Watchdog win service to watch another win service

Question

Hi, I want to make a windows service that monitors another windows service, and make sure that it is working. sometimes the Win Service that I want to watch stay in the memory (appear in task manager, so it is considered a running service, but the fact is that it is doing nothing, it is dead, its timer is not firing for one reason, which is not the subject for this question).

what I need is to make a watch dog Win Service that somehow reads a value in the memory that the other watched service is periodically writing. I thought about using Named Pipes but I don't want to add communication issues to my services, I want to know if there is a way to create such a shared memory between 2 applications (possibly using a named system wide Mutex?)

Answer 1

Since you have to deal with detecting a zombie service I don't think using a kernel object like a mutex will help, you need to detect activity. A semaphore isn't a good fit either.

My personal preference would be a named pipe sending small heartbeat messages (since that could be detected across a network as well), but if you want to avoid the complexity of pipe comms - which I guess is understandable - then you could update a DWORD in a predetermined registry key. If both services run under LocalSystem you could write a key/value into HKEY_LOCAL_MACHINE. Run a pump-up timer and watch for changes to the key every so often (watch out for counter wrap-around). You won't have a normal window/message pump so SetTimer is off-limits, but you can still use timeSetEvent or waitable timers.

HKLM won't be available if one of the services runs under a non-admin account, but that's a pretty rare situation for services. Of course all this assumes you have access to the code of both services. Watching a third-party service would severely limit your options.