Bug #8933 Memory leak when making a large number of connections

• Submitted: 3 Mar 2005 22:25
• Modified: 7 May 2005 15:07
• Reporter: [ name withheld ]
• Status: Can't repeat
• Category: MySQL Server
• Severity: S3 (Non-critical)
• Version: 4.1.6-gamma-standard
• OS: Linux (Fedora Core 2 (2.6.9-1.6_FC2))
• CPU Architecture: Any

[3 Mar 2005 22:25] [ name withheld ]

Description:
The process size of the mysql processes appears to grow slowly if applications rapidly connect and disconnect from the database.

In a long running server (90+ days), this problem eventually caused the mysql processes to become so large as to impact performance.  Restarting the mysql server resolves the issue, but that shouldn't be necessary.

How to repeat:
If you execute the following perl script and do 'ps aux | grep mysql' every 5-10 minutes on the database host, you can watch the size (RSS) of the mysql processes grow slowly.

#!/usr/bin/perl

use DBI;

my $i;
for ($i=0; $i<50000; $i++) {
    my $mysql_dbh =
        DBI->connect("DBI:mysql:database=some_database;host=some_host",
                     "user", "the user's password",
                     {RaiseError => 1, AutoCommit => 1});

    $mysql_dbh->disconnect();

    print "$i...\n" if ($i % 100 == 0);
}

Suggested fix:
Run a version of mysql with a memory leak detector compiled in to see if the leak can be easily munched.

[12 Apr 2005 19:41] Bruno Dingfelder

I have an application in PHP that also requires a large number of connections,
and after a few days my server performance will drop fast. When I check the
mysql server process I also noticed it grows:

@ 12:51 Pm

RES = 6940, % MEM = 2.8

@ 12:58 Pm

RES = 7628, % MEM =  3.1

I am running Default Mysql Php Rpms in Fedora Core 2