Thanks for the great explanation! So I guess for now, it's not safe to do
leader election for rebalancing leadership? Or under what conditions can I
trigger re-election without losing messages? It seems like this issue can
always happen.
On Fri, Jul 25, 2014 at 5:09 PM, Guozhang Wang <wangg...@gmail.com> wrote:
> Hello Jad,
>
> The reason why the new leader needs to truncate to HW is to that only
> messages that are appended to all the ISR replicas and hence whose offset
> is within the HW are treated as "committed". Blindly follow the largest LEO
> may cause inconsistency between replicas and between servers and clients.
> Consider these two scenarios:
>
> 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
>
> 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 in a word, only messages below the HW are safe to be maintained upon
> leader migration. The issue here though, is that follower's HW update is
> slightly late the leader's HW update, and hence the truncation may cause
> data loss. We will try to fix this issue in KAFKA-1211.
>
> Guozhang
>
>
> On Fri, Jul 25, 2014 at 4:12 PM, Jad Naous <jad.na...@appdynamics.com>
> wrote:
>
> > Hi Guozhang,
> >
> > Yes, I think they are related.
> >
> > It seems odd to me that there should be any truncation at all since that
> is
> > always an opportunity for data loss. It seems like we would want to avoid
> > that at all costs, assuming we uphold the invariant that messages
> committed
> > to an offset on any replica will always be identical. There seems to be
> two
> > choices to make sure we don't lose data during leader election:
> >
> > 1- after leader election, requests going to the new leader should block
> > until the leader is caught up to the highest LEO in the set of replicas
> (or
> > until the HW reaches the highest LEO among replicas). I think this is
> less
> > "normal" since it would mean that the new leader has to fetch messages
> from
> > a non-leader. Maybe you can have the notion of a write-leader and a
> > read-leader. After leader election, the write-leader becomes whatever the
> > preferred leader today is, and the read-leader becomes the replica with
> the
> > highest LEO. If the write-leader is not also the read-leader, then writes
> > are blocked. All replicas and consumers fetch from the read-leader, and
> > when the write-leader is caught up to the read-leader, the write-leader
> > also becomes the read-leader and writes are unblocked.
> >
> > 2- After leader election, block actual leadership switching and block
> > responding to new requests until the HW reaches the LEO on the old
> leader,
> > then switch leadership, failing the blocked requests (or signaling a
> retry
> > for a new leader), which should then retry the writes on the new leader,
> > and things proceed as normal.
> >
> > Would either of these work?
> >
> > Thanks,
> > Jad.
> >
> >
> >
> >
> > 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
> > >
> >
> >
> >
> > --
> > *Jad Naous* | Engineering | AppDynamics
> > <http://www.appdynamics.com>
> >
>
>
>
> --
> -- Guozhang
>
--
*Jad Naous* | Engineering | AppDynamics
<http://www.appdynamics.com>
