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IDProjectCategoryView StatusLast Update
0006268CentOS-6mysqlpublic2013-04-25 20:15
PriorityhighSeveritymajorReproducibilityhave not tried
Status newResolutionopen 
Platformx86_64OSCentOSOS Version6.3
Product Version6.3 
Target VersionFixed in Version 
Summary0006268: MySQL 1023 connections limit
DescriptionHi *,

a few weeks ago i changed the OS on my server from SuSE-Enterprise-Linux to CentOS 6.3.

Since then I`m having some issues regarding the MySQL server on it. The whole configuration from the old OS was just copied to the new server and adapted.

The problem is, that a maximum of 1023 connections ("Max_used_connections") to the server can be established while the limit in MySQL is set to 2800 connections.
What i`ve done so far (without improvement):
-Changing the "/etc/security/limits.conf"
-Setting some kernel parameters:
-Disabling SELinux

I`ve also found a Bugreport from RHEL4, in which a user was suffering the same problem, but I`m not able to find this report at the moment.

Best regards,

Steps To ReproduceAs i don`t think you have any fat servers availible for just to reproduce this error, i may offer you to have a look via Teamviewer on this box if needed.
Just drop me a mail to maximilian DOT herrmann AT jambit DOT com
Additional Informationlimits.conf:
   mysql soft nofile 65536
   mysql hard nofile 65536
   mysql soft nproc 65536
   mysql hard nproc 65536
   mysql soft stack 65536
   mysql hard stack 65536

ulimit -a as mysql:
[root@www56 ~]# su - mysql
-bash-4.1$ ulimit -a
   core file size (blocks, -c) 0
   data seg size (kbytes, -d) unlimited
   scheduling priority (-e) 0
   file size (blocks, -f) unlimited
   pending signals (-i) 385852
   max locked memory (kbytes, -l) 64
   max memory size (kbytes, -m) unlimited
   open files (-n) 65536
   pipe size (512 bytes, -p) 8
   POSIX message queues (bytes, -q) 819200
   real-time priority (-r) 0
   stack size (kbytes, -s) 65536
   cpu time (seconds, -t) unlimited
   max user processes (-u) 65536
   virtual memory (kbytes, -v) unlimited
   file locks (-x) unlimited

Kernel parameters optimized:
    /proc/sys/net/netfilter/nf_conntrack_expect_max (now set to 4096)
    /proc/sys/net/core/netdev_max_backlog (now set to 50000)
    /proc/sys/net/ipv4/tcp_max_syn_backlog (now set to 30000)
    /proc/sys/net/ipv4/tcp_max_tw_buckets (now set to 200000)
    /proc/sys/kernel/shmmax (now set to 67645734912)
    /proc/sys/kernel/shmall (now set to 16515072)
    /proc/sys/net/core/somaxconn (now set to 65535)
TagsNo tags attached.




2013-03-13 19:22

reporter   ~0016699


may anyone review this bug, please?
It`s a very unpleasant situation for me...




2013-04-25 20:15

reporter   ~0017313


this is definitly a bug at CentOS, a collegue of me fixed this.

You have to write your limits down to /etc/security/limits.d /91-mysql.conf, because there`s the file "90-nproc.conf", which overrides all settings and doesn`t show up these limits on a ulimit.
It`s also possible to write these settings to a running process, for this you will need the PID and then do the following:
echo -n "Max processes=385852:385852" > /proc/<YOURPROCESSPID>/limits

Thanks for your REAL GREAT help!! Sorry, but i don`t understand this. It`s a serious problem for EVERYONE by using a bit more connections than the default settings, and nobody even answers with an question. I know that CentOS is an community product, but there are much more insignificant/nonrelevant "Bugs" (i mean some Layer-8-errors) which are getting much more RESPONSE than my question. I`m really nerved about this situation, and this is understated.


Issue History

Date Modified Username Field Change
2013-02-23 23:37 mherrman-jambit New Issue
2013-03-13 19:22 mherrman-jambit Note Added: 0016699
2013-04-25 20:15 mherrman-jambit Note Added: 0017313