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I am using MySQL Galera cluster as a backed database for Cloudera CDH environment. Recently I upgraded MySQL version from 5.6 to 5.7, My CDH version is 5.14.But post upgrade I am facing max_connections issues sometimes, max connection limit is 512 but those also getting exhausted sometimes even with 5.6 max_connection limit was 214 and I never faced issues.

I am wondering whether MySQL Galera 5.7 is having some bug where its not closing connections. I upgraded to 5.7 as it is the pre-requisite for CDH 6.

Looking for your help. Thank you so much in advance!

Thanks, Anurag

Anurag
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Many things can lead to hitting max_connections; all of them are under your control:

  • Lots clients that are connecting but never disconnecting.
  • The client software (Apache/Tomcat/...) is configured to allow lots of clients.
  • Connection pooling is configured too high.
  • wait_timeout is too high.
Rick James
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  • Thanks much James for inputs. The thing is it was working fine with MySQL 5.6, issues are coming with 5.7. Even we increased Max_connection limit to 1800 then also we were able to see at one time all 1800 were occupied. It means connections are not closing or some bug with Galera+5.7. If lot of client connecting and not disconnecting then issues should be permanently not randomly. No new software installation post 5.7 upgrade. Connection pooling and wait timeout is same as with 5.6. – Anurag Jan 10 '19 at 14:46