Enis Soztutar created HBASE-9759:
------------------------------------
Summary: IntegrationTestBulkLoad random number collision
Key: HBASE-9759
URL: https://issues.apache.org/jira/browse/HBASE-9759
Project: HBase
Issue Type: Bug
Components: test
Reporter: Enis Soztutar
Assignee: Enis Soztutar
Fix For: 0.98.0, 0.96.1
ITBL failed recently in our test harness. Inspecting the failure made me
believe that the only reason that particular failure might have happened is
that there is a collision in random longs generated by the test.
The test creates 50 mappers by default, and each mapper writes a 500K random
rows starting with row = 0. By default there are 5 iterations.
The check job outputs these counters:
{code}
2013-10-13 07:48:01,134 Map input records=124999751
2013-10-13 07:48:01,134 Map output records=124999999
{code}
The number of input records seems fine because
{code}
124999751 = 1 + 5 * (0.5M - 1) * 50
{code}
5 = num iterations, 0.5M = num rows, 50 = num mappers, and 1 is for row =0
which every chain writes to.
Output records should be 125M, however we see one cell missing. Since the map
input records matches expected number of distinct rows, I suspect that row = 0
had a collision.
In one of the generate jobs, we can see that the reducer output count does not
match the reducer input count. Given that we are using KVSortReducer, this
confirms that there is a collision in KeyValues received by this task.
{code}
2013-10-13 06:48:12,738 Reduce input records=75000000
2013-10-13 06:48:12,738 Reduce output records=74999997
{code}
The count is off by 3 because we are writing 3 columns per row.
My only theory for explaining this is that we had a collision in chainId's or
one of the chains reused row = 0 as the next row.
This is similar to HBASE-8700, however, in this the probability is much much
much lower.
--
This message was sent by Atlassian JIRA
(v6.1#6144)
