We will be having a maintenance window tonight from 2. A very small amount of web unavailability will be required during this period.
We will be upgrading some core libraries to versions that are not compatible with what is currently running, so all daemons must be restarted simultaneously. For this to go smoothly, we will be disabling the web app for perhaps 30 seconds.
UPDATE: Maintenance was completed successfully. Total web unavailability was a tad more than estimated at one minute and 40 seconds. Some job runners did not restart cleanly and as a result some jobs failed, but all job runners are operating normally now. If you experienced any problems during the maintenance window, don’t hesitate to contact us at http://support.github.com.