Onur Karaman created KAFKA-5310:
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Summary: 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.
It looks like this bug has been around for quite some time (definitely before
0.10.2).
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