Difinition
File descriptors are required so that the OpenSearch process can keep track of all the files it has open at any given time as well as all network connections to other nodes.
Running out of file descriptors would result in the OpenSearch process not being able to keep track of the files it has open or not being able to open new files or socket connections when it needs to, and will most probably lead to data loss.
The OpenSearch process should be permitted up to 65,536 or more.
How to resolve it
If you used systemd or yum to install OpenSearch, then the setting should be applied automatically. If you installed a tarball then you will need to do the following:
Edit /etc/security/limits.conf
Add the line:
opensearch - nofile 65535
MacOS users must also add the following line to the jvm.options file (not necessary for Linux):
-XX:-MaxFDLimit
Restart OpenSearch.
You can check the setting has taken effect:
GET _nodes/stats/process?filter_path=**.max_file_descriptors
