Also with 2 brokers initially, is the replication factor also 2 at the
beginning or just 1?
On Mon, Jul 28, 2014 at 1:55 PM, Jad Naous <jad.na...@appdynamics.com>
wrote:
> The logs are quite large. I've sifted through them, and I'm attaching the
> logs for the relevant parts where the lost message goes through the system.
> Here's what the test does:
>
> 0) Start two brokers, one producer, one consumer. Topic has 20 partitions,
> using default partitioning scheme (which seems to send data to only a
> couple of partitions when the keys are null, but that doesn't matter for
> this test).
> 1) Start a data generator sending data through Kafka continuously
> 2) Start a new broker
> 3) Reassign partitions: {"version": 1, "partitions":[
> {"topic":"EventServiceUpsertTopic","partition":0, "replicas":
> [0, 1, 2]},
> {"topic":"EventServiceUpsertTopic","partition":1, "replicas":
> [1, 2, 0]},
> {"topic":"EventServiceUpsertTopic","partition":2, "replicas":
> [2, 0, 1]},
> {"topic":"EventServiceUpsertTopic","partition":3, "replicas":
> [0, 1, 2]},
> {"topic":"EventServiceUpsertTopic","partition":4, "replicas":
> [1, 2, 0]},
> {"topic":"EventServiceUpsertTopic","partition":5, "replicas":
> [2, 0, 1]},
> {"topic":"EventServiceUpsertTopic","partition":6, "replicas":
> [0, 1, 2]},
> {"topic":"EventServiceUpsertTopic","partition":7, "replicas":
> [1, 2, 0]},
> {"topic":"EventServiceUpsertTopic","partition":8, "replicas":
> [2, 0, 1]},
> {"topic":"EventServiceUpsertTopic","partition":9, "replicas":
> [0, 1, 2]},
> {"topic":"EventServiceUpsertTopic","partition":10, "replicas":
> [1, 2, 0]},
> {"topic":"EventServiceUpsertTopic","partition":11, "replicas":
> [2, 0, 1]},
> {"topic":"EventServiceUpsertTopic","partition":12, "replicas":
> [0, 1, 2]},
> {"topic":"EventServiceUpsertTopic","partition":13, "replicas":
> [1, 2, 0]},
> {"topic":"EventServiceUpsertTopic","partition":14, "replicas":
> [2, 0, 1]},
> {"topic":"EventServiceUpsertTopic","partition":15, "replicas":
> [0, 1, 2]},
> {"topic":"EventServiceUpsertTopic","partition":16, "replicas":
> [1, 2, 0]},
> {"topic":"EventServiceUpsertTopic","partition":17, "replicas":
> [2, 0, 1]},
> {"topic":"EventServiceUpsertTopic","partition":18, "replicas":
> [0, 1, 2]},
> {"topic":"EventServiceUpsertTopic","partition":19, "replicas":
> [1, 2, 0]}]}
> 4) Wait until reassignment is complete (i.e. until
> ZkUtils.getPartitionsBeingReassigned() returns empty map)
> 5) Wait until all replicas are caught up (i.e. until
> ZkUtils.getLeaderAndIsrForPartition() returns all brokers in the ISR for
> each partition)
> 6) Trigger leader re-election by calling the
> PreferredReplicaLeaderElectionCommand
> 7) Wait until all the leaders are the preferred leaders for partitions
> according to the replica reassignment from step 3
> 8) Stop the data generator
> 9) Check that all the data was consumed
>
> You can seem from the producer.log that the data: {"field1": ["10"],
> "idField": "id-5-59"} was sent to broker0 successfully, but the consumer
> never sees it.
>
> Thanks,
> Jad.
>
>
>
> On Mon, Jul 28, 2014 at 10:33 AM, Guozhang Wang <wangg...@gmail.com>
> wrote:
>
>> Also, for the initial two replica case did you see any error/warning logs
>> on your producers?
>>
>> Guozhang
>>
>>
>> On Mon, Jul 28, 2014 at 10:32 AM, Guozhang Wang <wangg...@gmail.com>
>> wrote:
>>
>> > Hi Jad,
>> >
>> > Just to clarify, you also see data loss when you created the topic with
>> > replica factor 2, and two replicas running, and after an auto leader
>> > election triggered? If that is the case could you attach the logs of all
>> > involved brokers here?
>> >
>> > For your second question, KAFKA-1211 is designed to handle that case.
>> >
>> > Guozhang
>> >
>> >
>> > On Mon, Jul 28, 2014 at 10:18 AM, Jad Naous <jad.na...@appdynamics.com>
>> > wrote:
>> >
>> >> Guozhang,
>> >>
>> >> I have actually also seen this happen when there are two replicas
>> >> initially. So this problem is not limited to 1 replica. The issue is
>> the
>> >> truncation after leader election, which will also happen on the second
>> >> replica.
>> >>
>> >> Coming back to your objections:
>> >>
>> >>
>> >> First case: inconsistency between replicas
>> >> > 1) currently replica 1 is the current leader
>> >> > replica 1: m1 m2 m3
>> >> > replica 2: m1 m2
>> >> > 2) replica 1 fails, and replica 2 becomes the new leader and accept
>> >> > messages 4 and 5:
>> >> > replica 1: m1 m2 m3
>> >> > replica 2: m1 m2 m4 m5
>> >> > 3) replica 1 resumes, and does not truncate to HW, then it will still
>> >> > maintain m3, which is actually never "committed". Say leader moves to
>> >> > replica 1 again, we can ended up with:
>> >> > replica 1: m1 m2 m3 m6
>> >> > replica 2: m1 m2 m4 m5
>> >>
>> >>
>> >> I see. So when a replica resumes, it has to truncate to the last HW it
>> saw
>> >> before it died.
>> >>
>> >>
>> >> >
>> >> > Second case: inconsistency between server and clients:
>> >> > 1) producer send message m3 with ack=-1:
>> >> > replica 1: m1 m2 m3
>> >> > replica 2: m1 m2 m3
>> >> > replica 3: m1 m2
>> >> > 2) the response is held until all replicas also gets m3, say at this
>> >> time
>> >> > current leader replica 1 fails and replica 3 re-elects. If replica 3
>> >> gets
>> >> > up to the largest LEO it will also get m3.
>> >> > replica 2: m1 m2 m3
>> >> > replica 3: m1 m2 m3
>> >> > 3) But m3 is not actually "committed" by the time replica 1 fails;
>> when
>> >> > producer gets the error at the time replica 1 fails, it will think
>> that
>> >> m3
>> >> > was not successfully sent, so retry sending m3:
>> >> > replica 2: m1 m2 m3 m3
>> >> > replica 3: m1 m2 m3 m3
>> >>
>> >>
>> >> So on failure, all nodes need to truncate to the HW. But if there's no
>> >> failure, then truncating would lose data unnecessarily. Maybe those two
>> >> scenarios need to be handled differently?
>> >>
>> >> Jad.
>> >>
>> >>
>> >> On Mon, Jul 28, 2014 at 9:58 AM, Guozhang Wang <wangg...@gmail.com>
>> >> wrote:
>> >>
>> >> > Jun, Jad,
>> >> >
>> >> > I think in this case data loss can still happen, since the replica
>> >> factor
>> >> > was previously one, and in handling the produce requests, if the
>> server
>> >> > decides that all the produced partitions have a replica factor of 1
>> it
>> >> will
>> >> > also directly send back the response instead of putting the request
>> into
>> >> > purgatory even if currently the number of replicas is 2 (for details
>> >> look
>> >> > at ReplicaManager.getReplicationFactorForPartition and search of the
>> >> usage
>> >> > of Partition.replicationFactor).
>> >> >
>> >> > I now agree that this is not related to KAFKA-1211 but a different
>> small
>> >> > bug. We need to probably file another JIRA for this. But I think
>> after
>> >> this
>> >> > one is fixed (which should be much easier than KAFKA-1211), Jad's
>> >> scenario
>> >> > should not cause data loss anymore.
>> >> >
>> >> > Guozhang
>> >> >
>> >> >
>> >> > On Sun, Jul 27, 2014 at 6:11 PM, Jad Naous <
>> jad.na...@appdynamics.com>
>> >> > wrote:
>> >> >
>> >> > > So in summary, is it true to say that currently triggering leader
>> >> > > reelection is not a safe operation? I have been able to reproduce
>> that
>> >> > > message loss pretty reliably in tests. If that is the case, isn't
>> >> that an
>> >> > > important operation in a large cluster where nodes go up and down?
>> >> > > On Jul 25, 2014 10:00 PM, "Jun Rao" <jun...@gmail.com> wrote:
>> >> > >
>> >> > > > Actually, I don't think KAFKA-1211 will happen with just 2
>> replicas.
>> >> > > When a
>> >> > > > replica becomes a leader, it never truncates its log. Only when a
>> >> > replica
>> >> > > > becomes follower, it truncates its log to HW. So in this
>> particular
>> >> > case,
>> >> > > > the new leader will not truncate data to offset 8.
>> >> > > >
>> >> > > > Thanks,
>> >> > > >
>> >> > > > Jun
>> >> > > >
>> >> > > >
>> >> > > > On Fri, Jul 25, 2014 at 3:37 PM, Guozhang Wang <
>> wangg...@gmail.com>
>> >> > > wrote:
>> >> > > >
>> >> > > > > Hi Jad,
>> >> > > > >
>> >> > > > > Yes. In this case I think you are actually hitting KAFKA-1211.
>> The
>> >> > > > summary
>> >> > > > > of the issue is that, it takes one more fetch request round
>> trip
>> >> for
>> >> > > the
>> >> > > > > follower replica to advance the HW after the leader has
>> advanced
>> >> HW.
>> >> > So
>> >> > > > for
>> >> > > > > your case, the whole process is like this:
>> >> > > > >
>> >> > > > > 1. leader LEO at 10, follower LEO at 8. Both leader and
>> follower
>> >> > knows
>> >> > > > the
>> >> > > > > LEO is at 8.
>> >> > > > > 2. Follower fetch data on Leader starting at 8, leader records
>> its
>> >> > LEO
>> >> > > as
>> >> > > > > 8.
>> >> > > > > 3. Follower gets 9 and 10 and append to its local log.
>> >> > > > > 4. Follower fetch data on Leader starting at 10, leader records
>> >> its
>> >> > LEO
>> >> > > > as
>> >> > > > > 10; now leader knows follower has caught up, it advances its HW
>> >> to 10
>> >> > > and
>> >> > > > > adds the follower to ISR (but follower does not know that yet!
>> It
>> >> > still
>> >> > > > > think the HW is 8).
>> >> > > > > 5. Leader's fetch response gets back to follower, and now the
>> >> > follower
>> >> > > > > knows that HW has been updated to 10.
>> >> > > > >
>> >> > > > > And let's say there is a leader election between step 4) and
>> 5),
>> >> for
>> >> > > your
>> >> > > > > case it is due to preferred leader election, but it could also
>> be
>> >> > that
>> >> > > > > current leader fails, etc. Then on becoming the new leader the
>> >> > follower
>> >> > > > > will truncate its data to 8, which is the HW it knows. Hence
>> the
>> >> data
>> >> > > > loss.
>> >> > > > >
>> >> > > > > The proposed solution in KAFKA-1211 will tackle this issue.
>> >> > > > >
>> >> > > > > Guozhang
>> >> > > > >
>> >> > > > >
>> >> > > > > On Fri, Jul 25, 2014 at 2:48 PM, Jad Naous <
>> >> > jad.na...@appdynamics.com>
>> >> > > > > wrote:
>> >> > > > >
>> >> > > > > > Hi Guozhang,
>> >> > > > > >
>> >> > > > > > Yes, broker 1 is in the ISR (in fact, I wait for broker 1 to
>> be
>> >> in
>> >> > > the
>> >> > > > > ISR
>> >> > > > > > before triggering election). However, I think there is
>> something
>> >> > > still
>> >> > > > > > amiss. I still see data loss. Here are some relevant log
>> lines
>> >> from
>> >> > > > > broker
>> >> > > > > > 0 (different test run). The log on broker 0 is getting
>> >> truncated,
>> >> > > > losing
>> >> > > > > > some messages.
>> >> > > > > >
>> >> > > > > > [2014-07-25 10:40:02,134] [DEBUG] [kafka-request-handler-5]
>> >> > > > > > [kafka.cluster.Partition] Partition
>> >> [EventServiceUpsertTopic,19]
>> >> > on
>> >> > > > > broker
>> >> > > > > > 0: Old hw for partition [EventServiceUpsertTopic,19] is 8082.
>> >> New
>> >> > hw
>> >> > > is
>> >> > > > > > 8082. All leo's are 8111,8082
>> >> > > > > >
>> >> > > > > > [2014-07-25 10:40:02,134] [DEBUG] [kafka-request-handler-5]
>> >> > > > > > [kafka.server.KafkaApis] [KafkaApi-0] Produce to local log
>> in
>> >> 1 ms
>> >> > > > > >
>> >> > > > > > [2014-07-25 10:40:02,134] [DEBUG]
>> >> > > [main-SendThread(localhost:49893)]
>> >> > > > > > [org.apache.zookeeper.ClientCnxn] Reading reply
>> >> > > > > > sessionid:0x476e9a9e9a0001, packet:: clientPath:null
>> >> > serverPath:null
>> >> > > > > > finished:false header:: 729,5 replyHeader:: 729,4294968217,0
>> >> > > > request::
>> >> > > > > >
>> >> > > > > >
>> >> > > > >
>> >> > > >
>> >> > >
>> >> >
>> >>
>> '/brokers/topics/EventServiceUpsertTopic/partitions/5/state,#7b22636f6e74726f6c6c65725f65706f6368223a312c226c6561646572223a312c2276657273696f6e223a312c226c65616465725f65706f6368223a332c22697372223a5b302c315d7d,3
>> >> > > > > > response::
>> >> > > > > >
>> >> > > > > >
>> >> > > > >
>> >> > > >
>> >> > >
>> >> >
>> >>
>> s{4294967416,4294968217,1406309966419,1406310002132,4,0,0,0,74,0,4294967416}
>> >> > > > > >
>> >> > > > > > [2014-07-25 10:40:02,134] [DEBUG] [kafka-processor-49917-2]
>> >> > > > > > [kafka.request.logger] Completed request:Name:
>> ProducerRequest;
>> >> > > > Version:
>> >> > > > > > 0; CorrelationId: 16248; ClientId: ; RequiredAcks: -1;
>> >> > AckTimeoutMs:
>> >> > > > > 10000
>> >> > > > > > ms from client /127.0.0.1:50168
>> >> > > > > >
>> >> > > > > >
>> >> > > > >
>> >> > > >
>> >> > >
>> >> >
>> >>
>> ;totalTime:1,requestQueueTime:0,localTime:1,remoteTime:0,responseQueueTime:0,sendTime:0
>> >> > > > > >
>> >> > > > > > [2014-07-25 10:40:02,134] [DEBUG]
>> >> > > > > >
>> >> > > >
>> >> >
>> >>
>> [ZkClient-EventThread-13-localhost:49893,localhost:49896,localhost:49899]
>> >> > > > > > [kafka.utils.ZkUtils$] Conditional update of path
>> >> > > > > > /brokers/topics/EventServiceUpsertTopic/partitions/5/state
>> with
>> >> > value
>> >> > > > > >
>> >> > > > >
>> >> > > >
>> >> > >
>> >> >
>> >>
>> {"controller_epoch":1,"leader":1,"version":1,"leader_epoch":3,"isr":[0,1]}
>> >> > > > > > and expected version 3 succeeded, returning the new version:
>> 4
>> >> > > > > >
>> >> > > > > > [2014-07-25 10:40:02,136] [DEBUG]
>> >> > > > > >
>> >> > > >
>> >> >
>> >>
>> [ZkClient-EventThread-13-localhost:49893,localhost:49896,localhost:49899]
>> >> > > > > > [k.controller.PartitionStateMachine] [Partition state
>> machine
>> >> on
>> >> > > > > > Controller 0]: After leader election, leader cache is
>> updated to
>> >> > > > > > Map([EventServiceUpsertTopic,18] ->
>> >> > > > > > (Leader:0,ISR:0,LeaderEpoch:0,ControllerEpoch:1),
>> >> > > > > > [EventServiceUpsertTopic,4] ->
>> >> > > > > > (Leader:0,ISR:0,LeaderEpoch:0,ControllerEpoch:1),
>> >> > > > > > [EventServiceUpsertTopic,7] ->
>> >> > > > > > (Leader:1,ISR:0,1,LeaderEpoch:3,ControllerEpoch:1),
>> >> > > > > > [EventServiceUpsertTopic,17] ->
>> >> > > > > > (Leader:1,ISR:0,1,LeaderEpoch:3,ControllerEpoch:1),
>> >> > > > > > [EventServiceUpsertTopic,16] ->
>> >> > > > > > (Leader:0,ISR:0,LeaderEpoch:0,ControllerEpoch:1),
>> >> > > > > > [EventServiceUpsertTopic,5] ->
>> >> > > > > > (Leader:1,ISR:0,1,LeaderEpoch:3,ControllerEpoch:1),
>> >> > > > > > [EventServiceUpsertTopic,10] ->
>> >> > > > > > (Leader:0,ISR:0,LeaderEpoch:0,ControllerEpoch:1),
>> >> > > > > > [EventServiceUpsertTopic,1] ->
>> >> > > > > > (Leader:1,ISR:0,1,LeaderEpoch:3,ControllerEpoch:1),
>> >> > > > > > [EventServiceUpsertTopic,13] ->
>> >> > > > > > (Leader:1,ISR:0,1,LeaderEpoch:3,ControllerEpoch:1),
>> >> > > > > > [EventServiceUpsertTopic,9] ->
>> >> > > > > > (Leader:1,ISR:0,1,LeaderEpoch:3,ControllerEpoch:1),
>> >> > > > > > [EventServiceUpsertTopic,8] ->
>> >> > > > > > (Leader:0,ISR:0,LeaderEpoch:0,ControllerEpoch:1),
>> >> > > > > > [EventServiceUpsertTopic,11] ->
>> >> > > > > > (Leader:1,ISR:0,1,LeaderEpoch:3,ControllerEpoch:1),
>> >> > > > > > [EventServiceUpsertTopic,6] ->
>> >> > > > > > (Leader:0,ISR:0,LeaderEpoch:0,ControllerEpoch:1),
>> >> > > > > > [EventServiceUpsertTopic,12] ->
>> >> > > > > > (Leader:0,ISR:0,LeaderEpoch:0,ControllerEpoch:1),
>> >> > > > > > [EventServiceUpsertTopic,2] ->
>> >> > > > > > (Leader:0,ISR:0,LeaderEpoch:0,ControllerEpoch:1),
>> >> > > > > > [EventServiceUpsertTopic,3] ->
>> >> > > > > > (Leader:1,ISR:0,1,LeaderEpoch:3,ControllerEpoch:1),
>> >> > > > > > [EventServiceUpsertTopic,14] ->
>> >> > > > > > (Leader:0,ISR:0,LeaderEpoch:0,ControllerEpoch:1), [
>> >> > > > > > EventServiceUpsertTopic,19] ->
>> >> > > > > > (Leader:1,ISR:0,1,LeaderEpoch:3,ControllerEpoch:1),
>> >> > > > > > [EventServiceUpsertTopic,0] ->
>> >> > > > > > (Leader:0,ISR:0,LeaderEpoch:0,ControllerEpoch:1),
>> >> > > > > > [EventServiceUpsertTopic,15] ->
>> >> > > > > > (Leader:1,ISR:0,1,LeaderEpoch:3,ControllerEpoch:1))
>> >> > > > > >
>> >> > > > > > [2014-07-25 10:40:02,136] [DEBUG] [kafka-request-handler-1]
>> >> > > > > > [kafka.cluster.Partition] Partition
>> >> [EventServiceUpsertTopic,19]
>> >> > on
>> >> > > > > broker
>> >> > > > > > 0: Old hw for partition [EventServiceUpsertTopic,19] is 8082.
>> >> New
>> >> > hw
>> >> > > is
>> >> > > > > > 8082. All leo's are 8112,8082
>> >> > > > > >
>> >> > > > > > [2014-07-25 10:40:02,136] [DEBUG] [kafka-request-handler-1]
>> >> > > > > > [kafka.server.KafkaApis] [KafkaApi-0] Produce to local log
>> in
>> >> 0 ms
>> >> > > > > >
>> >> > > > > > [2014-07-25 10:40:02,137] [DEBUG] [kafka-processor-49917-2]
>> >> > > > > > [kafka.request.logger] Completed request:Name:
>> ProducerRequest;
>> >> > > > Version:
>> >> > > > > > 0; CorrelationId: 16250; ClientId: ; RequiredAcks: -1;
>> >> > AckTimeoutMs:
>> >> > > > > 10000
>> >> > > > > > ms from client /127.0.0.1:50168
>> >> > > > > >
>> >> > > > > >
>> >> > > > >
>> >> > > >
>> >> > >
>> >> >
>> >>
>> ;totalTime:1,requestQueueTime:0,localTime:1,remoteTime:0,responseQueueTime:0,sendTime:0
>> >> > > > > >
>> >> > > > > > [2014-07-25 10:40:02,140] [INFO ]
>> >> > > > > >
>> >> > > >
>> >> >
>> >>
>> [ZkClient-EventThread-13-localhost:49893,localhost:49896,localhost:49899]
>> >> > > > > > [kafka.controller.KafkaController] [Controller 0]:
>> Partition [
>> >> > > > > > EventServiceUpsertTopic,19] completed preferred replica
>> leader
>> >> > > > election.
>> >> > > > > > New leader is 1
>> >> > > > > >
>> >> > > > > > [2014-07-25 10:40:02,140] [INFO ]
>> >> > > > > >
>> >> > > >
>> >> >
>> >>
>> [ZkClient-EventThread-13-localhost:49893,localhost:49896,localhost:49899]
>> >> > > > > > [kafka.controller.KafkaController] [Controller 0]: Partition
>> >> > > > > > [EventServiceUpsertTopic,5] completed preferred replica
>> leader
>> >> > > > election.
>> >> > > > > > New leader is 1
>> >> > > > > >
>> >> > > > > > [2014-07-25 10:40:02,142] [DEBUG]
>> >> > > [main-SendThread(localhost:49893)]
>> >> > > > > > [org.apache.zookeeper.ClientCnxn] Got notification
>> >> > > > > > sessionid:0x476e9a9e9a0001
>> >> > > > > >
>> >> > > > > > [2014-07-25 10:40:02,142] [DEBUG]
>> >> > > [main-SendThread(localhost:49893)]
>> >> > > > > > [org.apache.zookeeper.ClientCnxn] Got WatchedEvent
>> >> > > state:SyncConnected
>> >> > > > > > type:NodeDeleted path:/admin/preferred_replica_election for
>> >> > sessionid
>> >> > > > > > 0x476e9a9e9a0001
>> >> > > > > >
>> >> > > > > > [2014-07-25 10:40:02,143] [DEBUG]
>> >> > > [main-SendThread(localhost:49893)]
>> >> > > > > > [org.apache.zookeeper.ClientCnxn] Reading reply
>> >> > > > > > sessionid:0x476e9a9e9a0001, packet:: clientPath:null
>> >> > serverPath:null
>> >> > > > > > finished:false header:: 730,2 replyHeader:: 730,4294968218,0
>> >> > > > request::
>> >> > > > > > '/admin/preferred_replica_election,-1 response:: null
>> >> > > > > >
>> >> > > > > > [2014-07-25 10:40:02,145] [INFO ] [kafka-request-handler-0]
>> >> > > > > > [kafka.server.ReplicaFetcherManager] [ReplicaFetcherManager
>> on
>> >> > > broker
>> >> > > > 0]
>> >> > > > > > Removed fetcher for partitions
>> >> > > > > >
>> >> > > > > >
>> >> > > > >
>> >> > > >
>> >> > >
>> >> >
>> >>
>> [EventServiceUpsertTopic,13],[EventServiceUpsertTopic,11],[EventServiceUpsertTopic,17],[EventServiceUpsertTopic,7],[EventServiceUpsertTopic,9],[EventServiceUpsertTopic,1],[EventServiceUpsertTopic,15],[
>> >> > > > > > EventServiceUpsertTopic,19
>> >> > > > > > ],[EventServiceUpsertTopic,3],[EventServiceUpsertTopic,5]
>> >> > > > > >
>> >> > > > > > [2014-07-25 10:40:02,153] [INFO ] [kafka-request-handler-0]
>> >> > > > > > [kafka.log.Log] Truncating log EventServiceUpsertTopic-19 to
>> >> > offset
>> >> > > > > 8082.
>> >> > > > > >
>> >> > > > > > [2014-07-25 10:40:02,159] [INFO ] [kafka-request-handler-0]
>> >> > > > > > [kafka.log.Log] Truncating log EventServiceUpsertTopic-5 to
>> >> offset
>> >> > > 0.
>> >> > > > > >
>> >> > > > > >
>> >> > > > > > I have removed some irrelevant lines. As you can see, the log
>> >> for
>> >> > > > > > EventServiceUpsertTopic-19 is being truncated, losing
>> messages
>> >> that
>> >> > > > have
>> >> > > > > > not yet been replicated to broker 1. I'm not sure exactly
>> what
>> >> the
>> >> > > > issue
>> >> > > > > > is. Maybe new requests should be completely blocked after
>> leader
>> >> > > > election
>> >> > > > > > until the new leader catches up to the messages that have
>> been
>> >> > acked
>> >> > > > and
>> >> > > > > it
>> >> > > > > > has not yet received.
>> >> > > > > >
>> >> > > > > > Thanks,
>> >> > > > > >
>> >> > > > > > Jad.
>> >> > > > > >
>> >> > > > > >
>> >> > > > > > On Fri, Jul 25, 2014 at 2:14 PM, Guozhang Wang <
>> >> wangg...@gmail.com
>> >> > >
>> >> > > > > wrote:
>> >> > > > > >
>> >> > > > > > > Hello Jad,
>> >> > > > > > >
>> >> > > > > > > I double-checked the source code again, and found that
>> >> actually
>> >> > the
>> >> > > > > > > preferred leader elector does consider whether the selected
>> >> > replica
>> >> > > > is
>> >> > > > > in
>> >> > > > > > > ISR or not. This means that by the time the election is
>> >> > triggered,
>> >> > > > > > broker 1
>> >> > > > > > > is added to ISR by broker 0. Could you check before step
>> 3, is
>> >> > > there
>> >> > > > > any
>> >> > > > > > > log entries on broker 0 adding broker 1 to ISR or updating
>> HW
>> >> to
>> >> > > 975?
>> >> > > > > > >
>> >> > > > > > >
>> >> > > > > > > On Thu, Jul 24, 2014 at 4:21 PM, Jad Naous <
>> >> > > > jad.na...@appdynamics.com>
>> >> > > > > > > wrote:
>> >> > > > > > >
>> >> > > > > > > > Hi,
>> >> > > > > > > >
>> >> > > > > > > > I have a test that continuously sends messages to one
>> >> broker,
>> >> > > > brings
>> >> > > > > up
>> >> > > > > > > > another broker, and adds it as a replica for all
>> partitions,
>> >> > with
>> >> > > > it
>> >> > > > > > > being
>> >> > > > > > > > the preferred replica for some. I have
>> >> > > > > > auto.leader.rebalance.enable=true,
>> >> > > > > > > > so replica election gets triggered. Data is being pumped
>> to
>> >> the
>> >> > > old
>> >> > > > > > > broker
>> >> > > > > > > > all the while. It seems that some data gets lost while
>> >> > switching
>> >> > > > over
>> >> > > > > > to
>> >> > > > > > > > the new leader. Is this a bug, or do I have something
>> >> > > > misconfigured?
>> >> > > > > I
>> >> > > > > > > also
>> >> > > > > > > > have request.required.acks=-1 on the producer.
>> >> > > > > > > >
>> >> > > > > > > > Here's what I think is happening:
>> >> > > > > > > >
>> >> > > > > > > > 1. Producer writes message to broker 0,
>> >> > > > [EventServiceUpsertTopic,13],
>> >> > > > > > w/
>> >> > > > > > > > broker 0 currently leader, with ISR=(0), so write returns
>> >> > > > > successfully,
>> >> > > > > > > > even when acks = -1. Correlation id 35836
>> >> > > > > > > >
>> >> > > > > > > > Producer log:
>> >> > > > > > > >
>> >> > > > > > > > [2014-07-24 14:44:26,991] [DEBUG] [dw-97 - PATCH
>> >> > > > > > > >
>> >> > > > > > > >
>> >> > > > > > >
>> >> > > > > >
>> >> > > > >
>> >> > > >
>> >> > >
>> >> >
>> >>
>> /v1/events/type_for_test_bringupNewBroker_shouldRebalance_shouldNotLoseData/event?_idPath=idField&_mergeFields=field1]
>> >> > > > > > > > [kafka.producer.BrokerPartitionInfo] Partition
>> >> > > > > > > > [EventServiceUpsertTopic,13] has leader 0
>> >> > > > > > > >
>> >> > > > > > > > [2014-07-24 14:44:26,993] [DEBUG] [dw-97 - PATCH
>> >> > > > > > > >
>> >> > > > > > > >
>> >> > > > > > >
>> >> > > > > >
>> >> > > > >
>> >> > > >
>> >> > >
>> >> >
>> >>
>> /v1/events/type_for_test_bringupNewBroker_shouldRebalance_shouldNotLoseData/event?_idPath=idField&_mergeFields=field1]
>> >> > > > > > > > [k.producer.async.DefaultEventHandler] Producer sent
>> >> messages
>> >> > > with
>> >> > > > > > > > correlation id 35836 for topics
>> >> [EventServiceUpsertTopic,13] to
>> >> > > > > broker
>> >> > > > > > 0
>> >> > > > > > > on
>> >> > > > > > > > localhost:56821
>> >> > > > > > > > 2. Broker 1 is still catching up
>> >> > > > > > > >
>> >> > > > > > > > Broker 0 Log:
>> >> > > > > > > >
>> >> > > > > > > > [2014-07-24 14:44:26,992] [DEBUG]
>> >> [kafka-request-handler-3]
>> >> > > > > > > > [kafka.cluster.Partition] Partition
>> >> > [EventServiceUpsertTopic,13]
>> >> > > > on
>> >> > > > > > > broker
>> >> > > > > > > > 0: Old hw for partition [EventServiceUpsertTopic,13] is
>> 971.
>> >> > New
>> >> > > hw
>> >> > > > > is
>> >> > > > > > > 971.
>> >> > > > > > > > All leo's are 975,971
>> >> > > > > > > >
>> >> > > > > > > > [2014-07-24 14:44:26,992] [DEBUG]
>> >> [kafka-request-handler-3]
>> >> > > > > > > > [kafka.server.KafkaApis] [KafkaApi-0] Produce to local
>> log
>> >> in
>> >> > 0
>> >> > > ms
>> >> > > > > > > >
>> >> > > > > > > > [2014-07-24 14:44:26,992] [DEBUG]
>> >> [kafka-processor-56821-0]
>> >> > > > > > > > [kafka.request.logger] Completed request:Name:
>> >> > ProducerRequest;
>> >> > > > > > Version:
>> >> > > > > > > > 0; CorrelationId: 35836; ClientId: ; RequiredAcks: -1;
>> >> > > > AckTimeoutMs:
>> >> > > > > > > 10000
>> >> > > > > > > > ms from client /127.0.0.1:57086
>> >> > > > > > > >
>> >> > > > > > > >
>> >> > > > > > >
>> >> > > > > >
>> >> > > > >
>> >> > > >
>> >> > >
>> >> >
>> >>
>> ;totalTime:0,requestQueueTime:0,localTime:0,remoteTime:0,responseQueueTime:0,sendTime:0
>> >> > > > > > > > 3. Leader election is triggered by the scheduler:
>> >> > > > > > > >
>> >> > > > > > > > Broker 0 Log:
>> >> > > > > > > >
>> >> > > > > > > > [2014-07-24 14:44:26,991] [INFO ] [kafka-scheduler-0]
>> >> > > > > > > > [k.c.PreferredReplicaPartitionLeaderSelector]
>> >> > > > > > > > [PreferredReplicaPartitionLeaderSelector]: Current
>> leader 0
>> >> for
>> >> > > > > > > partition [
>> >> > > > > > > > EventServiceUpsertTopic,13] is not the preferred replica.
>> >> > > > Trigerring
>> >> > > > > > > > preferred replica leader election
>> >> > > > > > > >
>> >> > > > > > > > [2014-07-24 14:44:26,993] [DEBUG] [kafka-scheduler-0]
>> >> > > > > > > > [kafka.utils.ZkUtils$] Conditional update of path
>> >> > > > > > > >
>> /brokers/topics/EventServiceUpsertTopic/partitions/13/state
>> >> > with
>> >> > > > > value
>> >> > > > > > > >
>> >> > > > > > >
>> >> > > > > >
>> >> > > > >
>> >> > > >
>> >> > >
>> >> >
>> >>
>> {"controller_epoch":1,"leader":1,"version":1,"leader_epoch":3,"isr":[0,1]}
>> >> > > > > > > > and expected version 3 succeeded, returning the new
>> >> version: 4
>> >> > > > > > > >
>> >> > > > > > > > [2014-07-24 14:44:26,994] [DEBUG] [kafka-scheduler-0]
>> >> > > > > > > > [k.controller.PartitionStateMachine] [Partition state
>> >> machine
>> >> > on
>> >> > > > > > > > Controller 0]: After leader election, leader cache is
>> >> updated
>> >> > to
>> >> > > > > > > >
>> >> > > > > > >
>> >> > > > > >
>> >> > > > >
>> >> > > >
>> >> > >
>> >> >
>> >>
>> Map(<Snipped>(Leader:1,ISR:0,1,LeaderEpoch:3,ControllerEpoch:1),<EndSnip>)
>> >> > > > > > > >
>> >> > > > > > > > [2014-07-24 14:44:26,994] [INFO ] [kafka-scheduler-0]
>> >> > > > > > > > [kafka.controller.KafkaController] [Controller 0]:
>> >> Partition [
>> >> > > > > > > > EventServiceUpsertTopic,13] completed preferred replica
>> >> leader
>> >> > > > > > election.
>> >> > > > > > > > New leader is 1
>> >> > > > > > > > 4. Broker 1 is still behind, but it sets the high water
>> >> mark to
>> >> > > > > 971!!!
>> >> > > > > > > >
>> >> > > > > > > > Broker 1 Log:
>> >> > > > > > > >
>> >> > > > > > > > [2014-07-24 14:44:26,999] [INFO ]
>> >> [kafka-request-handler-6]
>> >> > > > > > > > [kafka.server.ReplicaFetcherManager]
>> >> [ReplicaFetcherManager on
>> >> > > > > broker
>> >> > > > > > 1]
>> >> > > > > > > > Removed fetcher for partitions
>> [EventServiceUpsertTopic,13]
>> >> > > > > > > >
>> >> > > > > > > > [2014-07-24 14:44:27,000] [DEBUG]
>> >> [kafka-request-handler-6]
>> >> > > > > > > > [kafka.cluster.Partition] Partition
>> >> > [EventServiceUpsertTopic,13]
>> >> > > > on
>> >> > > > > > > broker
>> >> > > > > > > > 1: Old hw for partition [EventServiceUpsertTopic,13] is
>> 970.
>> >> > New
>> >> > > hw
>> >> > > > > is
>> >> > > > > > > -1.
>> >> > > > > > > > All leo's are -1,971
>> >> > > > > > > >
>> >> > > > > > > > [2014-07-24 14:44:27,098] [DEBUG]
>> >> [kafka-request-handler-3]
>> >> > > > > > > > [kafka.server.KafkaApis] [KafkaApi-1] Maybe update
>> >> partition
>> >> > HW
>> >> > > > due
>> >> > > > > to
>> >> > > > > > > > fetch request: Name: FetchRequest; Version: 0;
>> >> CorrelationId:
>> >> > 1;
>> >> > > > > > > ClientId:
>> >> > > > > > > > ReplicaFetcherThread-0-1; ReplicaId: 0; MaxWait: 500 ms;
>> >> > > MinBytes:
>> >> > > > 1
>> >> > > > > > > bytes;
>> >> > > > > > > > RequestInfo: [EventServiceUpsertTopic,13] ->
>> >> > > > > > > > PartitionFetchInfo(971,1048576), <Snipped>
>> >> > > > > > > >
>> >> > > > > > > > [2014-07-24 14:44:27,098] [DEBUG]
>> >> [kafka-request-handler-3]
>> >> > > > > > > > [kafka.cluster.Partition] Partition
>> >> > [EventServiceUpsertTopic,13]
>> >> > > > on
>> >> > > > > > > broker
>> >> > > > > > > > 1: Recording follower 0 position 971 for partition [
>> >> > > > > > > > EventServiceUpsertTopic,13].
>> >> > > > > > > >
>> >> > > > > > > > [2014-07-24 14:44:27,100] [DEBUG]
>> >> [kafka-request-handler-3]
>> >> > > > > > > > [kafka.cluster.Partition] Partition
>> >> > [EventServiceUpsertTopic,13]
>> >> > > > on
>> >> > > > > > > broker
>> >> > > > > > > > 1: Highwatermark for partition
>> [EventServiceUpsertTopic,13]
>> >> > > updated
>> >> > > > > to
>> >> > > > > > > 971
>> >> > > > > > > > 5. Consumer is none the wiser. All data that was in
>> offsets
>> >> > > 972-975
>> >> > > > > > > doesn't
>> >> > > > > > > > show up!
>> >> > > > > > > >
>> >> > > > > > > > I tried this with 2 initial replicas, and adding a 3rd
>> >> which is
>> >> > > > > > supposed
>> >> > > > > > > to
>> >> > > > > > > > be the leader for some new partitions, and this problem
>> also
>> >> > > > happens
>> >> > > > > > > there.
>> >> > > > > > > > The log on the old leader gets truncated to the offset on
>> >> the
>> >> > new
>> >> > > > > > leader.
>> >> > > > > > > > What's the solution? Can I make a new broker leader for
>> >> > > partitions
>> >> > > > > that
>> >> > > > > > > are
>> >> > > > > > > > currently active without losing data?
>> >> > > > > > > >
>> >> > > > > > > > Thanks,
>> >> > > > > > > > Jad.
>> >> > > > > > > >
>> >> > > > > > > > --
>> >> > > > > > > > *Jad Naous* | Engineering | AppDynamics
>> >> > > > > > > > <http://www.appdynamics.com>
>> >> > > > > > > >
>> >> > > > > > >
>> >> > > > > > >
>> >> > > > > > >
>> >> > > > > > > --
>> >> > > > > > > -- Guozhang
>> >> > > > > > >
>> >> > > > > >
>> >> > > > > >
>> >> > > > > >
>> >> > > > > > --
>> >> > > > > > *Jad Naous* | Engineering | AppDynamics
>> >> > > > > > <http://www.appdynamics.com>
>> >> > > > > >
>> >> > > > >
>> >> > > > >
>> >> > > > >
>> >> > > > > --
>> >> > > > > -- Guozhang
>> >> > > > >
>> >> > > >
>> >> > >
>> >> >
>> >> >
>> >> >
>> >> > --
>> >> > -- Guozhang
>> >> >
>> >>
>> >>
>> >>
>> >> --
>> >> *Jad Naous* | Engineering | AppDynamics
>> >> <http://www.appdynamics.com>
>> >>
>> >
>> >
>> >
>> > --
>> > -- Guozhang
>> >
>>
>>
>>
>> --
>> -- Guozhang
>>
>
>
>
> --
> *Jad Naous* | Engineering | AppDynamics
> <http://www.appdynamics.com>
>
--
-- Guozhang
