[ http://issues.apache.org/jira/browse/HADOOP-387?page=all ]
Sami Siren updated HADOOP-387:
------------------------------
Attachment: hadoop-fix-dup-id-0.4.patch
fix for hadoop 0.4
> LocalJobRunner assigns duplicate mapid's
> ----------------------------------------
>
> Key: HADOOP-387
> URL: http://issues.apache.org/jira/browse/HADOOP-387
> Project: Hadoop
> Issue Type: Bug
> Components: mapred
> Affects Versions: 0.4.0
> Environment: xp, cygwin, jdk1.4.2_12
> Reporter: Sami Siren
> Attachments: hadoop-fix-dup-id-0.4.patch,
> hadoop-fix-dup-id-trunk.patch
>
>
> While hunting down nutch issue NUTCH-266 i discovered that id's are generated
> with following fragment of code:
> private String newId() {
> return Integer.toString(Math.abs(new Random().nextInt()),36);
> }
> and the related Javadoc:
> "
> public Random()
> Creates a new random number generator. Its seed is initialized to a value
> based on the current time:
> public Random() { this(System.currentTimeMillis()); }
> Two Random objects created within the same millisecond will have the same
> sequence of random numbers.
> "
> it appears that in this case there are more than one Random pobject generated
> at the same millisecond and id's are
> no longer unique.
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