > > > a > > >> > >> > > > > > > > > > > > > > > bit > > >> > >> > > > > > > > > > > > > > > > harder for me to know a priori > if > > i > > >> > will > > >> > >> or > > >> > >> > > > won't. > > >> > >> > > > > > > > > > > > > > > > 2. Calculating the available CPU > > >> time > > >> > is > > >> > >> a > > >> > >> > bit > > >> > >> > > > > > > difficult > > >> > >> > > > > > > > > > since > > >> > >> > > > > > > > > > > > > there > > >> > >> > > > > > > > > > > > > > > are > > >> > >> > > > > > > > > > > > > > > > actually two thread pools--the > I/O > > >> > >> threads > > >> > >> > and > > >> > >> > > > the > > >> > >> > > > > > > > network > > >> > >> > > > > > > > > > > > > threads. > > >> > >> > > > > > > > > > > > > > I > > >> > >> > > > > > > > > > > > > > > > think > > >> > >> > > > > > > > > > > > > > > > it might be workable to count > just > > >> the > > >> > >> I/O > > >> > >> > > > thread > > >> > >> > > > > > time > > >> > >> > > > > > > > as > > >> > >> > > > > > > > > in > > >> > >> > > > > > > > > > > the > > >> > >> > > > > > > > > > > > > > > > proposal, > > >> > >> > > > > > > > > > > > > > > > but the network thread work is > > >> actually > > >> > >> > > > > non-trivial > > >> > >> > > > > > > > (e.g. > > >> > >> > > > > > > > > > all > > >> > >> > > > > > > > > > > > the > > >> > >> > > > > > > > > > > > > > disk > > >> > >> > > > > > > > > > > > > > > > reads for fetches happen in that > > >> > >> thread). If > > >> > >> > > you > > >> > >> > > > > > count > > >> > >> > > > > > > > > both > > >> > >> > > > > > > > > > > the > > >> > >> > > > > > > > > > > > > > > network > > >> > >> > > > > > > > > > > > > > > > and > > >> > >> > > > > > > > > > > > > > > > I/O threads it can skew things a > > >> bit. > > >> > >> E.g. > > >> > >> > say > > >> > >> > > > you > > >> > >> > > > > > > have > > >> > >> > > > > > > > 50 > > >> > >> > > > > > > > > > > > network > > >> > >> > > > > > > > > > > > > > > > threads, > > >> > >> > > > > > > > > > > > > > > > 10 I/O threads, and 8 cores, > what > > is > > >> > the > > >> > >> > > > available > > >> > >> > > > > > cpu > > >> > >> > > > > > > > > time > > >> > >> > > > > > > > > > > > > > available > > >> > >> > > > > > > > > > > > > > > > in a > > >> > >> > > > > > > > > > > > > > > > second? I suppose this is a > > problem > > >> > >> whenever > > >> > >> > > you > > >> > >> > > > > > have > > >> > >> > > > > > > a > > >> > >> > > > > > > > > > > > bottleneck > > >> > >> > > > > > > > > > > > > > > > between > > >> > >> > > > > > > > > > > > > > > > I/O and network threads or if > you > > >> end > > >> > up > > >> > >> > > > > > significantly > > >> > >> > > > > > > > > > > > > > > over-provisioning > > >> > >> > > > > > > > > > > > > > > > one pool (both of which are hard > > to > > >> > >> avoid). > > >> > >> > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > An alternative for CPU throttling > > >> would be > > >> > >> to > > >> > >> > use > > >> > >> > > > > this > > >> > >> > > > > > > api: > > >> > >> > > > > > > > > > > > > > > > http://docs.oracle.com/javase/ > > >> > >> > > > > > 1.5.0/docs/api/java/lang/ > > >> > >> > > > > > > > > > > > > > > > management/ThreadMXBean.html# > > >> > >> > > > getThreadCpuTime(long) > > >> > >> > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > That would let you track actual CPU > > >> usage > > >> > >> > across > > >> > >> > > > the > > >> > >> > > > > > > > network, > > >> > >> > > > > > > > > > I/O > > >> > >> > > > > > > > > > > > > > > threads, > > >> > >> > > > > > > > > > > > > > > > and purgatory threads and look at > it > > >> as a > > >> > >> > > > percentage > > >> > >> > > > > of > > >> > >> > > > > > > > total > > >> > >> > > > > > > > > > > > cores. > > >> > >> > > > > > > > > > > > > I > > >> > >> > > > > > > > > > > > > > > > think this fixes many problems in > the > > >> > >> > reliability > > >> > >> > > > of > > >> > >> > > > > > the > > >> > >> > > > > > > > > > metric. > > >> > >> > > > > > > > > > > > It's > > >> > >> > > > > > > > > > > > > > > > meaning is slightly different as it > > is > > >> > just > > >> > >> CPU > > >> > >> > > > (you > > >> > >> > > > > > > don't > > >> > >> > > > > > > > > get > > >> > >> > > > > > > > > > > > > charged > > >> > >> > > > > > > > > > > > > > > for > > >> > >> > > > > > > > > > > > > > > > time blocking on I/O) but that may > be > > >> okay > > >> > >> > > because > > >> > >> > > > we > > >> > >> > > > > > > > already > > >> > >> > > > > > > > > > > have > > >> > >> > > > > > > > > > > > a > > >> > >> > > > > > > > > > > > > > > > throttle on I/O. The downside is I > > >> think > > >> > it > > >> > >> is > > >> > >> > > > > possible > > >> > >> > > > > > > > this > > >> > >> > > > > > > > > > api > > >> > >> > > > > > > > > > > > can > > >> > >> > > > > > > > > > > > > be > > >> > >> > > > > > > > > > > > > > > > disabled or isn't always available > > and > > >> it > > >> > >> may > > >> > >> > > also > > >> > >> > > > be > > >> > >> > > > > > > > > expensive > > >> > >> > > > > > > > > > > > (also > > >> > >> > > > > > > > > > > > > > > I've > > >> > >> > > > > > > > > > > > > > > > never used it so not sure if it > > really > > >> > works > > >> > >> > the > > >> > >> > > > way > > >> > >> > > > > i > > >> > >> > > > > > > > > think). > > >> > >> > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > -Jay > > >> > >> > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > On Mon, Feb 20, 2017 at 3:17 PM, > > Becket > > >> > Qin > > >> > >> < > > >> > >> > > > > > > > > > > becket....@gmail.com> > > >> > >> > > > > > > > > > > > > > > wrote: > > >> > >> > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > If the purpose of the KIP is only > > to > > >> > >> protect > > >> > >> > > the > > >> > >> > > > > > > cluster > > >> > >> > > > > > > > > from > > >> > >> > > > > > > > > > > > being > > >> > >> > > > > > > > > > > > > > > > > overwhelmed by crazy clients and > is > > >> not > > >> > >> > > intended > > >> > >> > > > to > > >> > >> > > > > > > > address > > >> > >> > > > > > > > > > > > > resource > > >> > >> > > > > > > > > > > > > > > > > allocation problem among the > > >> clients, I > > >> > am > > >> > >> > > > > wondering > > >> > >> > > > > > if > > >> > >> > > > > > > > > using > > >> > >> > > > > > > > > > > > > request > > >> > >> > > > > > > > > > > > > > > > > handling time quota (CPU time > > quota) > > >> is > > >> > a > > >> > >> > > better > > >> > >> > > > > > > option. > > >> > >> > > > > > > > > Here > > >> > >> > > > > > > > > > > are > > >> > >> > > > > > > > > > > > > the > > >> > >> > > > > > > > > > > > > > > > > reasons: > > >> > >> > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > 1. request handling time quota > has > > >> > better > > >> > >> > > > > protection. > > >> > >> > > > > > > Say > > >> > >> > > > > > > > > we > > >> > >> > > > > > > > > > > have > > >> > >> > > > > > > > > > > > > > > request > > >> > >> > > > > > > > > > > > > > > > > rate quota and set that to some > > value > > >> > like > > >> > >> > 100 > > >> > >> > > > > > > > > requests/sec, > > >> > >> > > > > > > > > > it > > >> > >> > > > > > > > > > > > is > > >> > >> > > > > > > > > > > > > > > > possible > > >> > >> > > > > > > > > > > > > > > > > that some of the requests are > very > > >> > >> expensive > > >> > >> > > > > actually > > >> > >> > > > > > > > take > > >> > >> > > > > > > > > a > > >> > >> > > > > > > > > > > lot > > >> > >> > > > > > > > > > > > of > > >> > >> > > > > > > > > > > > > > > time > > >> > >> > > > > > > > > > > > > > > > to > > >> > >> > > > > > > > > > > > > > > > > handle. In that case a few > clients > > >> may > > >> > >> still > > >> > >> > > > > occupy a > > >> > >> > > > > > > lot > > >> > >> > > > > > > > > of > > >> > >> > > > > > > > > > > CPU > > >> > >> > > > > > > > > > > > > time > > >> > >> > > > > > > > > > > > > > > > even > > >> > >> > > > > > > > > > > > > > > > > the request rate is low. Arguably > > we > > >> can > > >> > >> > > > carefully > > >> > >> > > > > > set > > >> > >> > > > > > > > > > request > > >> > >> > > > > > > > > > > > rate > > >> > >> > > > > > > > > > > > > > > quota > > >> > >> > > > > > > > > > > > > > > > > for each request and client id > > >> > >> combination, > > >> > >> > but > > >> > >> > > > it > > >> > >> > > > > > > could > > >> > >> > > > > > > > > > still > > >> > >> > > > > > > > > > > be > > >> > >> > > > > > > > > > > > > > > tricky > > >> > >> > > > > > > > > > > > > > > > to > > >> > >> > > > > > > > > > > > > > > > > get it right for everyone. > > >> > >> > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > If we use the request time > handling > > >> > >> quota, we > > >> > >> > > can > > >> > >> > > > > > > simply > > >> > >> > > > > > > > > say > > >> > >> > > > > > > > > > no > > >> > >> > > > > > > > > > > > > > clients > > >> > >> > > > > > > > > > > > > > > > can > > >> > >> > > > > > > > > > > > > > > > > take up to more than 30% of the > > total > > >> > >> request > > >> > >> > > > > > handling > > >> > >> > > > > > > > > > capacity > > >> > >> > > > > > > > > > > > > > > (measured > > >> > >> > > > > > > > > > > > > > > > > by time), regardless of the > > >> difference > > >> > >> among > > >> > >> > > > > > different > > >> > >> > > > > > > > > > requests > > >> > >> > > > > > > > > > > > or > > >> > >> > > > > > > > > > > > > > what > > >> > >> > > > > > > > > > > > > > > > is > > >> > >> > > > > > > > > > > > > > > > > the client doing. In this case > > maybe > > >> we > > >> > >> can > > >> > >> > > quota > > >> > >> > > > > all > > >> > >> > > > > > > the > > >> > >> > > > > > > > > > > > requests > > >> > >> > > > > > > > > > > > > if > > >> > >> > > > > > > > > > > > > > > we > > >> > >> > > > > > > > > > > > > > > > > want to. > > >> > >> > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > 2. The main benefit of using > > request > > >> > rate > > >> > >> > limit > > >> > >> > > > is > > >> > >> > > > > > that > > >> > >> > > > > > > > it > > >> > >> > > > > > > > > > > seems > > >> > >> > > > > > > > > > > > > more > > >> > >> > > > > > > > > > > > > > > > > intuitive. It is true that it is > > >> > probably > > >> > >> > > easier > > >> > >> > > > to > > >> > >> > > > > > > > explain > > >> > >> > > > > > > > > > to > > >> > >> > > > > > > > > > > > the > > >> > >> > > > > > > > > > > > > > user > > >> > >> > > > > > > > > > > > > > > > > what does that mean. However, in > > >> > practice > > >> > >> it > > >> > >> > > > looks > > >> > >> > > > > > the > > >> > >> > > > > > > > > impact > > >> > >> > > > > > > > > > > of > > >> > >> > > > > > > > > > > > > > > request > > >> > >> > > > > > > > > > > > > > > > > rate quota is not more > quantifiable > > >> than > > >> > >> the > > >> > >> > > > > request > > >> > >> > > > > > > > > handling > > >> > >> > > > > > > > > > > > time > > >> > >> > > > > > > > > > > > > > > quota. > > >> > >> > > > > > > > > > > > > > > > > Unlike the byte rate quota, it is > > >> still > > >> > >> > > difficult > > >> > >> > > > > to > > >> > >> > > > > > > > give a > > >> > >> > > > > > > > > > > > number > > >> > >> > > > > > > > > > > > > > > about > > >> > >> > > > > > > > > > > > > > > > > impact of throughput or latency > > when > > >> a > > >> > >> > request > > >> > >> > > > rate > > >> > >> > > > > > > quota > > >> > >> > > > > > > > > is > > >> > >> > > > > > > > > > > hit. > > >> > >> > > > > > > > > > > > > So > > >> > >> > > > > > > > > > > > > > it > > >> > >> > > > > > > > > > > > > > > > is > > >> > >> > > > > > > > > > > > > > > > > not better than the request > > handling > > >> > time > > >> > >> > > quota. > > >> > >> > > > In > > >> > >> > > > > > > fact > > >> > >> > > > > > > > I > > >> > >> > > > > > > > > > feel > > >> > >> > > > > > > > > > > > it > > >> > >> > > > > > > > > > > > > is > > >> > >> > > > > > > > > > > > > > > > > clearer to tell user that "you > are > > >> > limited > > >> > >> > > > because > > >> > >> > > > > > you > > >> > >> > > > > > > > have > > >> > >> > > > > > > > > > > taken > > >> > >> > > > > > > > > > > > > 30% > > >> > >> > > > > > > > > > > > > > > of > > >> > >> > > > > > > > > > > > > > > > > the CPU time on the broker" than > > >> > otherwise > > >> > >> > > > > something > > >> > >> > > > > > > like > > >> > >> > > > > > > > > > "your > > >> > >> > > > > > > > > > > > > > request > > >> > >> > > > > > > > > > > > > > > > > rate quota on metadata request > has > > >> > >> reached". > > >> > >> > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > Thanks, > > >> > >> > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > Jiangjie (Becket) Qin > > >> > >> > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > On Mon, Feb 20, 2017 at 2:23 PM, > > Jay > > >> > >> Kreps < > > >> > >> > > > > > > > > j...@confluent.io > > >> > >> > > > > > > > > > > > > >> > >> > > > > > > > > > > > > wrote: > > >> > >> > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > I think this proposal makes a > lot > > >> of > > >> > >> sense > > >> > >> > > > > > > (especially > > >> > >> > > > > > > > > now > > >> > >> > > > > > > > > > > that > > >> > >> > > > > > > > > > > > > it > > >> > >> > > > > > > > > > > > > > is > > >> > >> > > > > > > > > > > > > > > > > > oriented around request rate) > and > > >> > fills > > >> > >> the > > >> > >> > > > > biggest > > >> > >> > > > > > > > > > remaining > > >> > >> > > > > > > > > > > > gap > > >> > >> > > > > > > > > > > > > > in > > >> > >> > > > > > > > > > > > > > > > the > > >> > >> > > > > > > > > > > > > > > > > > multi-tenancy story. > > >> > >> > > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > I think for intra-cluster > > >> > communication > > >> > >> > > > > > (StopReplica, > > >> > >> > > > > > > > > etc) > > >> > >> > > > > > > > > > we > > >> > >> > > > > > > > > > > > > could > > >> > >> > > > > > > > > > > > > > > > avoid > > >> > >> > > > > > > > > > > > > > > > > > throttling entirely. You can > > >> secure or > > >> > >> > > > otherwise > > >> > >> > > > > > > > > lock-down > > >> > >> > > > > > > > > > > the > > >> > >> > > > > > > > > > > > > > > cluster > > >> > >> > > > > > > > > > > > > > > > > > communication to avoid any > > >> > unauthorized > > >> > >> > > > external > > >> > >> > > > > > > party > > >> > >> > > > > > > > > from > > >> > >> > > > > > > > > > > > > trying > > >> > >> > > > > > > > > > > > > > to > > >> > >> > > > > > > > > > > > > > > > > > initiate these requests. As a > > >> result > > >> > we > > >> > >> are > > >> > >> > > as > > >> > >> > > > > > likely > > >> > >> > > > > > > > to > > >> > >> > > > > > > > > > > cause > > >> > >> > > > > > > > > > > > > > > problems > > >> > >> > > > > > > > > > > > > > > > > as > > >> > >> > > > > > > > > > > > > > > > > > solve them by throttling these, > > >> right? > > >> > >> > > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > I'm not so sure that we should > > >> exempt > > >> > >> the > > >> > >> > > > > consumer > > >> > >> > > > > > > > > requests > > >> > >> > > > > > > > > > > > such > > >> > >> > > > > > > > > > > > > as > > >> > >> > > > > > > > > > > > > > > > > > heartbeat. It's true that if we > > >> > >> throttle an > > >> > >> > > > app's > > >> > >> > > > > > > > > heartbeat > > >> > >> > > > > > > > > > > > > > requests > > >> > >> > > > > > > > > > > > > > > it > > >> > >> > > > > > > > > > > > > > > > > may > > >> > >> > > > > > > > > > > > > > > > > > cause it to fall out of its > > >> consumer > > >> > >> group. > > >> > >> > > > > However > > >> > >> > > > > > > if > > >> > >> > > > > > > > we > > >> > >> > > > > > > > > > > don't > > >> > >> > > > > > > > > > > > > > > > throttle > > >> > >> > > > > > > > > > > > > > > > > it > > >> > >> > > > > > > > > > > > > > > > > > it may DDOS the cluster if the > > >> > heartbeat > > >> > >> > > > interval > > >> > >> > > > > > is > > >> > >> > > > > > > > set > > >> > >> > > > > > > > > > > > > > incorrectly > > >> > >> > > > > > > > > > > > > > > or > > >> > >> > > > > > > > > > > > > > > > > if > > >> > >> > > > > > > > > > > > > > > > > > some client in some language > has > > a > > >> > bug. > > >> > >> I > > >> > >> > > think > > >> > >> > > > > the > > >> > >> > > > > > > > > policy > > >> > >> > > > > > > > > > > with > > >> > >> > > > > > > > > > > > > > this > > >> > >> > > > > > > > > > > > > > > > kind > > >> > >> > > > > > > > > > > > > > > > > > of throttling is to protect the > > >> > cluster > > >> > >> > above > > >> > >> > > > any > > >> > >> > > > > > > > > > individual > > >> > >> > > > > > > > > > > > app, > > >> > >> > > > > > > > > > > > > > > > right? > > >> > >> > > > > > > > > > > > > > > > > I > > >> > >> > > > > > > > > > > > > > > > > > think in general this should be > > >> okay > > >> > >> since > > >> > >> > > for > > >> > >> > > > > most > > >> > >> > > > > > > > > > > deployments > > >> > >> > > > > > > > > > > > > > this > > >> > >> > > > > > > > > > > > > > > > > > setting is meant as more of a > > >> safety > > >> > >> > > > valve---that > > >> > >> > > > > > is > > >> > >> > > > > > > > > rather > > >> > >> > > > > > > > > > > > than > > >> > >> > > > > > > > > > > > > > set > > >> > >> > > > > > > > > > > > > > > > > > something very close to what > you > > >> > expect > > >> > >> to > > >> > >> > > need > > >> > >> > > > > > (say > > >> > >> > > > > > > 2 > > >> > >> > > > > > > > > > > req/sec > > >> > >> > > > > > > > > > > > or > > >> > >> > > > > > > > > > > > > > > > > whatever) > > >> > >> > > > > > > > > > > > > > > > > > you would have something quite > > high > > >> > >> (like > > >> > >> > 100 > > >> > >> > > > > > > req/sec) > > >> > >> > > > > > > > > with > > >> > >> > > > > > > > > > > > this > > >> > >> > > > > > > > > > > > > > > meant > > >> > >> > > > > > > > > > > > > > > > to > > >> > >> > > > > > > > > > > > > > > > > > prevent a client gone crazy. I > > >> think > > >> > >> when > > >> > >> > > used > > >> > >> > > > > this > > >> > >> > > > > > > way > > >> > >> > > > > > > > > > > > allowing > > >> > >> > > > > > > > > > > > > > > those > > >> > >> > > > > > > > > > > > > > > > to > > >> > >> > > > > > > > > > > > > > > > > > be throttled would actually > > provide > > >> > >> > > meaningful > > >> > >> > > > > > > > > protection. > > >> > >> > > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > -Jay > > >> > >> > > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > On Fri, Feb 17, 2017 at 9:05 > AM, > > >> > Rajini > > >> > >> > > > Sivaram < > > >> > >> > > > > > > > > > > > > > > > rajinisiva...@gmail.com > > >> > >> > > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > wrote: > > >> > >> > > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > > Hi all, > > >> > >> > > > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > > I have just created KIP-124 > to > > >> > >> introduce > > >> > >> > > > > request > > >> > >> > > > > > > rate > > >> > >> > > > > > > > > > > quotas > > >> > >> > > > > > > > > > > > to > > >> > >> > > > > > > > > > > > > > > > Kafka: > > >> > >> > > > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/ > > >> > >> > > > > > > > confluence/display/KAFKA/KIP- > > >> > >> > > > > > > > > > > > > > > > > > > 124+-+Request+rate+quotas > > >> > >> > > > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > > The proposal is for a simple > > >> > >> percentage > > >> > >> > > > request > > >> > >> > > > > > > > > handling > > >> > >> > > > > > > > > > > time > > >> > >> > > > > > > > > > > > > > quota > > >> > >> > > > > > > > > > > > > > > > > that > > >> > >> > > > > > > > > > > > > > > > > > > can be allocated to > > >> *<client-id>*, > > >> > >> > *<user>* > > >> > >> > > > or > > >> > >> > > > > > > > *<user, > > >> > >> > > > > > > > > > > > > > client-id>*. > > >> > >> > > > > > > > > > > > > > > > > There > > >> > >> > > > > > > > > > > > > > > > > > > are a few other suggestions > > also > > >> > under > > >> > >> > > > > "Rejected > > >> > >> > > > > > > > > > > > alternatives". > > >> > >> > > > > > > > > > > > > > > > > Feedback > > >> > >> > > > > > > > > > > > > > > > > > > and suggestions are welcome. > > >> > >> > > > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > > Thank you... > > >> > >> > > > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > > Regards, > > >> > >> > > > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > > Rajini > > >> > >> > > > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > -- > > >> > >> > > > > > > > > > > > > > > -- Guozhang > > >> > >> > > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > > >> > >> > > > > > > > > > > > > >> > >> > > > > > > > > > > > >> > >> > > > > > > > > > > >> > >> > > > > > > > > > >> > >> > > > > > > > > >> > >> > > > > > > > >> > >> > > > > > > > >> > >> > > > > > > > >> > >> > > > > > -- > > >> > >> > > > > > -- Guozhang > > >> > >> > > > > > > > >> > >> > > > > > > >> > >> > > > > > >> > >> > > > > >> > >> > > > >> > >> > > >> > > > > >> > > > > >> > > > >> > > > > > > > > >