calestyo at scientia
Apr 9, 2012, 8:04 AM
Post #1 of 1
ControlMaster and ControlPersist leads to zombie processes
Perhaps you can help me with this:
What I do is using Nagios (actually Icinga) and having checks on remote
hosts executed via ssh.
In order to dramatically speed checks up (from about 0,300 ms to 0,010
ms) I use ControlMaster = auto, which also makes the mux process spawned
on the first check.
As checks are typically sequentially scheduled I want the mux process
to persist but it should also go away automatically after some days if
not re-used (e.g. when I don't check a host anymore).
So I have something like ControlPersist 2d.
Now I stumbled across the following problem (and I'm actually not sure
whether it's a ssh issue or Icinga):
The first time the check is done (which is when the mux process is
spawned) it times out.
The mux process keeps running and everything works on subsequent
The timeout is one enforced by Icinga (60s), when it thinks the command
I made some checks and the following turns out to happen on the FIRST
- executing the command on the remote side is actually done
- on the local side, the ssh process (or a wrapper shell script around)
becomes a zombie as soon as the remote command was executed
- after 60s, when Icinga enforces it's timeout, the zombie goes away
- the (local) mux process continues to run
Any ideas why this could happen? Is there perhaps something that lets
the parent processes notice that there is still a running child (i.e.
the mux process)?
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