Values:
REVISION_REASON_UNDEFINED (0):
Default value.
PENDING (1):
Revision in Pending state.
RESERVE (2):
Revision is in Reserve state.
RETIRED (3):
Revision is Retired.
RETIRING (4):
Revision is being retired.
RECREATING (5):
Revision is being recreated.
HEALTH_CHECK_CONTAINER_ERROR (6):
There was a health check error.
CUSTOMIZED_PATH_RESPONSE_PENDING (7):
Health check failed due to user error from
customized path of the container. System will
retry.
MIN_INSTANCES_NOT_PROVISIONED (8):
A revision with min_instance_count > 0 was created and is
reserved, but it was not configured to serve traffic, so
it's not live. This can also happen momentarily during
traffic migration.
ACTIVE_REVISION_LIMIT_REACHED (9):
The maximum allowed number of active
revisions has been reached.
NO_DEPLOYMENT (10):
There was no deployment defined.
This value is no longer used, but Services
created in older versions of the API might
contain this value.
HEALTH_CHECK_SKIPPED (11):
A revision's container has no port specified
since the revision is of a manually scaled
service with 0 instance count
MIN_INSTANCES_WARMING (12):
A revision with min_instance_count > 0 was created and is
waiting for enough instances to begin a traffic migration.