Prevent ConcurrentModificationException for PushOne.refBatchesToPush
The PushOne.refBatchesToPush was a plain HashSet but r/w access to it
wasn't synchronized. Under some circumstances, traversing a stream
created on refBatchesToPush threw ConcurrentModificationException [1]
which caused the thread to die. As a side effect of the thread-death,
the replication task would never reschedule itself but would remain in
the pending tasks and all follow-up replications to the same URI would
be consolidated into that pending task which would never run. Only a
restart of the replication plugin would resolve the issue.
[1]
ERROR com.google.gerrit.server.git.WorkQueue : WorkQueue thread ReplicateTo-some-uri-2 threw exception
java.util.ConcurrentModificationException
at java.base/java.util.HashMap$KeySpliterator.tryAdvance(HashMap.java:1730)
at java.base/java.util.stream.ReferencePipeline.forEachWithCancel(ReferencePipeline.java:129)
at java.base/java.util.stream.AbstractPipeline.copyIntoWithCancel(AbstractPipeline.java:527)
at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:513)
at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921)
at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:682)
at com.googlesource.gerrit.plugins.replication.PushOne.getLimitedRefs(PushOne.java:255)
at com.googlesource.gerrit.plugins.replication.PushOne.toString(PushOne.java:221)
at com.google.gerrit.server.git.WorkQueue$ProjectTask.toString(WorkQueue.java:760)
at java.base/java.lang.StringConcatHelper.stringOf(StringConcatHelper.java:453)
at com.google.gerrit.server.git.WorkQueue$Task.run(WorkQueue.java:678)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
at java.base/java.lang.Thread.run(Thread.java:840)
Change-Id: I3f29779fd150868412e4994d307303d1dd8bde7b
diff --git a/src/main/java/com/googlesource/gerrit/plugins/replication/PushOne.java b/src/main/java/com/googlesource/gerrit/plugins/replication/PushOne.java
index ed84087..c25f375 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/replication/PushOne.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/replication/PushOne.java
@@ -122,7 +122,7 @@
private final Project.NameKey projectName;
private final URIish uri;
- private final Set<ImmutableSet<String>> refBatchesToPush = Sets.newHashSetWithExpectedSize(4);
+ private final Set<ImmutableSet<String>> refBatchesToPush = Sets.newConcurrentHashSet();
private boolean pushAllRefs;
private Repository git;
private boolean isCollision;
