On some occasions, ClusterControl backup might fail or stall with the following errors:
InnoDB: Error number 24 means 'Too many open files'.
It indicates that you have reached the OS's maximum number of open file descriptors. The default value (1024) is too low for Xtrabackup. To increase open files limitation to a recommended value, which is 16384, you can use our script s9s_ulimit available in our Git repository.
Clone the Git repo in ClusterControl host (run this on the controller) and navigate into "cluster" directory :
$ git clone https://github.com/severalnines/s9s-admin.git
$ cd s9s-admin/cluster
Execute the script:
$ ./s9s_ulimit
Explanation
This script will automatically insert two lines into /etc/security/limits.conf, the soft limit and hard limit respectively. Example of output of the file if above command has executed:
# /etc/security/limits.conf
* soft nofile 16384
* hard nofile 16384
** The settings will be applied in each host in the cluster including ClusterControl host.
Please note that all limit settings are set per login. They are not global, nor are they permanent; existing only for the duration of the session. The script will insert a command into /root/.bashrc which will run and set the specified limit every time the root user login. To activate the changes, you need to re-login the SSH or console session.
Use following command to get the summary of current limits (as root):
$ ulimit -a
Other Parameters
This script is also able to accept two parameters; -t or --item and -n or --value which can be used to adjust any other items related to ulimit.
$ ./s9s_ulimit -t core -n 0
You may refer to this manual for supported items and values: http://ss64.com/bash/limits.conf.html
Notes
This script will not accept "unlimited" value as it could cause problem in some areas as reported in this bug report: https://bugzilla.redhat.com/show_bug.cgi?id=485955. Nevertheless, you can still change the value to "unlimited" using your own way.
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Encountering 'Error number 24 - Too many open files' during ClusterControl backup? This issue arises when the OS's file descriptor limit is surpassed. Solve it by adjusting the open files limit to 16384 using our convenient s9s_ulimit script. Clone the Git repo, run the script, and effortlessly elevate your open files limit. The changes apply to all hosts in the cluster, ensuring a smooth backup process. Check cissp online training and adjust other ulimit parameters if needed. Simple yet effective solution for seamless operations!
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