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https://issues.apache.org/jira/browse/HADOOP-1989?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12538148
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Konstantin Shvachko commented on HADOOP-1989:
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AbstractFSDataset.java
- AbstractFSDataset should be an interface rather than an abstract class, since
it does not implement any methods,
and all methods are declared abstract public. Therefore, it should be called
FSDatasetInteface.
I also think it should not be dependent on FSContants.
- @author field should be removed. See HADOOP-1147.
- Javadoc: missing descriptions of public methods.
- Long lines.
- Too many line breaks between methods.
SimulatedFSDataset.java
- redundant import java.io.OutputStream;
- Needs javadoc desciption of SimulatedFSDataset class.
- needs line break between class and method declarations.
- subclasses BInfo and Storage should private.
- Storage is not a good name for the class, since it is already used. May be
SimulatedStorage.
Is it possible to reuse classes like DF or DatanodeInfo here?
DataNode.java
- Javadoc description for method startDataNode().
- You do not need extra variable sendBlockReportatNextHeartbeat.
Instead the new method sendBlockReport() should set
lastHeartbeat=0;
lastBlockReport=0;
as it is done in case DatanodeProtocol.DNA_REGISTER:
I'd then call this method scheduleBlockReport(), and it should not be public.
- In readMetadata() both methods
{code}
checksumIn = data.getMetaDataInStream(block);
long fileSize = data.getMetaDataLength(block);
{code}
perform access to the data-node block map, which is not efficient.
Can it be optimized?
DataChecksum.java
- Would it be more clean to have SimulatedFSDataset.getChecksumHeader(checkSum)
rather than DataChecksum.getHeader() so that to keep all simulated methods
inside the simulated classes?
simulatedStreams
- SimulatedInputStream and SimulatedOutputStream should be private subclasses of
SimulatedFSDataset, because they are not used outside of the dataset directly.
PendingReplicationBlocks.java
- remove(Block block){
empty line included.
ClusterTestDFS.java
- This is the only place where AbstractFSDataset.getVolumeNames() is used.
I think it toString() should be use here insted, getVolumeNames() can then be
removed from the abstract class.
TestFileCreation.java
- In conf.setBoolean("dfs.datanode.simulateddatastorage", true);
constant CONFIG_PROPERTY_SIMULATED for should be used or not used consistently
in all cases.
May be it is more consistent with hadoop current practices to use config name
directly.
TestSetrepIncreasing.java
- testSetrepIncreasingSimulatedStorage(): Tabs are off.
- same constant as in TestFileCreation.
TestSmallBlock.java
- Tabs should be 2 and replaced by spaces.
TestInjectionForSimulatedStorage.java
- A lot of redundant imports.
- writeFile(): formatting.
MiniDFSCluter
- The NOTE: in Javadoc for MiniDFSCluter constructor does not make sense any
more.
- the line
if (dataSet.getClass() != SimulatedFSDataset.class)
should probably read
if (dataSet instanceof SimulatedFSDataset)
TestPRead.java
- methods should be separated by a blank line.
TestReplication.java
- System.out.println() should be removed. LOG should be used instead if
necessary.
TestSimulatedFSDataset.java
- redundant import org.apache.hadoop.dfs.AbstractFSDataset.BlockWriteStreams;
- testWriteRead(): bytesAdded is never used
> 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
>
>
> 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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