> KAFKA-7707 was just created which proposes enabling connectors to override consumer properties
Thanks Sönke, I think something along those lines will be super useful for Connect. To some extent, enabling connectors to override some worker properties obviates the need for multiple worker configs, multiple herders, or multiple Kafka clusters in Connect itself. We'd still need multiple herders in MM2, but I imagine operators using MM2 Connectors in existing Connect clusters will benefit immensely from that change. Ryanne On Thu, Dec 20, 2018 at 4:26 AM Sönke Liebau <soenke.lie...@opencore.com.invalid> wrote: > Hi, > > just to briefly mention this, as it is somewhat related to the discussion > we had: > KAFKA-7707 was just created which proposes enabling connectors to override > consumer properties. It would currently appear to be a bit narrow in scope, > but that can probably be expanded upon. > > Not sure if that has any actual impact on MM2 but wanted to at least > mention it. > > Best regards, > Sönke > > On Wed, Dec 19, 2018 at 11:00 PM Ryanne Dolan <ryannedo...@gmail.com> > wrote: > > > Becket, thanks for taking a look. > > > > > 1. Only relying on the topic naming seems a little fragile. > > > > I think the limitations on topic names are imposed by Kafka itself > (beyond > > those from Zookeeper and the file system), so it might be possible to > add a > > reserved character for this purpose. This would essentially promote the > > concept of "remote topics" from MirrorMaker to Kafka in general, which > > might be nice. In particular, we could add native support for remote > topics > > to KafkaConsumer if we had a baked-in way to distinguish remote vs > > non-remote topics. Definitely worth investigating for a future KIP :) > > > > > 2. For ACLs, is it possible that the local topic and remote topic have > > different ACLs? Will the connector do the sanity check? > > > > MM2 won't do full two-way sync of ACLs between clusters, but instead will > > simply propagate ACL changes from source topics to their downstream > remote > > topics. For example, if a principal can READ from topic1 in cluster A, > the > > same principal should be able to READ A.topic1 in cluster B. Otherwise, > > migrating a consumer from A -> B wouldn't work reliably. > > > > OTOH, say a super-user force-changes the ACL for a remote topic, that > > change would not be sync'd upstream to the source topic. In all cases, > the > > "normal" source topics are the source-of-truth for ACL and configuration > of > > remote topics managed by MM2. > > > > So to your specific question: no, MM2 will not sanity-check remote > topics, > > since MM2 should be the only principal making any changes to remote > topics, > > just as MM2 is the only principal allowed to WRITE to remote topics. > > > > > 3. For the checkpoint. Because the consumer may commit at arbitrary > > offset. Does the connector need to keep a mapping between each source > > offset to destination offset? If so how would that be done? > > > > Offset translation will not be possible for arbitrary offsets. Instead, > > checkpoints simply provide recent offsets that are safe for a foreign > > consumer to seek to. To accomplish this, MirrorSourceConnector will > > periodically (every checkpoint.interval.seconds) emit local-remote offset > > pairs for the records being replicated. The connector knows this mapping > > because it gets upstream offsets from the consumer and corresponding > > downstream offsets from the producer ACK. Then MirrorCheckpointConnector > > can use this sparse mapping when emitting checkpoints to the target > > cluster. > > > > For example, if a consumer group has committed up to offset 100, and the > > connector knows that offset 99 is equivalent to offset 199 on the target > > cluster, then the connector can safely emit a checkpoint for that > consumer > > group with target offset 199 == source offset 99, since 99 < 100. Notice > > the consumer is actually past 100 on the source cluster, but it's only > safe > > to seek to 199 on the target cluster. > > > > If we checkpoint every 5 seconds in this way, we can be sure that a > > failed-over consumer won't end up re-processing much more than 5 seconds > of > > data. > > > > Thanks for the great questions. > > Ryanne > > > > > > On Thu, Dec 13, 2018 at 12:07 AM Becket Qin <becket....@gmail.com> > wrote: > > > > > Hi Ryanne, > > > > > > Thanks for the KIP. In general, I think the proposal makes a lot of > sense > > > to me. Unifying Kafka clusters in different locations has been a very > > > important scenario. Right now open source community does not have a > > > standard solution to that. > > > > > > A few comments/questions are following: > > > > > > 1. Only relying on the topic naming seems a little fragile. It seems > > > difficult to prevent conflict names. One workaround might be adding a > > > config to the broker, preventing topics with character such as "_" or > "." > > > from being created, unless it is from some specific client such as MM2 > > > admin clients. > > > > > > 2. For ACLs, is it possible that the local topic and remote topic have > > > different ACLs? Will the connector do the sanity check? > > > > > > 3. For the checkpoint. Because the consumer may commit at arbitrary > > offset. > > > Does the connector need to keep a mapping between each source offset to > > > destination offset? If so how would that be done? > > > > > > Thanks, > > > > > > Jiangjie (Becket) Qin > > > > > > On Thu, Dec 13, 2018 at 8:23 AM Ryanne Dolan <ryannedo...@gmail.com> > > > wrote: > > > > > > > > Consuming system restarts and restates from compacted topics, using > > > > *.account_state > > > > > > > > Michael, I think I understand your concern. With MM2's remote topic > > > > concept, it's the consumer's responsibility to aggregate records > across > > > > .*account_state. MM2 will not merge these for you (by design). This > > > > complicates your consumer that expects a single topic to be compacted > > > > across all clusters, since log-compaction does not span topics. > > > > > > > > Notice that MM2 isn't really breaking anything here. The problem is > > that > > > > you are using MirrorMaker to aggregate records from multiple clusters > > > into > > > > a single topic, which MM2 will not do by default. > > > > > > > > It's easy to accomplish the same thing with MM2 though. You have a > > couple > > > > options: > > > > > > > > 1) turn off topic renaming or use "legacy mode". MM2 won't get in > your > > > way, > > > > but it won't help much for DR, failover/failback etc. You're on your > > own > > > :) > > > > > > > > 2) Aggregate your topic downstream of MM2. Turn .*account_state into > > > > account_state.aggregate, which itself is log-compacted. KTables make > > this > > > > trivial! > > > > > > > > With (2) you still get the nice DR semantics. The KTable will > represent > > > the > > > > latest account states aggregated across all clusters. If your > producers > > > > need to migrate/failover/failback, the KTable in each region will be > > > > eventually consistent, and downstream consumers won't notice. I'd > > > recommend > > > > blacklisting .*aggregate in MM2 so these don't get replicated > > themselves. > > > > > > > > TBH, I thought about including this as a feature in MM2, s.t. you > would > > > get > > > > a foo.aggregate topic automatically. Personally, I think Streams is > > > better > > > > suited than Connect for this, but I won't rule it out for a future > KIP. > > > > > > > > Thanks again! > > > > Ryanne > > > > > > > > > > > > > > > > On Wed, Dec 12, 2018 at 2:49 PM Michael Pearce < > michael.pea...@ig.com> > > > > wrote: > > > > > > > > > Ok so you have your transaction system running master master. > > > > > > > > > > You have three dcs, regions where-ever. > > > > > > > > > > Accounts are distributed across area based on an number of factors > > > > > > > > > > Account A + B are in Ireland > > > > > Account C + D are in Germany > > > > > Account E are in UK > > > > > > > > > > Lets prefix call kafka cluster in Ireland Z, Germany Y and UK X > > > > > > > > > > So now I have topics: > > > > > > > > > > Z.account_state (holding state for accounts A + B) > > > > > Y.account_state (holding state for accounts C + D) > > > > > X.account_state (holding state for account E) > > > > > > > > > > To get a full view of all accounts a consumer would consume > > > > *.account_state > > > > > Great! > > > > > > > > > > Now image we take a planned or unplanned outage in the UK. > > > > > We move/shift the transactional processing of account E to Ireland. > > > > > > > > > > Now we end up with > > > > > Z.account_state (holding state for accounts A + B + current state > > for > > > > > account E) > > > > > Y.account_state (holding state for accounts C + D) > > > > > X.account_state (holding outdated state for account E) > > > > > > > > > > > > > > > Consuming system restarts and restates from compacted topics, using > > > > > *.account_state > > > > > > > > > > It will get both current state and also outdated state for E, which > > > state > > > > > would it use? And this gets worse as it scales and you move the > > > > processing > > > > > of accounts around over time. > > > > > > > > > > > > > > > Likewise the issue is the same without compacted state. > > > > > > > > > > Imagine order of state change is important by account globally, how > > do > > > > you > > > > > re-order the state changes? As order guarantee can be given within > a > > > > single > > > > > topic partition only. You only care for order by the account (not > for > > > > > offets being same, we simply care that updates are in order and > > latest > > > > > state is at head on restart we ignore offsets). So it doesn’t > matter > > if > > > > in > > > > > Z cluster you see update A1, A2, B1, A3, B2, E1, E2 and in cluster > Y > > > you > > > > > see B1,B2, A1,E1, A2, A3, E2 as the ordering by of the updates > > account > > > is > > > > > preserved. > > > > > > > > > > With the topic solution your suggesting we would have no way true > way > > > of > > > > > replaying and re-constituting the order between X.account_state and > > > > > Z.account_state topics in the case of E, as messages will be in > > > different > > > > > topics and partitions. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -----Original Message----- > > > > > From: Ryanne Dolan <ryannedo...@gmail.com> > > > > > Sent: Wednesday, December 12, 2018 4:37 PM > > > > > To: dev@kafka.apache.org > > > > > Subject: Re: [DISCUSS] KIP-382: MirrorMaker 2.0 > > > > > > > > > > > You haven’t described how one would handle the ordering issues > and > > > also > > > > > the compaction issues where transactional processing is > master-master > > > in > > > > > regions, where the processing is sticky to region but of failure or > > > > > planned, processing of certain accounts move regions. > > > > > > > > > > Michael, a couple points: > > > > > > > > > > - With "remote topics", the order of events is consistent between > > > > clusters. > > > > > Cluster A's "topic1" is the same records in the same order as > cluster > > > B's > > > > > "A.topic1". The plan is to enable exactly-once semantics within MM2 > > so > > > > > there aren't additional dupes either (though I believe this will > > > require > > > > > support within Connect and a separate KIP). > > > > > > > > > > - A consumer that is only interested in events produced in a > > particular > > > > > region can migrate to a cluster in a different region by updating > > it's > > > > > subscription accordingly. For example, a consumer in us-west > > processing > > > > > events local to us-west would consume topics like "topic1" (a > normal > > > > > topic). If you migrate this consumer to us-east, it would need to > > > > subscribe > > > > > to "us-west.topic1" instead. It's clear from the naming convention > > that > > > > > "us-west.topic1" is a replicated topic with records originating > from > > a > > > > > remote cluster. > > > > > > > > > > I'm not sure I understand your concern w.r.t compacted topics and > > > state. > > > > > Can you elaborate? > > > > > > > > > > Ryanne > > > > > > > > > > > > > > > On Wed, Dec 12, 2018 at 8:41 AM Michael Pearce < > > michael.pea...@ig.com> > > > > > wrote: > > > > > > > > > > > Ryanne, > > > > > > > > > > > > You haven’t described how one would handle the ordering issues > and > > > also > > > > > > the compaction issues where transactional processing is > > master-master > > > > in > > > > > > regions, where the processing is sticky to region but of failure > or > > > > > > planned, processing of certain accounts move regions. > > > > > > > > > > > > Also I ask that you keep compatibility of the handler api > interface > > > in > > > > MM > > > > > > into MM2. > > > > > > > > > > > > > > > > > > > > > > > > -----Original Message----- > > > > > > From: Ryanne Dolan <ryannedo...@gmail.com> > > > > > > Sent: Wednesday, December 12, 2018 6:41 AM > > > > > > To: dev@kafka.apache.org > > > > > > Subject: Re: [DISCUSS] KIP-382: MirrorMaker 2.0 > > > > > > > > > > > > > One based on hops using headers, and another based on topic > > naming. > > > > > > > > > > > > Michael, this was also suggested by Alex Mironov. Other > replication > > > > > engines > > > > > > use headers as you describe, but there are several issues with > this > > > > > > approach: > > > > > > > > > > > > - The Connect framework provides Transformations that could be > used > > > for > > > > > > this purpose, so MM2 doesn't necessarily need to address this > > feature > > > > > > directly. For example, a Transformation could tag each record > with > > > its > > > > > > source cluster alias or could decrement a hop/TTL value if you > > like. > > > > > > > > > > > > - We want MM2 to benefit from "shallow iteration", meaning that > > e.g. > > > > > > compressed message sets should pass through MM2 without being > > > > > decompressed > > > > > > and decomposed. In many cases, this can result in significant > > > > performance > > > > > > gains. But since these message sets are not decomposed into > > > individual > > > > > > messages and so on, we cannot reliably tag each message that > passes > > > > > > through. > > > > > > > > > > > > - Fundamentally, I believe it is a bad idea to treat topics on > > > > different > > > > > > clusters as if they are the same topic. If two clusters have > topics > > > of > > > > > the > > > > > > same name, they are still inherently different topics, as they > > exist > > > on > > > > > > different clusters, with potentially different records and > > certainly > > > > > > different offsets. Moreover, there is no robust way to keep such > > > topics > > > > > > consistent and in sync. > > > > > > > > > > > > - Some applications are interested in events from a particular > data > > > > > > center/region/cluster, while other applications will want to > > process > > > > > events > > > > > > regardless of where they are produced. Indeed, a common use-case > > for > > > > > > building out multiple clusters in the first place is to support > > this > > > > sort > > > > > > of geolocation-aware processing and aggregation. It sounds like > > your > > > > org > > > > > > attempts to make topics the same everywhere, which is undesirable > > in > > > > many > > > > > > cases. > > > > > > > > > > > > - Advanced operations such as automatic failover and failback > rely > > on > > > > the > > > > > > ability to segregate records based on their cluster of origin, > > while > > > > > > preserving order within each topic-partition. This is extremely > > > > difficult > > > > > > if your app's producers and MM's producers "cross streams" by > > writing > > > > > into > > > > > > the same topic. (Your mention of "ensure inflight processing at > the > > > old > > > > > > region ceased" etc is hand-holding symptomatic of this problem.) > > > > > > > > > > > > - With a consistent naming convention in place (along with > > > > checkpointing, > > > > > > heartbeats and the other "best practices" mentioned in the KIP), > we > > > can > > > > > > build tooling that understands multi-cluster environments. For > > > example, > > > > > the > > > > > > KIP describes a utility for translating consumer offsets between > > > > > clusters. > > > > > > This will enable operators to migrate consumer groups between > > > clusters > > > > > > without knowing anything about the topics involved. > > > > > > > > > > > > That all said, I am sure some organizations will want to apply > > their > > > > own > > > > > > conventions, and I don't believe MM2 should get in the way of > that. > > > > > > > > > > > > Thanks again! > > > > > > Ryanne > > > > > > > > > > > > On Tue, Dec 11, 2018 at 7:20 PM michael.andre.pearce > > > > > > <michael.andre.pea...@me.com.invalid> wrote: > > > > > > > > > > > > > Another benefit of using hops vs topic naming (also how we > > > currently > > > > do > > > > > > > master master in my org) > > > > > > > You have a transactional processing app that's multi regioned. > So > > > for > > > > > > sake > > > > > > > of discussion all A and B accounts process normally in ireland > > > region > > > > > > all C > > > > > > > and D in germany region and all E in Uk region. Increase > regions > > to > > > > > > across > > > > > > > the globe almost one per financial centre where close regions > > might > > > > > mesh > > > > > > > together one to one and continental regions form some backbones > > > > trunks. > > > > > > > If uk region goes down planned or unplanned we move the > > > transactional > > > > > > > routing and processing to germany region. During this flip over > > we > > > > > ensure > > > > > > > inflight processing at the old region ceased and restate > account > > > > states > > > > > > > from topics before further processing thus ensuring no out of > > order > > > > > > message > > > > > > > production by account. > > > > > > > The with using region broker or some other topic prefixes this > > will > > > > > mean > > > > > > > now i have a topic for uk region with some E account data and > > after > > > > > > process > > > > > > > movement will end up with E accounts in the topic for germany > > > region. > > > > > Now > > > > > > > ordering is lost. Worst still if compacted topic i will have > two > > > > states > > > > > > as > > > > > > > state would be in two topics. > > > > > > > With using hops and single named topic (as we do already in our > > own > > > > > > custom > > > > > > > handlers which do hop logic with todays mirrormakers) we can > > avoid > > > > this > > > > > > > issue entirely as ordering by account is preserved as is all in > > one > > > > > topic > > > > > > > still and also when using compacted we have only one state. > > > > > > > > > > > > > > Before you say why not name topics a. b. I use that to simplify > > the > > > > > case > > > > > > > to be able describe it. Accounts are autogenrated e.g. A16E45T1 > > and > > > > > > C43F4SA > > > > > > > could be processing in germany region currently and C43F2SA > could > > > be > > > > in > > > > > > uk > > > > > > > region currently. > > > > > > > > > > > > > > > > > > > > > > > > > > > > Sent from my Samsung Galaxy smartphone. > > > > > > > -------- Original message --------From: Andrew Otto < > > > > > o...@wikimedia.org> > > > > > > > Date: 11/12/2018 14:28 (GMT+00:00) To: dev@kafka.apache.org > > > > Subject: > > > > > > > Re: [DISCUSS] KIP-382: MirrorMaker 2.0 > > > > > > > Wikimedia currently implements 'master <-> master' replication > by > > > > > > manually > > > > > > > prefixing topics with datacenter names, and then configuring > > > > > MirrorMaker > > > > > > to > > > > > > > only replicate topics that begin with a DC name to another. > > > > > > > > > > > > > > While having topics named with topological details is > > manageable, I > > > > > > > wouldn't say it is desirable. It pushes knowledge of the > > > replication > > > > > > > topology up to clients. Even if MirrorMaker was the one doing > > the > > > > > topic > > > > > > > prefixing, downstream consumers of a group of replicated topics > > are > > > > > still > > > > > > > going to have to know to subscribe to the correctly prefixed > > > topics. > > > > > > > > > > > > > > If possible I'd much prefer header + hops based replication > > rather > > > > than > > > > > > > lots of renamed topics. But either way, this KIP would be > > > > tremendously > > > > > > > useful to us so I support it all the way! :) > > > > > > > > > > > > > > On Tue, Dec 11, 2018 at 5:32 AM Michael Pearce < > > > > michael.pea...@ig.com> > > > > > > > wrote: > > > > > > > > > > > > > > > So this is indeed what using headers with hops avoids is > > creating > > > > > lots > > > > > > > and > > > > > > > > lots of topics __, so you can have more complex topology > > setups. > > > > > > > > > > > > > > > > I ask why not support having two ways of setting up and > closing > > > the > > > > > > door? > > > > > > > > > > > > > > > > One based on hops using headers, and another based on topic > > > naming. > > > > > > After > > > > > > > > all flexibility is what we want its for end users how to use > > > right? > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On 12/7/18, 8:19 PM, "Ryanne Dolan" <ryannedo...@gmail.com> > > > > wrote: > > > > > > > > > > > > > > > > Michael, thanks for the comments! > > > > > > > > > > > > > > > > > would like to see support for this to be done by hops, > > as > > > > well > > > > > > > [...] > > > > > > > > This then allows ring (hops = number of brokers in the > > ring), > > > > > mesh > > > > > > > > (every > > > > > > > > cluster interconnected so hop=1), or even a tree (more > fine > > > > > grained > > > > > > > > setup) > > > > > > > > cluster topology. > > > > > > > > > > > > > > > > That's a good idea, though we can do this at the topic > > level > > > > > > without > > > > > > > > tagging individual records. A max.hop of 1 would mean > > > > "A.topic1" > > > > > is > > > > > > > > allowed, but not "B.A.topic1". I think the default > behavior > > > > would > > > > > > > need > > > > > > > > to > > > > > > > > be max.hops = 1 to avoid unexpectedly creating a bunch of > > > > > > D.C.B.A... > > > > > > > > topics > > > > > > > > when you create a fully-connected mesh topology. > > > > > > > > > > > > > > > > Looking ahead a bit, I can imagine an external tool > > computing > > > > the > > > > > > > > spanning > > > > > > > > tree of topics among a set of clusters based on > > inter-cluster > > > > > > > > replication > > > > > > > > lag, and setting up MM2 accordingly. But that's probably > > > > outside > > > > > > the > > > > > > > > scope > > > > > > > > of this KIP :) > > > > > > > > > > > > > > > > > ...standalone MirrorMaker connector... > > > > > > > > > ./bin/kafka-mirror-maker-2.sh --consumer > > > > > consumer.properties > > > > > > > > --producer producer.properties > > > > > > > > > > > > > > > > Eventually, I'd like MM2 to completely replace legacy MM, > > > > > including > > > > > > > the > > > > > > > > ./bin/kafka-mirror-maker.sh script. In the meantime, > it's a > > > > good > > > > > > idea > > > > > > > > to > > > > > > > > include a standalone driver. Something like > > > > > > > > ./bin/connect-mirror-maker-standalone.sh with the same > > > > high-level > > > > > > > > configuration file. I'll do that, thanks. > > > > > > > > > > > > > > > > > I see no section on providing support for mirror maker > > > > > Handlers, > > > > > > > > today > > > > > > > > people can add handlers to have a little extra custom > logic > > > if > > > > > > > needed, > > > > > > > > and > > > > > > > > the handler api is public today so should be supported > > going > > > > > > forwards > > > > > > > > so > > > > > > > > people are not on mass re-writing these. > > > > > > > > > > > > > > > > Great point. Connect offers single-message > transformations > > > and > > > > > > > > converters > > > > > > > > for this purpose, but I agree that we should honor the > > > existing > > > > > API > > > > > > > if > > > > > > > > possible. This might be as easy as providing an adapter > > class > > > > > > between > > > > > > > > connect's Transformation and mirror-maker's Handler. > Maybe > > > > file a > > > > > > > Jira > > > > > > > > ticket to track this? > > > > > > > > > > > > > > > > Really appreciate your feedback! > > > > > > > > > > > > > > > > Ryanne > > > > > > > > > > > > > > > > > > > > > > > > On Thu, Dec 6, 2018 at 7:03 PM Michael Pearce < > > > > > > michael.pea...@ig.com > > > > > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > Re hops to stop the cycle and to allow a range of multi > > > > cluster > > > > > > > > > topologies, see > > > > > > https://www.rabbitmq.com/federated-exchanges.html > > > > > > > > where > > > > > > > > > very similar was done in rabbit. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On 12/7/18, 12:47 AM, "Michael Pearce" < > > > > michael.pea...@ig.com> > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > Nice proposal. > > > > > > > > > > > > > > > > > > Some comments. > > > > > > > > > > > > > > > > > > > > > > > > > > > On the section around cycle detection. > > > > > > > > > > > > > > > > > > I would like to see support for this to be done by > > > hops, > > > > as > > > > > > > well > > > > > > > > e.g. > > > > > > > > > using approach is to use a header for the number of > hops, > > > as > > > > > the > > > > > > > mm2 > > > > > > > > > replicates it increases the hop count and you can make > > the > > > > mm2 > > > > > > > > configurable > > > > > > > > > to only produce messages onwards where hops are less > than > > > x. > > > > > > > > > This then allows ring (hops = number of brokers in > > the > > > > > ring), > > > > > > > > mesh > > > > > > > > > (every cluster interconnected so hop=1), or even a tree > > > (more > > > > > > fine > > > > > > > > grained > > > > > > > > > setup) cluster topology. > > > > > > > > > FYI we do this currently with the current mirror > > maker, > > > > > > using a > > > > > > > > custom > > > > > > > > > handler. > > > > > > > > > > > > > > > > > > > > > > > > > > > On the section around running a standalone > > MirrorMaker > > > > > > > connector > > > > > > > > > > > > > > > > > > I would suggest making this as easy to run as the > > > > > > mirrormakers > > > > > > > > are > > > > > > > > > today, with a simple single sh script. > > > > > > > > > I assume this is what is proposed in section > "Running > > > > > > > > MirrorMaker in > > > > > > > > > legacy mode" but I would even do this before MM would > be > > > > > removed, > > > > > > > > with a -2 > > > > > > > > > varient. > > > > > > > > > e.g. > > > > > > > > > ./bin/kafka-mirror-maker-2.sh --consumer > > > > > consumer.properties > > > > > > > > > --producer producer.properties > > > > > > > > > > > > > > > > > > Lastly > > > > > > > > > > > > > > > > > > I see no section on providing support for mirror > > maker > > > > > > > Handlers, > > > > > > > > today > > > > > > > > > people can add handlers to have a little extra custom > > logic > > > > if > > > > > > > > needed, and > > > > > > > > > the handler api is public today so should be supported > > > going > > > > > > > > forwards so > > > > > > > > > people are not on mass re-writing these. > > > > > > > > > > > > > > > > > > On 12/5/18, 5:36 PM, "Ryanne Dolan" < > > > > ryannedo...@gmail.com > > > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > Sönke, > > > > > > > > > > > > > > > > > > > The only thing that I could come up with is > the > > > > > > > limitation > > > > > > > > to a > > > > > > > > > single > > > > > > > > > offset commit interval > > > > > > > > > > > > > > > > > > Yes, and other internal properties, e.g. those > > used > > > > by > > > > > > the > > > > > > > > internal > > > > > > > > > consumers and producers, which, granted, > probably > > > are > > > > > not > > > > > > > > often > > > > > > > > > changed > > > > > > > > > from their defaults, but that apply to > Connectors > > > > > across > > > > > > > the > > > > > > > > > entire cluster. > > > > > > > > > > > > > > > > > > Ryanne > > > > > > > > > > > > > > > > > > On Wed, Dec 5, 2018 at 3:21 AM Sönke Liebau > > > > > > > > > <soenke.lie...@opencore.com.invalid> wrote: > > > > > > > > > > > > > > > > > > > Hi Ryanne, > > > > > > > > > > > > > > > > > > > > when you say "Currently worker configs apply > > > across > > > > > the > > > > > > > > entire > > > > > > > > > cluster, > > > > > > > > > > which is limiting even for use-cases > involving > > a > > > > > single > > > > > > > > Kafka > > > > > > > > > cluster.", > > > > > > > > > > may I ask you to elaborate on those > > limitations a > > > > > > little? > > > > > > > > > > The only thing that I could come up with is > the > > > > > > > limitation > > > > > > > > to a > > > > > > > > > single > > > > > > > > > > offset commit interval value for all running > > > > > > connectors. > > > > > > > > > > Maybe also the limitation to shared config > > > > > providers.. > > > > > > > > > > > > > > > > > > > > But you sound like you had painful > experiences > > > with > > > > > > this > > > > > > > > before, > > > > > > > > > maybe > > > > > > > > > > you'd like to share the burden :) > > > > > > > > > > > > > > > > > > > > Best regards, > > > > > > > > > > Sönke > > > > > > > > > > > > > > > > > > > > On Wed, Dec 5, 2018 at 5:15 AM Ryanne Dolan < > > > > > > > > > ryannedo...@gmail.com> wrote: > > > > > > > > > > > > > > > > > > > > > Sönke, > > > > > > > > > > > > > > > > > > > > > > I think so long as we can keep the > > differences > > > > at a > > > > > > > very > > > > > > > > high > > > > > > > > > level (i.e. > > > > > > > > > > > the "control plane"), there is little > > downside > > > to > > > > > MM2 > > > > > > > and > > > > > > > > > Connect > > > > > > > > > > > coexisting. I do expect them to converge to > > > some > > > > > > > extent, > > > > > > > > with > > > > > > > > > features > > > > > > > > > > from > > > > > > > > > > > MM2 being pulled into Connect whenever this > > is > > > > > > possible > > > > > > > > > without breaking > > > > > > > > > > > things. > > > > > > > > > > > > > > > > > > > > > > I could definitely see your idea re > > hierarchies > > > > or > > > > > > > > groups of > > > > > > > > > connectors > > > > > > > > > > > being useful outside MM2. Currently "worker > > > > > configs" > > > > > > > > apply > > > > > > > > > across the > > > > > > > > > > > entire cluster, which is limiting even for > > > > > use-cases > > > > > > > > involving > > > > > > > > > a single > > > > > > > > > > > Kafka cluster. If Connect supported > multiple > > > > > workers > > > > > > in > > > > > > > > the > > > > > > > > > same cluster, > > > > > > > > > > > it would start to look a lot like a MM2 > > > cluster. > > > > > > > > > > > > > > > > > > > > > > Ryanne > > > > > > > > > > > > > > > > > > > > > > On Tue, Dec 4, 2018 at 3:26 PM Sönke Liebau > > > > > > > > > > > <soenke.lie...@opencore.com.invalid> > wrote: > > > > > > > > > > > > > > > > > > > > > > > Hi Ryanne, > > > > > > > > > > > > > > > > > > > > > > > > thanks for your response! > > > > > > > > > > > > > > > > > > > > > > > > It seems like you have already done a lot > > of > > > > > > > > investigation > > > > > > > > > into the > > > > > > > > > > > > existing code and the solution design and > > all > > > > of > > > > > > what > > > > > > > > you > > > > > > > > > write makes > > > > > > > > > > > sense > > > > > > > > > > > > to me. Would it potentially be worth > adding > > > > this > > > > > to > > > > > > > > the KIP, > > > > > > > > > now that > > > > > > > > > > you > > > > > > > > > > > > had to write it up because of me anyway? > > > > > > > > > > > > > > > > > > > > > > > > However, I am afraid that I am still not > > > > entirely > > > > > > > > convinced > > > > > > > > > of the > > > > > > > > > > > > fundamental benefit this provides over an > > > > > extended > > > > > > > > Connect > > > > > > > > > that has the > > > > > > > > > > > > following functionality: > > > > > > > > > > > > - allow for organizing connectors into a > > > > > > hierarchical > > > > > > > > > structure - > > > > > > > > > > > > "clusters/us-west/..." > > > > > > > > > > > > - allow defining external Kafka clusters > to > > > be > > > > > used > > > > > > > by > > > > > > > > > Source and Sink > > > > > > > > > > > > connectors instead of the local cluster > > > > > > > > > > > > > > > > > > > > > > > > Personally I think both of these features > > are > > > > > > useful > > > > > > > > > additions to > > > > > > > > > > > Connect, > > > > > > > > > > > > I'll address both separately below. > > > > > > > > > > > > > > > > > > > > > > > > Allowing to structure connectors in a > > > hierarchy > > > > > > > > > > > > Organizing running connectors will grow > > more > > > > > > > important > > > > > > > > as > > > > > > > > > corporate > > > > > > > > > > > > customers adapt Connect and installations > > > grow > > > > in > > > > > > > size. > > > > > > > > > Additionally > > > > > > > > > > this > > > > > > > > > > > > could be useful for ACLs in case they are > > > ever > > > > > > added > > > > > > > to > > > > > > > > > Connect, as you > > > > > > > > > > > > could allow specific users access only to > > > > > specific > > > > > > > > > namespaces (and > > > > > > > > > > until > > > > > > > > > > > > ACLs are added it would facilitate using > a > > > > > reverse > > > > > > > > proxy for > > > > > > > > > the same > > > > > > > > > > > > effect). > > > > > > > > > > > > > > > > > > > > > > > > Allow accessing multiple external > clusters > > > > > > > > > > > > The reasoning for this feature is pretty > > much > > > > the > > > > > > > same > > > > > > > > as > > > > > > > > > for a central > > > > > > > > > > > > Mirror Maker cluster, if a company has > > > multiple > > > > > > > > clusters for > > > > > > > > > whatever > > > > > > > > > > > > reason but wants to have ingest > centralized > > > in > > > > > one > > > > > > > > system > > > > > > > > > aka one > > > > > > > > > > Connect > > > > > > > > > > > > cluster they would need the ability to > read > > > > from > > > > > > and > > > > > > > > write > > > > > > > > > to an > > > > > > > > > > > arbitrary > > > > > > > > > > > > number of Kafka clusters. > > > > > > > > > > > > I haven't really looked at the code, just > > > poked > > > > > > > around > > > > > > > > a > > > > > > > > > couple of > > > > > > > > > > > minutes, > > > > > > > > > > > > but it appears like this could be done > with > > > > > fairly > > > > > > > low > > > > > > > > > effort. My > > > > > > > > > > general > > > > > > > > > > > > idea would be to leave the existing > > > > configuration > > > > > > > > options > > > > > > > > > untouched - > > > > > > > > > > > > Connect will always need a "primary" > > cluster > > > > that > > > > > > is > > > > > > > > used > > > > > > > > > for storage > > > > > > > > > > of > > > > > > > > > > > > internal data (config, offsets, status) > > there > > > > is > > > > > no > > > > > > > > need to > > > > > > > > > break > > > > > > > > > > > existing > > > > > > > > > > > > configs. But additionally allow adding > > named > > > > > extra > > > > > > > > clusters > > > > > > > > > by > > > > > > > > > > specifying > > > > > > > > > > > > options like > > > > > > > > > > > > > > > external.sales_cluster.bootstrap_servers=... > > > > > > > > > > > > > > > > > external.sales_cluster.ssl.keystore.location=... > > > > > > > > > > > > > > > > > external.marketing_cluster.bootstrap_servers=... > > > > > > > > > > > > > > > > > > > > > > > > The code for status, offset and config > > > storage > > > > is > > > > > > > > mostly > > > > > > > > > isolated in > > > > > > > > > > the > > > > > > > > > > > > Kafka[Offset|Status|Config]BackingStore > > > classes > > > > > and > > > > > > > > could > > > > > > > > > remain pretty > > > > > > > > > > > > much unchanged. > > > > > > > > > > > > > > > > > > > > > > > > Producer and consumer creation for Tasks > is > > > > done > > > > > in > > > > > > > the > > > > > > > > > Worker as of > > > > > > > > > > > > KAFKA-7551 and is isolated in two > > functions. > > > We > > > > > > could > > > > > > > > add a > > > > > > > > > two more > > > > > > > > > > > > functions with an extra argument for the > > > > external > > > > > > > > cluster > > > > > > > > > name to be > > > > > > > > > > used > > > > > > > > > > > > and return fitting consumers/producers. > > > > > > > > > > > > The source and sink config would then > > simply > > > > gain > > > > > > an > > > > > > > > > optional setting > > > > > > > > > > to > > > > > > > > > > > > specify the cluster name. > > > > > > > > > > > > > > > > > > > > > > > > I am very sure that I am missing a few > > large > > > > > issues > > > > > > > > with > > > > > > > > > these ideas, > > > > > > > > > > I'm > > > > > > > > > > > > mostly back-of-the-napkin designing here, > > but > > > > it > > > > > > > might > > > > > > > > be > > > > > > > > > worth a > > > > > > > > > > second > > > > > > > > > > > > look. > > > > > > > > > > > > > > > > > > > > > > > > Once we decide to diverge into two > > clusters: > > > > > > > > MirrorMaker and > > > > > > > > > Connect, I > > > > > > > > > > > > think realistically the chance of those > two > > > > ever > > > > > > > being > > > > > > > > > merged again > > > > > > > > > > > because > > > > > > > > > > > > they grow back together is practically > > zero - > > > > > hence > > > > > > > my > > > > > > > > > hesitation. > > > > > > > > > > > > > > > > > > > > > > > > ---- > > > > > > > > > > > > > > > > > > > > > > > > All of that being said, I am absolutely > > happy > > > > to > > > > > > > agree > > > > > > > > to > > > > > > > > > disagree, I > > > > > > > > > > > think > > > > > > > > > > > > to a certain extent this is down to a > > > question > > > > of > > > > > > > > personal > > > > > > > > > > > > style/preference. And as this is your > baby > > > and > > > > > you > > > > > > > > have put > > > > > > > > > a lot more > > > > > > > > > > > > effort and thought into it than I ever > will > > > > I'll > > > > > > shut > > > > > > > > up now > > > > > > > > > :) > > > > > > > > > > > > > > > > > > > > > > > > Again, thanks for all your good work! > > > > > > > > > > > > > > > > > > > > > > > > Best regards, > > > > > > > > > > > > Sönke > > > > > > > > > > > > > > > > > > > > > > > > On Fri, Nov 30, 2018 at 9:00 PM Ryanne > > Dolan > > > < > > > > > > > > > ryannedo...@gmail.com> > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > Thanks Sönke. > > > > > > > > > > > > > > > > > > > > > > > > > > > it just feels to me like an awful lot > > of > > > > > > Connect > > > > > > > > > functionality > > > > > > > > > > would > > > > > > > > > > > > need > > > > > > > > > > > > > to be reimplemented or at least wrapped > > > > > > > > > > > > > > > > > > > > > > > > > > Connect currently has two drivers, > > > > > > > > ConnectDistributed and > > > > > > > > > > > > > ConnectStandalone. Both set up a > Herder, > > > > which > > > > > > > > manages > > > > > > > > > Workers. I've > > > > > > > > > > > > > implemented a third driver which sets > up > > > > > multiple > > > > > > > > Herders, > > > > > > > > > one for > > > > > > > > > > each > > > > > > > > > > > > > Kafka cluster as specified in a config > > > file. > > > > > From > > > > > > > the > > > > > > > > > Herder level > > > > > > > > > > > down, > > > > > > > > > > > > > nothing is changed or duplicated -- > it's > > > just > > > > > > > > Connect. > > > > > > > > > > > > > > > > > > > > > > > > > > For the REST API, Connect wraps a > Herder > > > in a > > > > > > > > RestServer > > > > > > > > > class, which > > > > > > > > > > > > > creates a Jetty server with a few > JAX-RS > > > > > > resources. > > > > > > > > One of > > > > > > > > > these > > > > > > > > > > > > resources > > > > > > > > > > > > > is ConnectorsResource, which is the > real > > > meat > > > > > of > > > > > > > the > > > > > > > > REST > > > > > > > > > API, > > > > > > > > > > enabling > > > > > > > > > > > > > start, stop, creation, deletion, and > > > > > > configuration > > > > > > > of > > > > > > > > > Connectors. > > > > > > > > > > > > > > > > > > > > > > > > > > I've added MirrorRestServer, which > wraps > > a > > > > set > > > > > of > > > > > > > > Herders > > > > > > > > > instead of > > > > > > > > > > > one. > > > > > > > > > > > > > The server exposes a single resource, > > > > > > > > ClustersResource, > > > > > > > > > which is > > > > > > > > > > only a > > > > > > > > > > > > few > > > > > > > > > > > > > lines of code: > > > > > > > > > > > > > > > > > > > > > > > > > > @GET > > > > > > > > > > > > > @Path("/") > > > > > > > > > > > > > public Collection<String> > listClusters() > > { > > > > > > > > > > > > > return clusters.keySet(); > > > > > > > > > > > > > } > > > > > > > > > > > > > > > > > > > > > > > > > > @Path("/{cluster}") > > > > > > > > > > > > > public ConnectorsResource > > > > > > > > > > getConnectorsForCluster(@PathParam("cluster") > > > > > > > > > > > > > cluster) { > > > > > > > > > > > > > return new > > > > > > > > ConnectorsResource(clusters.get(cluster)); > > > > > > > > > > > > > } > > > > > > > > > > > > > > > > > > > > > > > > > > (simplified a bit and subject to > change) > > > > > > > > > > > > > > > > > > > > > > > > > > The ClustersResource defers to the > > existing > > > > > > > > > ConnectorsResource, which > > > > > > > > > > > > again > > > > > > > > > > > > > is most of the Connect API. With this > in > > > > > place, I > > > > > > > > can make > > > > > > > > > requests > > > > > > > > > > > like: > > > > > > > > > > > > > > > > > > > > > > > > > > GET /clusters > > > > > > > > > > > > > > > > > > > > > > > > > > GET /clusters/us-west/connectors > > > > > > > > > > > > > > > > > > > > > > > > > > PUT > > > > /clusters/us-west/connectors/us-east/config > > > > > > > > > > > > > { "topics" : "topic1" } > > > > > > > > > > > > > > > > > > > > > > > > > > etc. > > > > > > > > > > > > > > > > > > > > > > > > > > So on the whole, very little code is > > > involved > > > > > in > > > > > > > > > implementing > > > > > > > > > > > > "MirrorMaker > > > > > > > > > > > > > clusters". I won't rule out adding > > > additional > > > > > > > > features on > > > > > > > > > top of this > > > > > > > > > > > > basic > > > > > > > > > > > > > API, but nothing should require > > > > re-implementing > > > > > > > what > > > > > > > > is > > > > > > > > > already in > > > > > > > > > > > > Connect. > > > > > > > > > > > > > > > > > > > > > > > > > > > Wouldn't it be a viable alternative > to > > > look > > > > > > into > > > > > > > > > extending Connect > > > > > > > > > > > > itself > > > > > > > > > > > > > > > > > > > > > > > > > > Maybe Connect will evolve to the point > > > where > > > > > > > Connect > > > > > > > > > clusters and > > > > > > > > > > > > > MirrorMaker clusters are > > indistinguishable, > > > > > but I > > > > > > > > think > > > > > > > > > this is > > > > > > > > > > > unlikely, > > > > > > > > > > > > > since really no use-case outside > > > replication > > > > > > would > > > > > > > > benefit > > > > > > > > > from the > > > > > > > > > > > added > > > > > > > > > > > > > complexity. Moreover, I think support > for > > > > > > multiple > > > > > > > > Kafka > > > > > > > > > clusters > > > > > > > > > > would > > > > > > > > > > > > be > > > > > > > > > > > > > hard to add without significant changes > > to > > > > the > > > > > > > > existing > > > > > > > > > APIs and > > > > > > > > > > > configs, > > > > > > > > > > > > > which all assume a single Kafka > cluster. > > I > > > > > think > > > > > > > > > Connect-as-a-Service > > > > > > > > > > > and > > > > > > > > > > > > > Replication-as-a-Service are > sufficiently > > > > > > different > > > > > > > > > use-cases that we > > > > > > > > > > > > > should expect the APIs and > configuration > > > > files > > > > > to > > > > > > > be > > > > > > > > at > > > > > > > > > least > > > > > > > > > > slightly > > > > > > > > > > > > > different, even if both use the same > > > > framework > > > > > > > > underneath. > > > > > > > > > That > > > > > > > > > > said, I > > > > > > > > > > > > do > > > > > > > > > > > > > plan to contribute a few improvements > to > > > the > > > > > > > Connect > > > > > > > > > framework in > > > > > > > > > > > support > > > > > > > > > > > > > of MM2 -- just nothing within the scope > > of > > > > the > > > > > > > > current KIP. > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks again! > > > > > > > > > > > > > Ryanne > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Fri, Nov 30, 2018 at 3:47 AM Sönke > > > Liebau > > > > > > > > > > > > > <soenke.lie...@opencore.com.invalid> > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > Hi Ryanne, > > > > > > > > > > > > > > > > > > > > > > > > > > > > thanks. I missed the remote to remote > > > > > > replication > > > > > > > > > scenario in my > > > > > > > > > > > train > > > > > > > > > > > > of > > > > > > > > > > > > > > thought, you are right. > > > > > > > > > > > > > > > > > > > > > > > > > > > > That being said I have to admit that > I > > am > > > > not > > > > > > yet > > > > > > > > fully > > > > > > > > > on board > > > > > > > > > > with > > > > > > > > > > > > the > > > > > > > > > > > > > > concept, sorry. But I might just be > > > > > > > > misunderstanding > > > > > > > > > what your > > > > > > > > > > > > intention > > > > > > > > > > > > > > is. Let me try and explain what I > think > > > it > > > > is > > > > > > you > > > > > > > > are > > > > > > > > > trying to do > > > > > > > > > > > and > > > > > > > > > > > > > why > > > > > > > > > > > > > > I am on the fence about that and take > > it > > > > from > > > > > > > > there. > > > > > > > > > > > > > > > > > > > > > > > > > > > > You want to create an extra > mirrormaker > > > > > driver > > > > > > > > class > > > > > > > > > which will > > > > > > > > > > take > > > > > > > > > > > > > > multiple clusters as configuration > > > options. > > > > > > Based > > > > > > > > on > > > > > > > > > these clusters > > > > > > > > > > > it > > > > > > > > > > > > > will > > > > > > > > > > > > > > then reuse the connect workers and > > create > > > > as > > > > > > many > > > > > > > > as > > > > > > > > > necessary to > > > > > > > > > > be > > > > > > > > > > > > able > > > > > > > > > > > > > > to replicate to/from each of those > > > > configured > > > > > > > > clusters. > > > > > > > > > It will > > > > > > > > > > then > > > > > > > > > > > > > > expose a rest api (since you stated > > > subset > > > > of > > > > > > > > Connect > > > > > > > > > rest api I > > > > > > > > > > > assume > > > > > > > > > > > > > it > > > > > > > > > > > > > > will be a new / own one?) that > allows > > > > users > > > > > to > > > > > > > > send > > > > > > > > > requests like > > > > > > > > > > > > > > "replicate topic a from cluster 1 to > > > > cluster > > > > > 1" > > > > > > > and > > > > > > > > > start a > > > > > > > > > > connector > > > > > > > > > > > > on > > > > > > > > > > > > > > the relevant worker that can offer > this > > > > > > "route". > > > > > > > > > > > > > > This can be extended to a cluster by > > > > starting > > > > > > > > mirror > > > > > > > > > maker drivers > > > > > > > > > > on > > > > > > > > > > > > > other > > > > > > > > > > > > > > nodes with the same config and it > would > > > > offer > > > > > > all > > > > > > > > the > > > > > > > > > connect > > > > > > > > > > > features > > > > > > > > > > > > of > > > > > > > > > > > > > > balancing restarting in case of > failure > > > > etc. > > > > > > > > > > > > > > > > > > > > > > > > > > > > If this understanding is correct then > > it > > > > just > > > > > > > > feels to > > > > > > > > > me like an > > > > > > > > > > > awful > > > > > > > > > > > > > lot > > > > > > > > > > > > > > of Connect functionality would need > to > > be > > > > > > > > reimplemented > > > > > > > > > or at least > > > > > > > > > > > > > > wrapped, which potentially could mean > > > > > > additional > > > > > > > > effort > > > > > > > > > for > > > > > > > > > > > maintaining > > > > > > > > > > > > > and > > > > > > > > > > > > > > extending Connect down the line. > > Wouldn't > > > > it > > > > > > be a > > > > > > > > viable > > > > > > > > > > alternative > > > > > > > > > > > to > > > > > > > > > > > > > > look into extending Connect itself to > > > allow > > > > > > > > defining > > > > > > > > > "remote > > > > > > > > > > > clusters" > > > > > > > > > > > > > > which can then be specified in the > > > > connector > > > > > > > > config to > > > > > > > > > be used > > > > > > > > > > > instead > > > > > > > > > > > > of > > > > > > > > > > > > > > the local cluster? I imagine that > > change > > > > > itself > > > > > > > > would > > > > > > > > > not be too > > > > > > > > > > > > > extensive, > > > > > > > > > > > > > > the main effort would probably be in > > > coming > > > > > up > > > > > > > > with a > > > > > > > > > sensible > > > > > > > > > > config > > > > > > > > > > > > > > structure and ensuring backwards > > > > > compatibility > > > > > > > with > > > > > > > > > existing > > > > > > > > > > > connector > > > > > > > > > > > > > > configs. > > > > > > > > > > > > > > This would still allow to use a > regular > > > > > Connect > > > > > > > > cluster > > > > > > > > > for an > > > > > > > > > > > > arbitrary > > > > > > > > > > > > > > number of clusters, thus still > having a > > > > > > dedicated > > > > > > > > > MirrorMaker > > > > > > > > > > cluster > > > > > > > > > > > > by > > > > > > > > > > > > > > running only MirrorMaker Connectors > in > > > > there > > > > > if > > > > > > > > you want > > > > > > > >
