Shibboleth SP Thread key creation failed

[Rod Widdowson]

> It is using DB for clustering the SP; restart fixes the problem. Server running out of resources?

Looks like it:

> The pthread_create() function shall fail if:
> EAGAIN
> The system lacked the necessary resources to create another thread, or the system-imposed limit on the total number 
> of threads in a process {PTHREAD_THREADS_MAX} would be exceeded.

(with thanks to Stackoverflow).