Attila Doroszlai created RATIS-1490:
---------------------------------------
Summary: Follower should not change to candidate if already stopped
Key: RATIS-1490
URL: https://issues.apache.org/jira/browse/RATIS-1490
Project: Ratis
Issue Type: Bug
Components: server
Reporter: Attila Doroszlai
Assignee: Attila Doroszlai
{{RaftServerImpl}} creates a new {{FollowerState}} for each vote request
received. The old {{FollowerState}} may trigger change to candidate role after
it was shutdown by the server. Both {{RaftServerImpl#requestVote}} and the
change to candidate by {{FollowerState}} requires lock on {{server}}
({{RaftServerImpl}} object). The order of events which triggers the problem:
# {{RaftServerImpl}} executing {{requestVote}} [with lock on
itself|https://github.com/apache/ratis/blob/b57be797fe97c00abc0e3d7353d30e1b2961714d/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java#L1099]
# {{FollowerState}} [checks conditions, then waits for lock on
{{server}}|https://github.com/apache/ratis/blob/b57be797fe97c00abc0e3d7353d30e1b2961714d/ratis-server/src/main/java/org/apache/ratis/server/impl/FollowerState.java#L126-L130]
# {{RaftServerImpl}} [shuts down old {{FollowerState}}, starts new
one|https://github.com/apache/ratis/blob/b57be797fe97c00abc0e3d7353d30e1b2961714d/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java#L475-L477]
# {{RaftServerImpl}} [sets last RPC time on new
{{FollowerState}}|https://github.com/apache/ratis/blob/b57be797fe97c00abc0e3d7353d30e1b2961714d/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java#L1116-L1117]
# {{RaftServerImpl}} [releases
lock|https://github.com/apache/ratis/blob/b57be797fe97c00abc0e3d7353d30e1b2961714d/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java#L1127]
# *old* {{FollowerState}} [enters block with lock on {{server}}, triggers
change to
candidate|https://github.com/apache/ratis/blob/b57be797fe97c00abc0e3d7353d30e1b2961714d/ratis-server/src/main/java/org/apache/ratis/server/impl/FollowerState.java#L130-L138]
--
This message was sent by Atlassian Jira
(v8.20.1#820001)
