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Posted to common-dev@hadoop.apache.org by "Hemanth Yamijala (JIRA)" <ji...@apache.org> on 2009/06/25 11:53:07 UTC
[jira] Created: (HADOOP-6105) Provide a way to automatically handle
backward compatibility of deprecated keys
Provide a way to automatically handle backward compatibility of deprecated keys
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Key: HADOOP-6105
URL: https://issues.apache.org/jira/browse/HADOOP-6105
Project: Hadoop Common
Issue Type: Improvement
Components: conf
Reporter: Hemanth Yamijala
There are cases when we have had to deprecate configuration keys. Use cases include, changing the names of variables to better match intent, splitting a single parameter into two - for maps, reduces etc.
In such cases, we typically provide a backwards compatible option for the old keys. The handling of such cases might typically be common enough to actually add support for it in a generic fashion in the Configuration class. Some initial discussion around this started in HADOOP-5919, but since the project split happened in between we decided to open this issue to fix it in common.
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[jira] Commented: (HADOOP-6105) Provide a way to automatically
handle backward compatibility of deprecated keys
Posted by "Hemanth Yamijala (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/HADOOP-6105?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12723992#action_12723992 ]
Hemanth Yamijala commented on HADOOP-6105:
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There are atleast two issues that were discussed about this approach in HADOOP-5919:
- With project split, how would we add deprecated keys from mapreduce or hdfs into common.
- What if there's no one-to-one mapping from old keys to new keys.
With the project split over now, maybe the first issue requires a solution as part of this JIRA. Owen's suggestion was to define a key like hadoop.conf.extra.classes which would be a list of class names that will be loaded by Configuration when it is loaded. By default this could be null, but in a cluster installation, we could put up basic classes like JobConf. This would give an opportunity for the extra classes to add more mappings to the new keys.
The second problem is a bit more involved, though some obvious solutions exist. And we could take the approach that we will not solve it in this patch, but only restrict the utility of this framework for the more straightforward mapping cases.
Thoughts ?
> Provide a way to automatically handle backward compatibility of deprecated keys
> -------------------------------------------------------------------------------
>
> Key: HADOOP-6105
> URL: https://issues.apache.org/jira/browse/HADOOP-6105
> Project: Hadoop Common
> Issue Type: Improvement
> Components: conf
> Reporter: Hemanth Yamijala
>
> There are cases when we have had to deprecate configuration keys. Use cases include, changing the names of variables to better match intent, splitting a single parameter into two - for maps, reduces etc.
> In such cases, we typically provide a backwards compatible option for the old keys. The handling of such cases might typically be common enough to actually add support for it in a generic fashion in the Configuration class. Some initial discussion around this started in HADOOP-5919, but since the project split happened in between we decided to open this issue to fix it in common.
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[jira] Commented: (HADOOP-6105) Provide a way to automatically
handle backward compatibility of deprecated keys
Posted by "Hemanth Yamijala (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/HADOOP-6105?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12723987#action_12723987 ]
Hemanth Yamijala commented on HADOOP-6105:
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Initial proposal is to keep it dead simple:
- Keep a static map of keys in the Configuration class that maps the deprecated key to a set of new keys.
- get of the deprecated key will return the value of the first new key in the mapping set.
- set of the deprecated key will set the same value to all new keys in the mapping set.
- There will be a provision to define a custom message in the configuration class whenever access is done on the deprecated keys. Otherwise, a standard message such as: "This key is deprecated. Use this other key instead" will be printed.
- When both old and new keys are defined, the new keys will always take precedence.
> Provide a way to automatically handle backward compatibility of deprecated keys
> -------------------------------------------------------------------------------
>
> Key: HADOOP-6105
> URL: https://issues.apache.org/jira/browse/HADOOP-6105
> Project: Hadoop Common
> Issue Type: Improvement
> Components: conf
> Reporter: Hemanth Yamijala
>
> There are cases when we have had to deprecate configuration keys. Use cases include, changing the names of variables to better match intent, splitting a single parameter into two - for maps, reduces etc.
> In such cases, we typically provide a backwards compatible option for the old keys. The handling of such cases might typically be common enough to actually add support for it in a generic fashion in the Configuration class. Some initial discussion around this started in HADOOP-5919, but since the project split happened in between we decided to open this issue to fix it in common.
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[jira] Commented: (HADOOP-6105) Provide a way to automatically
handle backward compatibility of deprecated keys
Posted by "Arun C Murthy (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/HADOOP-6105?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12723993#action_12723993 ]
Arun C Murthy commented on HADOOP-6105:
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+1 for this direction.
> Provide a way to automatically handle backward compatibility of deprecated keys
> -------------------------------------------------------------------------------
>
> Key: HADOOP-6105
> URL: https://issues.apache.org/jira/browse/HADOOP-6105
> Project: Hadoop Common
> Issue Type: Improvement
> Components: conf
> Reporter: Hemanth Yamijala
>
> There are cases when we have had to deprecate configuration keys. Use cases include, changing the names of variables to better match intent, splitting a single parameter into two - for maps, reduces etc.
> In such cases, we typically provide a backwards compatible option for the old keys. The handling of such cases might typically be common enough to actually add support for it in a generic fashion in the Configuration class. Some initial discussion around this started in HADOOP-5919, but since the project split happened in between we decided to open this issue to fix it in common.
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