Logging a Daemon's Output with Upstart

Question

I have a custom daemon that is managed by upstart on my Ubuntu server. It works perfectly except that I need to capture (log) the daemon's output. The official stanzas page says that I can use console logged to do this, but what file does it log to?

I've also read that console logged is no longer a valid stanza. I'm currently using 0.3.9 (Hardy) but will upgrade to 0.6.x (Lucid) in a few months. If console logged in fact won't work with later versions, what do I use instead?

Answer 1

This is ugly but so far the best I have found

exec /path/to/server >> /tmp/upstart.log 2>&1

Answer 2

This snippet will pipe the output of your service into logger, while still allowing you to exec the service process (thus replacing the shell process) so that upstart doesn't get confused. It also makes sure the logger process is reparented to init, so it's not a child of your service, and it avoids leaving cruft sitting around in the filesystem, even though it needs to create a fifo temporarily.

script
  set -e
  mkfifo /tmp/myservice-log-fifo
  ( logger -t myservice </tmp/myservice-log-fifo & )
  exec >/tmp/myservice-log-fifo
  rm /tmp/myservice-log-fifo
  exec myservice 2>/dev/null
end script

Here's how it works:

1. mkfifo /tmp/myservice-log-fifo simply makes the fifo special file (aka named pipe). Type man 7 fifo for more info.
2. ( logger ... </tmp/myservice-log-fifo & ) starts logger reading from the fifo, in the background. The parens cause the logger process to be reparented to init, rather than remaining a child of the current shell process.
3. exec >/tmp/myservice-log-fifo redirects the current shell's stdout to the fifo. Now we have an open file descriptor for that fifo, and we don't actually need the filesystem entry any more...
4. rm /tmp/myservice-log-fifo so we'll remove it.
5. exec myservice 2>/dev/null simply runs the service in the usual way. Stdout is already going to the fifo, and that won't change when the new program executes.

Answer 3

You can also redirect the output to syslog, e.g.

exec $SERVER 2>&1 | logger -t myservice -p local0.info

However, the pipeline may cause upstart to confuse the PID of the logging process with the PID of the daemon.