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https://issues.apache.org/jira/browse/CASSANDRA-12649?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15643580#comment-15643580
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Alwyn Davis commented on CASSANDRA-12649:
-----------------------------------------
Sure. I ran cassandra-stress on a separate EC2 instance against a 3-node
cluster with trunk and then with the batch metrics patch. The results summary
is (I've also attached the full stress output):
TRUNK
--------
LOGGED
Row rate: 13,965 row/s, 95th latency: 1.4ms
Row rate: 14,351 row/s, 95th latency: 1.3ms
Row rate: 14,359 row/s, 95th latency: 1.7ms
UNLOGGED
Row rate: 14,674 row/s, 95th latency: 1.3ms
Row rate: 14,168 row/s, 95th latency: 1.7ms
Row rate: 14,128 row/s, 95th latency: 1.7ms
BATCH METRICS
--------------------
LOGGED
Row rate: 13,531 row/s, 95th latency: 1.9ms
Row rate: 13,943 row/s, 95th latency: 1.7ms
Row rate: 14,210 row/s, 95th latency: 1.7ms
UNLOGGED
Row rate: 14,552 row/s, 95th latency: 1.3ms
Row rate: 14,568 rwo/s, 95th latency: 1.3ms
Row rate: 14,627 row/s, 95th latency: 1.2ms
I also ran the BatchMetrics test class with the metrics patch and just trunk
for comparison (10,000 iterations of single queries, logged, unlogged and CAS
batches):
WITH BATCH METRICS
query: 378410 ms, loggedBatch: 31638 ms, unloggedBatch: 21466 ms, cas: 33880 ms
query: 392960 ms, loggedBatch: 26284 ms, unloggedBatch: 21114 ms, cas: 30566 ms
query: 386964 ms, loggedBatch: 28724 ms, unloggedBatch: 22257 ms, cas: 33323 ms
TRUNK
query: 395683 ms, loggedBatch: 29994 ms, unloggedBatch: 21638 ms, cas: 33096 ms
query: 379503 ms, loggedBatch: 29911 ms, unloggedBatch: 21346 ms, cas: 32364 ms
query: 396935 ms, loggedBatch: 42124 ms, unloggedBatch: 21679 ms, cas: 34353 ms
Regarding the usefulness of Logged / Unlogged Partitions per batch, I believe
that it would allow correlation of batch size to performance. Standard advice
is to process a single partition per unlogged batch, so comparing the number of
partitions per batch against throughput should highlight poor usage of batches.
> Add BATCH metrics
> -----------------
>
> Key: CASSANDRA-12649
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12649
> Project: Cassandra
> Issue Type: Wish
> Reporter: Alwyn Davis
> Priority: Minor
> Fix For: 3.x
>
> Attachments: 12649-3.x.patch, stress-batch-metrics.tar.gz,
> stress-trunk.tar.gz, trunk-12649.txt
>
>
> To identify causes of load on a cluster, it would be useful to have some
> additional metrics:
> * *Mutation size distribution:* I believe this would be relevant when
> tracking the performance of unlogged batches.
> * *Logged / Unlogged Partitions per batch distribution:* This would also give
> a count of batch types processed. Multiple distinct tables in batch would
> just be considered as separate partitions.
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