If you’ve ever tried to update a large WordPress multisite network, then you’ve undoubtedly experienced the frustration of watching that spinning indicator hang once it’s found a domain that can’t be reached. This is quite common in the case of domain mapping.
A ticket exists for fixing this issue in WordPress, but in the meantime the folks at Maintainn have released a solution that anyone can apply to fix this problem. Broken Site Checker, authored by Ryan Duff, is a plugin that will keep you from pulling your hair out while updating your multisite network.
Once installed, the plugin will appear under the Sites menu in the network admin. Here you can initiate a process that will check for any broken/inaccessible sites on the network. Inaccessible sites will be archived and the plugin will display information about each site as it cycles through.
On networks with sites that reach into the thousands, inaccessible sites can drive you mad during an update, because you’ll constantly have to restart the update process. WordPress contributors are still working out some of the rougher edges of multisite network administration, but you don’t have to wait on this issue. Download the Broken Site Checker plugin from Github before you start your next network update.