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Posted to dev@kafka.apache.org by "Neha Narkhede (JIRA)" <ji...@apache.org> on 2015/02/22 06:47:12 UTC
[jira] [Resolved] (KAFKA-783) Preferred replica assignment on
leader failure may not be correct
[ https://issues.apache.org/jira/browse/KAFKA-783?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Neha Narkhede resolved KAFKA-783.
---------------------------------
Resolution: Not a Problem
Not sure if this is a problem. There were a bunch of fixes that went in to both 0.8.1.1 and 0.8.2 and we also automated preferred replica election. So closing for now.
> Preferred replica assignment on leader failure may not be correct
> -----------------------------------------------------------------
>
> Key: KAFKA-783
> URL: https://issues.apache.org/jira/browse/KAFKA-783
> Project: Kafka
> Issue Type: Bug
> Components: replication
> Affects Versions: 0.8.0
> Environment: $ uname -a
> Linux vrd01.atlnp1 2.6.32-279.el6.x86_64 #1 SMP Fri Jun 22 12:19:21 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
> $ java -version
> java version "1.6.0_25"
> Java(TM) SE Runtime Environment (build 1.6.0_25-b06)
> Java HotSpot(TM) 64-Bit Server VM (build 20.0-b11, mixed mode)
> Kafka 0.8.0 loaded from HEAD on 1/29/2013
> Reporter: Chris Curtin
> Assignee: Sriram Subramanian
> Labels: kafka-0.8, p2
>
> Based on an email thread in the user group, Neha asked me to submit this.
> Original question: "> I ran another test, again starting with a full cluster and all partitions
> > had a full set of copies. When I stop the broker which was leader for 9 of
> > the 10 partitions, the leaders were all elected on one machine instead of
> > the set of 3. Should the leaders have been better spread out? Also the
> > copies weren’t fully populated either."
> Neha: "For problem 2, we always try to make the preferred replica (1st replica
> in the list of all replicas for a partition) the leader, if it is
> available. We intended to spread the preferred replica for all partitions
> for a topic evenly across the brokers. If this is not happening, we need to
> look into it. Please can you file a bug and describe your test case there ?"
> Configuration:
> 4 node cluster
> 1 topic with 3 replicas
> 10 partitions: 0-9 below
> Current status:
> Partition: 0:vrd01.atlnp1 R:[ vrd03.atlnp1 vrd04.atlnp1 vrd01.atlnp1] I:[ vrd01.atlnp1 vrd03.atlnp1 vrd04.atlnp1]
> Partition: 1:vrd01.atlnp1 R:[ vrd04.atlnp1 vrd01.atlnp1 vrd02.atlnp1] I:[ vrd01.atlnp1 vrd04.atlnp1 vrd02.atlnp1]
> Partition: 2:vrd01.atlnp1 R:[ vrd01.atlnp1 vrd02.atlnp1 vrd03.atlnp1] I:[ vrd01.atlnp1 vrd03.atlnp1 vrd02.atlnp1]
> Partition: 3:vrd03.atlnp1 R:[ vrd02.atlnp1 vrd03.atlnp1 vrd04.atlnp1] I:[ vrd03.atlnp1 vrd04.atlnp1 vrd02.atlnp1]
> Partition: 4:vrd01.atlnp1 R:[ vrd03.atlnp1 vrd01.atlnp1 vrd02.atlnp1] I:[ vrd01.atlnp1 vrd03.atlnp1 vrd02.atlnp1]
> Partition: 5:vrd03.atlnp1 R:[ vrd04.atlnp1 vrd02.atlnp1 vrd03.atlnp1] I:[ vrd03.atlnp1 vrd04.atlnp1 vrd02.atlnp1]
> Partition: 6:vrd01.atlnp1 R:[ vrd01.atlnp1 vrd03.atlnp1 vrd04.atlnp1] I:[ vrd01.atlnp1 vrd03.atlnp1 vrd04.atlnp1]
> Partition: 7:vrd01.atlnp1 R:[ vrd02.atlnp1 vrd04.atlnp1 vrd01.atlnp1] I:[ vrd01.atlnp1 vrd04.atlnp1 vrd02.atlnp1]
> Partition: 8:vrd03.atlnp1 R:[ vrd03.atlnp1 vrd02.atlnp1 vrd04.atlnp1] I:[ vrd03.atlnp1 vrd04.atlnp1 vrd02.atlnp1]
> Partition: 9:vrd01.atlnp1 R:[ vrd04.atlnp1 vrd03.atlnp1 vrd01.atlnp1] I:[ vrd01.atlnp1 vrd03.atlnp1 vrd04.atlnp1]
> Shutdown vrd03:
> Partition: 0:vrd01.atlnp1 R:[ ] I:[]
> Partition: 1:vrd01.atlnp1 R:[ vrd04.atlnp1 vrd01.atlnp1 vrd02.atlnp1] I:[ vrd01.atlnp1 vrd04.atlnp1 vrd02.atlnp1]
> Partition: 2:vrd01.atlnp1 R:[ ] I:[]
> *Partition: 3:vrd04.atlnp1 R:[ ] I:[]
> Partition: 4:vrd01.atlnp1 R:[ ] I:[]
> *Partition: 5:vrd04.atlnp1 R:[ ] I:[]
> Partition: 6:vrd01.atlnp1 R:[ ] I:[]
> Partition: 7:vrd01.atlnp1 R:[ vrd02.atlnp1 vrd04.atlnp1 vrd01.atlnp1] I:[ vrd01.atlnp1 vrd04.atlnp1 vrd02.atlnp1]
> *Partition: 8:vrd04.atlnp1 R:[ ] I:[]
> Partition: 9:vrd01.atlnp1 R:[ ] I:[]
> (* means leader changed)
> Note that partitions 3, 5 and 8 were assigned new leaders.
> Per an email group thread with Neha, the new leader should be assigned from the preferred replica. So 3 should have gotten vrd02, 5, vrd04 and 8 vrd02 (since 03 was shutdown). Instead 3 got vrd04, 5 got vrd04 and 8 got vrd04.
> Restarting vrd03 led to:
> Partition: 0:vrd01.atlnp1 R:[ vrd03.atlnp1 vrd04.atlnp1 vrd01.atlnp1] I:[ vrd01.atlnp1 vrd04.atlnp1 vrd03.atlnp1]
> Partition: 1:vrd01.atlnp1 R:[ vrd04.atlnp1 vrd01.atlnp1 vrd02.atlnp1] I:[ vrd01.atlnp1 vrd04.atlnp1 vrd02.atlnp1]
> Partition: 2:vrd01.atlnp1 R:[ vrd01.atlnp1 vrd02.atlnp1 vrd03.atlnp1] I:[ vrd01.atlnp1 vrd02.atlnp1 vrd03.atlnp1]
> Partition: 3:vrd04.atlnp1 R:[ vrd02.atlnp1 vrd03.atlnp1 vrd04.atlnp1] I:[ vrd04.atlnp1 vrd02.atlnp1 vrd03.atlnp1]
> Partition: 4:vrd01.atlnp1 R:[ vrd03.atlnp1 vrd01.atlnp1 vrd02.atlnp1] I:[ vrd01.atlnp1 vrd02.atlnp1 vrd03.atlnp1]
> Partition: 5:vrd04.atlnp1 R:[ vrd04.atlnp1 vrd02.atlnp1 vrd03.atlnp1] I:[ vrd04.atlnp1 vrd02.atlnp1 vrd03.atlnp1]
> Partition: 6:vrd01.atlnp1 R:[ vrd01.atlnp1 vrd03.atlnp1 vrd04.atlnp1] I:[ vrd01.atlnp1 vrd04.atlnp1 vrd03.atlnp1]
> Partition: 7:vrd01.atlnp1 R:[ vrd02.atlnp1 vrd04.atlnp1 vrd01.atlnp1] I:[ vrd01.atlnp1 vrd04.atlnp1 vrd02.atlnp1]
> Partition: 8:vrd04.atlnp1 R:[ vrd03.atlnp1 vrd02.atlnp1 vrd04.atlnp1] I:[ vrd04.atlnp1 vrd02.atlnp1 vrd03.atlnp1]
> Partition: 9:vrd01.atlnp1 R:[ vrd04.atlnp1 vrd03.atlnp1 vrd01.atlnp1] I:[ vrd01.atlnp1 vrd04.atlnp1 vrd03.atlnp1]
> Stopping vrd01 now led to:
> *Partition: 0:vrd04.atlnp1 R:[ ] I:[]
> *Partition: 1:vrd04.atlnp1 R:[ ] I:[]
> *Partition: 2:vrd02.atlnp1 R:[ ] I:[]
> Partition: 3:vrd04.atlnp1 R:[ vrd02.atlnp1 vrd03.atlnp1 vrd04.atlnp1] I:[ vrd04.atlnp1 vrd02.atlnp1 vrd03.atlnp1]
> *Partition: 4:vrd02.atlnp1 R:[ ] I:[]
> Partition: 5:vrd04.atlnp1 R:[ vrd04.atlnp1 vrd02.atlnp1 vrd03.atlnp1] I:[ vrd04.atlnp1 vrd02.atlnp1 vrd03.atlnp1]
> *Partition: 6:vrd04.atlnp1 R:[ ] I:[]
> *Partition: 7:vrd04.atlnp1 R:[ ] I:[]
> Partition: 8:vrd04.atlnp1 R:[ vrd03.atlnp1 vrd02.atlnp1 vrd04.atlnp1] I:[ vrd04.atlnp1 vrd02.atlnp1 vrd03.atlnp1]
> *Partition: 9:vrd04.atlnp1 R:[ ] I:[]
> (* means leader changed)
> So 0, 2, 4, 6 and 7 were assigned the wrong leader (If preferred was first in the list. If last in list 1 & 2 are wrong)
> Java code:
> kafka.javaapi.consumer.SimpleConsumer consumer = new SimpleConsumer("vrd04.atlnp1",
> 9092,
> 100000,
> 64 * 1024, "test");
> List<String> topics2 = new ArrayList<String>();
> topics2.add("storm-anon");
> TopicMetadataRequest req = new TopicMetadataRequest(topics2);
> kafka.javaapi.TopicMetadataResponse resp = consumer.send(req);
> List<kafka.javaapi.TopicMetadata> data3 = resp.topicsMetadata();
> for (kafka.javaapi.TopicMetadata item : data3) {
> for (kafka.javaapi.PartitionMetadata part: item.partitionsMetadata() ) {
> String replicas = "";
> String isr = "";
> for (kafka.cluster.Broker replica: part.replicas() ) {
> replicas += " " + replica.host();
> }
> for (kafka.cluster.Broker replica: part.isr() ) {
> isr += " " + replica.host();
> }
> System.out.println( "Partition: " + part.partitionId() + ":" + part.leader().host() + " R:[ " + replicas + "] I:[" + isr + "]");
> }
> }
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