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From Yogesh Sangvikar <yogesh.sangvi...@gmail.com>
Subject Re: Data loss while upgrading confluent 3.0.0 kafka cluster to confluent 3.2.2
Date Tue, 19 Sep 2017 11:33:45 GMT
Hi Team,

Thanks for providing comments.

Here adding more details on steps followed for upgrade,

Cluster details: We are using 4 node kafka cluster and topics with 3
replication factor. For upgrade test, we are using a topic with 5
partitions & 3 replication factor.

Topic:student-activity  PartitionCount:5        ReplicationFactor:3
Configs:
        Topic: student-activity Partition: 0    Leader: 4       Replicas:
4,2,3 Isr: 4,2,3
        Topic: student-activity Partition: 1    Leader: 1       Replicas:
1,3,4 Isr: 1,4,3
        Topic: student-activity Partition: 2    Leader: 2       Replicas:
2,4,1 Isr: 2,4,1
        Topic: student-activity Partition: 3    Leader: 3       Replicas:
3,1,2 Isr: 1,2,3
        Topic: student-activity Partition: 4    Leader: 4       Replicas:
4,3,1 Isr: 4,1,3

We are using a test script to publish events continuously to one of the
topic partition (here partition 3) and monitoring the scripts total
published events count  with the partition 3 offset value.

[ Note: The topic partitions offset count may differ from CLI utility and
screenshot due to capture delay. ]

   - First, we have rolling restarted all kafka brokers for explicit
   protocol and message version to 0.10.0,
   inter.broker.protocol.version=0.10.0
   log.message.format.version=0.10.0

   - During this restarted, the events are getting published as expected
   and counters are increasing & in-sync replicas are coming up immediately
   post restart.

   [***@***.***.***.*** confluent-3.2.2]$ ./bin/kafka-run-class
   kafka.tools.GetOffsetShell --broker-list
   ***.***.***.***:9092,***.***.***.***:9092,***.***.***.***:9092,***.***.***.***:9092
   --topic student-activity --time -1
   student-activity:2:1
   student-activity:4:1
   student-activity:1:68
   student-activity:3:785
   student-activity:0:1
   [image: Inline image 1]


   - Next, we  have rolling restarted kafka brokers for
   "inter.broker.protocol.version=0.10.2" in below broker sequence. (note
   that, test script is publishing events to the topic partition continuously)

   - Restarted server with  broker.id = 4,

   [***@***.***.***.*** confluent-3.2.2]$ ./bin/kafka-run-class
   kafka.tools.GetOffsetShell --broker-list
   ***.***.***.***:9092,***.***.***.***:9092,***.***.***.***:9092,***.***.***.***:9092
   --topic student-activity --time -1
   student-activity:2:1
   student-activity:4:1
   student-activity:1:68
   student-activity:3:1189
   student-activity:0:1

   [image: Inline image 2]

   - Restarted server with  broker.id = 3,

   [***@***.***.***.*** confluent-3.2.2]$ ./bin/kafka-run-class
   kafka.tools.GetOffsetShell --broker-list
   ***.***.***.***:9092,***.***.***.***:9092,***.***.***.***:9092,***.***.***.***:9092
   --topic student-activity --time -1
   student-activity:2:1
   student-activity:4:1
   student-activity:1:68
   *student-activity:3:1430*
   student-activity:0:1


       [image: Inline image 3]


   - Restarted server with  broker.id = 2, (here, observe the partition 3
   offset count is decreased from last restart offset)

   [***@***.***.***.*** confluent-3.2.2]$ ./bin/kafka-run-class
   kafka.tools.GetOffsetShell --broker-list
   ***.***.***.***:9092,***.***.***.***:9092,***.***.***.***:9092,***.***.***.***:9092
   --topic student-activity --time -1
   student-activity:2:1
   student-activity:4:1
   student-activity:1:68
   *student-activity:3:1357*
   student-activity:0:1

           [image: Inline image 4]


   - Restarted last server with  broker.id = 1,

   [***@***.***.***.*** confluent-3.2.2]$ ./bin/kafka-run-class
   kafka.tools.GetOffsetShell --broker-list
   ***.***.***.***:9092,***.***.***.***:9092,***.***.***.***:9092,***.***.***.***:9092
   --topic student-activity --time -1
   student-activity:2:1
   student-activity:4:1
   student-activity:1:68
   student-activity:3:1613
   student-activity:0:1
   [image: Inline image 5]

   - Finally, rolling restarted all brokers (in same sequence above) for
   "log.message.format.version=0.10.2"


‚Äč [image: Inline image 6]
[image: Inline image 7]
[image: Inline image 8]

[image: Inline image 9]

   - The topic offset counter after final restart,

   [***@***.***.***.*** confluent-3.2.2]$ ./bin/kafka-run-class
   kafka.tools.GetOffsetShell --broker-list
   ***.***.***.***:9092,***.***.***.***:9092,***.***.***.***:9092,***.***.***.***:9092
   --topic student-activity --time -1
   student-activity:2:1
   student-activity:4:1
   student-activity:1:68
   student-activity:3:2694
   student-activity:0:1


   - And, the topic offset counter after stopping events publish script,

   [***@***.***.***.*** confluent-3.2.2]$ ./bin/kafka-run-class
   kafka.tools.GetOffsetShell --broker-list
   ***.***.***.***:9092,***.***.***.***:9092,***.***.***.***:9092,***.***.***.***:9092
   --topic student-activity --time -1
   student-activity:2:1
   student-activity:4:1
   student-activity:1:68
   student-activity:3:2769
   student-activity:0:1

   - Calculating missing events counts,
   Total events published by script to partition 3 :
*3090 *Offset count on Partition 3 :
*2769 *
   Missing events count : 3090 - 2769 = *321*


As per above observation during rolling restart for protocol version,

   1. The partition 3 leader changed to in-sync replica 2 (with older
   protocol version) and upgraded replicas (3 & 4) are missing from in-sync
   replica list.
   2. And, one we down server 2 down for upgrade, suddenly replicas 3 & 4
   appear in in-sync replica list and partition offset count resets.
   3. Post server 2 & 1 upgrade, 3 in-sync replicas shown for partition 3
   but, missing events lag is not recovered.

Please let us know your comments on our observations and correct us if we
are missing any upgrade steps.

Thanks,
Yogesh

On Tue, Sep 19, 2017 at 2:07 AM, Ismael Juma <ismael@juma.me.uk> wrote:

> Hi Scott,
>
> There is nothing preventing a replica running a newer version from being in
> sync as long as the instructions are followed (i.e.
> inter.broker.protocol.version has to be set correctly and, if there's a
> message format change, log.message.format.version). That's why I asked
> Yogesh for more details. The upgrade path he mentioned (0.10.0 -> 0.10.2)
> is straightforward, there isn't a message format change, so only
> inter.broker.protocol.version needs to be set.
>
> Ismael
>
> On Mon, Sep 18, 2017 at 5:50 PM, Scott Reynolds <
> sreynolds@twilio.com.invalid> wrote:
>
> > Can we get some clarity on this point:
> > >older version leader is not allowing newer version replicas to be in
> sync,
> > so the data pushed using this older version leader
> >
> > That is super scary.
> >
> > What protocol version is the older version leader running?
> >
> > Would this happen if you are skipping a protocol version bump?
> >
> >
> >
> > On Mon, Sep 18, 2017 at 9:33 AM Ismael Juma <ismael@juma.me.uk> wrote:
> >
> > > Hi Yogesh,
> > >
> > > Can you please clarify what you mean by "observing data loss"?
> > >
> > > Ismael
> > >
> > > On Mon, Sep 18, 2017 at 5:08 PM, Yogesh Sangvikar <
> > > yogesh.sangvikar@gmail.com> wrote:
> > >
> > > > Hi Team,
> > > >
> > > > Please help to find resolution for below kafka rolling upgrade issue.
> > > >
> > > > Thanks,
> > > >
> > > > Yogesh
> > > >
> > > > On Monday, September 18, 2017 at 9:03:04 PM UTC+5:30, Yogesh
> Sangvikar
> > > > wrote:
> > > >>
> > > >> Hi Team,
> > > >>
> > > >> Currently, we are using confluent 3.0.0 kafka cluster in our
> > production
> > > >> environment. And, we are planing to upgrade the kafka cluster for
> > > confluent
> > > >> 3.2.2
> > > >> We are having topics with millions on records and data getting
> > > >> continuously published to those topics. And, also, we are using
> other
> > > >> confluent services like schema-registry, kafka connect and kafka
> rest
> > to
> > > >> process the data.
> > > >>
> > > >> So, we can't afford downtime upgrade for the platform.
> > > >>
> > > >> We have tries rolling kafka upgrade as suggested on blogs in
> > Development
> > > >> environment,
> > > >>
> > > >>
> > > https://urldefense.proofpoint.com/v2/url?u=https-3A__docs.
> > confluent.io_3.2.2_upgrade.html&d=DwIBaQ&c=x_Y1Lz9GyeGp2OvBCa_eow&r=
> > ChXZJWKniTslJvQGptpIW7qAh4kkrpgYSer_wfh4G5w&m=JGTnLlVIAvVddNas19L_
> > w54zWrVd48xst46GuPGCxV0&s=DMcA8JOnGXNNa_dRFpkNOd7AJoIQUgkEcw6q06RHgl0&e=
> > > >>
> > > >>
> > > https://urldefense.proofpoint.com/v2/url?u=https-3A__kafka.
> > apache.org_documentation_-23upgrade&d=DwIBaQ&c=x_Y1Lz9GyeGp2OvBCa_eow&r=
> > ChXZJWKniTslJvQGptpIW7qAh4kkrpgYSer_wfh4G5w&m=JGTnLlVIAvVddNas19L_
> > w54zWrVd48xst46GuPGCxV0&s=0p4Fn8sKMbVJMR6nk42C-lhyujAEVUXTYZJhteC11Fs&e=
> > > >>
> > > >> But, we are observing data loss on topics while doing rolling
> upgrade
> > /
> > > >> restart of kafka servers for "inter.broker.protocol.
> version=0.10.2".
> > > >>
> > > >> As per our observation, we suspect the root cause for the data loss
> > > >> (explained for a topic partition having 3 replicas),
> > > >>
> > > >>    - As the kafka broker protocol version updates from 0.10.0 to
> > 0.10.2
> > > >>    in rolling fashion, the in-sync replicas having older version
> will
> > > not
> > > >>    allow updated replicas (0.10.2) to be in sync unless are all
> > updated.
> > > >>    - Also, we have explicitly disabled "unclean.leader.election.
> > enabled"
> > > >>    property, so only in-sync replicas will be elected as leader for
> > the
> > > given
> > > >>    partition.
> > > >>    - While doing rolling fashion update, as mentioned above, older
> > > >>    version leader is not allowing newer version replicas to be in
> > sync,
> > > so the
> > > >>    data pushed using this older version leader, will not be synced
> > with
> > > other
> > > >>    replicas and if this leader(older version)  goes down for an
> > > upgrade, other
> > > >>    updated replicas will be shown in in-sync column and become
> leader,
> > > but
> > > >>    they lag in offset with old version leader and shows the offset
> of
> > > the data
> > > >>    till they have synced.
> > > >>    - And, once the last replica comes up with updated version, will
> > > >>    start syncing data from the current leader.
> > > >>
> > > >>
> > > >> Please let us know comments on our observation and suggest proper
> way
> > > for
> > > >> rolling kafka upgrade as we can't afford downtime.
> > > >>
> > > >> Thanks,
> > > >> Yogesh
> > > >>
> > > >
> > >
> > --
> >
> > Scott Reynolds
> > Principal Engineer
> > [image: twilio] <http://www.twilio.com/?utm_source=email_signature>
> > MOBILE (630) 254-2474
> > EMAIL sreynolds@twilio.com
> >
>

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