Hi Anna and Neha, I think it makes a lot of sense to try and keep the interface lean and to add more methods later when/if there is a need. What is the current thinking with regards to compatibility when/if we add new methods? A few options come to mind:
1. Change the interface to an abstract class with empty implementations for all the methods. This means that the path to adding new methods is clear. 2. Hope we have moved to Java 8 by the time we need to add new methods and use default methods with an empty implementation for any new method (and potentially make existing methods default methods too at that point for consistency) 3. Introduce a new interface that inherits from the existing Interceptor interface when we need to add new methods. Option 1 is the easiest and it also means that interceptor users only need to override the methods that they are interested (more useful if the number of methods grows). The downside is that interceptor implementations cannot inherit from another class (a straightforward workaround is to make the interceptor a forwarder that calls another class). Also, our existing callbacks are interfaces, so seems a bit inconsistent. Option 2 may be the most appealing one as both users and ourselves retain flexibility. The main downside is that it relies on us moving to Java 8, which may be more than a year away potentially (if we support the last 2 Java releases). Thoughts? Ismael On Tue, Jan 26, 2016 at 4:59 AM, Neha Narkhede <n...@confluent.io> wrote: > Anna, > > I'm also in favor of including just the APIs for which we have a clear use > case. If more use cases for finer monitoring show up in the future, we can > always update the interface. Would you please highlight in the KIP the APIs > that you think we have an immediate use for? > > Joel, > > Broker-side monitoring makes a lot of sense in the long term though I don't > think it is a requirement for end-to-end monitoring. With the producer and > consumer interceptors, you have the ability to get full > publish-to-subscribe end-to-end monitoring. The broker interceptor > certainly improves the resolution of monitoring but it is also a riskier > change. I prefer an incremental approach over a big-bang and recommend > taking baby-steps. Let's first make sure the producer/consumer interceptors > are successful. And then come back and add the broker interceptor > carefully. > > Having said that, it would be great to understand your proposal for the > broker interceptor independently. We can either add an interceptor > on-append or on-commit. If people want to use this for monitoring, then > possibly on-commit might be more useful? > > Thanks, > Neha > > On Mon, Jan 25, 2016 at 6:47 PM, Jay Kreps <j...@confluent.io> wrote: > > > Hey Joel, > > > > What is the interface you are thinking of? Something like this: > > onAppend(String topic, int partition, Records records, long time) > > ? > > > > One challenge right now is that we are still using the old > > Message/MessageSet classes on the broker which I'm not sure if we'd want > to > > support over the long haul but it might be okay just to create the > records > > instance for this interface. > > > > -Jay > > > > On Mon, Jan 25, 2016 at 12:37 PM, Joel Koshy <jjkosh...@gmail.com> > wrote: > > > > > I'm definitely in favor of having such hooks in the produce/consume > > > life-cycle. Not sure if people remember this but in Kafka 0.7 this was > > > pretty much how it was: > > > > > > > > > https://github.com/apache/kafka/blob/0.7/core/src/main/scala/kafka/producer/async/CallbackHandler.scala > > > i.e., we had something similar to the interceptor proposal for various > > > stages of the producer request. The producer provided call-backs for > > > beforeEnqueue, afterEnqueue, afterDequeuing, beforeSending, etc. So at > > > LinkedIn we in fact did auditing within these call-backs (and not > > > explicitly in the wrapper). Over time and with 0.8 we moved that out to > > the > > > wrapper libraries. > > > > > > On a side-note while audit and other monitoring can be done internally > > in a > > > convenient way I think it should be clarified that having a wrapper is > in > > > general not a bad idea and I would even consider it to be a > > best-practice. > > > Even with 0.7 we still had a wrapper library and that API has largely > > > stayed the same and has helped protect against (sometimes backwards > > > incompatible) changes in open source. > > > > > > While we are on this topic I have one comment and Anna, you may have > > > already considered this but I don't see mention of it in the KIP: > > > > > > Add a custom message interceptor/validator on the broker on message > > > arrival. > > > > > > We decompress and do basic validation of messages on arrival. I think > > there > > > is value in supporting custom validation and expand it to support > custom > > > on-arrival processing. Here is a specific use-case I have in mind. The > > blog > > > that James referenced describes our auditing infrastructure. In order > to > > > audit the Kafka cluster itself we need to run a "console auditor" > service > > > that consumes everything and spits out audit events back to the > cluster. > > I > > > would prefer not having to run this service because: > > > > > > - Well, it is one more service that we have to run and monitor > > > - Consuming everything takes up bandwidth which can be avoided > > > - The console auditor consumer itself can lag and cause temporary > > audit > > > discrepancies > > > > > > One way we can mitigate this is by having mirror-makers in between > > clusters > > > emit audit events. The problem is that the very last cluster in the > > > pipeline will not have any audit which is why we need to have something > > to > > > audit the cluster. > > > > > > If we had a custom message validator then the audit can be done > > on-arrival > > > and we won't need a console auditor. > > > > > > One potential issue in this approach and any elaborate on-arrival > > > processing for that matter is that you may need to deserialize the > > message > > > as well which can drive up produce request handling times. However I'm > > not > > > terribly concerned about that especially if the audit header can be > > > separated out easily or even deserialized partially as this Avro thread > > > touches on > > > > > > > > > http://search-hadoop.com/m/F2svI1HDLY12W8tnH1&subj=Re+any+optimization+in+reading+a+partial+schema+in+the+decoder+ > > > > > > Thanks, > > > > > > Joel > > > > > > On Mon, Jan 25, 2016 at 12:02 PM, Mayuresh Gharat < > > > gharatmayures...@gmail.com> wrote: > > > > > > > Nice KIP. Excellent idea. > > > > Was just thinking if we can add onDequed() to the ProducerIterceptor > > > > interface. Since we have the onEnqueued(), it will help the client or > > the > > > > tools to know how much time the message spent in the > RecordAccumulator. > > > > Also an API to check if there are any messages left for a particular > > > topic > > > > in the RecordAccumulator would help. > > > > > > > > Thanks, > > > > > > > > Mayuresh > > > > > > > > On Mon, Jan 25, 2016 at 11:29 AM, Todd Palino <tpal...@gmail.com> > > wrote: > > > > > > > > > Great idea. I’ve been talking about this for 2 years, and I’m glad > > > > someone > > > > > is finally picking it up. Will take a look at the KIP at some point > > > > > shortly. > > > > > > > > > > -Todd > > > > > > > > > > > > > > > On Mon, Jan 25, 2016 at 11:24 AM, Jay Kreps <j...@confluent.io> > > wrote: > > > > > > > > > > > Hey Becket, > > > > > > > > > > > > Yeah this is really similar to the callback. The difference is > > really > > > > in > > > > > > who sets the behavior. The idea of the interceptor is that it > > doesn't > > > > > > require any code change in apps so you can globally add behavior > to > > > > your > > > > > > Kafka usage without changing app code. Whereas the callback is > > added > > > by > > > > > the > > > > > > app. The idea is to kind of obviate the need for the wrapper code > > > that > > > > > e.g. > > > > > > LinkedIn maintains to hold this kind of stuff. > > > > > > > > > > > > -Jay > > > > > > > > > > > > On Sun, Jan 24, 2016 at 4:21 PM, Becket Qin < > becket....@gmail.com> > > > > > wrote: > > > > > > > > > > > > > This could be a useful feature. And I think there are some use > > > cases > > > > to > > > > > > > mutate the data like rejected alternative one mentioned. > > > > > > > > > > > > > > I am wondering if there is functional overlapping between > > > > > > > ProducerInterceptor.onAcknowledgement() and the producer > > callback? > > > I > > > > > can > > > > > > > see that the Callback could be a per record setting while > > > > > > > onAcknowledgement() is a producer level setting. Other than > that, > > > is > > > > > > there > > > > > > > any difference between them? > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > > > > Jiangjie (Becket) Qin > > > > > > > > > > > > > > On Fri, Jan 22, 2016 at 6:21 PM, Neha Narkhede < > > n...@confluent.io> > > > > > > wrote: > > > > > > > > > > > > > > > James, > > > > > > > > > > > > > > > > That is one of the many monitoring use cases for the > > interceptor > > > > > > > interface. > > > > > > > > > > > > > > > > Thanks, > > > > > > > > Neha > > > > > > > > > > > > > > > > On Fri, Jan 22, 2016 at 6:18 PM, James Cheng < > jch...@tivo.com> > > > > > wrote: > > > > > > > > > > > > > > > > > Anna, > > > > > > > > > > > > > > > > > > I'm trying to understand a concrete use case. It sounds > like > > > > > producer > > > > > > > > > interceptors could be used to implement part of LinkedIn's > > > Kafak > > > > > > Audit > > > > > > > > > tool? > > > https://engineering.linkedin.com/kafka/running-kafka-scale > > > > > > > > > > > > > > > > > > Part of that is done by a wrapper library around the kafka > > > > producer > > > > > > > that > > > > > > > > > keeps a count of the number of messages produced, and then > > > sends > > > > > that > > > > > > > > count > > > > > > > > > to a side-topic. It sounds like the producer interceptors > > could > > > > > > > possibly > > > > > > > > be > > > > > > > > > used to implement that? > > > > > > > > > > > > > > > > > > -James > > > > > > > > > > > > > > > > > > > On Jan 22, 2016, at 4:33 PM, Anna Povzner < > > a...@confluent.io > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > Hi, > > > > > > > > > > > > > > > > > > > > I just created a KIP-42 for adding producer and consumer > > > > > > interceptors > > > > > > > > for > > > > > > > > > > intercepting messages at different points on producer and > > > > > consumer. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-42%3A+Add+Producer+and+Consumer+Interceptors > > > > > > > > > > > > > > > > > > > > Comments and suggestions are welcome! > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > Anna > > > > > > > > > > > > > > > > > > > > > > > > > > > ________________________________ > > > > > > > > > > > > > > > > > > This email and any attachments may contain confidential and > > > > > > privileged > > > > > > > > > material for the sole use of the intended recipient. Any > > > review, > > > > > > > copying, > > > > > > > > > or distribution of this email (or any attachments) by > others > > is > > > > > > > > prohibited. > > > > > > > > > If you are not the intended recipient, please contact the > > > sender > > > > > > > > > immediately and permanently delete this email and any > > > > attachments. > > > > > No > > > > > > > > > employee or agent of TiVo Inc. is authorized to conclude > any > > > > > binding > > > > > > > > > agreement on behalf of TiVo Inc. by email. Binding > agreements > > > > with > > > > > > TiVo > > > > > > > > > Inc. may only be made by a signed written agreement. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > > Thanks, > > > > > > > > Neha > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > *—-* > > > > > *Todd Palino* > > > > > Staff Site Reliability Engineer > > > > > Data Infrastructure Streaming > > > > > > > > > > > > > > > > > > > > linkedin.com/in/toddpalino > > > > > > > > > > > > > > > > > > > > > -- > > > > -Regards, > > > > Mayuresh R. Gharat > > > > (862) 250-7125 > > > > > > > > > > > > > -- > Thanks, > Neha >
