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From Tom Brown <tombrow...@gmail.com>
Subject Tracking down coprocessor pauses
Date Mon, 10 Sep 2012 17:32:48 GMT
Hi,

We have our system setup such that all interaction is done through
co-processors. We update the database via a co-processor (it has the
appropriate logic for dealing with concurrent access to rows), and we
also query/aggregate via co-processor (since we don't want to send all
the data over the network).

This generally works very well. However, some times one of the region
servers will "pause". This doesn't appear to be a GC pause since it
still serves up the UI, and adds occasional messages to the log
regarding the LRU. The only thing I've found is that when I check the
server that's causing the problem (easy to tell, since all the
"working" servers have a low load, and the problem server has a higher
load), I can see that there are a number of execCoprocessor requests
that have been executing for much longer than they should.

I want to know more details about the specifics of those requests; Is
there an API I can use that will allow my coprocessor requests to be
tracked more functionally? Is there a way to hook into the UI so I can
provide my own list of running processes? Or would I have to write
that all myself?

I am using HBase 0.92.1, but will be upgrading to 0.94.1 soon.

Thanks in advance!

--Tom

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