[SOLR-10130] Serious performance degradation in Solr 6.4.1 due to the new metrics collection

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 6.4, 6.4.1
• Fix Version/s: 6.4.2, 7.0
• Component/s: metrics
• Labels: perfomance

Environment

Centos 7, OpenJDK 1.8.0 update 111

• Assignee: Andrzej Bialecki
• Reporter: Ere Maijala
• Created: 13/Feb/17 11:58
• Updated: 08/Jun/19 15:30
• Resolved: 15/Feb/17 13:58

Description

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.

Issue Links

• is broken by: SOLR-9854 Collect metrics for index merges and index store IO
• is duplicated by: SOLR-10172 Sorl 6 with jetty issues
• is duplicated by: SOLR-10150 Solr 6.4 up to 10x slower than 6.3
• is duplicated by: SOLR-10140 Performance degradation and CPU spike when moving to Solr 6.4.1
• is related to: SOLR-10182 Backout directory metrics collection that caused performance degradation