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From "David Bowen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1915) adding counters methods using String (as opposed to Enum)
Date Tue, 18 Sep 2007 17:15:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1915?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12528452
] 

David Bowen commented on HADOOP-1915:
-------------------------------------

Couldn't you write a simple subclass of Enum with a static initialization method which reads
the configuration and generates the Enum instances? It could also create a static hashmap
so that the elements can be looked up by string.

I think that there would be a problem with the API you suggest, because the enum ordinal values
would have to be generated on the fly, and we want them to be the same in different processes
(as counters are transmitted between Java processes).





> adding counters methods using String (as opposed to Enum)
> ---------------------------------------------------------
>
>                 Key: HADOOP-1915
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1915
>             Project: Hadoop
>          Issue Type: New Feature
>         Environment: all
>            Reporter: Alejandro Abdelnur
>            Priority: Minor
>             Fix For: 0.15.0
>
>
> Currently to use the counters from within Map/Reduce code Enums have to be used, the
Enum class defines the group and the Enum itself the counter. Internally they are converted
to Strings (the class name and the enum toString) and you can retrieve them as strings from
the client API.
> Using dynamic counters (driven by configuration of the map/reduce) is not easy with the
counters Enum based API. For example, currently I have an Enum class with 50 enums and we
have to map the cardinality to the counter name on the client. This is cumbersome.
> This could be easily improve by adding a String based counter method increment(String
group, String counter, long count) to allow use of the counters without Enums.
> Internally this method already exists, so the changes are minimal.

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