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From Young <youngma...@gmail.com>
Subject counters and scanners inconsistency
Date Sat, 14 Jan 2012 00:59:26 GMT
I'm having an odd problem with incrementing counters simultaneously during a scan (both in
separate processes).

For low rate counters, there is no problem (< 1 increment per second), but for the higher
rate counters (>10 increments per second), there is an inconsistency in the counter values.

Averaging the values over time gives the correct count (i.e. the counter itself is still increasing
correctly), but at certain samples the counter drops down to some seemingly random number.
 This random number is consistent for about a day and a half then jumps to a different random
number for the next day and a half - this cycle coincides exactly with compaction of the table
in question.

Again, the counter value itself, when it is not equal to the random number of the day, is
correct.  I'm wondering if there is something going on underneath that would cause
1) the incorrect but consistent number when incrementing and scanning simultaneously
2) the random number reset and its relationship with compaction of the table

Keep in mind that most of the hbase settings are at default.

Thanks!
p.s. I ran a smaller experiment using hbase shell, and found the counters to be consistent
even for the high rate counters.  I am wondering if there is a buffering issue with the htable
scanner object if it is unable to obtain a lock on the row it will default to the data on
disk?


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