Hi, all, Recently, one of our HBase 0.98.5 instance meet with issues: when run some specific workload, all region servers will suddenly shut down at same time, but master is still running. When I check the log, in master log, I can see messages like 2014-12-01 08:28:11,072 DEBUG [main-EventThread] master.ServerManager: Added=n008.cluster,60020,1417413986550 to dead servers, submitted shutdown handler to be executed meta=false And on n008, regionserver log file, there is no ERROR message, the last log entry looks very like a ZooKeeper startup message. The log just stopped with that last ZooKeeper startup message, and the Region Server process was gone when we check with 'jps'.
We then increased the heap size of regionserver, and it work fine. RegionServer no longer disappear. So we doubt there was a Out Of Memory issue, so the region server processes are killed. But my questions are: 1. What log message will indicate there is a OOM? Since the region server is 'kill -9', so I think there is no message can tell this. 2. If there is no typical log message about OOM, then how can an admin make sure there is a region server OOM happened? We just guess, but can not make sure. We hope there is a method to tell OOM occured for sure. 3. Does the Zookeeper message appears every time with RegionServer OOM (if it is a OOM). Or it is just a random event just in our system? So in sum, I want to know what is the typical clue that people can make sure there is a OOM issue in HBase region server? Thank you, Ming
