status module. If I have some spare time soon, I'll try
to produce an
nginx patch to implement this.
Excellent indeed! At the most basic level it would be extremely useful if nginx could signal an external process once it declared one of the upstream servers offline (based on the timeout configs in its main conf file).
My intention from such a thing would be to receive an email letting me know 'oh no upstream xyz is down!!' and 'oh good, upstream xyz is back online'.
Some people have argued that such a thing should be left to external monitoring tools like heartbeat etc. However such monitoring is no where near the same IMO. For instance, heartbeat could see the upstream as up because it is alive and pingable, but it wouldn't be aware if nginx declared it as offline due to timeouts or 500 errors (again, based on settings in its conf file)!!