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From "Sean Busbey (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-14177) Full GC on client may lead to missing scan results
Date Fri, 31 Jul 2015 19:44:21 GMT

     [ https://issues.apache.org/jira/browse/HBASE-14177?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Sean Busbey updated HBASE-14177:
    Priority: Critical  (was: Major)

> Full GC on client may lead to missing scan results
> --------------------------------------------------
>                 Key: HBASE-14177
>                 URL: https://issues.apache.org/jira/browse/HBASE-14177
>             Project: HBase
>          Issue Type: Bug
>          Components: Client
>    Affects Versions: 1.1.0, 0.98.12, 0.98.13
>            Reporter: James Estes
>            Priority: Critical
>              Labels: dataloss
>             Fix For: 2.0.0, 1.3.0
> After adding a large row, scanning back that row winds up being empty. After a few attempts
it will succeed (all attempts over the same data on an hbase getting no other writes).
> Looking at logs, it seems this happens when there is memory pressure on the client and
there are several Full GCs that happen. Then messages that indicate that region locations
are being removed from the local client cache:
> 2015-07-31 12:50:24,647 [main] DEBUG org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation
 - Removed as a location of big_row_1438368609944,,1438368610048.880c849594807bdc7412f4f982337d6c.
for tableName=big_row_1438368609944 from cache
> Blaming the GC may sound crazy, but if the test is run with -Xms4g -Xmx4g then it always
passes on the first scan attempt. Maybe the pause is enough to remove something from the cache,
or the client is using weak references somewhere?
> More info http://mail-archives.apache.org/mod_mbox/hbase-user/201507.mbox/%3CCAE8tVdnFf%3Dob569%3DfJkpw1ndVWOVTkihYj9eo6qt0FrzihYHgw%40mail.gmail.com%3E
> Test used to reproduce:
> https://github.com/housejester/hbase-debugging#fullgctest

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