It would be nice if an ApplicationMaster could send signals to contaniers such as SIGQUIT, SIGUSR1, etc.
For example, in order to replicate the jstack-on-task-timeout feature implemented by
MAPREDUCE-1119 in Hadoop 0.21 the NodeManager needs an interface for sending SIGQUIT to a container. For that specific feature we could implement it as an additional field in the StopContainerRequest. However that would not address other potential features like the ability for an AM to trigger jstacks on arbitrary tasks without killing them. The latter feature would be a very useful debugging tool for users who do not have shell access to the nodes.