fork: retry: Resource temporarily unavailable [closed]

This is commonly caused by running out of file descriptors.

There is the systems total file descriptor limit, what do you get from the command:

sysctl fs.file-nr

This returns counts of file descriptors:

<in_use> <unused_but_allocated> <maximum>

To find out what a users file descriptor limit is run the commands:

sudo su - <username>
ulimit -Hn

To find out how many file descriptors are in use by a user run the command:

sudo lsof -u <username> 2>/dev/null | wc -l

So now if you are having a system file descriptor limit issue you will need to edit your /etc/sysctl.conf file and add, or modify it it already exists, a line with fs.file-max and set it to a value large enough to deal with the number of file descriptors you need and reboot.

fs.file-max = 204708

Another possibility is too many threads. We just ran into this error message when running a test harness against an app that uses a thread pool. We used

watch -n 5 -d "ps -eL <java_pid> | wc -l"

to watch the ongoing count of Linux native threads running within the given Java process ID. After this hit about 1,000 (for us--YMMV), we started getting the error message you mention.