Damien Obrist created OAK-566:
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Summary: MongoMK throws exception when adding nodes concurrently
Key: OAK-566
URL: https://issues.apache.org/jira/browse/OAK-566
Project: Jackrabbit Oak
Issue Type: Bug
Components: mongomk
Reporter: Damien Obrist
Priority: Minor
It seems that there is a problem in the MongoDB microkernel when lots of
threads try to commit new nodes concurrently. I have attached a JUnit test
which reproduces the error. The test creates 16 microkernels, each committing
two nodes in a separate thread. Some threads will throw an exception saying
that the node they're trying to commit already exists:
java.lang.RuntimeException: There's already a child node with name 'node6'
at
org.apache.jackrabbit.mongomk.impl.instruction.CommitCommandInstructionVisitor.visit(CommitCommandInstructionVisitor.java:97)
at
org.apache.jackrabbit.mongomk.impl.instruction.AddNodeInstructionImpl.accept(AddNodeInstructionImpl.java:40)
at
org.apache.jackrabbit.mongomk.impl.command.CommitCommandNew.createMongoNodes(CommitCommandNew.java:155)
at
org.apache.jackrabbit.mongomk.impl.command.CommitCommandNew.execute(CommitCommandNew.java:97)
at
org.apache.jackrabbit.mongomk.impl.command.CommitCommandNew.execute(CommitCommandNew.java:1)
at
org.apache.jackrabbit.mongomk.impl.command.DefaultCommandExecutor.execute(DefaultCommandExecutor.java:38)
at
org.apache.jackrabbit.mongomk.impl.MongoNodeStore.commit(MongoNodeStore.java:110)
at
org.apache.jackrabbit.mongomk.impl.MongoMicroKernel.commit(MongoMicroKernel.java:112)
... 7 more
This cannot be the case however, as the nodes added by the different threads do
not overlap / conflict. No exceptions are thrown if setting the number of
threads to some lower number, but I have observed that in this case the problem
still exists when trying to add a larger number of nodes (more than just 2).
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