memory leak in CompactionManager's estimatedCompactions
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Key: CASSANDRA-2708
URL: https://issues.apache.org/jira/browse/CASSANDRA-2708
Project: Cassandra
Issue Type: Bug
Components: Core
Affects Versions: 0.7.6
Reporter: Dan LaRocque
Priority: Minor
CompactionManager's estimatedCompactions map seems to hold all or most
ColumnFamilyStores in the system as keys. Keys are never removed from
estimatedCompactions.
I have a project that embeds Cassandra as a storage backend. Some of my
integration tests create and drop a single keyspace and pair of column families
a hundred or 150 times in one JVM. These tests always OOM'd. Loading some
near-death heapdumps in mat suggested CompactionManager's estimatedCompactions
held over 80% of total heap via its ColumnFamilyStore keys.
estimatedCompactions had the only inbound reference to these CFSs, and the CFSs
themselves had invalid = true.
As a workaround, I changed estimatedCompactions to a WeakReference-keyed map
(using Guava MapMaker). My integration tests no longer OOM.
I'm generally unfamiliar with Cassandra's guts. I don't know whether weak
referencing the keys of estimatedCompactions is correct (or ideal). But, that
did seem to confirm my guess that retained references to dead CFSs in
estimatedCompactions were swamping my heap after lots of Keyspace+ColumnFamily
drops.
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