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Posted to dev@kafka.apache.org by "Onur Karaman (JIRA)" <ji...@apache.org> on 2017/05/23 06:19:04 UTC
[jira] [Updated] (KAFKA-5310) reset ControllerContext during
resignation
[ https://issues.apache.org/jira/browse/KAFKA-5310?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Onur Karaman updated KAFKA-5310:
--------------------------------
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:
{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.
was:
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).
> 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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