Ere Maijala created SOLR-10130:
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Summary: Serious performance degradation in Solr 6.4.1 due to the
new metrics collection
Key: SOLR-10130
URL: https://issues.apache.org/jira/browse/SOLR-10130
Project: Solr
Issue Type: Bug
Security Level: Public (Default Security Level. Issues are Public)
Components: metrics
Affects Versions: 6.4.1
Environment: Centos 7, OpenJDK 1.8.0 update 111
Reporter: Ere Maijala
Attachments: solr-8983-console-f1.log
We've stumbled on serious performance issues after upgrading to Solr 6.4.1.
Looks like the new metrics collection system in MetricsDirectoryFactory is
causing a major slowdown. This happens with an index configuration that, as far
as I can see, has no metrics specific configuration and uses luceneMatchVersion
5.5.0. In practice a moderate load will completely bog down the server with
Solr threads constantly using up all CPU (600% on 6 core machine) capacity with
a load that normally where we normally see an average load of < 50%.
I took stack traces (I'll attach them) and noticed that the threads are
spending time in com.codahale.metrics.Meter.mark. I tested building Solr 6.4.1
with the metrics collection disabled in MetricsDirectoryFactory getByte and
getBytes methods and was unable to reproduce the issue.
As far as I can see there are several issues:
1. Collecting metrics on every single byte read is slow.
2. Having it enabled by default is not a good idea.
3. The comment "enable coarse-grained metrics by default" at
https://github.com/apache/lucene-solr/blob/branch_6x/solr/core/src/java/org/apache/solr/update/SolrIndexConfig.java#L104
implies that only coarse-grained metrics should be enabled by default, and
this contradicts with collecting metrics on every single byte read.
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