I am running multiple instances of a worker as described in this answer: Starting multiple upstart instances automatically
Question: Can I restart all instan
Consider adding to the worker.conf one more event:
stop on shutdown or workers-stop
Then you can call from the command line
sudo initctl emit workers-stop
You can add similar event to start workers. To achieve restarting all workers create a task that will emit workers-stop and then workers-start events.