Hey Tong, I don't think there is any way to infer if you are being throttled unless Kafka exposes it, though. I think the question we're discussing is just whether we expose it on the server side or change the protocol to send that back to the client to expose. We are not adding any kind of general monitoring capabilities, just figuring out what metrics are needed.
The point I was trying to make is that it is important to think about the eventual usage to do even this well, though. -Jay On Tue, Apr 7, 2015 at 8:10 AM, Tong Li <liton...@us.ibm.com> wrote: > see some response inline below. > Tong Li > OpenStack & Kafka Community Development > Building 501/B205 > liton...@us.ibm.com > > Jay Kreps <jay.kr...@gmail.com> wrote on 04/07/2015 10:41:19 AM: > > > From: Jay Kreps <jay.kr...@gmail.com> > > To: "dev@kafka.apache.org" <dev@kafka.apache.org> > > Date: 04/07/2015 10:44 AM > > Subject: Re: [KIP-DISCUSSION] KIP-13 Quotas > > > > Totally. But is that the only use? What I wanted to flesh out was whether > > the goal was: > > 1. Expose throttling in the client metrics > > 2. Enable programmatic response (i.e. stop sending stuff or something > like > > that) > > > > I think I kind of understand (1) but let's get specific on the metric we > > would be adding and what exactly you would expose in a dashboard. For > > example if the goal is just monitoring do I really want a boolean flag > for > > is_throttled or do I want to know how much I am being throttled (i.e. > > throttle_pct might indicate the percent of your request time that was due > > to throttling or something like that)? If I am 1% throttled that may be > > irrelevant but 99% throttled would be quite relevant? Not sure I agree, > > just throwing that out there... > > > Jay, great point, I think Kafka should really just sent metrics, how to > judge if > a system is throttled should be someone other people's job. I would think > this comes down to design principles, if we follow the principal of > "separation > of the concerns", then this should not be really part of Kafka. > I have been doing monitoring systems for awhile, the system being monitored > normally just > send the fact of itself, such as CPU usage, network usage, disk usage etc > to the > monitoring system, the monitoring system will run various algorithms to > eventually > decide if a system is throttled by setting up threshold and other measures. > The monitoring > system will also send out notifications/alarms if things turns bad. Just > to make this discussion even easier, a set of general purpose of agents > collecting > these data have been developed and available as part of a monitoring system > named > Monasca. If you are interested, I can provide more information. For Kafka > to have > the features such as judging if the system is throttling seems to be a > moving-away > from its core values. Just my 2 cents of course. > > > > For (2) the prior discussion seemed to kind of allude to this but I can't > > really come up with a use case. Is there one? > > > > If it is just (1) I think the question is whether it really helps much to > > have the metric on the client vs the server. I suppose this is a bit > > environment specific. If you have a central metrics system it shouldn't > > make any difference, but if you don't I suppose it does. > > > > -Jay > > > > On Mon, Apr 6, 2015 at 7:57 PM, Gwen Shapira <gshap...@cloudera.com> > wrote: > > > > > Here's a wild guess: > > > > > > An app developer included a Kafka Producer in his app, and is not happy > > > with the throughput. He doesn't have visibility into the brokers since > they > > > are owned by a different team. Obviously the first instinct of a > developer > > > who knows that throttling exists is to blame throttling for any > slowdown in > > > the app. > > > If he doesn't have a way to know from the responses whether or not his > app > > > is throttled, he may end up calling Aditya at 4am asked "Hey, is my app > > > throttled?". > > > > > > I assume Aditya is trying to avoid this scenario. > > > > > > On Mon, Apr 6, 2015 at 7:47 PM, Jay Kreps <jay.kr...@gmail.com> wrote: > > > > > > > Hey Aditya, > > > > > > > > 2. I kind of buy it, but I really like to understand the details of > the > > > use > > > > case before we make protocol changes. What changes are you proposing > in > > > the > > > > clients for monitoring and how would that be used? > > > > > > > > -Jay > > > > > > > > On Mon, Apr 6, 2015 at 10:36 AM, Aditya Auradkar < > > > > aaurad...@linkedin.com.invalid> wrote: > > > > > > > > > Hi Jay, > > > > > > > > > > 2. At this time, the proposed response format changes are only for > > > > > monitoring/informing clients. As Jun mentioned, we get instance > level > > > > > monitoring in this case since each instance that got throttled will > > > have > > > > a > > > > > metric confirming the same. Without client level monitoring for > this, > > > > it's > > > > > hard for application developers to find if they are being throttled > > > since > > > > > they will also have to be aware of all the brokers in the cluster. > This > > > > is > > > > > quite problematic for large clusters. > > > > > > > > > > It seems nice for app developers to not have to think about kafka > > > > internal > > > > > metrics and only focus on the metrics exposed on their instances. > > > > Analogous > > > > > to having client-sde request latency metrics. Basically, we want an > > > easy > > > > > way for clients to be aware if they are being throttled. > > > > > > > > > > 4. For purgatory v delay queue, I think we are on the same page. I > feel > > > > it > > > > > is nicer to use the purgatory but I'm happy to use a DelayQueue if > > > there > > > > > are performance implications. I don't know enough about the current > and > > > > > Yasuhiro's new implementation to be sure one way or the other. > > > > > > > > > > Stepping back, I think these two things are the only remaining > point of > > > > > discussion within the current proposal. Any concerns if I started a > > > > voting > > > > > thread on the proposal after the KIP discussion tomorrow? (assuming > we > > > > > reach consensus on these items) > > > > > > > > > > Thanks, > > > > > Aditya > > > > > ________________________________________ > > > > > From: Jay Kreps [jay.kr...@gmail.com] > > > > > Sent: Saturday, April 04, 2015 1:36 PM > > > > > To: dev@kafka.apache.org > > > > > Subject: Re: [KIP-DISCUSSION] KIP-13 Quotas > > > > > > > > > > Hey Aditya, > > > > > > > > > > 2. For the return flag I'm not terribly particular. If we want to > add > > > it > > > > > let's fully think through how it will be used. The only concern I > have > > > is > > > > > adding to the protocol without really thinking through the use > cases. > > > So > > > > > let's work out the APIs we want to add to the Java consumer and > > > producer > > > > > and the use cases for how clients will make use of these. For my > part I > > > > > actually don't see much use other than monitoring since it isn't an > > > error > > > > > condition to be at your quota. And if it is just monitoring I don't > > > see a > > > > > big enough difference between having the monitoring on the > server-side > > > > > versus in the clients to justify putting it in the protocol. But I > > > think > > > > > you guys may have other use cases in mind of how a client would > make > > > some > > > > > use of this? Let's work that out. I also don't feel strongly about > > > it--it > > > > > wouldn't be *bad* to have the monitoring available on the client, > just > > > > > doesn't seem that much better. > > > > > > > > > > 4. For the purgatory vs delay queue I think is arguably nicer to > reuse > > > > the > > > > > purgatory we just have to be ultra-conscious of efficiency. I think > our > > > > > goal is to turn quotas on across the board, so at LinkedIn that > would > > > > mean > > > > > potentially every request will need a small delay. I haven't worked > out > > > > the > > > > > efficiency implications of this choice, so as long as we do that > I'm > > > > happy. > > > > > > > > > > -Jay > > > > > > > > > > On Fri, Apr 3, 2015 at 1:10 PM, Aditya Auradkar < > > > > > aaurad...@linkedin.com.invalid> wrote: > > > > > > > > > > > Some responses to Jay's points. > > > > > > > > > > > > 1. Using commas - Cool. > > > > > > > > > > > > 2. Adding return flag - I'm inclined to agree with Joel that this > is > > > > good > > > > > > to have in the initial implementation. > > > > > > > > > > > > 3. Config - +1. I'll remove it from the KIP. We can discuss this > in > > > > > > parallel. > > > > > > > > > > > > 4. Purgatory vs Delay queue - I feel that it is simpler to reuse > the > > > > > > existing purgatories for both delayed produce and fetch requests. > > > IIUC, > > > > > all > > > > > > we need for quotas is a minWait parameter for DelayedOperation > (or > > > > > > something equivalent) since there is already a max wait. The > > > completion > > > > > > criteria can check if minWait time has elapsed before declaring > the > > > > > > operation complete. For this to impact performance, a significant > > > > number > > > > > of > > > > > > clients may need to exceed their quota at the same time and even > then > > > > I'm > > > > > > not very clear on the scope of the impact. Two layers of delays > might > > > > add > > > > > > complexity to the implementation which I'm hoping to avoid. > > > > > > > > > > > > Aditya > > > > > > > > > > > > ________________________________________ > > > > > > From: Joel Koshy [jjkosh...@gmail.com] > > > > > > Sent: Friday, April 03, 2015 12:48 PM > > > > > > To: dev@kafka.apache.org > > > > > > Subject: Re: [KIP-DISCUSSION] KIP-13 Quotas > > > > > > > > > > > > Aditya, thanks for the updated KIP and Jay/Jun thanks for the > > > > > > comments. Couple of comments in-line: > > > > > > > > > > > > > 2. I would advocate for adding the return flag when we next > bump > > > the > > > > > > > request format version just to avoid proliferation. I agree > this > > > is a > > > > > > good > > > > > > > thing to know about, but at the moment I don't think we have a > very > > > > > well > > > > > > > flushed out idea of how the client would actually make use of > this > > > > > info. > > > > > > I > > > > > > > > > > > > I'm somewhat inclined to having something appropriate off the bat > - > > > > > > mainly because (i) clients really should know that they have been > > > > > > throttled (ii) a smart producer/consumer implementation would > want to > > > > > > know how much to back off. So perhaps this and config-management > > > > > > should be moved to a separate discussion, but it would be good to > > > have > > > > > > this discussion going and incorporated into the first quota > > > > > > implementation. > > > > > > > > > > > > > 3. Config--I think we need to generalize the topic stuff so we > can > > > > > > override > > > > > > > at multiple levels. We have topic and client, but I suspect > "user" > > > > and > > > > > > > "broker" will also be important. I recommend we take config > stuff > > > out > > > > > of > > > > > > > this KIP since we really need to fully think through a proposal > > > that > > > > > will > > > > > > > cover all these types of overrides. > > > > > > > > > > > > +1 - it is definitely orthogonal to the core quota implementation > > > > > > (although necessary for its operability). Having a config-related > > > > > > discussion in this KIP would only draw out the discussion and > vote > > > > > > even if the core quota design looks good to everyone. > > > > > > > > > > > > So basically I think we can remove the portions on dynamic config > as > > > > > > well as the response format but I really think we should close on > > > > > > those while the implementation is in progress and before quotas > is > > > > > > officially released. > > > > > > > > > > > > > 4. Instead of using purgatories to implement the delay would it > > > make > > > > > more > > > > > > > sense to just use a delay queue? I think all the additional > stuff > > > in > > > > > the > > > > > > > purgatory other than the delay queue doesn't make sense as the > > > quota > > > > > is a > > > > > > > hard N ms penalty with no chance of early eviction. If there is > no > > > > perf > > > > > > > penalty for the full purgatory that may be fine (even good) to > > > reuse, > > > > > > but I > > > > > > > haven't looked into that. > > > > > > > > > > > > A simple delay queue sounds good - I think Aditya was also trying > to > > > > > > avoid adding a new quota purgatory. i.e., it may be possible to > use > > > > > > the existing purgatory instances to enforce quotas. That may be > > > > > > simpler, but would be incur a slight perf penalty if too many > clients > > > > > > are being throttled. > > > > > > > > > > > > Thanks, > > > > > > > > > > > > Joel > > > > > > > > > > > > > > > > > > > > -Jay > > > > > > > > > > > > > > On Fri, Apr 3, 2015 at 10:45 AM, Aditya Auradkar < > > > > > > > aaurad...@linkedin.com.invalid> wrote: > > > > > > > > > > > > > >> Update, I added a proposal on doing dynamic client based > > > > configuration > > > > > > >> that can be used for quotas. > > > > > > >> https://cwiki.apache.org/confluence/display/KAFKA/KIP-13 > +-+Quotas > > > > > > >> > > > > > > >> Please take a look and let me know if there are any concerns. > > > > > > >> > > > > > > >> Thanks, > > > > > > >> Aditya > > > > > > >> ________________________________________ > > > > > > >> From: Aditya Auradkar > > > > > > >> Sent: Friday, April 03, 2015 10:10 AM > > > > > > >> To: dev@kafka.apache.org > > > > > > >> Subject: RE: [KIP-DISCUSSION] KIP-13 Quotas > > > > > > >> > > > > > > >> Thanks Jun. > > > > > > >> > > > > > > >> Some thoughts: > > > > > > >> > > > > > > >> 10) I think it is better we throttle regardless of the > > > produce/fetch > > > > > > >> version. This is a nice feature where clients can tell if they > are > > > > > being > > > > > > >> throttled or not. If we only throttle newer clients, then we > have > > > > > > >> inconsistent behavior across clients in a multi-tenant > cluster. > > > > Having > > > > > > >> quota metrics on the client side is also a nice incentive to > > > upgrade > > > > > > client > > > > > > >> versions. > > > > > > >> > > > > > > >> 11) I think we can call metric.record(fetchSize) before adding > the > > > > > > >> delayedFetch request into the purgatory. This will give us the > > > > > estimated > > > > > > >> delay of the request up-front. The timeout on the DelayedFetch > is > > > > the > > > > > > >> Max(maxWait, quotaDelay). The DelayedFetch completion criteria > can > > > > > > change a > > > > > > >> little to accomodate quotas. > > > > > > >> > > > > > > >> - I agree the quota code should return the estimated delay > time in > > > > > > >> QuotaViolationException. > > > > > > >> > > > > > > >> Thanks, > > > > > > >> Aditya > > > > > > >> > > > > > > >> ________________________________________ > > > > > > >> From: Jun Rao [j...@confluent.io] > > > > > > >> Sent: Friday, April 03, 2015 9:16 AM > > > > > > >> To: dev@kafka.apache.org > > > > > > >> Subject: Re: [KIP-DISCUSSION] KIP-13 Quotas > > > > > > >> > > > > > > >> Thanks for the update. > > > > > > >> > > > > > > >> 10. About whether to return a new field in the response to > > > indicate > > > > > > >> throttling. Earlier, the plan was to not change the response > > > format > > > > > and > > > > > > >> just have a metric on the broker to indicate whether a > clientId is > > > > > > >> throttled or not. The issue is that we don't know whether a > > > > particular > > > > > > >> clientId instance is throttled or not (since there could be > > > multiple > > > > > > >> clients with the same clientId). Your proposal of adding an > > > > > isThrottled > > > > > > >> field in the response addresses and seems better. Then, do we > just > > > > > > throttle > > > > > > >> the new version of produce/fetch request or both the old and > the > > > new > > > > > > >> versions? Also, we probably still need a separate metric on > the > > > > broker > > > > > > side > > > > > > >> to indicate whether a clientId is throttled or not. > > > > > > >> > > > > > > >> 11. Just to clarify. For fetch requests, when will > > > > > > metric.record(fetchSize) > > > > > > >> be called? Is it when we are ready to send the fetch response > > > (after > > > > > > >> minBytes and maxWait are satisfied)? > > > > > > >> > > > > > > >> As an implementation detail, it may be useful for the quota > code > > > to > > > > > > return > > > > > > >> an estimated delay time (to bring the measurement within the > > > limit) > > > > in > > > > > > >> QuotaViolationException. > > > > > > >> > > > > > > >> Thanks, > > > > > > >> > > > > > > >> Jun > > > > > > >> > > > > > > >> On Wed, Apr 1, 2015 at 3:27 PM, Aditya Auradkar < > > > > > > >> aaurad...@linkedin.com.invalid> wrote: > > > > > > >> > > > > > > >> > Hey everyone, > > > > > > >> > > > > > > > >> > I've made changes to the KIP to capture our discussions over > the > > > > > last > > > > > > >> > couple of weeks. > > > > > > >> > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-13+-+Quotas > > > > > > >> > > > > > > > >> > I'll start a voting thread after people have had a chance to > > > > > > >> read/comment. > > > > > > >> > > > > > > > >> > Thanks, > > > > > > >> > Aditya > > > > > > >> > > > > > > > >> > ________________________________________ > > > > > > >> > From: Steven Wu [stevenz...@gmail.com] > > > > > > >> > Sent: Friday, March 20, 2015 9:14 AM > > > > > > >> > To: dev@kafka.apache.org > > > > > > >> > Subject: Re: [KIP-DISCUSSION] KIP-13 Quotas > > > > > > >> > > > > > > > >> > +1 on Jun's suggestion of maintaining one set/style of > metrics > > > at > > > > > > broker. > > > > > > >> > In Netflix, we have to convert the yammer metrics to servo > > > metrics > > > > > at > > > > > > >> > broker. it will be painful to know some metrics are in a > > > different > > > > > > style > > > > > > >> > and get to be handled differently. > > > > > > >> > > > > > > > >> > On Fri, Mar 20, 2015 at 8:17 AM, Jun Rao <j...@confluent.io> > > > > wrote: > > > > > > >> > > > > > > > >> > > Not so sure. People who use quota will definitely want to > > > > monitor > > > > > > the > > > > > > >> new > > > > > > >> > > metrics at the client id level. Then they will need to > deal > > > with > > > > > > those > > > > > > >> > > metrics differently from the rest of the metrics. It would > be > > > > > > better if > > > > > > >> > we > > > > > > >> > > can hide this complexity from the users. > > > > > > >> > > > > > > > > >> > > Thanks, > > > > > > >> > > > > > > > > >> > > Jun > > > > > > >> > > > > > > > > >> > > On Thu, Mar 19, 2015 at 10:45 PM, Joel Koshy < > > > > jjkosh...@gmail.com > > > > > > > > > > > > >> > wrote: > > > > > > >> > > > > > > > > >> > > > Actually thinking again - since these will be a few new > > > > metrics > > > > > at > > > > > > >> the > > > > > > >> > > > client id level (bytes in and bytes out to start with) > maybe > > > > it > > > > > is > > > > > > >> fine > > > > > > >> > > to > > > > > > >> > > > have the two type of metrics coexist and we can migrate > the > > > > > > existing > > > > > > >> > > > metrics in parallel. > > > > > > >> > > > > > > > > > >> > > > On Thursday, March 19, 2015, Joel Koshy < > > > jjkosh...@gmail.com> > > > > > > wrote: > > > > > > >> > > > > > > > > > >> > > > > That is a valid concern but in that case I think it > would > > > be > > > > > > better > > > > > > >> > to > > > > > > >> > > > > just migrate completely to the new metrics package > first. > > > > > > >> > > > > > > > > > > >> > > > > On Thursday, March 19, 2015, Jun Rao < > j...@confluent.io > > > > > > >> > > > > <javascript:_e(%7B%7D,'cvml','j...@confluent.io');>> > > > wrote: > > > > > > >> > > > > > > > > > > >> > > > >> Hmm, I was thinking a bit differently on the metrics > > > > stuff. I > > > > > > >> think > > > > > > >> > it > > > > > > >> > > > >> would be confusing to have some metrics defined in > the > > > new > > > > > > metrics > > > > > > >> > > > package > > > > > > >> > > > >> while some others defined in Coda Hale. Those metrics > > > will > > > > > look > > > > > > >> > > > different > > > > > > >> > > > >> (e.g., rates in Coda Hale will have special > attributes > > > such > > > > > as > > > > > > >> > > > >> 1-min-average). People may need different ways to > export > > > > the > > > > > > >> metrics > > > > > > >> > > to > > > > > > >> > > > >> external systems such as Graphite. So, instead of > using > > > the > > > > > new > > > > > > >> > > metrics > > > > > > >> > > > >> package on the broker, I was thinking that we can > just > > > > > > implement a > > > > > > >> > > > >> QuotaMetrics that wraps the Coda Hale metrics. The > > > > > > implementation > > > > > > >> > can > > > > > > >> > > be > > > > > > >> > > > >> the same as what's in the new metrics package. > > > > > > >> > > > >> > > > > > > >> > > > >> Thanks, > > > > > > >> > > > >> > > > > > > >> > > > >> Jun > > > > > > >> > > > >> > > > > > > >> > > > >> On Thu, Mar 19, 2015 at 8:09 PM, Jay Kreps < > > > > > > jay.kr...@gmail.com> > > > > > > >> > > wrote: > > > > > > >> > > > >> > > > > > > >> > > > >> > Yeah I was saying was that we are blocked on > picking an > > > > > > approach > > > > > > >> > for > > > > > > >> > > > >> > metrics but not necessarily the full conversion. > > > Clearly > > > > if > > > > > > we > > > > > > >> > pick > > > > > > >> > > > the > > > > > > >> > > > >> new > > > > > > >> > > > >> > metrics package we would need to implement the two > > > > metrics > > > > > we > > > > > > >> want > > > > > > >> > > to > > > > > > >> > > > >> quota > > > > > > >> > > > >> > on. But the conversion of the remaining metrics can > be > > > > done > > > > > > >> > > > >> asynchronously. > > > > > > >> > > > >> > > > > > > > >> > > > >> > -Jay > > > > > > >> > > > >> > > > > > > > >> > > > >> > On Thu, Mar 19, 2015 at 5:56 PM, Joel Koshy < > > > > > > >> jjkosh...@gmail.com> > > > > > > >> > > > >> wrote: > > > > > > >> > > > >> > > > > > > > >> > > > >> > > > in KAFKA-1930). I agree that this KIP doesn't > need > > > to > > > > > > block > > > > > > >> on > > > > > > >> > > the > > > > > > >> > > > >> > > > migration of the metrics package. > > > > > > >> > > > >> > > > > > > > > >> > > > >> > > Can you clarify the above? i.e., if we are going > to > > > > quota > > > > > > on > > > > > > >> > > > something > > > > > > >> > > > >> > > then we would want to have migrated that metric > over > > > > > > right? Or > > > > > > >> > do > > > > > > >> > > > you > > > > > > >> > > > >> > > mean we don't need to complete the migration of > all > > > > > > metrics to > > > > > > >> > the > > > > > > >> > > > >> > > metrics package right? > > > > > > >> > > > >> > > > > > > > > >> > > > >> > > I think most of us now feel that the delay + no > error > > > > is > > > > > a > > > > > > >> good > > > > > > >> > > > >> > > approach, but it would be good to make sure > everyone > > > is > > > > > on > > > > > > the > > > > > > >> > > same > > > > > > >> > > > >> > > page. > > > > > > >> > > > >> > > > > > > > > >> > > > >> > > As Aditya requested a couple of days ago I think > we > > > > > should > > > > > > go > > > > > > >> > over > > > > > > >> > > > >> > > this at the next KIP hangout. > > > > > > >> > > > >> > > > > > > > > >> > > > >> > > Joel > > > > > > >> > > > >> > > > > > > > > >> > > > >> > > On Thu, Mar 19, 2015 at 09:24:09AM -0700, Jun Rao > > > > wrote: > > > > > > >> > > > >> > > > 1. Delay + no error seems reasonable to me. > > > However, > > > > I > > > > > do > > > > > > >> feel > > > > > > >> > > > that > > > > > > >> > > > >> we > > > > > > >> > > > >> > > need > > > > > > >> > > > >> > > > to give the client an indicator that it's being > > > > > > throttled, > > > > > > >> > > instead > > > > > > >> > > > >> of > > > > > > >> > > > >> > > doing > > > > > > >> > > > >> > > > this silently. For that, we probably need to > evolve > > > > the > > > > > > >> > > > >> produce/fetch > > > > > > >> > > > >> > > > protocol to include an extra status field in > the > > > > > > response. > > > > > > >> We > > > > > > >> > > > >> probably > > > > > > >> > > > >> > > need > > > > > > >> > > > >> > > > to think more about whether we just want to > return > > > a > > > > > > simple > > > > > > >> > > status > > > > > > >> > > > >> code > > > > > > >> > > > >> > > > (e.g., 1 = throttled) or a value that indicates > how > > > > > much > > > > > > is > > > > > > >> > > being > > > > > > >> > > > >> > > throttled. > > > > > > >> > > > >> > > > > > > > > > >> > > > >> > > > 2. We probably need to improve the histogram > > > support > > > > in > > > > > > the > > > > > > >> > new > > > > > > >> > > > >> metrics > > > > > > >> > > > >> > > > package before we can use it more widely on the > > > > server > > > > > > side > > > > > > >> > > (left > > > > > > >> > > > a > > > > > > >> > > > >> > > comment > > > > > > >> > > > >> > > > in KAFKA-1930). I agree that this KIP doesn't > need > > > to > > > > > > block > > > > > > >> on > > > > > > >> > > the > > > > > > >> > > > >> > > > migration of the metrics package. > > > > > > >> > > > >> > > > > > > > > > >> > > > >> > > > Thanks, > > > > > > >> > > > >> > > > > > > > > > >> > > > >> > > > Jun > > > > > > >> > > > >> > > > > > > > > > >> > > > >> > > > On Wed, Mar 18, 2015 at 4:02 PM, Aditya > Auradkar < > > > > > > >> > > > >> > > > aaurad...@linkedin.com.invalid> wrote: > > > > > > >> > > > >> > > > > > > > > > >> > > > >> > > > > Hey everyone, > > > > > > >> > > > >> > > > > > > > > > > >> > > > >> > > > > Thanks for the great discussion. There are > > > > currently > > > > > a > > > > > > few > > > > > > > >> > > > points > > > > > > >> > > > >> on > > > > > > >> > > > >> > > this > > > > > > >> > > > >> > > > > KIP that need addressing and I want to make > sure > > > we > > > > > > are on > > > > > > >> > the > > > > > > >> > > > >> same > > > > > > >> > > > >> > > page > > > > > > >> > > > >> > > > > about those. > > > > > > >> > > > >> > > > > > > > > > > >> > > > >> > > > > 1. Append and delay response vs delay and > return > > > > > error > > > > > > >> > > > >> > > > > - I think we've discussed the pros and cons > of > > > each > > > > > > >> approach > > > > > > >> > > but > > > > > > >> > > > >> > > haven't > > > > > > >> > > > >> > > > > chosen an approach yet. Where does everyone > stand > > > > on > > > > > > this > > > > > > >> > > issue? > > > > > > >> > > > >> > > > > > > > > > > >> > > > >> > > > > 2. Metrics Migration and usage in quotas > > > > > > >> > > > >> > > > > - The metrics library in clients has a notion > of > > > > > quotas > > > > > > >> that > > > > > > >> > > we > > > > > > >> > > > >> > should > > > > > > >> > > > >> > > > > reuse. For that to happen, we need to migrate > the > > > > > > server > > > > > > >> to > > > > > > >> > > the > > > > > > >> > > > >> new > > > > > > >> > > > >> > > metrics > > > > > > >> > > > >> > > > > package. > > > > > > >> > > > >> > > > > - Need more clarification on how to compute > > > > > throttling > > > > > > >> time > > > > > > >> > > and > > > > > > >> > > > >> > > windowing > > > > > > >> > > > >> > > > > for quotas. > > > > > > >> > > > >> > > > > > > > > > > >> > > > >> > > > > I'm going to start a new KIP to discuss > metrics > > > > > > migration > > > > > > >> > > > >> separately. > > > > > > >> > > > >> > > That > > > > > > >> > > > >> > > > > will also contain a section on quotas. > > > > > > >> > > > >> > > > > > > > > > > >> > > > >> > > > > 3. Dynamic Configuration management - Being > > > > discussed > > > > > > in > > > > > > >> > > KIP-5. > > > > > > >> > > > >> > > Basically > > > > > > >> > > > >> > > > > we need something that will model default > quotas > > > > and > > > > > > allow > > > > > > >> > > > >> per-client > > > > > > >> > > > >> > > > > overrides. > > > > > > >> > > > >> > > > > > > > > > > >> > > > >> > > > > Is there something else that I'm missing? > > > > > > >> > > > >> > > > > > > > > > > >> > > > >> > > > > Thanks, > > > > > > >> > > > >> > > > > Aditya > > > > > > >> > > > >> > > > > ________________________________________ > > > > > > >> > > > >> > > > > From: Jay Kreps [jay.kr...@gmail.com] > > > > > > >> > > > >> > > > > Sent: Wednesday, March 18, 2015 2:10 PM > > > > > > >> > > > >> > > > > To: dev@kafka.apache.org > > > > > > >> > > > >> > > > > Subject: Re: [KIP-DISCUSSION] KIP-13 Quotas > > > > > > >> > > > >> > > > > > > > > > > >> > > > >> > > > > Hey Steven, > > > > > > >> > > > >> > > > > > > > > > > >> > > > >> > > > > The current proposal is actually to enforce > > > quotas > > > > at > > > > > > the > > > > > > >> > > > >> > > > > client/application level, NOT the topic > level. So > > > > if > > > > > > you > > > > > > >> > have > > > > > > >> > > a > > > > > > >> > > > >> > service > > > > > > >> > > > >> > > > > with a few dozen instances the quota is > against > > > all > > > > > of > > > > > > >> those > > > > > > >> > > > >> > instances > > > > > > >> > > > >> > > > > added up across all their topics. So actually > the > > > > > > effect > > > > > > >> > would > > > > > > >> > > > be > > > > > > >> > > > >> the > > > > > > >> > > > >> > > same > > > > > > >> > > > >> > > > > either way but throttling gives the producer > the > > > > > > choice of > > > > > > >> > > > either > > > > > > >> > > > >> > > blocking > > > > > > >> > > > >> > > > > or dropping. > > > > > > >> > > > >> > > > > > > > > > > >> > > > >> > > > > -Jay > > > > > > >> > > > >> > > > > > > > > > > >> > > > >> > > > > On Tue, Mar 17, 2015 at 10:08 AM, Steven Wu < > > > > > > >> > > > stevenz...@gmail.com > > > > > > >> > > > >> > > > > > > > >> > > > >> > > wrote: > > > > > > >> > > > >> > > > > > > > > > > >> > > > >> > > > > > Jay, > > > > > > >> > > > >> > > > > > > > > > > > >> > > > >> > > > > > let's say an app produces to 10 different > > > topics. > > > > > > one of > > > > > > >> > the > > > > > > >> > > > >> topic > > > > > > >> > > > >> > is > > > > > > >> > > > >> > > > > sent > > > > > > >> > > > >> > > > > > from a library. due to whatever > condition/bug, > > > > this > > > > > > lib > > > > > > >> > > starts > > > > > > >> > > > >> to > > > > > > >> > > > >> > > send > > > > > > >> > > > >> > > > > > messages over the quota. if we go with the > > > > delayed > > > > > > >> > response > > > > > > >> > > > >> > > approach, it > > > > > > >> > > > >> > > > > > will cause the whole shared > RecordAccumulator > > > > > buffer > > > > > > to > > > > > > >> be > > > > > > >> > > > >> filled > > > > > > >> > > > >> > up. > > > > > > >> > > > >> > > > > that > > > > > > >> > > > >> > > > > > will penalize other 9 topics who are within > the > > > > > > quota. > > > > > > >> > that > > > > > > >> > > is > > > > > > >> > > > >> the > > > > > > >> > > > >> > > > > > unfairness point that Ewen and I were > trying to > > > > > make. > > > > > > >> > > > >> > > > > > > > > > > > >> > > > >> > > > > > if broker just drop the msg and return an > > > > > > error/status > > > > > > >> > code > > > > > > >> > > > >> > > indicates the > > > > > > >> > > > >> > > > > > drop and why. then producer can just move > on > > > and > > > > > > accept > > > > > > >> > the > > > > > > >> > > > >> drop. > > > > > > >> > > > >> > > shared > > > > > > >> > > > >> > > > > > buffer won't be saturated and other 9 > topics > > > > won't > > > > > be > > > > > > >> > > > penalized. > > > > > > >> > > > >> > > > > > > > > > > > >> > > > >> > > > > > Thanks, > > > > > > >> > > > >> > > > > > Steven > > > > > > >> > > > >> > > > > > > > > > > > >> > > > >> > > > > > > > > > > > >> > > > >> > > > > > > > > > > > >> > > > >> > > > > > On Tue, Mar 17, 2015 at 9:44 AM, Jay Kreps > < > > > > > > >> > > > jay.kr...@gmail.com > > > > > > >> > > > >> > > > > > > > >> > > > >> > > wrote: > > > > > > >> > > > >> > > > > > > > > > > > >> > > > >> > > > > > > Hey Steven, > > > > > > >> > > > >> > > > > > > > > > > > > >> > > > >> > > > > > > It is true that hitting the quota will > cause > > > > > > >> > back-pressure > > > > > > >> > > > on > > > > > > >> > > > >> the > > > > > > >> > > > >> > > > > > producer. > > > > > > >> > > > >> > > > > > > But the solution is simple, a producer > that > > > > wants > > > > > > to > > > > > > >> > avoid > > > > > > >> > > > >> this > > > > > > >> > > > >> > > should > > > > > > >> > > > >> > > > > > stay > > > > > > >> > > > >> > > > > > > under its quota. In other words this is a > > > > > contract > > > > > > >> > between > > > > > > >> > > > the > > > > > > >> > > > >> > > cluster > > > > > > >> > > > >> > > > > > and > > > > > > >> > > > >> > > > > > > the client, with each side having > something > > > to > > > > > > uphold. > > > > > > >> > > Quite > > > > > > >> > > > >> > > possibly > > > > > > >> > > > >> > > > > the > > > > > > >> > > > >> > > > > > > same thing will happen in the absence of > a > > > > > quota, a > > > > > > >> > client > > > > > > >> > > > >> that > > > > > > >> > > > >> > > > > produces > > > > > > >> > > > >> > > > > > an > > > > > > >> > > > >> > > > > > > unexpected amount of load will hit the > limits > > > > of > > > > > > the > > > > > > >> > > server > > > > > > >> > > > >> and > > > > > > >> > > > >> > > > > > experience > > > > > > >> > > > >> > > > > > > backpressure. Quotas just allow you to > set > > > that > > > > > > same > > > > > > >> > limit > > > > > > >> > > > at > > > > > > >> > > > >> > > something > > > > > > >> > > > >> > > > > > > lower than 100% of all resources on the > > > server, > > > > > > which > > > > > > >> is > > > > > > >> > > > >> useful > > > > > > >> > > > >> > > for a > > > > > > >> > > > >> > > > > > > shared cluster. > > > > > > >> > > > >> > > > > > > > > > > > > >> > > > >> > > > > > > -Jay > > > > > > >> > > > >> > > > > > > > > > > > > >> > > > >> > > > > > > On Mon, Mar 16, 2015 at 11:34 PM, Steven > Wu < > > > > > > >> > > > >> > stevenz...@gmail.com> > > > > > > >> > > > >> > > > > > wrote: > > > > > > >> > > > >> > > > > > > > > > > > > >> > > > >> > > > > > > > wait. we create one kafka producer for > each > > > > > > cluster. > > > > > > >> > > each > > > > > > >> > > > >> > > cluster can > > > > > > >> > > > >> > > > > > > have > > > > > > >> > > > >> > > > > > > > many topics. if producer buffer got > filled > > > up > > > > > > due to > > > > > > >> > > > delayed > > > > > > >> > > > >> > > response > > > > > > >> > > > >> > > > > > for > > > > > > >> > > > >> > > > > > > > one throttled topic, won't that > penalize > > > > other > > > > > > >> topics > > > > > > >> > > > >> unfairly? > > > > > > >> > > > >> > > it > > > > > > >> > > > >> > > > > > seems > > > > > > >> > > > >> > > > > > > to > > > > > > >> > > > >> > > > > > > > me that broker should just return error > > > > without > > > > > > >> delay. > > > > > > >> > > > >> > > > > > > > > > > > > > >> > > > >> > > > > > > > sorry that I am chatting to myself :) > > > > > > >> > > > >> > > > > > > > > > > > > > >> > > > >> > > > > > > > On Mon, Mar 16, 2015 at 11:29 PM, > Steven > > > Wu < > > > > > > >> > > > >> > > stevenz...@gmail.com> > > > > > > >> > > > >> > > > > > > wrote: > > > > > > >> > > > >> > > > > > > > > > > > > > >> > > > >> > > > > > > > > I think I can answer my own question. > > > > delayed > > > > > > >> > response > > > > > > >> > > > >> will > > > > > > >> > > > >> > > cause > > > > > > >> > > > >> > > > > the > > > > > > >> > > > >> > > > > > > > > producer buffer to be full, which > then > > > > result > > > > > > in > > > > > > >> > > either > > > > > > >> > > > >> > thread > > > > > > >> > > > >> > > > > > blocking > > > > > > >> > > > >> > > > > > > > or > > > > > > >> > > > >> > > > > > > > > message drop. > > > > > > >> > > > >> > > > > > > > > > > > > > > >> > > > >> > > > > > > > > On Mon, Mar 16, 2015 at 11:24 PM, > Steven > > > > Wu < > > > > > > >> > > > >> > > stevenz...@gmail.com> > > > > > > >> > > > >> > > > > > > > wrote: > > > > > > >> > > > >> > > > > > > > > > > > > > > >> > > > >> > > > > > > > >> please correct me if I am missing > sth > > > > here. > > > > > I > > > > > > am > > > > > > >> > not > > > > > > >> > > > >> > > understanding > > > > > > >> > > > >> > > > > > how > > > > > > >> > > > >> > > > > > > > >> would throttle work without > > > > > > cooperation/back-off > > > > > > >> > from > > > > > > >> > > > >> > > producer. > > > > > > >> > > > >> > > > > new > > > > > > >> > > > >> > > > > > > Java > > > > > > >> > > > >> > > > > > > > >> producer supports non-blocking API. > why > > > > > would > > > > > > >> > delayed > > > > > > >> > > > >> > > response be > > > > > > >> > > > >> > > > > > able > > > > > > >> > > > >> > > > > > > > to > > > > > > >> > > > >> > > > > > > > >> slow down producer? producer will > > > continue > > > > > to > > > > > > >> fire > > > > > > >> > > > async > > > > > > >> > > > >> > > sends. > > > > > > >> > > > >> > > > > > > > >> > > > > > > >> > > > >> > > > > > > > >> On Mon, Mar 16, 2015 at 10:58 PM, > > > Guozhang > > > > > > Wang < > > > > > > >> > > > >> > > > > wangg...@gmail.com > > > > > > >> > > > >> > > > > > > > > > > > > >> > > > >> > > > > > > > >> wrote: > > > > > > >> > > > >> > > > > > > > >> > > > > > > >> > > > >> > > > > > > > >>> I think we are really discussing > two > > > > > separate > > > > > > >> > issues > > > > > > >> > > > >> here: > > > > > > >> > > > >> > > > > > > > >>> > > > > > > >> > > > >> > > > > > > > >>> 1. Whether we should a) > > > > > > >> > > > >> > > > > append-then-block-then-returnOKButThrottled > > > > > > >> > > > >> > > > > > > or > > > > > > >> > > > >> > > > > > > > b) > > > > > > >> > > > >> > > > > > > > >>> block-then-returnFailDuetoThrottled > for > > > > > quota > > > > > > >> > > actions > > > > > > >> > > > on > > > > > > >> > > > >> > > produce > > > > > > >> > > > >> > > > > > > > >>> requests. > > > > > > >> > > > >> > > > > > > > >>> > > > > > > >> > > > >> > > > > > > > >>> Both these approaches assume some > kind > > > of > > > > > > >> > > > >> well-behaveness > > > > > > >> > > > >> > of > > > > > > >> > > > >> > > the > > > > > > >> > > > >> > > > > > > > clients: > > > > > > >> > > > >> > > > > > > > >>> option a) assumes the client sets > an > > > > proper > > > > > > >> > timeout > > > > > > >> > > > >> value > > > > > > >> > > > >> > > while > > > > > > >> > > > >> > > > > can > > > > > > >> > > > >> > > > > > > > just > > > > > > >> > > > >> > > > > > > > >>> ignore "OKButThrottled" response, > while > > > > > > option > > > > > > >> b) > > > > > > >> > > > >> assumes > > > > > > >> > > > >> > the > > > > > > >> > > > >> > > > > > client > > > > > > >> > > > >> > > > > > > > >>> handles the "FailDuetoThrottled" > > > > > > appropriately. > > > > > > >> > For > > > > > > >> > > > any > > > > > > >> > > > >> > > malicious > > > > > > >> > > > >> > > > > > > > clients > > > > > > >> > > > >> > > > > > > > >>> that, for example, just keep > retrying > > > > > either > > > > > > >> > > > >> intentionally > > > > > > >> > > > >> > or > > > > > > >> > > > >> > > > > not, > > > > > > >> > > > >> > > > > > > > >>> neither > > > > > > >> > > > >> > > > > > > > >>> of these approaches are actually > > > > effective. > > > > > > >> > > > >> > > > > > > > >>> > > > > > > >> > > > >> > > > > > > > >>> 2. For "OKButThrottled" and > > > > > > "FailDuetoThrottled" > > > > > > >> > > > >> responses, > > > > > > >> > > > >> > > shall > > > > > > >> > > > >> > > > > > we > > > > > > >> > > > >> > > > > > > > >>> encode > > > > > > >> > > > >> > > > > > > > >>> them as error codes or augment the > > > > protocol > > > > > > to > > > > > > >> > use a > > > > > > >> > > > >> > separate > > > > > > >> > > > >> > > > > field > > > > > > >> > > > >> > > > > > > > >>> indicating "status codes". > > > > > > >> > > > >> > > > > > > > >>> > > > > > > >> > > > >> > > > > > > > >>> Today we have already incorporated > some > > > > > > status > > > > > > >> > code > > > > > > >> > > as > > > > > > >> > > > >> > error > > > > > > >> > > > >> > > > > codes > > > > > > >> > > > >> > > > > > in > > > > > > >> > > > >> > > > > > > > the > > > > > > >> > > > >> > > > > > > > >>> responses, e.g. ReplicaNotAvailable > in > > > > > > >> > > > MetadataResponse, > > > > > > >> > > > >> > the > > > > > > >> > > > >> > > pros > > > > > > >> > > > >> > > > > > of > > > > > > >> > > > >> > > > > > > > this > > > > > > >> > > > >> > > > > > > > >>> is of course using a single field > for > > > > > > response > > > > > > >> > > status > > > > > > >> > > > >> like > > > > > > >> > > > >> > > the > > > > > > >> > > > >> > > > > HTTP > > > > > > >> > > > >> > > > > > > > >>> status > > > > > > >> > > > >> > > > > > > > >>> codes, while the cons is that it > > > requires > > > > > > >> clients > > > > > > >> > to > > > > > > >> > > > >> handle > > > > > > >> > > > >> > > the > > > > > > >> > > > >> > > > > > error > > > > > > >> > > > >> > > > > > > > >>> codes > > > > > > >> > > > >> > > > > > > > >>> carefully. > > > > > > >> > > > >> > > > > > > > >>> > > > > > > >> > > > >> > > > > > > > >>> I think maybe we can actually > extend > > > the > > > > > > >> > single-code > > > > > > >> > > > >> > > approach to > > > > > > >> > > > >> > > > > > > > overcome > > > > > > >> > > > >> > > > > > > > >>> its drawbacks, that is, wrap the > error > > > > > codes > > > > > > >> > > semantics > > > > > > >> > > > >> to > > > > > > >> > > > >> > the > > > > > > >> > > > >> > > > > users > > > > > > >> > > > >> > > > > > > so > > > > > > >> > > > >> > > > > > > > >>> that > > > > > > >> > > > >> > > > > > > > >>> users do not need to handle the > codes > > > > > > >> one-by-one. > > > > > > >> > > More > > > > > > >> > > > >> > > > > concretely, > > > > > > >> > > > >> > > > > > > > >>> following Jay's example the client > > > could > > > > > > write > > > > > > >> > sth. > > > > > > >> > > > like > > > > > > >> > > > >> > > this: > > > > > > >> > > > >> > > > > > > > >>> > > > > > > >> > > > >> > > > > > > > >>> > > > > > > >> > > > >> > > > > > > > >>> ----------------- > > > > > > >> > > > >> > > > > > > > >>> > > > > > > >> > > > >> > > > > > > > >>> if(error.isOK()) > > > > > > >> > > > >> > > > > > > > >>> // status code is good or the > code > > > > can > > > > > > be > > > > > > >> > > simply > > > > > > >> > > > >> > > ignored for > > > > > > >> > > > >> > > > > > > this > > > > > > >> > > > >> > > > > > > > >>> request type, process the request > > > > > > >> > > > >> > > > > > > > >>> else if(error.needsRetry()) > > > > > > >> > > > >> > > > > > > > >>> // throttled, transient error, > > > etc: > > > > > > retry > > > > > > >> > > > >> > > > > > > > >>> else if(error.isFatal()) > > > > > > >> > > > >> > > > > > > > >>> // non-retriable errors, etc: > > > > notify / > > > > > > >> > > terminate > > > > > > >> > > > / > > > > > > >> > > > >> > other > > > > > > >> > > > >> > > > > > > handling > > > > > > >> > > > >> > > > > > > > >>> > > > > > > >> > > > >> > > > > > > > >>> ----------------- > > > > > > >> > > > >> > > > > > > > >>> > > > > > > >> > > > >> > > > > > > > >>> Only when the clients really want > to > > > > > handle, > > > > > > for > > > > > > >> > > > example > > > > > > >> > > > >> > > > > > > > >>> FailDuetoThrottled > > > > > > >> > > > >> > > > > > > > >>> status code specifically, it needs > to: > > > > > > >> > > > >> > > > > > > > >>> > > > > > > >> > > > >> > > > > > > > >>> if(error.isOK()) > > > > > > >> > > > >> > > > > > > > >>> // status code is good or the > code > > > > can > > > > > > be > > > > > > >> > > simply > > > > > > >> > > > >> > > ignored for > > > > > > >> > > > >> > > > > > > this > > > > > > >> > > > >> > > > > > > > >>> request type, process the request > > > > > > >> > > > >> > > > > > > > >>> else if(error == > FailDuetoThrottled ) > > > > > > >> > > > >> > > > > > > > >>> // throttled: log it > > > > > > >> > > > >> > > > > > > > >>> else if(error.needsRetry()) > > > > > > >> > > > >> > > > > > > > >>> // transient error, etc: retry > > > > > > >> > > > >> > > > > > > > >>> else if(error.isFatal()) > > > > > > >> > > > >> > > > > > > > >>> // non-retriable errors, etc: > > > > notify / > > > > > > >> > > terminate > > > > > > >> > > > / > > > > > > >> > > > >> > other > > > > > > >> > > > >> > > > > > > handling > > > > > > >> > > > >> > > > > > > > >>> > > > > > > >> > > > >> > > > > > > > >>> ----------------- > > > > > > >> > > > >> > > > > > > > >>> > > > > > > >> > > > >> > > > > > > > >>> And for implementation we can > probably > > > > > group > > > > > > the > > > > > > >> > > codes > > > > > > >> > > > >> > > > > accordingly > > > > > > >> > > > >> > > > > > > like > > > > > > >> > > > >> > > > > > > > >>> HTTP status code such that we can > do: > > > > > > >> > > > >> > > > > > > > >>> > > > > > > >> > > > >> > > > > > > > >>> boolean Error.isOK() { > > > > > > >> > > > >> > > > > > > > >>> return code < 300 && code >= 200; > > > > > > >> > > > >> > > > > > > > >>> } > > > > > > >> > > > >> > > > > > > > >>> > > > > > > >> > > > >> > > > > > > > >>> Guozhang > > > > > > >> > > > >> > > > > > > > >>> > > > > > > >> > > > >> > > > > > > > >>> On Mon, Mar 16, 2015 at 10:24 PM, > Ewen > > > > > > >> > > > Cheslack-Postava > > > > > > >> > > > >> < > > > > > > >> > > > >> > > > > > > > >>> e...@confluent.io> > > > > > > >> > > > >> > > > > > > > >>> wrote: > > > > > > >> > > > >> > > > > > > > >>> > > > > > > >> > > > >> > > > > > > > >>> > Agreed that trying to shoehorn > > > > non-error > > > > > > codes > > > > > > >> > > into > > > > > > >> > > > >> the > > > > > > >> > > > >> > > error > > > > > > >> > > > >> > > > > > field > > > > > > >> > > > >> > > > > > > > is > > > > > > >> > > > >> > > > > > > > >>> a > > > > > > >> > > > >> > > > > > > > >>> > bad idea. It makes it *way* too > easy > > > to > > > > > > write > > > > > > >> > code > > > > > > >> > > > >> that > > > > > > >> > > > >> > > looks > > > > > > >> > > > >> > > > > > (and > > > > > > >> > > > >> > > > > > > > >>> should > > > > > > >> > > > >> > > > > > > > >>> > be) correct but is actually > > > incorrect. > > > > If > > > > > > >> > > > necessary, I > > > > > > >> > > > >> > > think > > > > > > >> > > > >> > > > > it's > > > > > > >> > > > >> > > > > > > > much > > > > > > >> > > > >> > > > > > > > >>> > better to to spend a couple of > extra > > > > > bytes > > > > > > to > > > > > > >> > > encode > > > > > > >> > > > >> that > > > > > > >> > > > >> > > > > > > information > > > > > > >> > > > >> > > > > > > > >>> > separately (a "status" or > "warning" > > > > > > section of > > > > > > >> > the > > > > > > >> > > > >> > > response). > > > > > > >> > > > >> > > > > An > > > > > > >> > > > >> > > > > > > > >>> indication > > > > > > >> > > > >> > > > > > > > >>> > that throttling is occurring is > > > > something > > > > > > I'd > > > > > > >> > > expect > > > > > > >> > > > >> to > > > > > > >> > > > >> > be > > > > > > >> > > > >> > > > > > > indicated > > > > > > >> > > > >> > > > > > > > >>> by a > > > > > > >> > > > >> > > > > > > > >>> > bit flag in the response rather > than > > > as > > > > > an > > > > > > >> error > > > > > > >> > > > code. > > > > > > >> > > > >> > > > > > > > >>> > > > > > > > >> > > > >> > > > > > > > >>> > Gwen - I think an error code > makes > > > > sense > > > > > > when > > > > > > >> > the > > > > > > >> > > > >> request > > > > > > >> > > > >> > > > > > actually > > > > > > >> > > > >> > > > > > > > >>> failed. > > > > > > >> > > > >> > > > > > > > >>> > Option B, which Jun was > advocating, > > > > would > > > > > > have > > > > > > >> > > > >> appended > > > > > > >> > > > >> > the > > > > > > >> > > > >> > > > > > > messages > > > > > > >> > > > >> > > > > > > > >>> > successfully. If the > rate-limiting > > > case > > > > > > you're > > > > > > >> > > > talking > > > > > > >> > > > >> > > about > > > > > > >> > > > >> > > > > had > > > > > > >> > > > >> > > > > > > > >>> > successfully committed the > messages, > > > I > > > > > > would > > > > > > >> say > > > > > > >> > > > >> that's > > > > > > >> > > > >> > > also a > > > > > > >> > > > >> > > > > > bad > > > > > > >> > > > >> > > > > > > > use > > > > > > >> > > > >> > > > > > > > >>> of > > > > > > >> > > > >> > > > > > > > >>> > error codes. > > > > > > >> > > > >> > > > > > > > >>> > > > > > > > >> > > > >> > > > > > > > >>> > > > > > > > >> > > > >> > > > > > > > >>> > On Mon, Mar 16, 2015 at 10:16 PM, > > > Gwen > > > > > > >> Shapira < > > > > > > >> > > > >> > > > > > > > gshap...@cloudera.com> > > > > > > >> > > > >> > > > > > > > >>> > wrote: > > > > > > >> > > > >> > > > > > > > >>> > > > > > > > >> > > > >> > > > > > > > >>> > > We discussed an error code for > > > > > > rate-limiting > > > > > > >> > > > (which > > > > > > >> > > > >> I > > > > > > >> > > > >> > > think > > > > > > >> > > > >> > > > > > made > > > > > > >> > > > >> > > > > > > > >>> > > sense), isn't it a similar > case? > > > > > > >> > > > >> > > > > > > > >>> > > > > > > > > >> > > > >> > > > > > > > >>> > > On Mon, Mar 16, 2015 at 10:10 > PM, > > > Jay > > > > > > Kreps > > > > > > >> < > > > > > > >> > > > >> > > > > > jay.kr...@gmail.com > > > > > > >> > > > >> > > > > > > > > > > > > > >> > > > >> > > > > > > > >>> wrote: > > > > > > >> > > > >> > > > > > > > >>> > > > My concern is that as soon as > you > > > > > start > > > > > > >> > > encoding > > > > > > >> > > > >> > > non-error > > > > > > >> > > > >> > > > > > > > response > > > > > > >> > > > >> > > > > > > > >>> > > > information into error codes > the > > > > next > > > > > > >> > question > > > > > > >> > > > is > > > > > > >> > > > >> > what > > > > > > >> > > > >> > > to > > > > > > >> > > > >> > > > > do > > > > > > >> > > > >> > > > > > if > > > > > > >> > > > >> > > > > > > > two > > > > > > >> > > > >> > > > > > > > >>> > such > > > > > > >> > > > >> > > > > > > > >>> > > > codes apply (i.e. you have a > > > > replica > > > > > > down > > > > > > >> > and > > > > > > >> > > > the > > > > > > >> > > > >> > > response > > > > > > >> > > > >> > > > > is > > > > > > >> > > > >> > > > > > > > >>> > quota'd). I > > > > > > >> > > > >> > > > > > > > >>> > > > think I am trying to argue > that > > > > error > > > > > > >> should > > > > > > >> > > > mean > > > > > > >> > > > >> > "why > > > > > > >> > > > >> > > we > > > > > > >> > > > >> > > > > > > failed > > > > > > >> > > > >> > > > > > > > >>> your > > > > > > >> > > > >> > > > > > > > >>> > > > request", for which there > will > > > > really > > > > > > only > > > > > > >> > be > > > > > > >> > > > one > > > > > > >> > > > >> > > reason, > > > > > > >> > > > >> > > > > and > > > > > > >> > > > >> > > > > > > any > > > > > > >> > > > >> > > > > > > > >>> other > > > > > > >> > > > >> > > > > > > > >>> > > > useful information we want to > > > send > > > > > > back is > > > > > > >> > > just > > > > > > >> > > > >> > another > > > > > > >> > > > >> > > > > field > > > > > > >> > > > >> > > > > > > in > > > > > > >> > > > >> > > > > > > > >>> the > > > > > > >> > > > >> > > > > > > > >>> > > > response. > > > > > > >> > > > >> > > > > > > > >>> > > > > > > > > > >> > > > >> > > > > > > > >>> > > > -Jay > > > > > > >> > > > >> > > > > > > > >>> > > > > > > > > > >> > > > >> > > > > > > > >>> > > > On Mon, Mar 16, 2015 at 9:51 > PM, > > > > Gwen > > > > > > >> > Shapira > > > > > > >> > > < > > > > > > >> > > > >> > > > > > > > >>> gshap...@cloudera.com> > > > > > > >> > > > >> > > > > > > > >>> > > wrote: > > > > > > >> > > > >> > > > > > > > >>> > > > > > > > > > >> > > > >> > > > > > > > >>> > > >> I think its not too late to > > > > reserve > > > > > a > > > > > > set > > > > > > >> > of > > > > > > >> > > > >> error > > > > > > >> > > > >> > > codes > > > > > > >> > > > >> > > > > > > > >>> (200-299?) > > > > > > >> > > > >> > > > > > > > >>> > > >> for "non-error" codes. > > > > > > >> > > > >> > > > > > > > >>> > > >> > > > > > > >> > > > >> > > > > > > > >>> > > >> It won't be backward > compatible > > > > > (i.e. > > > > > > >> > clients > > > > > > >> > > > >> that > > > > > > >> > > > >> > > > > currently > > > > > > >> > > > >> > > > > > > do > > > > > > >> > > > >> > > > > > > > >>> "else > > > > > > >> > > > >> > > > > > > > >>> > > >> throw" will throw on > > > non-errors), > > > > > but > > > > > > >> > perhaps > > > > > > >> > > > its > > > > > > >> > > > >> > > > > > worthwhile. > > > > > > >> > > > >> > > > > > > > >>> > > >> > > > > > > >> > > > >> > > > > > > > >>> > > >> On Mon, Mar 16, 2015 at 9:42 > PM, > > > > Jay > > > > > > >> Kreps > > > > > > >> > < > > > > > > >> > > > >> > > > > > > jay.kr...@gmail.com > > > > > > >> > > > >> > > > > > > > > > > > > > > >> > > > >> > > > > > > > >>> > wrote: > > > > > > >> > > > >> > > > > > > > >>> > > >> > Hey Jun, > > > > > > >> > > > >> > > > > > > > >>> > > >> > > > > > > > >> > > > >> > > > > > > > >>> > > >> > I'd really really really > like > > > to > > > > > > avoid > > > > > > >> > > that. > > > > > > >> > > > >> > Having > > > > > > >> > > > >> > > just > > > > > > >> > > > >> > > > > > > > spent a > > > > > > >> > > > >> > > > > > > > >>> > > bunch of > > > > > > >> > > > >> > > > > > > > >>> > > >> > time on the clients, using > the > > > > > error > > > > > > >> > codes > > > > > > >> > > to > > > > > > >> > > > >> > encode > > > > > > >> > > > >> > > > > other > > > > > > >> > > > >> > > > > > > > >>> > information > > > > > > >> > > > >> > > > > > > > >>> > > >> > about the response is > super > > > > > > dangerous. > > > > > > >> > The > > > > > > >> > > > >> error > > > > > > >> > > > >> > > > > handling > > > > > > >> > > > >> > > > > > is > > > > > > >> > > > >> > > > > > > > >>> one of > > > > > > >> > > > >> > > > > > > > >>> > > the > > > > > > >> > > > >> > > > > > > > >>> > > >> > hardest parts of the > client > > > > > > (Guozhang > > > > > > >> > chime > > > > > > >> > > > in > > > > > > >> > > > >> > > here). > > > > > > >> > > > >> > > > > > > > >>> > > >> > > > > > > > >> > > > >> > > > > > > > >>> > > >> > Generally the error > handling > > > > looks > > > > > > like > > > > > > >> > > > >> > > > > > > > >>> > > >> > if(error == none) > > > > > > >> > > > >> > > > > > > > >>> > > >> > // good, process the > > > > request > > > > > > >> > > > >> > > > > > > > >>> > > >> > else if(error == > > > > KNOWN_ERROR_1) > > > > > > >> > > > >> > > > > > > > >>> > > >> > // handle known error > 1 > > > > > > >> > > > >> > > > > > > > >>> > > >> > else if(error == > > > > KNOWN_ERROR_2) > > > > > > >> > > > >> > > > > > > > >>> > > >> > // handle known error > 2 > > > > > > >> > > > >> > > > > > > > >>> > > >> > else > > > > > > >> > > > >> > > > > > > > >>> > > >> > throw > > > > > > >> > > Errors.forCode(error).exception(); > > > > > > >> > > > >> // > > > > > > >> > > > >> > or > > > > > > >> > > > >> > > some > > > > > > >> > > > >> > > > > > > other > > > > > > >> > > > >> > > > > > > > >>> > default > > > > > > >> > > > >> > > > > > > > >>> > > >> > behavior > > > > > > >> > > > >> > > > > > > > >>> > > >> > > > > > > > >> > > > >> > > > > > > > >>> > > >> > This works because we have > a > > > > > > convention > > > > > > >> > > that > > > > > > >> > > > >> and > > > > > > >> > > > >> > > error > > > > > > >> > > > >> > > > > is > > > > > > >> > > > >> > > > > > > > >>> something > > > > > > >> > > > >> > > > > > > > >>> > > that > > > > > > >> > > > >> > > > > > > > >>> > > >> > prevented your getting the > > > > > response > > > > > > so > > > > > > >> > the > > > > > > >> > > > >> default > > > > > > >> > > > >> > > > > > handling > > > > > > >> > > > >> > > > > > > > >>> case is > > > > > > >> > > > >> > > > > > > > >>> > > sane > > > > > > >> > > > >> > > > > > > > >>> > > >> > and forward compatible. It > is > > > > > > tempting > > > > > > >> to > > > > > > >> > > use > > > > > > >> > > > >> the > > > > > > >> > > > >> > > error > > > > > > >> > > > >> > > > > > code > > > > > > >> > > > >> > > > > > > > to > > > > > > >> > > > >> > > > > > > > >>> > convey > > > > > > >> > > > >> > > > > > > > >>> > > >> > information in the success > > > case. > > > > > For > > > > > > >> > > example > > > > > > >> > > > we > > > > > > >> > > > >> > > could > > > > > > >> > > > >> > > > > use > > > > > > >> > > > >> > > > > > > > error > > > > > > >> > > > >> > > > > > > > >>> > codes > > > > > > >> > > > >> > > > > > > > >>> > > to > > > > > > >> > > > >> > > > > > > > >>> > > >> > encode whether quotas were > > > > > enforced, > > > > > > >> > > whether > > > > > > >> > > > >> the > > > > > > >> > > > >> > > request > > > > > > >> > > > >> > > > > > was > > > > > > >> > > > >> > > > > > > > >>> served > > > > > > >> > > > >> > > > > > > > >>> > > out > > > > > > >> > > > >> > > > > > > > >>> > > >> of > > > > > > >> > > > >> > > > > > > > >>> > > >> > cache, whether the stock > > > market > > > > is > > > > > > up > > > > > > >> > > today, > > > > > > >> > > > or > > > > > > >> > > > >> > > > > whatever. > > > > > > >> > > > >> > > > > > > The > > > > > > >> > > > >> > > > > > > > >>> > problem > > > > > > >> > > > >> > > > > > > > >>> > > is > > > > > > >> > > > >> > > > > > > > >>> > > >> > that since these are not > > > errors > > > > as > > > > > > far > > > > > > >> as > > > > > > >> > > the > > > > > > >> > > > >> > > client is > > > > > > >> > > > >> > > > > > > > >>> concerned it > > > > > > >> > > > >> > > > > > > > >>> > > >> should > > > > > > >> > > > >> > > > > > > > >>> > > >> > not throw an exception but > > > > process > > > > > > the > > > > > > >> > > > >> response, > > > > > > >> > > > >> > > but now > > > > > > >> > > > >> > > > > > we > > > > > > >> > > > >> > > > > > > > >>> created > > > > > > >> > > > >> > > > > > > > >>> > an > > > > > > >> > > > >> > > > > > > > >>> > > >> > explicit requirement that > that > > > > > > error be > > > > > > >> > > > handled > > > > > > >> > > > >> > > > > explicitly > > > > > > >> > > > >> > > > > > > > >>> since it > > > > > > >> > > > >> > > > > > > > >>> > is > > > > > > >> > > > >> > > > > > > > >>> > > >> > different. I really think > that > > > > > this > > > > > > >> kind > > > > > > >> > of > > > > > > >> > > > >> > > information > > > > > > >> > > > >> > > > > is > > > > > > >> > > > >> > > > > > > not > > > > > > >> > > > >> > > > > > > > >>> an > > > > > > >> > > > >> > > > > > > > >>> > > error, > > > > > > >> > > > >> > > > > > > > >>> > > >> it > > > > > > >> > > > >> > > > > > > > >>> > > >> > is just information, and > if we > > > > > want > > > > > > it > > > > > > >> in > > > > > > >> > > the > > > > > > >> > > > >> > > response > > > > > > >> > > > >> > > > > we > > > > > > >> > > > >> > > > > > > > >>> should do > > > > > > >> > > > >> > > > > > > > >>> > > the > > > > > > >> > > > >> > > > > > > > >>> > > >> > right thing and add a new > > > field > > > > to > > > > > > the > > > > > > >> > > > >> response. > > > > > > >> > > > >> > > > > > > > >>> > > >> > > > > > > > >> > > > >> > > > > > > > >>> > > >> > I think you saw the Samza > bug > > > > that > > > > > > was > > > > > > >> > > > >> literally > > > > > > >> > > > >> > an > > > > > > >> > > > >> > > > > > example > > > > > > >> > > > >> > > > > > > of > > > > > > >> > > > >> > > > > > > > >>> this > > > > > > >> > > > >> > > > > > > > >>> > > >> > happening and leading to > an > > > > > infinite > > > > > > >> > retry > > > > > > >> > > > >> loop. > > > > > > >> > > > >> > > > > > > > >>> > > >> > > > > > > > >> > > > >> > > > > > > > >>> > > >> > Further more I really want > to > > > > > > emphasize > > > > > > >> > > that > > > > > > >> > > > >> > hitting > > > > > > >> > > > >> > > > > your > > > > > > >> > > > >> > > > > > > > quota > > > > > > >> > > > >> > > > > > > > >>> in > > > > > > >> > > > >> > > > > > > > >>> > the > > > > > > >> > > > >> > > > > > > > >>> > > >> > design that Adi has > proposed > > > is > > > > > > >> actually > > > > > > >> > > not > > > > > > >> > > > an > > > > > > >> > > > >> > > error > > > > > > >> > > > >> > > > > > > > condition > > > > > > >> > > > >> > > > > > > > >>> at > > > > > > >> > > > >> > > > > > > > >>> > > all. > > > > > > >> > > > >> > > > > > > > >>> > > >> It > > > > > > >> > > > >> > > > > > > > >>> > > >> > is totally reasonable in > any > > > > > > bootstrap > > > > > > >> > > > >> situation > > > > > > >> > > > >> > to > > > > > > >> > > > >> > > > > > > > >>> intentionally > > > > > > >> > > > >> > > > > > > > >>> > > want to > > > > > > >> > > > >> > > > > > > > >>> > > >> > run at the limit the > system > > > > > imposes > > > > > > on > > > > > > >> > you. > > > > > > >> > > > >> > > > > > > > >>> > > >> > > > > > > > >> > > > >> > > > > > > > >>> > > >> > -Jay > > > > > > >> > > > >> > > > > > > > >>> > > >> > > > > > > > >> > > > >> > > > > > > > >>> > > >> > > > > > > > >> > > > >> > > > > > > > >>> > > >> > > > > > > > >> > > > >> > > > > > > > >>> > > >> > On Mon, Mar 16, 2015 at > 4:27 > > > PM, > > > > > Jun > > > > > > >> Rao > > > > > > >> > < > > > > > > >> > > > >> > > > > > j...@confluent.io> > > > > > > >> > > > >> > > > > > > > >>> wrote: > > > > > > >> > > > >> > > > > > > > >>> > > >> > > > > > > > >> > > > >> > > > > > > > >>> > > >> >> It's probably useful for > a > > > > client > > > > > > to > > > > > > >> > know > > > > > > >> > > > >> whether > > > > > > >> > > > >> > > its > > > > > > >> > > > >> > > > > > > > requests > > > > > > >> > > > >> > > > > > > > >>> are > > > > > > >> > > > >> > > > > > > > >>> > > >> >> throttled or not (e.g., > for > > > > > > monitoring > > > > > > >> > and > > > > > > >> > > > >> > > alerting). > > > > > > >> > > > >> > > > > > From > > > > > > >> > > > >> > > > > > > > that > > > > > > >> > > > >> > > > > > > > >>> > > >> >> perspective, option B > (delay > > > > the > > > > > > >> > requests > > > > > > >> > > > and > > > > > > >> > > > >> > > return an > > > > > > >> > > > >> > > > > > > > error) > > > > > > >> > > > >> > > > > > > > >>> > seems > > > > > > >> > > > >> > > > > > > > >>> > > >> >> better. > > > > > > >> > > > >> > > > > > > > >>> > > >> 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> > > > > > >> > > > >> > > > > > > > > > > > > > > >> > > > >> > > > > > > > > > > > > > >> > > > >> > > > > > > > > > > > > >> > > > >> > > > > > > > > > > > >> > > > >> > > > > > > > > > > >> > > > >> > > > > > > > > >> > > > >> > > > > > > > > >> > > > >> > > > > > > > >> > > > >> > > > > > > >> > > > > > > > > > > >> > > > > > > > > > > >> > > > > -- > > > > > > >> > > > > Sent from Gmail Mobile > > > > > > >> > > > > > > > > > > >> > > > > > > > > > >> > > > > > > > > > >> > > > -- > > > > > > >> > > > Sent from Gmail Mobile > > > > > > >> > > > > > > > > > >> > > > > > > > > >> > > > > > > > >> > > > > > > > > > > > > > > > > > > >
