Region Server is starting normally even if clock skew is more than default 30 seconds(or any configured). -> Regionserver node time is greater than master node time

[Kashif Jawed Siddiqui]

Hi,



    When Region server's time is ahead of Master's time and the difference is 
more than hbase.master.maxclockskew value, region server startup is not failing 
with ClockOutOfSyncException.



    ServerManager.java#checkClockSkew



          long skew = System.currentTimeMillis() - serverCurrentTime;
        if (skew > maxSkew) {
          String message = "Server " + serverName + " has been " +
            "rejected; Reported time is too far out of sync with master.  " +
            "Time difference of " + skew + "ms > max allowed of " + maxSkew + 
"ms";
          LOG.warn(message);
          throw new ClockOutOfSyncException(message);
        }



    Above line results in negative value when Master's time is lesser than 
region server time and  " if (skew > maxSkew) " check fails to find the skew in 
this case.



    I will be raising an Issue in JIRA for fixing the same. Please let me know 
if any concerns.



    Please Note: This was tested in hbase 0.94.11 version and the trunk also 
currently has the same logic.



Regards,
Kashif Jawed Siddiqui
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