We experienced some trouble with the workflow gatekeeper process:
As far as I unterstood this process, it should prevent image rendering workflows to re-create all renditions if assets are imported via the package manager. So all our workflows contain the gatekeeper as first step - as seen in the original CQ DAM workflows.
But every time I import/reinstall a content package, all my rendering workflows start again and create renditions for every image. This is unnecessary and overwrites all manually modified renditions. So our editors are not amused.
What is the right way to use the gatekeeper or could it be, that it is buggy?
Gatekeeper is right one for your use case. Only possibility this could happen if somehow payload becomes null. Does your log has somethink like . If so then bug it should terminate. Still I am not sure why package installation makes asset null... Please file daycare and attach your logs for further investigation.
 execute: gatekeeping failed, asset ..... in payload doesn't exist for workflow .....
According to the DAM documentation, you have to disable the com.day.cq.workflow.launcher.impl.WorkflowLauncherImpl OSGi component before restoring DAM assets from a package to prevent the workflows from triggering again (see ).
Also, you mention "all our workflows" which leads me to think you're using some custom DAM workflows? You should be very careful there as it's really easy to trigger the DAM workflows multiple times. The gatekeeper step only seems to work the first time, so if you're triggering it multiple times it won't work. Your best bet is probably to disable the launchers component then as I mentioned above, but you might want to check if you're not running into problems when moving or copy pasting your assets as well. That's been causing us a lot of grief too...