In setting up a Watcher alarm with a PagerDuty action (we are using elasticsearch 5.0) looks like the instructions for setting up PagerDuty are incorrect based on my results.
I followed these instructions:
I created an API Key and configured it. Yet I got an error back from PagerDuty saying the service key was invalid.
I then replaced the API Key in elasticsearch.yml with the value for the "Integration Key" from one of our services. This finally worked. This actually makes sense, because using the integration key we are able to send the page to the correct service and escalation team.
In other words, I believe the instructions for setting up PagerDuty in elastic alarms should be updated, unless I am missing something here.