[CASSANDRA-9573] OOM when loading sstables (system.hints)

• Type: Bug
• Status: Resolved
• Priority: Urgent
• Resolution: Fixed
• Fix Version/s: 2.2.0 rc2
• Component/s: Legacy/Coordination
• Severity: Critical
• Assignee: Sam Tunnicliffe
• Reporter: Alan Boudreault

Authors

Sam Tunnicliffe

Reviewers

Aleksey Yeschenko

• Tester: Alan Boudreault
• Created: 10/Jun/15 15:02
• Updated: 16/Apr/19 09:31
• Resolved: 11/Jun/15 19:21

Description

andrew.tolbert discovered an issue while running endurance tests on 2.2. A Node was not able to start and was killed by the OOM Killer.

Briefly, Cassandra use an excessive amount of memory when loading compressed sstables (off-heap?). We have initially seen the issue with system.hints before knowing it was related to compression. system.hints use lz4 compression by default. If we have a sstable of, say 8-10G, Cassandra will be killed by the OOM killer after 1-2 minutes. I can reproduce that bug everytime locally.

• the issue also happens if we have 10G of data splitted in 13MB sstables.
• I can reproduce the issue if I put a lot of data in the system.hints table.
• I cannot reproduce the issue with a standard table using the same compression (LZ4). Something seems to be different when it's hints?

You wont see anything in the node system.log but you'll see this in /var/log/syslog.log:

Out of memory: Kill process 30777 (java) score 600 or sacrifice child

The issue has been introduced in this commit but is not related to the performance issue in CASSANDRA-9240: https://github.com/apache/cassandra/commit/aedce5fc6ba46ca734e91190cfaaeb23ba47a846

Here is the core dump and some yourkit snapshots in attachments. I am not sure you will be able to get useful information from them.
core dump: http://dl.alanb.ca/core.tar.gz

Not sure if this is related, but all dumps and snapshot points to EstimatedHistogramReservoir ... and we can see many javax.management.InstanceAlreadyExistsException: org.apache.cassandra.metrics:... exceptions in system.log before it hangs then crash.

To reproduce the issue:
1. created a cluster of 3 nodes
2. start the whole cluster
3. shutdown node2 and node3
4. writes 10-15G of data on node1 with replication factor 3. You should see a lot of hints.
5. stop node1
6. start node2 and node3
7. start node1, you should OOM.

//cc tjake benedict andrew.tolbert

Issue Links

• is broken by: CASSANDRA-9240 Performance issue after a restart