There are three new metrics added:
1. 'error_limiter.incremented_limit', when one node has accumulated
enough errors to trigger error suppression.
2. 'error_limiter.forced_limit', when one node runs into serious
error like Insufficient Storage.
3. 'error_limiter.is_limited', when one node is error limited
during node selection process due to suppression_limit.
UpgradeImpact:
There is change of log format when 'ERROR Insufficient Storage' is
raised, from '%(msg)s %(node)s' to
'Node will be error limited from now: %s, error: %s'.
Change-Id: Id9bec9b46dad82163517fd71cfdda5b751464588
38124221d7