Comment 0 for bug 1774527

So let's analyze what can cause a compute managers failed_builds to get incremented and point out that some of them should not be causing failed_builds to get incremented (which then can have the nice effect of auto-disabling a nova-computer service).

So the return code of self._do_build_and_run_instance returns a result code; the catch of all exceptions also triggers the setting of a result code to failed; when this is failed it will cause the failed_build counter to get incremented.

Some unrelated to nova-compute exceptions that from reading the code can trigger this to happen:

- Unable to base64 decode injected files.
- Failure of notify_about_instance_create to actually send (some inner exception perhaps?)
- exception.NoMoreNetworks, exception.NoMoreFixedIps
- exception.FlavorDiskTooSmall, exception.FlavorMemoryTooSmall,
  exception.ImageNotActive, exception.ImageUnacceptable,
  exception.InvalidDiskInfo, exception.InvalidDiskFormat,
  cursive_exception.SignatureVerificationError,
  exception.VolumeEncryptionNotSupported, exception.InvalidInput,
  exception.RequestedVRamTooHigh --- these bubble up as BuildAbortException
- exception.InstanceNotFound, exception.UnexpectedDeletingTaskStateError
- Anything that pops out of _build_resources

Any many more?