Hi Chris, I also have 2 other comments:
1. One more thing I came across is that should we provide the Retry-After header in the response in case of 503 response? Although I'm not sure how many clients honor this, we could add it just in case some does and if you also find it useful. (We could default it to retry.backoff.ms.) 2. Adding to Adrian's comments, storing timestamped worker statuses in an internal topic and then reading them from there would add valuable info about what the worker does. For instance GET /health?startTime=45345323346 could fetch events from the given timestamp additionally to your proposed behavior. Also, if the rest server isn't available, it would serve in itself as a log about the workers' behavior. I understand if you think it's such a scope change that it should be an improvement KIP, but would like to gauge what you think about this. Regards, Viktor On Tue, Jun 11, 2024 at 4:34 PM Chris Egerton <chr...@aiven.io.invalid> wrote: > Hi Adrian, > > Thanks for your comments/questions! The responses to them are related so > I'll try to address both at once. > > The most recent update I made to the KIP should help provide insight into > what's going wrong if a non-200 response is returned. I don't plan on > adding any structured data such as error codes or something like a "phase" > field with values like READING_CONFIG_TOPIC quite yet, but there is room > for us to add human-readable information on the causes of failure in the > "message" field (see KAFKA-15563 [1] and its PR [2] for an example of what > kind of information we might provide to users). Part of the problem is that > while I've heard plenty of (justified!) complaints about the Kafka Connect > REST API becoming unavailable and the difficulties users face with > debugging their workers when that happens, I still don't feel we have a > strong-enough grasp on the common causes for this scenario to commit to a > response format that could be more machine-readable, and it can be > surprisingly difficult to get to a root cause in some cases. > > I'm anticipating that users will rely on the endpoint primarily for two > things: > 1) Ensuring that a worker has completed startup successfully during a > rolling upgrade (if you don't get a 200 after long enough, abort the > upgrade, check the error message, and start investigating) > 2) Ensuring that a worker remains healthy after it has joined the cluster > (if you don't get a 200 for a sustained period of time, check the error > message, and then decide whether to restart the process or issue a page) > > It's primarily designed to be easy to incorporate with automated tooling > that has support for REST-based process health monitoring, while also > providing some human-readable information (when possible) if the worker > isn't healthy. This human-readable information should hopefully help people > gauge how to respond to non-200 responses, and we can try to improve > wording and granularity over time based on user feedback. You and other > users may develop automated responses based on the content of the error > messages, but beware that the wording may change across releases. > > Does that seem reasonable for V1 of this feature? I can definitely see room > for expansion of the response format in the future, but would like to hold > off on that for now. > > [1] - https://issues.apache.org/jira/browse/KAFKA-15563 > [2] - https://github.com/apache/kafka/pull/14562 > > Cheers, > > Chris > > On Tue, Jun 11, 2024 at 3:37 AM Adrian Preston <prest...@uk.ibm.com> > wrote: > > > Hi Chris, > > > > Good KIP – I think it will be very helpful in alerting and automating the > > resolution of common Connect problems. > > > > I have a couple of questions / suggestions: > > > > 1. What are you planning on documenting as guidance for using this new > > endpoint? My guess would be that if Connect doesn’t return a status of > 200 > > after some period I would either page someone, or restart the process? > But > > I’m missing the nuance of distinguishing between readiness and liveness, > is > > this for maintaining overall availability when rolling out updates to > > several Connect processes? > > > > 2. Would you consider providing a way to discover details about exactly > > which condition (or conditions) is/are failing? Perhaps by providing a > > richer JSON response? Something like this would help us adopt the health > > check, as we could start by paging someone for all failures, then over > time > > (as we gained confidence) transition more of the conditions over to being > > handled by automation. > > > > Regards, > > - Adrian > > > > > > From: Chris Egerton <chr...@aiven.io.INVALID> > > Date: Monday, 10 June 2024 at 15:26 > > To: dev@kafka.apache.org <dev@kafka.apache.org> > > Subject: [EXTERNAL] Re: [DISCUSS] KIP-1017: A health check endpoint for > > Kafka Connect > > Hi all, > > > > Thanks for the positive feedback! > > > > I've made one small addition to the KIP since there's been a change to > our > > REST timeout error messages that's worth incorporating here. Quoting the > > added section directly: > > > > > Note that the HTTP status codes and "status" fields in the JSON > response > > will match the exact examples above. However, the "message" field may be > > augmented to include, among other things, more information about the > > operation(s) the worker could be blocked on (such as was added in REST > > timeout error messages in KAFKA-15563 [1]). > > > > Assuming this still looks okay to everyone, I'll kick off a vote thread > > sometime this week or the next. > > > > [1] - https://issues.apache.org/jira/browse/KAFKA-15563 > > > > Cheers, > > > > Chris > > > > On Fri, Jun 7, 2024 at 12:01 PM Andrew Schofield < > > andrew_schofi...@live.com> > > wrote: > > > > > Hi Chris, > > > This KIP looks good to me. I particularly like the explanation of how > the > > > result will specifically > > > check the worker health in ways that have previously caused trouble. > > > > > > Thanks, > > > Andrew > > > > > > > On 7 Jun 2024, at 16:18, Mickael Maison <mickael.mai...@gmail.com> > > > wrote: > > > > > > > > Hi Chris, > > > > > > > > Happy Friday! The KIP looks good to me. +1 > > > > > > > > Thanks, > > > > Mickael > > > > > > > > On Fri, Jan 26, 2024 at 8:41 PM Chris Egerton > <chr...@aiven.io.invalid > > > > > > wrote: > > > >> > > > >> Hi all, > > > >> > > > >> Happy Friday! I'd like to kick off discussion for KIP-1017, which > (as > > > the > > > >> title suggests) proposes adding a health check endpoint for Kafka > > > Connect: > > > >> > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-1017%3A+Health+check+endpoint+for+Kafka+Connect > > > >> > > > >> This is one of the longest-standing issues with Kafka Connect and > I'm > > > >> hoping we can finally put it in the ground soon. Looking forward to > > > hearing > > > >> people's thoughts! > > > >> > > > >> Cheers, > > > >> > > > >> Chris > > > > > > > > > > Unless otherwise stated above: > > > > IBM United Kingdom Limited > > Registered in England and Wales with number 741598 > > Registered office: PO Box 41, North Harbour, Portsmouth, Hants. PO6 3AU > > >
