Thomas Steinmaurer created CASSANDRA-15430:
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Summary: Cassandra 3.0.18: BatchMessage.execute - 10x more on-heap
allocations compared to 2.1.18
Key: CASSANDRA-15430
URL: https://issues.apache.org/jira/browse/CASSANDRA-15430
Project: Cassandra
Issue Type: Bug
Reporter: Thomas Steinmaurer
Attachments: dashboard.png, jfr_allocations.png, mutation_stage.png
In a 6 node loadtest cluster, we have been running with 2.1.18 a certain
production-like workload constantly and sufficiently. After upgrading one node
to 3.0.18 (remaining 5 still on 2.1.18 after we have seen that sort of
regression described below), 3.0.18 is showing increased CPU usage, increase
GC, high mutation stage pending tasks, dropped mutation messages ...
Some spec. All 6 nodes equally sized:
* Bare metal, 32 physical cores, 512G RAM
* Xmx31G, G1, max pause millis = 2000ms
* cassandra.yaml basically unchanged, thus some settings in regard to number of
threads, compaction throttling etc.
Following dashboard shows highlighted areas (CPU, suspension) with metrics for
all 6 nodes and the outlier being the node upgraded to Cassandra 3.0.18.
!dashboard.png|width=1280!
Additionally we see a large increase on pending tasks in the mutation stage
after the upgrade:
!mutation_stage.png!
And dropped mutation messages, also confirmed in the Cassandra log:
{noformat}
INFO [ScheduledTasks:1] 2019-11-15 08:24:24,780 MessagingService.java:1022 -
MUTATION messages were dropped in last 5000 ms: 41552 for internal timeout and
0 for cross node timeout
INFO [ScheduledTasks:1] 2019-11-15 08:24:25,157 StatusLogger.java:52 - Pool
Name Active Pending Completed Blocked All Time
Blocked
INFO [ScheduledTasks:1] 2019-11-15 08:24:25,168 StatusLogger.java:56 -
MutationStage 256 81824 3360532756 0
0
INFO [ScheduledTasks:1] 2019-11-15 08:24:25,168 StatusLogger.java:56 -
ViewMutationStage 0 0 0 0
0
INFO [ScheduledTasks:1] 2019-11-15 08:24:25,168 StatusLogger.java:56 -
ReadStage 0 0 62862266 0
0
INFO [ScheduledTasks:1] 2019-11-15 08:24:25,169 StatusLogger.java:56 -
RequestResponseStage 0 0 2176659856 0
0
INFO [ScheduledTasks:1] 2019-11-15 08:24:25,169 StatusLogger.java:56 -
ReadRepairStage 0 0 0 0
0
INFO [ScheduledTasks:1] 2019-11-15 08:24:25,169 StatusLogger.java:56 -
CounterMutationStage 0 0 0 0
0
...
{noformat}
Judging from a 15min JFR session for both, 3.0.18 and 2.1.18 on a different
node, high-level, it looks like the code path underneath
{{BatchMessage.execute}} is producing ~ 10x more on-heap allocations in 3.0.18
compared to 2.1.18.
!jfr_allocations.png!
Left => 3.0.18
Right => 2.1.18
JFRs zipped are exceeding the 60MB limit to directly attach to the ticket. I
can upload them, if there is another destination available.
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