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Deploying to servers

I’m heading to the Philippines tomorrow, and to make life easer for the two other Windows-based PHP developers on my team, I updated the web-based deployment script I mentioned in
Development kaizen: deployment and testing. I added the ability to push a specified revision to the production server. It took me less time than I thought it would (I love it when things Just Work!), so I decided to spend time documenting it just in case I ever need to do it again (almost certainly) or just in case it breaks while I’m away (hope not).

Behind the scenes, there are a number of moving parts:

  • Key-based authentication. Because I need to copy files and run commands on the production and QA servers non-interactively, I needed to set up key-based authentication using SSH. I’m somewhat nervous about using a passphrase-less key, but I couldn’t see a way to work around this.
  • Rsync. I use rsync over ssh to transfer files to the remote system. It’s good at efficiently transferring changed files. I couldn’t use –delete to get rid of old files, though, as our source tree does not include the complete system.
  • A shell script with the suid bit. The shell script is responsible for exporting the requested revision to a temporary directory, rsyncing it over to the selected host, and running a few commands on the server in order to reset file permissions and clear the cache. The suid bit is there so that it takes my identity and uses the key that I set up. I resorted to suid because I couldn’t figure out how to make sure that Apache had its own key. I tried associating it with the user that Apache ran as, but I kept running into “no tty”-type errors. The suid workaround solved the problem quickly.
  • A PHP script that displays a form and the last 20 revisions. The form includes a drop-down box of the revisions displayed, a button for deploying to QA, and a button for deploying to the server. When submitted, the script does some error-checking, then uses system to call the relevant shell script. The script determines the list of revisions by using shell_exec to store the output of svn log … -limit 20 in a string, then using preg_match_all to match all instances of /r([0-9]+)/. Seems to work.