Contention on META stalls mapreduce job execution
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Key: HBASE-1477
URL: https://issues.apache.org/jira/browse/HBASE-1477
Project: Hadoop HBase
Issue Type: Bug
Reporter: Andrew Purtell
>From Jeremy Pinkham up on hbase-users@:
bq. A typical mapper in the job takes several minutes, how many minutes depends
on whether I use the the region partitioner and how many I let run
concurrently... it's been anywhere from 2 minutes with no partitioner and small
concurrency (5 mappers) to 8 minutes with the region partitioner and high
concurrency (150 mappers). This seems to directly correlate with how long it
takes to do a simple count of .META. while each job is running (2 seconds to 1
minute)
bq. I was able to get past this issue affecting my data load by reorganizing
some of my workflow and data structures to force the ordering of keys without
the region partitioner. Those changes appear to have side stepped the problem
for me as I can now load from 100+ mappers without seeing the degradation that
I was seeing with 40 when using the partitioner (and getting some sweet numbers
in the requests column of the UI). It's still an interesting scaling situation
with the region partitioner, but I'm good to go without it.
I have seen this also in the form of freezing of master UI during high load,
where the UI comes back as soon as load is reduced. When I thread dump it looks
like all IPC handlers on the region server hosting .META. are busy.
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