Dinesh Joshi created CASSANDRA-14554:
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Summary: LifecycleTransaction encounters
ConcurrentModificationException when used in multi-threaded context
Key: CASSANDRA-14554
URL: https://issues.apache.org/jira/browse/CASSANDRA-14554
Project: Cassandra
Issue Type: Bug
Reporter: Dinesh Joshi
Assignee: Dinesh Joshi
When LifecycleTransaction is used in a multi-threaded context, we encounter
this exception -
{quote}java.util.ConcurrentModificationException: null
at java.util.LinkedHashMap$LinkedHashIterator.nextNode(LinkedHashMap.java:719)
at java.util.LinkedHashMap$LinkedKeyIterator.next(LinkedHashMap.java:742)
at java.lang.Iterable.forEach(Iterable.java:74)
at
org.apache.cassandra.db.lifecycle.LogReplicaSet.maybeCreateReplica(LogReplicaSet.java:78)
at org.apache.cassandra.db.lifecycle.LogFile.makeRecord(LogFile.java:320)
at org.apache.cassandra.db.lifecycle.LogFile.add(LogFile.java:285)
at
org.apache.cassandra.db.lifecycle.LogTransaction.trackNew(LogTransaction.java:136)
at
org.apache.cassandra.db.lifecycle.LifecycleTransaction.trackNew(LifecycleTransaction.java:529)
{quote}
During streaming we create a reference to a {{LifeCycleTransaction}} and share
it between threads -
[https://github.com/apache/cassandra/blob/5cc68a87359dd02412bdb70a52dfcd718d44a5ba/src/java/org/apache/cassandra/db/streaming/CassandraStreamReader.java#L156]
This is used a multi-threaded context inside of {{CassandraIncomingFile}} which
is a {{IncomingStreamMessage}}. This is being deserialized in parallel.
{{LifecycleTransaction}} is not meant to be used in a multi-threaded context
and this leads to streaming failures due to object sharing. On trunk, this
object is shared across all threads that transfer sstables in parallel for the
given {{TableId}} in a {{StreamSession}}. There are two options to solve this -
make {{LifecycleTransaction}} and the associated objects thread safe, scope the
transaction to a single {{CassandraIncomingFile}}. The consequences of the
latter option is that if we experience streaming failure we may have redundant
SSTables on disk. This is ok as compaction should clean this up. A third option
is we synchronize access in the streaming infrastructure.
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