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https://issues.apache.org/jira/browse/HADOOP-9854?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13771187#comment-13771187
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Jason Lowe commented on HADOOP-9854:
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I'm wondering if the fix is simply to use the appropriate configuration object
for the tool in question. Since the tool requires supporting MapReduce
configs, have it use JobConf which is MapReduce-aware instead of Configuration
which is not. For example:
{code}
public static void main(String[] args) {
ToolRunner.run(new JobConf(), new MyClass(), args);
}
{code}
Otherwise I don't see how we can determine that the particular Configuration
object is really going to later be a JobConf object and load the deprecated
keys ahead of time. Even if we tried to fix it up after the fact we could
encounter situations where the config has conflicting values for keys. For
example, two different chunks of code use different keys for the same concept
and we end up with something like -Dmapred.reduce.tasks=20 and
-Dmapreduce.job.reduces=100. If these keys were set before the Configuration
morphed into a JobConf, we wouldn't know which was the correct setting that
should survive once JobConf arrives and tries to rectify the situation.
> Configuration.set() may be called before all the deprecated keys are
> registered, causing inconsistent state
> -----------------------------------------------------------------------------------------------------------
>
> Key: HADOOP-9854
> URL: https://issues.apache.org/jira/browse/HADOOP-9854
> Project: Hadoop Common
> Issue Type: Bug
> Components: conf
> Affects Versions: 2.0.5-alpha
> Reporter: Sangjin Lee
> Priority: Blocker
>
> Currently deprecated keys are registered at various times. Some are
> registered when the Configuration class itself is initialized, but the vast
> majority are registered when the JobConf class is initialized.
> Therefore, it is entirely possible (and does happen) that Configuration.set()
> is called for a key before its deprecation mapping is registered, thus
> leaving the internal state of Configuration in an inconsistent state.
> We actually had this problem occur in real life, causing the set value not to
> be recognized.
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