LinLog

Here's a little problem I ran across at work the other day. I was writing a little script to SSH into our 2 app servers and restart Memcached. Simple and easy, right?

Well, not quite. When I ran the script, the restart was hanging the SSH session. The service restarted properly, but my SSH connection never closed, so the script couldn't move on to the second server. What the heck?!?

Turns out that this is an issue with the way OpenSSH handles I/O streams. Apparently the init script for starting memcached didn't close standard output, so OpenSSH stuck around waiting for it. The solution: redirect STDOUT and STDERR on the server to /dev/null. That closes the streams and keeps the session from hanging. Of course, that could be a problem if you actually need to see any of the output, but in this case, I didn't.

Yes, this is yet another "reminder to myself" Postgres post, because I've had to look this up at least 3 times.

To turn on expanded query output formatting in psql, the Postgres command-line client, run either \pset expanded or simply \x. They both do the same thing - make Postgres output each column in a result set as a separate line. This is equivalent to the mysql command-line client trick of ending the query with \G instead of a semi-colon.

Incidentally both of the above commands are boolean toggles. You run them once to turn on expanded formatting and run them again to turn it off.