Details
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Sub-task
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Status: Resolved
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Major
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Resolution: Fixed
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None
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Description
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:
> 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
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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