这是一个特别令人头疼的问题。
1. Swallow IllegalStateExceptions thrown by removeShutdownHook in FileSystem. The javadoc states:
public boolean removeShutdownHook(Thread hook)
Throws:
IllegalStateException - If the virtual machine is already in the process of shutting down
So if we are getting this exception, it MEANS we are already in the process of shutdown, so we CANNOT, try what we may, removeShutdownHook. If Runtime had a method Runtime.isShutdownInProgress(), we could have checked for it before the removeShutdownHook call. As it stands, there is no such method. In my opinion, this would be a good patch regardless of the needs for this JIRA.
2. Not send SIGTERMs from the NM to the MR-AM in the first place. Rather we should expose a mechanism for the NM to politely tell the AM its no longer needed and should shutdown asap. Even after this, if an admin were to kill the MRAppMaster with a SIGTERM, the JobHistory would be lost defeating the purpose of 3614