Have a way of creating datanodes that throws an meaningful exception on failure
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Key: HDFS-890
URL: https://issues.apache.org/jira/browse/HDFS-890
Project: Hadoop HDFS
Issue Type: Improvement
Components: data-node
Affects Versions: 0.22.0
Reporter: Steve Loughran
Assignee: Steve Loughran
In HDFS-884, I proposed printing out more details on why things fail. This is
hard to test, because you need to subvert the log4j back end that your test
harness will itself have grabbed.
There is a way to make it testable, and to make it easier for anyone creating
datanodes in process to recognise and handle failure: have a static
CreateDatanode() method that throws exceptions when directories cannot be
created or other problems arise. Right now some problems trigger failure,
others just return a null reference saying "something went wrong but we won't
tell you what -hope you know where the logs go".
The HDFS-884 patch would be replaced by something that threw an exception; the
existing methods would catch this, log it and return null. The new method would
pass it straight up.
This is easier to test, better for others. If people think this is good, I will
code it up and mark the old API as deprecated.
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