That line means that appending to the log took x ms, we print it out when it takes more than 1 second. I'd be worried to see that a lot in my logs if I had a realtime-ish system because it would mean that my writes are taking seconds.
The usual reasons: - Heavy IO, I would expect those lines if I was writing a lot of data into HBase or running MR jobs that don't use HBase but do push a lot of data to their datanodes. - GC, for example you have a pretty busy system with not a lot of memory so it's running long-ish GCs every now and then well if it happens during the append operation it may appear that it took x ms, but in fact could have been super short but the JVM was blocked for some time. Hope this helps, J-D On Wed, Dec 21, 2011 at 1:11 AM, Mikael Sitruk <[email protected]> wrote: > Hi > > I have my log with lot of the following message in my hbase logs. > > 2011-12-21 00:32:05,035 WARN org.apache.hadoop.hbase.regionserver.wal.HLog: > IPC Server handler 38 on 60020 took 1247 ms appending an edit to hlog; > editcount=625, len~=61.4k > 2011-12-21 00:32:06,378 WARN org.apache.hadoop.hbase.regionserver.wal.HLog: > IPC Server handler 33 on 60020 took 1342 ms appending an edit to hlog; > editcount=627, len~=61.4k > > Can you explain the what does it mean? What should i do to remove this > warning? Does it have performance impact? > > Thanks > Mikael.S
