Recently I bumped twice into an issue with Google Cloud Network Load Balancer in which it decided a server was unhealthy regardless of if there was a health check or not.
The first time I cloned the machine and started a new one – which obviously fixed the issue.
The second time I’ve decided to try a bit harder.
I’ve bumped into this old bug detailing a race condition in google-address-manager.
google-address-manager is part of the Google Daemon, a set of processes that runs inside an image running in Google Compute Engine.
If google-address-manager is down, Network Load Balancing may not work at all, marking your instance as unhealthy even though it is working well.
If that happens, you might want to restart the service but issuing:
sudo service google-address-manager restart
sudo /etc/init.d/google-address-manager restart
This should make sure Network Load Balancing will work as it should. Also note that without this service, SSH keys will not get provisioned.
While I do not know what the process crashed (I couldn’t find any reasonable log) I suspect it had something to do with low disk space on that drive.