JMXCacheBuster resets the metrics state at various points in time. These
events can potentially race with a master shutdown. When the master is
tearing down, metrics initialization can touch a lot of unsafe state,
for example invalidated FS objects. To avoid this, this patch makes
the getMetrics() a no-op when the master is either stopped or in the
process of shutting down. Additionally, getClusterId() when the server
is shutting down is made a no-op.
Simulating a test for this is a bit tricky but with the patch I don't
locally see the long stacktraces from the jira.
Signed-off-by: Michael Stack <stack@apache.org>
(cherry picked from commit 6f213e9d5a15afcc40b6562ab4898f913cec91eb)
(cherry picked from commit 9384b8455252300a2f96f4eeedc96591e8e5d60a)
4d1309b6c4