[debian-mysql] Bug#1027337: mariadb-server-10.5: Huge increase in memory consumption (leak?) since upgrade from 10.5.15 to 10.5.18

[Matteo Valsasna]

Dear Mantainer,


We are experiencing a similar memory leak after porting an application from Debian 9 (mariadb 10.1.41-MariaDB-0+deb9u1) to Debian 11 (10.5.18-MariaDB-0+deb11u1)


  1.  the mariadb memory footprint (/proc/pid/status:VmSize) at mariadb startup is 3GB, with innodb_buffer_pool_size=512 MB
  2.  The virtual memory growth rate is around 500-800 MB / day (compatible with the 33MB / hour mentioned by Xan Charbonnet)

Using the following query, we were able to attribute the memory growth to the database connections used by the emqx MQTT broker (configured for mysql authentication)

SELECT id, db,command,progress,memory_used,max_memory_used,examined_rows, TIME, host, COMMAND   from INFORMATION_SCHEMA.PROCESSLIST  order by max_memory_used desc  ;

It seems that the only query being performed by emqx is quite simple:
select allow, ipaddr, username, clientid, access, topic from mqtt_acl where ipaddr = ? or username = ? or username = '$all' or clientid = ? order by allow asc

There are many other services using mariadb on the same machine, and they don't show a similar memory growth according to the PROCESSLIST table.


Thanks

MAtteo
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