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https://issues.apache.org/jira/browse/HADOOP-1989?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12540526
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Doug Cutting commented on HADOOP-1989:
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> For example startDataNode refers to the simulated impl if it is starting the
> simulated fsdataset [ ... ]
This could be handled other ways, that do not require test code in trunk, no?
For example, you could replace 'new SimulatedFoo' with
(FooInterface)ReflectionUtils.newInstance("org.apache.hadoop.dfs.SimulatedFoo"),
so that there's no compile-time dependency. This could be inside a factory
method, so that it's only done once per simulated class.
> Add support for simulated Data Nodes - helpful for testing and performance
> benchmarking of the Name Node without having a large cluster
> ----------------------------------------------------------------------------------------------------------------------------------------
>
> Key: HADOOP-1989
> URL: https://issues.apache.org/jira/browse/HADOOP-1989
> Project: Hadoop
> Issue Type: Improvement
> Components: dfs
> Reporter: Sanjay Radia
> Priority: Minor
> Attachments: SimulatedStoragePatchSubmit.txt,
> SimulatedStoragePatchSubmit5.txt
>
>
> Proposal is to add an implementation for a Simulated Data Node.
> This will
> - allow one to test certain parts of the system (especially the Name Node,
> protocols) much more easily and efficiently.
> - allow one to run performance benchmarks on the Name node without having a
> large cluster.
> - Inject faults for testing (e.g. one can add random faults based
> probability parameters).
> The idea is that the Simulated Data Node will
> - discard any data written to blocks (but remember the blocks and their
> sizes)
> - generate fixed data on the fly when blocks are read (e.g. block is fixed
> set of bytes or repeated sequence of strings).
> The Simulated Data Node can also be used for fault injection.
> The data node can be parameterized with probabilities that allow one to
> control:
> - Delays on reads and writes, creates, etc
> - IO Exceptions
> - Loss of blocks
> - Failures
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