tree 1b793e77d787a73e75c98a7bda02f110837f4b5f
parent ad0bc5f9df4bcb6c5713db6d2defdffed006210c
author Sameer Brenn <sbrenn@twitter.com> 1524255968 -0700
committer Santhosh Kumar <sshanmugham@twitter.com> 1524255968 -0700

Add --pid-file flag to `aurora task ssh` to write the PID of the underlying SSH command to a specified file.

My team has some scripts to start devel shards which create tunnels:

```
aurora task ssh -L 8002:http --ssh-options "-f -N" "$DC/$USER/devel/proxyapp/0"
aurora task ssh -L 9002:health --ssh-options "-f -N" "$DC/$USER/devel/proxyapp/0"
```

We use fixed local port numbers because that way we can run dependent services locally that look for locally-running copies of the
same service on a fixed port, but then those requests get tunnelled through to the devel shard.

When the devel shard is restarted, however, the tunnel is still running so the subsequent call to create a new tunnel fails because
it can't bind to the fixed port.

If we save the SSH process PID to a file, we can then kill existing tunnel to the old instance before starting up the new tunnel to the
new instance.

Testing Done:
```
$ ./pants test src/test/python/apache/aurora/client::
```

And when applying the same patch to our local repo at Twitter:

```
$ ./pants run twitter/src/main/python/twitter/aurora/client/cli_internal:aurora_internal -- task ssh -L 8005:http --ssh-options "-n -N" --pid-file /tmp/p "smf1/sbrenn/devel/proxyapp/0" &
$ ps -p `cat /tmp/p`
  PID TTY           TIME CMD
34729 ttys000    0:00.05 ssh -t -n -N -L 8005:smf1-aki-27-sr1.prod.twitter.com:31794 sbrenn@smf1-aki-27-sr1.prod.twitter.com cd /var/lib/mesos/slaves/*/frameworks/*/exec
```

Reviewed at https://reviews.apache.org/r/66697/