Hi Chris and all, Thank you for your feedback. Your proposals seems good to me. I did these changed to the KIP, please have a look at the change [1]
Best, Ivan [1] https://cwiki.apache.org/confluence/pages/diffpagesbyversion.action?pageId=240881396&selectedPageVersions=14&selectedPageVersions=12 On Thu, Apr 11, 2024, at 10:49, Chris Egerton wrote: > Hi Ivan, > > I agree with Andrew that we can save cluster ID checking for later. This > feature is opt-in and if necessary we can add a note to users about only > enabling it if they can be certain that the same cluster will always be > resolved by the bootstrap servers. This would apply regardless of whether > we did client ID checking anyways. > > Thanks for exploring a variety of options and ironing out the details on > this KIP. I think this is acceptable as-is but have a couple of final > suggestions we might consider: > > 1. Although the definition of an unavailable broker is useful ("A broker is > unavailable when the client doesn't have an established connection with it > and cannot establish a connection (e.g. due to the reconnect backoff)"), I > think this is a little too restrictive. It's useful to note this as an > example of what we may consider an unavailable broker, but if we leave some > more wiggle room, it could save us the trouble of a follow-up KIP when > tweaking behavior in the future. For example, to reduce discovery time for > a migrated Kafka cluster, it could be nice to re-bootstrap after a > connection attempt has failed for every currently-known broker with no > successful attempts in between, instead of waiting for the reconnection > backoff interval to kick in. Again, I don't think this needs to happen with > the initial implementation of the KIP, I just want us to be able to explore > options like this in the future. > > 2. In a similar vein, I think we can leave more room in our definition of > re-bootstrapping. Instead of "During the rebootstrap process, the client > forgets the brokers it knows about and falls back on the bootstrap brokers > (i.e. provided by bootstrap.servers provided by the client configuration) > as if it had just been initialized.", we could say something like "During > the rebootstrap process, the client attempts to re-contact the bootstrap > servers (i.e. ...) that it contacted during initialization." This could be > useful if we want to add the bootstrap servers to the previously-known list > of brokers instead of completely discarding the previously-known set. This > too can be left out of the initial implementation and just give us a bit > more room for future options. > > Cheers, > > Chris > > On Tue, Apr 9, 2024 at 11:51 AM Andrew Schofield <andrew_schofi...@live.com> > wrote: > > > Hi Ivan, > > I think you have to go one way or the other with the cluster ID, so I > > think removing that from this KIP might > > be the best. I think there’s another KIP waiting to be written for > > ensuring consistency of clusters, but > > I think that wouldn’t conflict at all with this one. > > > > Thanks, > > Andrew > > > > > On 9 Apr 2024, at 19:11, Ivan Yurchenko <i...@ivanyu.me> wrote: > > > > > > Hi Andrew and all, > > > > > > I looked deeper into the code [1] and it seems the Metadata class is OK > > with cluster ID changing. So I'm thinking that the rebootstrapping > > shouldn't introduce a new failure mode here. And I should remove the > > mention of this cluster ID checks from the KIP. > > > > > > Best, > > > Ivan > > > > > > [1] > > https://github.com/apache/kafka/blob/ff90f78c700c582f9800013faad827c36b45ceb7/clients/src/main/java/org/apache/kafka/clients/Metadata.java#L355 > > > > > > On Tue, Apr 9, 2024, at 09:28, Andrew Schofield wrote: > > >> Hi Ivan, > > >> Thanks for the KIP. I can see situations in which this would be > > helpful. I have one question. > > >> > > >> The KIP says the client checks the cluster ID when it re-bootstraps and > > that it will fail if the > > >> cluster ID doesn’t match the previously known one. How does it fail? > > Which exception does > > >> it throw and when? > > >> > > >> In a similar vein, now that we are checking cluster IDs, I wonder if it > > could be extended to > > >> cover all situations in which there are cluster ID mismatches, such as > > the bootstrap server > > >> list erroneously pointing at brokers from different clusters and the > > problem only being > > >> detectable later on. > > >> > > >> Thanks, > > >> Andrew > > >> > > >>> On 8 Apr 2024, at 18:24, Ivan Yurchenko <i...@ivanyu.me> wrote: > > >>> > > >>> Hello! > > >>> > > >>> I changed the KIP a bit, specifying that the certain benefit goes to > > consumers not participating in a group, but that other clients can benefit > > as well in certain situations. > > >>> > > >>> You can see the changes in the history [1] > > >>> > > >>> Thank you! > > >>> > > >>> Ivan > > >>> > > >>> [1] > > https://cwiki.apache.org/confluence/pages/diffpagesbyversion.action?pageId=240881396&originalVersion=10&revisedVersion=11 > > >>> > > >>> On 2023/07/15 16:37:52 Ivan Yurchenko wrote: > > >>>> Hello! > > >>>> > > >>>> I've made several changes to the KIP based on the comments: > > >>>> > > >>>> 1. Reduced the scope to producer and consumer clients only. > > >>>> 2. Added more details to the description of the rebootstrap process. > > >>>> 3. Documented the role of low values of reconnect.backoff.max.ms in > > >>>> preventing rebootstrapping. > > >>>> 4. Some wording changes. > > >>>> > > >>>> You can see the changes in the history [1] > > >>>> > > >>>> I'm planning to put the KIP to a vote in some days if there are no new > > >>>> comments. > > >>>> > > >>>> Thank you! > > >>>> > > >>>> Ivan > > >>>> > > >>>> [1] > > >>>> > > https://cwiki.apache.org/confluence/pages/diffpagesbyversion.action?pageId=240881396&selectedPageVersions=9&selectedPageVersions=5 > > >>>> > > >>>> On Tue, 30 May 2023 at 08:23, Ivan Yurchenko <iv...@gmail.com> > > >>>> wrote: > > >>>> > > >>>>> Hi Chris and all, > > >>>>> > > >>>>>> I believe the logic you've linked is only applicable for the > > producer and > > >>>>>> consumer clients; the admin client does something different (see > > [1]). > > >>>>> > > >>>>> I see, thank you for the pointer. It seems the admin client is fairly > > >>>>> different from the producer and consumer. Probably it makes sense to > > reduce > > >>>>> the scope of the KIP to the producer and consumer clients only. > > >>>>> > > >>>>>> it'd be nice to have a definition of when re-bootstrapping > > >>>>>> would occur that doesn't rely on internal implementation details. > > What > > >>>>>> user-visible phenomena can we identify that would lead to a > > >>>>>> re-bootstrapping? > > >>>>> > > >>>>> Let's put it this way: "Re-bootstrapping means that the client > > forgets > > >>>>> about nodes it knows about and falls back on the bootstrap nodes as > > if it > > >>>>> had just been initialized. Re-bootstrapping happens when, during a > > metadata > > >>>>> update (which may be scheduled by `metadata.max.age.ms` or caused by > > >>>>> certain error responses like NOT_LEADER_OR_FOLLOWER, > > REPLICA_NOT_AVAILABLE, > > >>>>> etc.), the client doesn't have a node with an established connection > > or > > >>>>> establishable connection." > > >>>>> Does this sound good? > > >>>>> > > >>>>>> I also believe that if someone has " > > >>>>>> reconnect.backoff.max.ms" set to a low-enough value, > > >>>>>> NetworkClient::leastLoadedNode may never return null. In that case, > > >>>>>> shouldn't we still attempt a re-bootstrap at some point (if the > > user has > > >>>>>> enabled this feature)? > > >>>>> > > >>>>> Yes, you're right. Particularly `canConnect` here [1] can always be > > >>>>> returning `true` if `reconnect.backoff.max.ms` is low enough. > > >>>>> It seems pretty difficult to find a good criteria when > > re-bootstrapping > > >>>>> should be forced in this case, so it'd be difficult to configure and > > reason > > >>>>> about. I think it's worth mentioning in the KIP and later in the > > >>>>> documentation, but we should not try to do anything special here. > > >>>>> > > >>>>>> Would it make sense to re-bootstrap only after " > > >>>>>> metadata.max.age.ms" has elapsed since the last metadata update, > > and > > >>>>> when > > >>>>>> at least one request has been made to contact each known server and > > been > > >>>>>> met with failure? > > >>>>> > > >>>>> The first condition is satisfied by the check in the beginning of > > >>>>> `maybeUpdate` [2]. > > >>>>> It seems to me, the second one is also satisfied by > > `leastLoadedNode`. > > >>>>> Admittedly, it's more relaxed than you propose: it tracks > > unavailability of > > >>>>> nodes that was detected by all types of requests, not only by > > metadata > > >>>>> requests. > > >>>>> What do you think, would this be enough? > > >>>>> > > >>>>> [1] > > >>>>> > > https://github.com/apache/kafka/blob/c9a42c85e2c903329b3550181d230527e90e3646/clients/src/main/java/org/apache/kafka/clients/NetworkClient.java#L698 > > >>>>> [2] > > >>>>> > > https://github.com/apache/kafka/blob/c9a42c85e2c903329b3550181d230527e90e3646/clients/src/main/java/org/apache/kafka/clients/NetworkClient.java#L1034-L1041 > > >>>>> > > >>>>> Best, > > >>>>> Ivan > > >>>>> > > >>>>> > > >>>>> On Tue, 21 Feb 2023 at 20:07, Chris Egerton <ch...@aiven.io.invalid> > > >>>>> wrote: > > >>>>> > > >>>>>> Hi Ivan, > > >>>>>> > > >>>>>> I believe the logic you've linked is only applicable for the > > producer and > > >>>>>> consumer clients; the admin client does something different (see > > [1]). > > >>>>>> > > >>>>>> Either way, it'd be nice to have a definition of when > > re-bootstrapping > > >>>>>> would occur that doesn't rely on internal implementation details. > > What > > >>>>>> user-visible phenomena can we identify that would lead to a > > >>>>>> re-bootstrapping? I also believe that if someone has " > > >>>>>> reconnect.backoff.max.ms" set to a low-enough value, > > >>>>>> NetworkClient::leastLoadedNode may never return null. In that case, > > >>>>>> shouldn't we still attempt a re-bootstrap at some point (if the > > user has > > >>>>>> enabled this feature)? Would it make sense to re-bootstrap only > > after " > > >>>>>> metadata.max.age.ms" has elapsed since the last metadata update, > > and when > > >>>>>> at least one request has been made to contact each known server and > > been > > >>>>>> met with failure? > > >>>>>> > > >>>>>> [1] - > > >>>>>> > > >>>>>> > > https://github.com/apache/kafka/blob/c9a42c85e2c903329b3550181d230527e90e3646/clients/src/main/java/org/apache/kafka/clients/admin/internals/AdminMetadataManager.java#L100 > > >>>>>> > > >>>>>> Cheers, > > >>>>>> > > >>>>>> Chris > > >>>>>> > > >>>>>> On Sun, Feb 19, 2023 at 3:39 PM Ivan Yurchenko <iv...@gmail.com> > > >>>>>> wrote: > > >>>>>> > > >>>>>>> Hi Chris, > > >>>>>>> > > >>>>>>> Thank you for your question. As a part of various lifecycle phases > > >>>>>>> (including node disconnect), NetworkClient can request metadata > > update > > >>>>>>> eagerly (the `Metadata.requestUpdate` method), which results in > > >>>>>>> `MetadataUpdater.maybeUpdate` being called during next poll. > > Inside, it > > >>>>>> has > > >>>>>>> a way to find a known node it can connect to for the fresh > > metadata. If > > >>>>>> no > > >>>>>>> such node is found, it backs off. (Code [1]). I'm thinking of > > >>>>>> piggybacking > > >>>>>>> on this logic and injecting the rebootstrap attempt before the > > backoff. > > >>>>>>> > > >>>>>>> As of the second part of you question: the re-bootstrapping means > > >>>>>> replacing > > >>>>>>> the node addresses in the client with the original bootstrap > > addresses, > > >>>>>> so > > >>>>>>> if the first bootstrap attempt fails, the client will continue > > using the > > >>>>>>> bootstrap addresses until success -- pretty much as if it were > > recreated > > >>>>>>> from scratch. > > >>>>>>> > > >>>>>>> Best, > > >>>>>>> Ivan > > >>>>>>> > > >>>>>>> [1] > > >>>>>>> > > >>>>>>> > > >>>>>> > > https://github.com/apache/kafka/blob/trunk/clients/src/main/java/org/apache/kafka/clients/NetworkClient.java#L1045-L1049 > > >>>>>>> > > >>>>>>> On Thu, 16 Feb 2023 at 17:18, Chris Egerton <ch...@aiven.io.invalid > > > > > >>>>>>> wrote: > > >>>>>>> > > >>>>>>>> Hi Ivan, > > >>>>>>>> > > >>>>>>>> I'm not very familiar with the clients side of things but the > > proposal > > >>>>>>>> seems reasonable. > > >>>>>>>> > > >>>>>>>> I like the flexibility of the "metadata.recovery.strategy" > > property > > >>>>>> as a > > >>>>>>>> string instead of, e.g., a "rebootstrap.enabled" boolean. We may > > want > > >>>>>> to > > >>>>>>>> adapt a different approach in the future, like the background > > thread > > >>>>>>>> mentioned in the rejected alternatives section. > > >>>>>>>> > > >>>>>>>> I also like handling this via configuration property instead of > > >>>>>> adding a > > >>>>>>>> Java-level API or suggesting that users re-instantiate their > > clients > > >>>>>>> since > > >>>>>>>> we may want to enable this new behavior by default in the future, > > and > > >>>>>> it > > >>>>>>>> also reduces the level of effort required for users to benefit > > from > > >>>>>> this > > >>>>>>>> improvement. > > >>>>>>>> > > >>>>>>>> One question I have--that may have an obvious answer to anyone > > more > > >>>>>>>> familiar with client internals--is under which conditions we will > > >>>>>>> determine > > >>>>>>>> a rebootstrap is appropriate. Taking the admin client as an > > example, > > >>>>>> the > > >>>>>>> " > > >>>>>>>> default.api.timeout.ms" property gives us a limit on the time an > > >>>>>>> operation > > >>>>>>>> will be allowed to take before it completes or fails (with > > optional > > >>>>>>>> per-request overrides in the various *Options classes), and the " > > >>>>>>>> request.timeout.ms" property gives us a limit on the time each > > >>>>>> request > > >>>>>>>> issued for that operation will be allowed to take before it > > >>>>>> completes, is > > >>>>>>>> retried, or causes the operation to fail (if no more retries can > > be > > >>>>>>>> performed). If all of the known servers (i.e., bootstrap servers > > for > > >>>>>> the > > >>>>>>>> first operation, or discovered brokers if bootstrapping has > > already > > >>>>>> been > > >>>>>>>> completed) are unavailable, the admin client will keep (re)trying > > to > > >>>>>>> fetch > > >>>>>>>> metadata until the API timeout is exhausted, issuing multiple > > >>>>>> requests to > > >>>>>>>> the same server if necessary. When would a re-bootstrapping occur > > >>>>>> here? > > >>>>>>>> Ideally we could find some approach that minimizes false positives > > >>>>>>> (where a > > >>>>>>>> re-bootstrapping is performed even though the current set of known > > >>>>>>> brokers > > >>>>>>>> is only temporarily unavailable, as opposed to permanently > > moved). Of > > >>>>>>>> course, given the opt-in nature of the re-bootstrapping feature, > > we > > >>>>>> can > > >>>>>>>> always shoot for "good enough" on that front, but, it'd be nice to > > >>>>>>>> understand some of the potential pitfalls of enabling it. > > >>>>>>>> > > >>>>>>>> Following up on the above, would we cache the need to perform a > > >>>>>>>> re-bootstrap across separate operations? For example, if I try to > > >>>>>>> describe > > >>>>>>>> a cluster, then a re-bootstrapping takes place and fails, and > > then I > > >>>>>> try > > >>>>>>> to > > >>>>>>>> describe the cluster a second time. With that second attempt, > > would we > > >>>>>>>> immediately resort to the bootstrap servers for any initial > > metadata > > >>>>>>>> updates, or would we still try to go through the last-known set of > > >>>>>>> brokers > > >>>>>>>> first? > > >>>>>>>> > > >>>>>>>> Cheers, > > >>>>>>>> > > >>>>>>>> Chris > > >>>>>>>> > > >>>>>>>> On Mon, Feb 6, 2023 at 4:32 AM Ivan Yurchenko < > > >>>>>> ivan0yurche...@gmail.com> > > >>>>>>>> wrote: > > >>>>>>>> > > >>>>>>>>> Hi! > > >>>>>>>>> > > >>>>>>>>> There seems to be not much more discussion going, so I'm > > planning to > > >>>>>>>> start > > >>>>>>>>> the vote in a couple of days. > > >>>>>>>>> > > >>>>>>>>> Thanks, > > >>>>>>>>> > > >>>>>>>>> Ivan > > >>>>>>>>> > > >>>>>>>>> On Wed, 18 Jan 2023 at 12:06, Ivan Yurchenko < > > >>>>>> ivan0yurche...@gmail.com > > >>>>>>>> > > >>>>>>>>> wrote: > > >>>>>>>>> > > >>>>>>>>>> Hello! > > >>>>>>>>>> I would like to start the discussion thread on KIP-899: Allow > > >>>>>> clients > > >>>>>>>> to > > >>>>>>>>>> rebootstrap. > > >>>>>>>>>> This KIP proposes to allow Kafka clients to repeat the bootstrap > > >>>>>>>> process > > >>>>>>>>>> when fetching metadata if none of the known nodes are available. > > >>>>>>>>>> > > >>>>>>>>>> > > >>>>>>>>> > > >>>>>>>> > > >>>>>>> > > >>>>>> > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-899%3A+Allow+clients+to+rebootstrap > > >>>>>>>>>> > > >>>>>>>>>> A question right away: should we eventually change the default > > >>>>>>> behavior > > >>>>>>>>> or > > >>>>>>>>>> it can remain configurable "forever"? The latter is proposed in > > >>>>>> the > > >>>>>>>> KIP. > > >>>>>>>>>> > > >>>>>>>>>> Thank you! > > >>>>>>>>>> > > >>>>>>>>>> Ivan > > > > > > >
