In GrpcLogAppender, disable retry and add minWait.

After grpc 1.48.1 release, we packaged ratis with master branch and thirdparty 1.0.2 and test whether out of direct memory issue is fixed. Unfortunately, this error is again reproduced.

See the error stack:

2022-08-16 15:28:45,962 [172.20.70.24_40010@group-000100000001->172.20.70.23_40010-GrpcLogAppender-LogAppenderDaemon] ERROR o.a.r.s.l.LogAppenderDaemon:86 - 172.20.70.24_40010@group-000100000001->172.20.70.23_40010-GrpcLogAppender-LogAppenderDaemon failed
org.apache.ratis.thirdparty.io.netty.util.internal.OutOfDirectMemoryError: failed to allocate 2097152 byte(s) of direct memory (used: 17177772311, max: 17179869184)
        at org.apache.ratis.thirdparty.io.netty.util.internal.PlatformDependent.incrementMemoryCounter(PlatformDependent.java:806)
        at org.apache.ratis.thirdparty.io.netty.util.internal.PlatformDependent.allocateDirectNoCleaner(PlatformDependent.java:735)
        at org.apache.ratis.thirdparty.io.netty.buffer.PoolArena$DirectArena.allocateDirect(PoolArena.java:649)
        at org.apache.ratis.thirdparty.io.netty.buffer.PoolArena$DirectArena.newChunk(PoolArena.java:624)
        at org.apache.ratis.thirdparty.io.netty.buffer.PoolArena.allocateNormal(PoolArena.java:203)
        at org.apache.ratis.thirdparty.io.netty.buffer.PoolArena.tcacheAllocateNormal(PoolArena.java:187)
        at org.apache.ratis.thirdparty.io.netty.buffer.PoolArena.allocate(PoolArena.java:136)
        at org.apache.ratis.thirdparty.io.netty.buffer.PoolArena.allocate(PoolArena.java:126)
        at org.apache.ratis.thirdparty.io.netty.buffer.PooledByteBufAllocator.newDirectBuffer(PooledByteBufAllocator.java:396)
        at org.apache.ratis.thirdparty.io.netty.buffer.AbstractByteBufAllocator.directBuffer(AbstractByteBufAllocator.java:188)
        at org.apache.ratis.thirdparty.io.netty.buffer.AbstractByteBufAllocator.buffer(AbstractByteBufAllocator.java:124)
        at org.apache.ratis.thirdparty.io.grpc.netty.NettyWritableBufferAllocator.allocate(NettyWritableBufferAllocator.java:51)
        at org.apache.ratis.thirdparty.io.grpc.internal.MessageFramer.writeRaw(MessageFramer.java:285)
        at org.apache.ratis.thirdparty.io.grpc.internal.MessageFramer.access$400(MessageFramer.java:43)
        at org.apache.ratis.thirdparty.io.grpc.internal.MessageFramer$OutputStreamAdapter.write(MessageFramer.java:375)
        at org.apache.ratis.thirdparty.com.google.protobuf.CodedOutputStream$OutputStreamEncoder.write(CodedOutputStream.java:3005)
        at org.apache.ratis.thirdparty.com.google.protobuf.CodedOutputStream$OutputStreamEncoder.writeLazy(CodedOutputStream.java:3013)
        at org.apache.ratis.thirdparty.com.google.protobuf.ByteString$LiteralByteString.writeTo(ByteString.java:1411)
        at org.apache.ratis.thirdparty.com.google.protobuf.CodedOutputStream$OutputStreamEncoder.writeBytesNoTag(CodedOutputStream.java:2801)
        at org.apache.ratis.thirdparty.com.google.protobuf.CodedOutputStream$OutputStreamEncoder.writeBytes(CodedOutputStream.java:2775)
        at org.apache.ratis.proto.RaftProtos$StateMachineLogEntryProto.writeTo(RaftProtos.java:7869)
        at org.apache.ratis.thirdparty.com.google.protobuf.CodedOutputStream$OutputStreamEncoder.writeMessageNoTag(CodedOutputStream.java:2855)
        at org.apache.ratis.thirdparty.com.google.protobuf.CodedOutputStream$OutputStreamEncoder.writeMessage(CodedOutputStream.java:2824)
        at org.apache.ratis.proto.RaftProtos$LogEntryProto.writeTo(RaftProtos.java:9503)
        at org.apache.ratis.thirdparty.com.google.protobuf.CodedOutputStream$OutputStreamEncoder.writeMessageNoTag(CodedOutputStream.java:2855)
        at org.apache.ratis.thirdparty.com.google.protobuf.CodedOutputStream$OutputStreamEncoder.writeMessage(CodedOutputStream.java:2824)
        at org.apache.ratis.proto.RaftProtos$AppendEntriesRequestProto.writeTo(RaftProtos.java:17799)
        at org.apache.ratis.thirdparty.com.google.protobuf.AbstractMessageLite.writeTo(AbstractMessageLite.java:83)
        at org.apache.ratis.thirdparty.io.grpc.protobuf.lite.ProtoInputStream.drainTo(ProtoInputStream.java:52)
        at org.apache.ratis.thirdparty.io.grpc.internal.MessageFramer.writeToOutputStream(MessageFramer.java:267)
        at org.apache.ratis.thirdparty.io.grpc.internal.MessageFramer.writeKnownLengthUncompressed(MessageFramer.java:229)
        at org.apache.ratis.thirdparty.io.grpc.internal.MessageFramer.writeUncompressed(MessageFramer.java:168)
        at org.apache.ratis.thirdparty.io.grpc.internal.MessageFramer.writePayload(MessageFramer.java:141)
        at org.apache.ratis.thirdparty.io.grpc.internal.AbstractStream.writeMessage(AbstractStream.java:65)
        at org.apache.ratis.thirdparty.io.grpc.internal.ForwardingClientStream.writeMessage(ForwardingClientStream.java:37)
        at org.apache.ratis.thirdparty.io.grpc.internal.RetriableStream.sendMessage(RetriableStream.java:545)
        at org.apache.ratis.thirdparty.io.grpc.internal.ClientCallImpl.sendMessageInternal(ClientCallImpl.java:520)
        at org.apache.ratis.thirdparty.io.grpc.internal.ClientCallImpl.sendMessage(ClientCallImpl.java:506)
        at org.apache.ratis.thirdparty.io.grpc.stub.ClientCalls$CallToStreamObserverAdapter.onNext(ClientCalls.java:374)
        at org.apache.ratis.grpc.server.GrpcLogAppender$StreamObservers.onNext(GrpcLogAppender.java:236)
        at org.apache.ratis.grpc.server.GrpcLogAppender.lambda$sendRequest$1(GrpcLogAppender.java:285)
        at java.util.Optional.map(Optional.java:215)
        at org.apache.ratis.grpc.server.GrpcLogAppender.sendRequest(GrpcLogAppender.java:284)
        at org.apache.ratis.grpc.server.GrpcLogAppender.appendLog(GrpcLogAppender.java:276)
        at org.apache.ratis.grpc.server.GrpcLogAppender.run(GrpcLogAppender.java:160)
        at org.apache.ratis.server.leader.LogAppenderDaemon.run(LogAppenderDaemon.java:77)
        at java.lang.Thread.run(Thread.java:748)
2022-08-16 15:28:45,963 [grpc-default-executor-2] WARN  o.a.ratis.util.LogUtils:122 - 172.20.70.24_40010@group-000100000001->172.20.70.23_40010-AppendLogResponseHandler: Failed appendEntries: org.apache.ratis.thirdparty.io.grpc.StatusRuntimeException: CANCELLED: Client sendMessage() failed with Error
2022-08-16 15:28:45,963 [172.20.70.24_40010@group-000100000001->172.20.70.23_40010-GrpcLogAppender-LogAppenderDaemon] INFO  o.a.r.s.i.LeaderStateImpl:531 - 172.20.70.24_40010@group-000100000001-LeaderStateImpl: Restarting GrpcLogAppender for 172.20.70.24_40010@group-000100000001->172.20.70.23_40010

However, we discover some other abnormalities.

That is, one follower often report that it receives inconsistent AppendEntries from leader as the first entry in AE already exists locally. After some complaining on "inconsistent appendEntry", this follower can still write logs to RaftLog from time to time. The "inconsistent AE" and "success log write" are interleaved. See follower log:

2022-08-16 15:25:43,253 [172.20.70.23_40010@group-000100000001-SegmentedRaftLogWorker] INFO  o.a.r.s.r.s.SegmentedRaftLogWorker$StartLogSegment:629 - 172.20.70.23_40010@group-000100000001-SegmentedRaftLogWorker: created new log segment /data/cluster/first-rest-test/DataNode/apache-iotdb/datanode/sbin/../data/consensus/data_region/47474747-4747-4747-4747-000100000001/current/log_inprogress_1376
2022-08-16 15:25:43,345 [172.20.70.23_40010-server-thread2] INFO  o.a.r.s.i.RaftServerImpl:1475 - 172.20.70.23_40010@group-000100000001: Failed appendEntries as the first entry (index 1283) already exists (snapshotIndex: -1, commitIndex: 1393)
2022-08-16 15:25:43,345 [172.20.70.23_40010-server-thread2] INFO  o.a.r.s.i.RaftServerImpl:1455 - 172.20.70.23_40010@group-000100000001: inconsistency entries. Reply:172.20.70.24_40010<-172.20.70.23_40010#2960:FAIL-t1,INCONSISTENCY,nextIndex=1394,followerCommit=1393,matchIndex=-1
2022-08-16 15:25:43,358 [172.20.70.23_40010-server-thread2] INFO  o.a.r.s.i.RaftServerImpl:1475 - 172.20.70.23_40010@group-000100000001: Failed appendEntries as the first entry (index 1287) already exists (snapshotIndex: -1, commitIndex: 1393)
2022-08-16 15:25:43,359 [172.20.70.23_40010-server-thread2] INFO  o.a.r.s.i.RaftServerImpl:1455 - 172.20.70.23_40010@group-000100000001: inconsistency entries. Reply:172.20.70.24_40010<-172.20.70.23_40010#2961:FAIL-t1,INCONSISTENCY,nextIndex=1394,followerCommit=1393,matchIndex=-1
2022-08-16 15:25:43,374 [172.20.70.23_40010-server-thread2] INFO  o.a.r.s.i.RaftServerImpl:1475 - 172.20.70.23_40010@group-000100000001: Failed appendEntries as the first entry (index 1290) already exists (snapshotIndex: -1, commitIndex: 1393)
2022-08-16 15:25:43,374 [172.20.70.23_40010-server-thread2] INFO  o.a.r.s.i.RaftServerImpl:1455 - 172.20.70.23_40010@group-000100000001: inconsistency entries. Reply:172.20.70.24_40010<-172.20.70.23_40010#2962:FAIL-t1,INCONSISTENCY,nextIndex=1394,followerCommit=1393,matchIndex=-1
2022-08-16 15:25:43,387 [172.20.70.23_40010-server-thread2] INFO  o.a.r.s.i.RaftServerImpl:1475 - 172.20.70.23_40010@group-000100000001: Failed appendEntries as the first entry (index 1294) already exists (snapshotIndex: -1, commitIndex: 1393)
2022-08-16 15:25:43,387 [172.20.70.23_40010-server-thread2] INFO  o.a.r.s.i.RaftServerImpl:1455 - 172.20.70.23_40010@group-000100000001: inconsistency entries. Reply:172.20.70.24_40010<-172.20.70.23_40010#2963:FAIL-t1,INCONSISTENCY,nextIndex=1394,followerCommit=1393,matchIndex=-1
2022-08-16 15:25:43,983 [172.20.70.23_40010-server-thread2] INFO  o.a.r.s.i.RaftServerImpl:1475 - 172.20.70.23_40010@group-000100000001: Failed appendEntries as the first entry (index 1297) already exists (snapshotIndex: -1, commitIndex: 1393)
2022-08-16 15:25:43,984 [172.20.70.23_40010-server-thread2] INFO  o.a.r.s.i.RaftServerImpl:1455 - 172.20.70.23_40010@group-000100000001: inconsistency entries. Reply:172.20.70.24_40010<-172.20.70.23_40010#2964:FAIL-t1,INCONSISTENCY,nextIndex=1394,followerCommit=1393,matchIndex=-1

(successfully write after some inconsistency AE)
2022-08-16 15:25:44,011 [172.20.70.23_40010-server-thread2] INFO  o.a.r.s.r.s.SegmentedRaftLogWorker:430 - 172.20.70.23_40010@group-000100000001-SegmentedRaftLogWorker: Rolling segment log-1376_1394 to index:1394
2022-08-16 15:25:44,017 [172.20.70.23_40010@group-000100000001-SegmentedRaftLogWorker] INFO  o.a.r.s.r.s.SegmentedRaftLogWorker$FinalizeLogSegment:586 - 172.20.70.23_40010@group-000100000001-SegmentedRaftLogWorker: Rolled log segment from /data/cluster/first-rest-test/DataNode/apache-iotdb/datanode/sbin/../data/consensus/data_region/47474747-4747-4747-4747-000100000001/current/log_inprogress_1376 to /data/cluster/first-rest-test/DataNode/apache-iotdb/datanode/sbin/../data/consensus/data_region/47474747-4747-4747-4747-000100000001/current/log_1376-1394
2022-08-16 15:25:44,028 [172.20.70.23_40010@group-000100000001-SegmentedRaftLogWorker] INFO  o.a.r.s.r.s.SegmentedRaftLogWorker$StartLogSegment:629 - 172.20.70.23_40010@group-000100000001-SegmentedRaftLogWorker: created new log segment /data/cluster/first-rest-test/DataNode/apache-iotdb/datanode/sbin/../data/consensus/data_region/47474747-4747-4747-4747-000100000001/current/log_inprogress_1395
2022-08-16 15:25:44,137 [172.20.70.23_40010-server-thread2] INFO  o.a.r.s.i.RaftServerImpl:1475 - 172.20.70.23_40010@group-000100000001: Failed appendEntries as the first entry (index 1394) already exists (snapshotIndex: -1, commitIndex: 1395)
2022-08-16 15:25:44,137 [172.20.70.23_40010-server-thread2] INFO  o.a.r.s.i.RaftServerImpl:1455 - 172.20.70.23_40010@group-000100000001: inconsistency entries. Reply:172.20.70.24_40010<-172.20.70.23_40010#2966:FAIL-t1,INCONSISTENCY,nextIndex=1396,followerCommit=1395,matchIndex=-1
2022-08-16 15:25:44,158 [172.20.70.23_40010-server-thread2] INFO  o.a.r.s.i.RaftServerImpl:1475 - 172.20.70.23_40010@group-000100000001: Failed appendEntries as the first entry (index 1394) already exists (snapshotIndex: -1, commitIndex: 1395)
2022-08-16 15:25:44,158 [172.20.70.23_40010-server-thread2] INFO  o.a.r.s.i.RaftServerImpl:1455 - 172.20.70.23_40010@group-000100000001: inconsistency entries. Reply:172.20.70.24_40010<-172.20.70.23_40010#2967:FAIL-t1,INCONSISTENCY,nextIndex=1396,followerCommit=1395,matchIndex=-1
2022-08-16 15:25:44,229 [172.20.70.23_40010-server-thread2] INFO  o.a.r.s.r.s.SegmentedRaftLogWorker:430 - 172.20.70.23_40010@group-000100000001-SegmentedRaftLogWorker: Rolling segment log-1395_1411 to index:1411
2022-08-16 15:25:44,247 [172.20.70.23_40010-server-thread2] INFO  o.a.r.s.i.RaftServerImpl:1475 - 172.20.70.23_40010@group-000100000001: Failed appendEntries as the first entry (index 1394) already exists (snapshotIndex: -1, commitIndex: 1403)
2022-08-16 15:25:44,248 [172.20.70.23_40010-server-thread2] INFO  o.a.r.s.i.RaftServerImpl:1455 - 172.20.70.23_40010@group-000100000001: inconsistency entries. Reply:172.20.70.24_40010<-172.20.70.23_40010#2980:FAIL-t1,INCONSISTENCY,nextIndex=1404,followerCommit=1403,matchIndex=-1

Meanwhile, the leader keeps reporting changing this follower's nextIndex

2022-08-16 15:25:43,291 [172.20.70.24_40010@group-000100000001-SegmentedRaftLogWorker] INFO  o.a.r.s.r.s.SegmentedRaftLogWorker$FinalizeLogSegment:586 - 172.20.70.24_40010@group-000100000001-SegmentedRaftLogWorker: Rolled log segment from /data/cluster/first-rest-test/DataNode/apache-iotdb/datanode/sbin/../data/consensus/data_region/47474747-4747-4747-4747-000100000001/current/log_inprogress_1430 to /data/cluster/first-rest-test/DataNode/apache-iotdb/datanode/sbin/../data/consensus/data_region/47474747-4747-4747-4747-000100000001/current/log_1430-1444

2022-08-16 15:25:43,826 [org.apache.ratis.util.JvmPauseMonitor$$Lambda$168/788892554@6273c5a4] WARN  o.a.r.u.JvmPauseMonitor:124 - JvmPauseMonitor-172.20.70.24_40010: Detected pause in JVM or host machine (eg GC): pause of approximately 163309780ns.
GC pool 'PS Scavenge' had collection(s): count=1 time=431ms
2022-08-16 15:25:43,826 [org.apache.ratis.util.JvmPauseMonitor$$Lambda$168/788892554@756cf158] WARN  o.a.r.u.JvmPauseMonitor:124 - JvmPauseMonitor-172.20.70.24_50010: Detected pause in JVM or host machine (eg GC): pause of approximately 163346070ns.
GC pool 'PS Scavenge' had collection(s): count=1 time=431ms

2022-08-16 15:25:43,876 [grpc-default-executor-0] INFO  o.a.r.s.i.FollowerInfoImpl:48 - 172.20.70.24_40010@group-000100000001->172.20.70.23_40010: nextIndex: updateUnconditionally 1299 -> 1394

2022-08-16 15:25:44,014 [grpc-default-executor-0] INFO  o.a.r.s.i.FollowerInfoImpl:48 - 172.20.70.24_40010@group-000100000001->172.20.70.23_40010: nextIndex: updateUnconditionally 1396 -> 1394

2022-08-16 15:25:44,118 [grpc-default-executor-0] INFO  o.a.r.s.i.FollowerInfoImpl:48 - 172.20.70.24_40010@group-000100000001->172.20.70.23_40010: nextIndex: updateUnconditionally 1396 -> 1394
2022-08-16 15:25:44,129 [grpc-default-executor-0] INFO  o.a.r.s.i.FollowerInfoImpl:48 - 172.20.70.24_40010@group-000100000001->172.20.70.23_40010: nextIndex: updateUnconditionally 1422 -> 1394

2022-08-16 15:25:44,130 [grpc-default-executor-0] INFO  o.a.r.s.i.FollowerInfoImpl:48 - 172.20.70.24_40010@group-000100000001->172.20.70.23_40010: nextIndex: updateUnconditionally 1396 -> 1394
2022-08-16 15:25:44,141 [grpc-default-executor-0] INFO  o.a.r.s.i.FollowerInfoImpl:48 - 172.20.70.24_40010@group-000100000001->172.20.70.23_40010: nextIndex: updateUnconditionally 1418 -> 1396

I looked back at previous directOOM logs and discovered this similar log pattern. Since these "inconsistent AppendEntries" are sent from leader almost with 0 waiting time (according to follower reply timestamp), I guess directOOM may related to continuous Leader "inconsistent AppendEntries", which consumes lots of direct memory for network transimission.

Through, I'm confused why a follower will report inconsistent from time to time while still can successfully append logs between these "inconsistent AppendEntries", why leader keeps sending “inconsistent AE" with zero waiting time.  There is no obvious network congestion. 

FYI, I've set RaftLog forceFlush to false. I'm not sure whether this async disk flush strategy is the cause for above abnormalities. 

I'll be grateful if anyone can help me with this issue. Thanks in advance!