Communications link failure

Vincent Raaijmakers

Hi, we keep getting this error. We followed all of the recommendations provided by the log analyzer and made sure we confirm to the requirements.

MySql runs local on the same server, that should exclude network errors.

Database driver: mysql-connector-java-5.1.44

MySQL version: 5.7.21

In dbconfig.xml we have the validation query:

<validation-query>select 1</validation-query>

    <min-evictable-idle-time-millis>60000</min-evictable-idle-time-millis>

    <time-between-eviction-runs-millis>300000</time-between-eviction-runs-millis>

    <pool-max-idle>20</pool-max-idle>

    <pool-remove-abandoned>true</pool-remove-abandoned>

    <pool-remove-abandoned-timeout>300</pool-remove-abandoned-timeout>

    <pool-test-while-idle>true</pool-test-while-idle>

    <validation-query-timeout>3</validation-query-timeout>

 

We also (re)index frequently.

Yet, the # timeout errors are increasing. What can we do more to avoid these errors?

 

Thanks!

Vincent

Andy Heinzer

What version of Jira is this?

Why are you indexing frequently? 

 

I would recommend that you setup your dbconfig.xml to look as closely as possible to the sample listed in Connecting Jira to MySQL.

This communication link failure error tends to happen because Jira is expecting to handle its own database connection pool and does this on the set intervals of those eviction parameters.  The problem you are likely seeing is that your MySQL variables called 'wait_timeout' and/or 'interactive_timeout' are set to be a time period that is shorter than the eviction process timing Jira is trying to do.

In essence, MySQL is configured to kill these idle connections before Jira can clean them up by its own processes.   By default MySQL is set to a value of 28800 (in seconds) which equals once every 8 hours where it does this kind of connection clean up. 

Jira is using milliseconds to do these evictions, so typically every 300000 ms = 5 minutes with these settings.  I'm guessing your MySQL has an interval set currently that is probably less than 10 minutes if you're seeing this sometimes, and probably 5 minutes or less if you're seeing this a lot.  The problem comes because Jira is not aware the MySQL has killed this connection.  So Jira still believes it has to cleanup and/or reuse this connection and it cannot at that point. Hence you see this error in the Jira logs. 

In short, I would recommend looking at the KB: Connection Timeout with MySQL Database and then adjusting the MySQL variables to a larger value than Jira's eviction timing.

Granted that is a KB for the Stash product using MySQL, but the concepts are the same in Jira.  I remember the tricky part of this is that you tend to have to look at all three sections in MySQL to find where the variable has been shortened.

Note that MySQL retains several scopes for the wait_timeout and interactive_timeout variable. Double check the same setting of the variable by running the following queries on the database:

1. SHOW VARIABLES
2. SHOW SESSION VARIABLES
3. SHOW GLOBAL VARIABLES