Docker Services crashes suddenly

Hi @ all,

I support a test docker installation, within a Open Stack. It works fine. But suddenly the docker service is not longer reachable.
I get the following messages.
$docker info
Cannot connect to the Docker daemon. Is the docker daemon running on this host?
restarting Daemon was not possible.
$sudo service docker restart
pid file found, ensure docker is not running or delete /var/run/
Deleting the pid file allows restart the daemon

After removing the pid and restarting the service, it works again for a while.

Has anybody an idea what happen here?