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From Doğacan Güney (JIRA) <>
Subject [jira] Commented: (NUTCH-893) DataStore.put() silently loses records when executed from multiple processes
Date Mon, 13 Sep 2010 12:50:32 GMT


Doğacan Güney commented on NUTCH-893:

I want to close this one as INVALID and continue work on NUTCH-879 . Any objections?

> DataStore.put() silently loses records when executed from multiple processes
> ----------------------------------------------------------------------------
>                 Key: NUTCH-893
>                 URL:
>             Project: Nutch
>          Issue Type: Bug
>    Affects Versions: 2.0
>         Environment: Gora HEAD, SqlStore, MySQL 5.1, Ubuntu 10.4 x64, Sun JDK 1.6
>            Reporter: Andrzej Bialecki 
>            Priority: Blocker
>             Fix For: 2.0
>         Attachments: NUTCH-893.patch, NUTCH-893_v2.patch
> In order to debug the issue described in NUTCH-879 I created a test to simulate multiple
clients appending to webtable (please see the patch), which is the situation that we have
in distributed map-reduce jobs.
> There are two tests there: one that uses multiple threads within the same JVM, and another
that uses single thread in multiple JVMs. Each test first clears webtable (be careful!), and
then puts a bunch of pages, and finally counts that all are present and their values correspond
to keys. To make things more interesting each execution context (thread or process) closes
and reopens its instance of DataStore a few times.
> The multithreaded test passes just fine. However, the multi-process test fails with missing
keys, as many as 30%.

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