The code will not work properly, sorry. The value returned by the state is whatever is stored under the key for which the function was called the last time. In addition, the unsynchronized access is most likely causing the RocksDB fault.
TL:DR - The "ValueState" / "ListState" / etc in Flink are not intended to be used across threads. On Fri, Mar 24, 2017 at 8:28 AM, Florian König <florian.koe...@micardo.com> wrote: > Hi, > > @Robert: I have uploaded all the log files that I could get my hands on to > https://www.dropbox.com/sh/l35q6979hy7mue7/AAAe1gABW59eQt6jGxA3pAYaa?dl=0. > I tried to remove all unrelated messages logged by the job itself. In > flink-root-jobmanager-0-micardo-dev.log I kept the Flink startup messages > and the last half hour before the segfault. > > @Stefan: Your theory could be the key. In the stack trace I see a call to > org.apache.flink.runtime.metrics.dump.MetricDumpSerialization.serializeGauge > that results in a call to > com.micardo.backend.tail.TransitionProcessor$2.getValue()Ljava/lang/Long > later. Here’s a slimmed-down snippet of the relevant code: > > class TransitionProcessor extends RichFlatMapFunction<Transition, > Reaction> { > > transient ValueState<IdSet> headSeenState; > > public void open(final Configuration parameters) throws Exception { > headSeenState = FlinkUtil.getStateHandle(this, > "head-seen", IdSet.class); > > getRuntimeContext() > .getMetricGroup() > .gauge("head-seen", new Gauge<Long>() { > public Long getValue() { > try { > return > headSeenState.value().count(); > } catch (IOException e) { > e.printStackTrace(); > return 0L; > } > } > }); > } > … > } > > FlinkUtil.getStateHandle instantiates a ValueStateDescriptor and acquires > a reference to that state via the RuntimeContext of the RichFunction passed > as ‚this‘ in the above code. > > Further along in the stack trace I see that headSeenState.value() results > in a call to > org.apache.flink.contrib.streaming.state.RocksDBValueState.value() > and then to org.rocksdb.RocksDB.get(J[BIJ). > > It looks like part of the metrics system asynchronously reads the value of > the gauge and needs RocksDB for that. Is it possible that this thread does > not hold the checkpointing lock you were talking about? > > Best regards > Florian > > > > Am 22.03.2017 um 18:19 schrieb Stefan Richter < > s.rich...@data-artisans.com>: > > > > Hi, > > > > for the first checkpoint, from the stacktrace I assume that the backend > is not accessed as part of processing an element, but by another thread. Is > that correct? RocksDB requires accessing threads to hold the task’s > checkpointing lock, otherwise they might call methods on an instance that > is already disposed. However, this should only happen when the task was > already about to shutdown anyways. Is that a plausible explanation for your > observed behaviour? I can also not rule out that segfaults can happen > inside RocksDB or due to the JNI bridge. > > > > Best, > > Stefan > > > >> Am 22.03.2017 um 16:53 schrieb Florian König < > florian.koe...@micardo.com>: > >> > >> Hi Stephen, > >> > >> you are right, the second stack trace is indeed from a run of Flink > 1.1.4. Sorry, my bad. > >> > >> That leaves us with the first trace of a segfault for which I can > guarantee that it brought down a 1.2.0 instance. Unfortunately I cannot > reproduce the problem. It has happened twice so far, but I can’t see any > pattern. Is there anything in the stack trace that could point us to a > probable cause? > >> > >> Florian > >> > >>> Am 22.03.2017 um 16:00 schrieb Stephan Ewen <se...@apache.org>: > >>> > >>> Hi! > >>> > >>> It looks like you are running the RocksDB state backend 1.1 (is still > an old version packaged into your JAR file?) > >>> > >>> This line indicates that: org.apache.flink.contrib.streaming.state. > RocksDBStateBackend.performSemiAsyncSnapshot (the method does not exist > in 1.2 any more) > >>> > >>> Can you try and run 1.2 and see if that still occurs? In general, I > cannot vouch 100% for RocksDBs JNI API, but in our 1.2 tests so far it was > stable. > >>> > >>> Stephan > >>> > >>> > >>> > >>> On Wed, Mar 22, 2017 at 3:13 PM, Florian König < > florian.koe...@micardo.com> wrote: > >>> Hi, > >>> > >>> I have experienced two crashes of Flink 1.2 by SIGSEGV, caused by > something in RocksDB. What is the preferred way to report them? All I got > at the moment are two hs_err_pid12345.log files. They are over 4000 lines > long each. Is there anything significant that I should extract to help you > guys and/or put into a JIRA ticket? > >>> > >>> The first thing that came to my mind was the stack traces (see below). > Anything else? > >>> > >>> Thanks > >>> Florian > >>> > >>> ---- > >>> > >>> Stack: [0x00007fec04341000,0x00007fec04442000], > sp=0x00007fec0443ff48, free space=1019k > >>> Java frames: (J=compiled Java code, j=interpreted, Vv=VM code) > >>> J 10252 org.rocksdb.RocksDB.get(J[BIJ)[B (0 bytes) @ > 0x00007fec925887cc [0x00007fec92588780+0x4c] > >>> J 27241 C2 org.apache.flink.contrib.streaming.state. > RocksDBValueState.value()Ljava/lang/Object; (78 bytes) @ > 0x00007fec94010ca4 [0x00007fec940109c0+0x2e4] > >>> j com.micardo.backend.TransitionProcessor$2. > getValue()Ljava/lang/Long;+7 > >>> j com.micardo.backend.TransitionProcessor$2. > getValue()Ljava/lang/Object;+1 > >>> J 38483 C2 org.apache.flink.runtime.metrics.dump. > MetricDumpSerialization.serializeGauge(Ljava/io/ > DataOutput;Lorg/apache/flink/runtime/metrics/dump/ > QueryScopeInfo;Ljava/lang/String;Lorg/apache/flink/metrics/Gauge;)V (114 > bytes) @ 0x00007fec918eabf0 [0x00007fec918eabc0+0x30] > >>> J 38522 C2 org.apache.flink.runtime.metrics.dump. > MetricDumpSerialization$MetricDumpSerializer.serialize(Ljava/util/Map; > Ljava/util/Map;Ljava/util/Map;Ljava/util/Map;)Lorg/apache/ > flink/runtime/metrics/dump/MetricDumpSerialization$MetricSerializationResult; > (471 bytes) @ 0x00007fec94eb6260 [0x00007fec94eb57a0+0xac0] > >>> J 47531 C2 org.apache.flink.runtime.metrics.dump. > MetricQueryService.onReceive(Ljava/lang/Object;)V (453 bytes) @ > 0x00007fec95ca57a0 [0x00007fec95ca4da0+0xa00] > >>> J 5815 C2 akka.actor.UntypedActor.aroundReceive(Lscala/ > PartialFunction;Ljava/lang/Object;)V (7 bytes) @ 0x00007fec91e3ae6c > [0x00007fec91e3adc0+0xac] > >>> J 5410 C2 akka.actor.ActorCell.invoke(Lakka/dispatch/Envelope;)V (104 > bytes) @ 0x00007fec91d5bc44 [0x00007fec91d5b9a0+0x2a4] > >>> J 6628 C2 scala.concurrent.forkjoin.ForkJoinPool$WorkQueue. > runTask(Lscala/concurrent/forkjoin/ForkJoinTask;)V (60 bytes) @ > 0x00007fec9212d050 [0x00007fec9212ccc0+0x390] > >>> J 40130 C2 scala.concurrent.forkjoin.ForkJoinWorkerThread.run()V (182 > bytes) @ 0x00007fec923f8170 [0x00007fec923f7fc0+0x1b0] > >>> v ~StubRoutines::call_stub > >>> > >>> -------------------------------------- > >>> > >>> Stack: [0x00007f167a5b7000,0x00007f167a6b8000], > sp=0x00007f167a6b5f40, free space=1019k > >>> Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, > C=native code) > >>> C [libstdc++.so.6+0xc026b] std::basic_string<char, > std::char_traits<char>, std::allocator<char> >::basic_string(std::string > const&)+0xb > >>> C [librocksdbjni8426686507832168508.so+0x2f14ca] > rocksdb::BackupEngine::Open(rocksdb::Env*, rocksdb::BackupableDBOptions > const&, rocksdb::BackupEngine**)+0x3a > >>> C [librocksdbjni8426686507832168508.so+0x180ad5] > Java_org_rocksdb_BackupEngine_open+0x25 > >>> J 50030 org.rocksdb.BackupEngine.open(JJ)J (0 bytes) @ > 0x00007f16cb79aa36 [0x00007f16cb79a980+0xb6] > >>> J 49809 C1 org.apache.flink.contrib.streaming.state. > RocksDBStateBackend.performSemiAsyncSnapshot(JJ)Ljava/util/HashMap; (416 > bytes) @ 0x00007f16cd2733d4 [0x00007f16cd2719a0+0x1a34] > >>> J 51766 C2 org.apache.flink.contrib.streaming.state. > RocksDBStateBackend.snapshotPartitionedState(JJ)Ljava/util/HashMap; (40 > bytes) @ 0x00007f16cb40a1fc [0x00007f16cb40a1a0+0x5c] > >>> J 50547 C2 org.apache.flink.streaming.api.operators. > AbstractUdfStreamOperator.snapshotOperatorState(JJ)Lorg/ > apache/flink/streaming/runtime/tasks/StreamTaskState; (206 bytes) @ > 0x00007f16cb8be89c [0x00007f16cb8be7e0+0xbc] > >>> J 52232 C2 > >>> org.apache.flink.streaming.runtime.tasks.StreamTask.performCheckpoint(JJ)Z > (650 bytes) @ 0x00007f16cbfbbf60 [0x00007f16cbfbb540+0xa20] > >>> J 52419 C2 org.apache.flink.streaming.runtime.io.BarrierBuffer. > notifyCheckpoint(Lorg/apache/flink/runtime/io/network/api/CheckpointBarrier;)V > (25 bytes) @ 0x00007f16cbdd2624 [0x00007f16cbdd25c0+0x64] > >>> J 41649 C2 org.apache.flink.streaming.runtime.io.StreamInputProcessor. > processInput(Lorg/apache/flink/streaming/api/operators/ > OneInputStreamOperator;Ljava/lang/Object;)Z (439 bytes) @ > 0x00007f16cc8aed5c [0x00007f16cc8add40+0x101c] > >>> J 33374% C2 > >>> org.apache.flink.streaming.runtime.tasks.OneInputStreamTask.run()V > (42 bytes) @ 0x00007f16cbdc21d0 [0x00007f16cbdc20c0+0x110] > >>> j org.apache.flink.streaming.runtime.tasks.StreamTask.invoke()V+301 > >>> j org.apache.flink.runtime.taskmanager.Task.run()V+700 > >>> j java.lang.Thread.run()V+11 > >>> v ~StubRoutines::call_stub > >>> V [libjvm.so+0x68c616] > >>> V [libjvm.so+0x68cb21] > >>> V [libjvm.so+0x68cfc7] > >>> V [libjvm.so+0x723d80] > >>> V [libjvm.so+0xa69dcf] > >>> V [libjvm.so+0xa69efc] > >>> V [libjvm.so+0x91d9d8] > >>> C [libpthread.so.0+0x8064] start_thread+0xc4 > >>> > >>> Java frames: (J=compiled Java code, j=interpreted, Vv=VM code) > >>> J 50030 org.rocksdb.BackupEngine.open(JJ)J (0 bytes) @ > 0x00007f16cb79a9c4 [0x00007f16cb79a980+0x44] > >>> J 49809 C1 org.apache.flink.contrib.streaming.state. > RocksDBStateBackend.performSemiAsyncSnapshot(JJ)Ljava/util/HashMap; (416 > bytes) @ 0x00007f16cd2733d4 [0x00007f16cd2719a0+0x1a34] > >>> J 51766 C2 org.apache.flink.contrib.streaming.state. > RocksDBStateBackend.snapshotPartitionedState(JJ)Ljava/util/HashMap; (40 > bytes) @ 0x00007f16cb40a1fc [0x00007f16cb40a1a0+0x5c] > >>> J 50547 C2 org.apache.flink.streaming.api.operators. > AbstractUdfStreamOperator.snapshotOperatorState(JJ)Lorg/ > apache/flink/streaming/runtime/tasks/StreamTaskState; (206 bytes) @ > 0x00007f16cb8be89c [0x00007f16cb8be7e0+0xbc] > >>> J 52232 C2 > >>> org.apache.flink.streaming.runtime.tasks.StreamTask.performCheckpoint(JJ)Z > (650 bytes) @ 0x00007f16cbfbbf60 [0x00007f16cbfbb540+0xa20] > >>> J 52419 C2 org.apache.flink.streaming.runtime.io.BarrierBuffer. > notifyCheckpoint(Lorg/apache/flink/runtime/io/network/api/CheckpointBarrier;)V > (25 bytes) @ 0x00007f16cbdd2624 [0x00007f16cbdd25c0+0x64] > >>> J 41649 C2 org.apache.flink.streaming.runtime.io.StreamInputProcessor. > processInput(Lorg/apache/flink/streaming/api/operators/ > OneInputStreamOperator;Ljava/lang/Object;)Z (439 bytes) @ > 0x00007f16cc8aed5c [0x00007f16cc8add40+0x101c] > >>> J 33374% C2 > >>> org.apache.flink.streaming.runtime.tasks.OneInputStreamTask.run()V > (42 bytes) @ 0x00007f16cbdc21d0 [0x00007f16cbdc20c0+0x110] > >>> j org.apache.flink.streaming.runtime.tasks.StreamTask.invoke()V+301 > >>> j org.apache.flink.runtime.taskmanager.Task.run()V+700 > >>> j java.lang.Thread.run()V+11 > >>> v ~StubRoutines::call_stub > >>> > >>> > >>> > >>> > >> > >> > > > > >
