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https://issues.apache.org/jira/browse/KAFKA-5310?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Onur Karaman updated KAFKA-5310:
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Status: Patch Available (was: Open)
> reset ControllerContext during resignation
> ------------------------------------------
>
> Key: KAFKA-5310
> URL: https://issues.apache.org/jira/browse/KAFKA-5310
> Project: Kafka
> Issue Type: Sub-task
> Reporter: Onur Karaman
> Assignee: Onur Karaman
>
> This ticket is all about ControllerContext initialization and teardown. The
> key points are:
> 1. we should teardown ControllerContext during resignation instead of waiting
> on election to fix it up. A heapdump shows that the former controller keeps
> pretty much all of its ControllerContext state laying around.
> 2. we don't properly teardown/reset
> {{ControllerContext.partitionsBeingReassigned}}. This caused problems for us
> in a production cluster at linkedin as shown in the scenario below:
> {code}
> > rm -rf /tmp/zookeeper/ /tmp/kafka-logs* logs*
> > ./gradlew clean jar
> > ./bin/zookeeper-server-start.sh config/zookeeper.properties
> > export LOG_DIR=logs0 && ./bin/kafka-server-start.sh
> > config/server0.properties
> > export LOG_DIR=logs1 && ./bin/kafka-server-start.sh
> > config/server1.properties
> > ./bin/kafka-topics.sh --zookeeper localhost:2181 --create --topic t
> > --replica-assignment 1
> > ./bin/zookeeper-shell.sh localhost:2181
> get /brokers/topics/t
> {"version":1,"partitions":{"0":[1]}}
> create /admin/reassign_partitions
> {"partitions":[{"topic":"t","partition":0,"replicas":[1,2]}],"version":1}
> Created /admin/reassign_partitions
> get /brokers/topics/t
> {"version":1,"partitions":{"0":[1,2]}}
> get /admin/reassign_partitions
> {"version":1,"partitions":[{"topic":"t","partition":0,"replicas":[1,2]}]}
> delete /admin/reassign_partitions
> delete /controller
> get /brokers/topics/t
> {"version":1,"partitions":{"0":[1,2]}}
> get /admin/reassign_partitions
> Node does not exist: /admin/reassign_partitions
> > echo
> > '{"partitions":[{"topic":"t","partition":0,"replicas":[1]}],"version":1}' >
> > reassignment.txt
> > ./bin/kafka-reassign-partitions.sh --zookeeper localhost:2181
> > --reassignment-json-file reassignment.txt --execute
> get /brokers/topics/t
> {"version":1,"partitions":{"0":[1]}}
> get /admin/reassign_partitions
> Node does not exist: /admin/reassign_partitions
> delete /controller
> get /brokers/topics/t
> {"version":1,"partitions":{"0":[1,2]}}
> get /admin/reassign_partitions
> Node does not exist: /admin/reassign_partitions
> {code}
> Notice that the replica set goes from \[1\] to \[1,2\] (as expected with the
> explicit {{/admin/reassign_partitions}} znode creation during the initial
> controller) back to \[1\] (as expected with the partition reassignment during
> the second controller) and again back to \[1,2\] after the original
> controller gets re-elected.
> That last transition from \[1\] to \[1,2\] is unexpected. It's due to the
> original controller not resetting its
> {{ControllerContext.partitionsBeingReassigned}} correctly.
> {{initializePartitionReassignment}} simply adds to what's already in
> {{ControllerContext.partitionsBeingReassigned}}.
> The explicit {{/admin/reassign_partitions}} znode creation is to circumvent
> KAFKA-5161 (95b48b157aca44beec4335e62a59f37097fe7499). Doing so is valid
> since:
> 1. our code in production doesn't have that change
> 2. KAFKA-5161 doesn't address the underlying race condition between a broker
> failure and the ReassignPartitionsCommand tool creating the znode.
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