Hi Kirk, Thanks for your question. You are correct that the presence or absence of the new RPCs in the ApiVersionsResponse tells the client whether to request the telemetry subscriptions and push metrics.
This is of course tricky in practice. It would be conceivable, as a cluster is upgraded to AK 3.7 or as a client metrics receiver plugin is deployed across the cluster, that a client connects to some brokers that support the new RPCs and some that do not. Here’s my suggestion: * If a client is not connected to any brokers that support in the new RPCs, it cannot push metrics. * If a client is only connected to brokers that support the new RPCs, it will use the new RPCs in accordance with the KIP. * If a client is connected to some brokers that support the new RPCs and some that do not, it will use the new RPCs with the supporting subset of brokers in accordance with the KIP. Comments? Thanks, Andrew > On 22 Sep 2023, at 16:01, Kirk True <k...@kirktrue.pro> wrote: > > Hi Andrew/Jun, > > I want to make sure I understand question/comment #119… In the case where a > cluster without a metrics client receiver is later reconfigured and restarted > to include a metrics client receiver, do we want the client to thereafter > begin pushing metrics to the cluster? From Andrew’s response to question > #119, it sounds like we’re using the presence/absence of the relevant RPCs in > ApiVersionsResponse as the to-push-or-not-to-push indicator. Do I have that > correct? > > Thanks, > Kirk > >> On Sep 21, 2023, at 7:42 AM, Andrew Schofield >> <andrew_schofield_j...@outlook.com> wrote: >> >> Hi Jun, >> Thanks for your comments. I’ve updated the KIP to clarify where necessary. >> >> 110. Yes, agree. The motivation section mentions this. >> >> 111. The replacement of ‘-‘ with ‘.’ for metric names and the replacement of >> ‘-‘ with ‘_’ for attribute keys is following the OTLP guidelines. I think >> it’s a bit >> of a debatable point. OTLP makes a distinction between a namespace and a >> multi-word component. If it was “client.id” then “client” would be a >> namespace with >> an attribute key “id”. But “client_id” is just a key. So, it was >> intentional, but debatable. >> >> 112. Thanks. The link target moved. Fixed. >> >> 113. Thanks. Fixed. >> >> 114.1. If a standard metric makes sense for a client, it should use the >> exact same >> name. If a standard metric doesn’t make sense for a client, then it can omit >> that metric. >> >> For a required metric, the situation is stronger. All clients must implement >> these >> metrics with these names in order to implement the KIP. But the required >> metrics >> are essentially the number of connections and the request latency, which do >> not >> reference the underlying implementation of the client (which >> producer.record.queue.time.max >> of course does). >> >> I suppose someone might build a producer-only client that didn’t have >> consumer metrics. >> In this case, the consumer metrics would conceptually have the value 0 and >> would not >> need to be sent to the broker. >> >> 114.2. If a client does not implement some metrics, they will not be >> available for >> analysis and troubleshooting. It just makes the ability to combine metrics >> from lots >> different clients less complete. >> >> 115. I think it was probably a mistake to be so specific about threading in >> this KIP. >> When the consumer threading refactor is complete, of course, it would do the >> appropriate >> equivalent. I’ve added a clarification and massively simplified this section. >> >> 116. I removed “client.terminating”. >> >> 117. Yes. Horrid. Fixed. >> >> 118. The Terminating flag just indicates that this is the final >> PushTelemetryRequest >> from this client. Any subsequent request will be rejected. I think this flag >> should remain. >> >> 119. Good catch. This was actually contradicting another part of the KIP. >> The current behaviour >> is indeed preserved. If the broker doesn’t have a client metrics receiver >> plugin, the new RPCs >> in this KIP are “turned off” and not reported in ApiVersionsResponse. The >> client will not >> attempt to push metrics. >> >> 120. The error handling table lists the error codes for >> PushTelemetryResponse. I’ve added one >> but it looked good to me. GetTelemetrySubscriptions doesn’t have any error >> codes, since the >> situation in which the client telemetry is not supported is handled by the >> RPCs not being offered >> by the broker. >> >> 121. Again, I think it’s probably a mistake to be specific about threading. >> Removed. >> >> 122. Good catch. For DescribeConfigs, the ACL operation should be >> “DESCRIBE_CONFIGS”. For AlterConfigs, the ACL operation should be >> “ALTER” (not “WRITE” as it said). The checks are made on the CLUSTER >> resource. >> >> Thanks for the detailed review. >> >> Thanks, >> Andrew >> >>> >>> 110. Another potential motivation is the multiple clients support. Some of >>> the places may not have good monitoring support for non-java clients. >>> >>> 111. OpenTelemetry Naming: We replace '-' with '.' for metric name and >>> replace '-' with '_' for attributes. Why is the inconsistency? >>> >>> 112. OTLP specification: Page is not found from the link. >>> >>> 113. "Defining standard and required metrics makes the monitoring and >>> troubleshooting of clients from various client types ": Incomplete sentence. >>> >>> 114. standard/required metrics >>> 114.1 Do other clients need to implement those metrics with the exact same >>> names? >>> 114.2 What happens if some of those metrics are missing from a client? >>> >>> 115. "KafkaConsumer: both the "heart beat" and application threads": We >>> have an ongoing effort to refactor the consumer threading model ( >>> https://cwiki.apache.org/confluence/display/KAFKA/Consumer+threading+refactor+design). >>> Once this is done, PRC requests will only be made from the background >>> thread. Should this KIP follow the new model only? >>> >>> 116. 'The metrics should contain the reason for the client termination by >>> including the client.terminating metric with the label “reason” ...'. Hmm, >>> are we introducing a new metric client.terminating? If so, that needs to be >>> explicitly listed. >>> >>> 117. "As the metrics plugin may need to add additional metrics on top of >>> this the generic metrics receiver in the broker will not add these labels >>> but rely on the plugins to do so," The sentence doesn't read well. >>> >>> 118. "it is possible for the client to send at most one accepted >>> out-of-profile per connection before the rate-limiter kicks in": If we do >>> this, do we still need the Terminating flag in PushTelemetryRequestV0? >>> >>> 119. "If there is no client metrics receiver plugin configured on the >>> broker, it will respond to GetTelemetrySubscriptionsRequest with >>> RequestedMetrics set to Null and a -1 SubscriptionId. The client should >>> send a new GetTelemetrySubscriptionsRequest after the PushIntervalMs has >>> expired. This allows the metrics receiver to be enabled or disabled without >>> having to restart the broker or reset the client connection." >>> "no client metrics receiver plugin configured" is defined by no metric >>> reporter implementing the ClientTelemetry interface, right? In that case, >>> it would be useful to avoid the clients sending >>> GetTelemetrySubscriptionsRequest periodically to preserve the current >>> behavior. >>> >>> 120. GetTelemetrySubscriptionsResponseV0 and PushTelemetryRequestV0: Could >>> we list error codes for each? >>> >>> 121. "ClientTelemetryReceiver.ClientTelemetryReceiver This method may be >>> called from the request handling thread": Where else can this method be >>> called? >>> >>> 122. DescribeConfigs/AlterConfigs already exist. Are we changing the ACL? >>> >>> Thanks, >>> >>> Jun >>> >>> On Mon, Jul 31, 2023 at 4:33 AM Andrew Schofield < >>> andrew_schofield_j...@outlook.com> wrote: >>> >>>> Hi Milind, >>>> Thanks for your question. >>>> >>>> On reflection, I agree that INVALID_RECORD is most likely to be caused by a >>>> problem in the serialization in the client. I have changed the client >>>> action in this case >>>> to “Log an error and stop pushing metrics”. >>>> >>>> I have updated the KIP text accordingly. >>>> >>>> Thanks, >>>> Andrew >>>> >>>>> On 31 Jul 2023, at 12:09, Milind Luthra <milut...@confluent.io.INVALID> >>>> wrote: >>>>> >>>>> Hi Andrew, >>>>> Thanks for the clarifications. >>>>> >>>>> About 2b: >>>>> In case a client has a bug while serializing, it might be difficult for >>>> the >>>>> client to recover from that without code changes. In that, it might be >>>> good >>>>> to just log the INVALID_RECORD as an error, and treat the error as fatal >>>>> for the client (only fatal in terms of sending the metrics, the client >>>> can >>>>> keep functioning otherwise). What do you think? >>>>> >>>>> Thanks >>>>> Milind >>>>> >>>>> On Mon, Jul 24, 2023 at 8:18 PM Andrew Schofield < >>>>> andrew_schofield_j...@outlook.com> wrote: >>>>> >>>>>> Hi Milind, >>>>>> Thanks for your questions about the KIP. >>>>>> >>>>>> 1) I did some archaeology and looked at historical versions of the KIP. >>>> I >>>>>> think this is >>>>>> just a mistake. 5 minutes is the default metric push interval. 30 >>>> minutes >>>>>> is a mystery >>>>>> to me. I’ve updated the KIP. >>>>>> >>>>>> 2) I think there are two situations in which INVALID_RECORD might occur. >>>>>> a) The client might perhaps be using a content-type that the broker does >>>>>> not support. >>>>>> The KIP mentions content-type as a future extension, but there’s only >>>> one >>>>>> supported >>>>>> to start with. Until we have multiple content-types, this seems out of >>>>>> scope. I think a >>>>>> future KIP would add another error code for this. >>>>>> b) The client might perhaps have a bug which means the metrics payload >>>> is >>>>>> malformed. >>>>>> Logging a warning and attempting the next metrics push on the push >>>>>> interval seems >>>>>> appropriate. >>>>>> >>>>>> UNKNOWN_SUBSCRIPTION_ID would indeed be handled by making an immediate >>>>>> GetTelemetrySubscriptionsRequest. >>>>>> >>>>>> UNSUPPORTED_COMPRESSION_TYPE seems like either a client bug or perhaps >>>>>> a situation in which a broker sends a compression type in a >>>>>> GetTelemetrySubscriptionsResponse >>>>>> which is subsequently not supported when its used with a >>>>>> PushTelemetryRequest. >>>>>> We do want the client to have the opportunity to get an up-to-date list >>>> of >>>>>> supported >>>>>> compression types. I think an immediate GetTelemetrySubscriptionsRequest >>>>>> is appropriate. >>>>>> >>>>>> 3) If a client attempts a subsequent handshake with a Null >>>>>> ClientInstanceId, the >>>>>> receiving broker may not already know the client's existing >>>>>> ClientInstanceId. If the >>>>>> receiving broker knows the existing ClientInstanceId, it simply responds >>>>>> the existing >>>>>> value back to the client. If it does not know the existing >>>>>> ClientInstanceId, it will create >>>>>> a new client instance ID and respond with that. >>>>>> >>>>>> I will update the KIP with these clarifications. >>>>>> >>>>>> Thanks, >>>>>> Andrew >>>>>> >>>>>>> On 17 Jul 2023, at 14:21, Milind Luthra <milut...@confluent.io.INVALID >>>>> >>>>>> wrote: >>>>>>> >>>>>>> Hi Andrew, thanks for this KIP. >>>>>>> >>>>>>> I had a few questions regarding the "Error handling" section. >>>>>>> >>>>>>> 1. It mentions that "The 5 and 30 minute retries are to eventually >>>>>> trigger >>>>>>> a retry and avoid having to restart clients if the cluster metrics >>>>>>> configuration is disabled temporarily, e.g., by operator error, rolling >>>>>>> upgrades, etc." >>>>>>> But this 30 min interval isn't mentioned anywhere else. What is it >>>>>>> referring to? >>>>>>> >>>>>>> 2. For the actual errors: >>>>>>> INVALID_RECORD : The action required is to "Log a warning to the >>>>>>> application and schedule the next GetTelemetrySubscriptionsRequest to 5 >>>>>>> minutes". Why is this 5 minutes, and not something like PushIntervalMs? >>>>>> And >>>>>>> also, why are we scheduling a GetTelemetrySubscriptionsRequest in this >>>>>>> case, if the serialization is broken? >>>>>>> UNKNOWN_SUBSCRIPTION_ID , UNSUPPORTED_COMPRESSION_TYPE : just to >>>> confirm, >>>>>>> the GetTelemetrySubscriptionsRequest needs to be scheduled immediately >>>>>>> after the PushTelemetry response, correct? >>>>>>> >>>>>>> 3. For "Subsequent GetTelemetrySubscriptionsRequests must include the >>>>>>> ClientInstanceId returned in the first response, regardless of broker": >>>>>>> Will a broker error be returned in case some implementation of this KIP >>>>>>> violates this accidentally and sends a request with ClientInstanceId = >>>>>> Null >>>>>>> even when it's been obtained already? Or will a new ClientInstanceId be >>>>>>> returned without an error? >>>>>>> >>>>>>> Thanks! >>>>>>> >>>>>>> On Tue, Jun 13, 2023 at 8:38 PM Andrew Schofield < >>>>>>> andrew_schofield_j...@outlook.com> wrote: >>>>>>> >>>>>>>> Hi, >>>>>>>> I would like to start a new discussion thread on KIP-714: Client >>>> metrics >>>>>>>> and observability. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>> >>>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-714%3A+Client+metrics+and+observability >>>>>>>> >>>>>>>> I have edited the proposal significantly to reduce the scope. The >>>>>> overall >>>>>>>> mechanism for client metric subscriptions is unchanged, but the >>>>>>>> KIP is now based on the existing client metrics, rather than >>>> introducing >>>>>>>> new metrics. The purpose remains helping cluster operators >>>>>>>> investigate performance problems experienced by clients without >>>>>> requiring >>>>>>>> changes to the client application code or configuration. >>>>>>>> >>>>>>>> Thanks, >>>>>>>> Andrew
