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runzhiwang updated RATIS-840: ----------------------------- Attachment: RATIS-840.002.patch > Memory leak of LogAppender > -------------------------- > > Key: RATIS-840 > URL: https://issues.apache.org/jira/browse/RATIS-840 > Project: Ratis > Issue Type: Bug > Components: server > Reporter: runzhiwang > Assignee: runzhiwang > Priority: Critical > Attachments: RATIS-840.001.patch, RATIS-840.002.patch, > image-2020-04-06-14-27-28-485.png, image-2020-04-06-14-27-39-582.png, > screenshot-1.png, screenshot-2.png > > > *What's the problem ?* > When run hadoop-ozone for 4 days, datanode memory leak. When dump heap, I > found there are 460710 instances of GrpcLogAppender. But there are only 6 > instances of SenderList, and each SenderList contains 1-2 instance of > GrpcLogAppender. And there are a lot of logs related to > [LeaderState::restartSender|https://github.com/apache/incubator-ratis/blob/master/ratis-server/src/main/java/org/apache/ratis/server/impl/LeaderState.java#L428]. > {code:java}INFO impl.RaftServerImpl: > 1665f5ea-ab17-4a0e-af6d-6958efd322fa@group-F64B465F37B5-LeaderState: > Restarting GrpcLogAppender for > 1665f5ea-ab17-4a0e-af6d-6958efd322fa@group-F64B465F37B5-\u003e229cbcc1-a3b2-4383-9c0d-c0f4c28c3d4a\n","stream":"stderr","time":"2020-04-06T03:59:53.37892512Z"}{code} > > So there are a lot of GrpcLogAppender did not stop the Daemon Thread when > removed from senders. > !image-2020-04-06-14-27-28-485.png! > !image-2020-04-06-14-27-39-582.png! > > *Why > [LeaderState::restartSender|https://github.com/apache/incubator-ratis/blob/master/ratis-server/src/main/java/org/apache/ratis/server/impl/LeaderState.java#L428] > so many times ?* > 1. As the image shows, when remove group, SegmentedRaftLog will close, then > GrpcLogAppender throw exception when find the SegmentedRaftLog was closed. > Then GrpcLogAppender will be > [restarted|https://github.com/apache/incubator-ratis/blob/master/ratis-server/src/main/java/org/apache/ratis/server/impl/LogAppender.java#L94], > and the new GrpcLogAppender throw exception again when find the > SegmentedRaftLog was closed, then GrpcLogAppender will be restarted again ... > . It results in an infinite restart of GrpcLogAppender. > 2. Actually, when remove group, GrpcLogAppender will be stoped: > RaftServerImpl::shutdown -> > [RoleInfo::shutdownLeaderState|https://github.com/apache/incubator-ratis/blob/master/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java#L266] > -> LeaderState::stop -> LogAppender::stopAppender, then SegmentedRaftLog > will be closed: RaftServerImpl::shutdown -> > [ServerState:close|https://github.com/apache/incubator-ratis/blob/master/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java#L271] > ... . Though RoleInfo::shutdownLeaderState called before ServerState:close, > but the GrpcLogAppender was stopped asynchronously. So infinite restart of > GrpcLogAppender happens, when GrpcLogAppender stop after SegmentedRaftLog > close. > !screenshot-1.png! > *Why GrpcLogAppender did not stop the Daemon Thread when removed from senders > ?* > I find a lot of GrpcLogAppender blocked inside logs4j. I think it's > GrpcLogAppender restart too fast, then blocked in logs4j. > !screenshot-2.png! > *Can the new GrpcLogAppender work normally ?* > 1. Even though without the above problem, the new created GrpcLogAppender > still can not work normally. > 2. When creat a new GrpcLogAppender, a new FollowerInfo will also be created: > LeaderState::addAndStartSenders -> > LeaderState::addSenders->RaftServerImpl::newLogAppender -> [new > FollowerInfo|https://github.com/apache/incubator-ratis/blob/master/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java#L129] > 3. When the new created GrpcLogAppender append entry to follower, then the > follower response SUCCESS. > 4. Then LeaderState::updateCommit -> [LeaderState::getMajorityMin | > https://github.com/apache/incubator-ratis/blob/master/ratis-server/src/main/java/org/apache/ratis/server/impl/LeaderState.java#L599] > -> > [voterLists.get(0) | > https://github.com/apache/incubator-ratis/blob/master/ratis-server/src/main/java/org/apache/ratis/server/impl/LeaderState.java#L607]. > {color:#DE350B}Error happens because voterLists.get(0) return the > FollowerInfo of the old GrpcLogAppender, not the FollowerInfo of the new > GrpcLogAppender. {color} > 5. Because the majority commit got from the FollowerInfo of the old > GrpcLogAppender never changes. So even though follower has append entry > successfully, the leader can not update commit. So the new created > GrpcLogAppender can never work normally. > 6. The reason of unit test of runTestRestartLogAppender can pass is that it > did not stop the old GrpcLogAppender, and the old GrpcLogAppender append > entry to follower, not the new GrpcLogAppender. If stop the old > GrpcLogAppender, runTestRestartLogAppender will fail. -- This message was sent by Atlassian Jira (v8.3.4#803005)