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https://issues.apache.org/jira/browse/HADOOP-13065?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15270492#comment-15270492
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Steve Loughran commented on HADOOP-13065:
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I like this patch, especially the {{isTracked()}} probe.
h3. in {{FileSystem.getStatistics()}}
# For performance, you could try using {{ConcurrentMap}} for the map, and only
if it is not present create the objects and call putIfAbsent() (or a
synchronized block create and update the maps (with a second lookup there to
eliminate the small race condition). This will eliminate the sync point on a
simple lookup when the entry exists.
# For testing a may to reset/remove an entry could be handy.
h3. In {{testConcurrentStatistics()}}
in the runnables, line 737, there's a {{fail("Child failed with exception: " +
t)}}
# tests shouldn't lose the inner stack. Just let it pass through
# and, as it will fail in a separate thread, isn't going to fail the test
anyway, as far as I can tell
Better to catch, store in a list of exceptions caught, and, once the
{{allDone.await()}} checkpoint is reached, look at that list, if non-empty log
all exceptions then throw the first one. That will promote it to a failure on
the test thread.
> Add a new interface for retrieving FS and FC Statistics
> -------------------------------------------------------
>
> Key: HADOOP-13065
> URL: https://issues.apache.org/jira/browse/HADOOP-13065
> Project: Hadoop Common
> Issue Type: Improvement
> Components: fs
> Reporter: Ram Venkatesh
> Assignee: Mingliang Liu
> Attachments: HADOOP-13065-007.patch, HADOOP-13065.008.patch,
> HDFS-10175.000.patch, HDFS-10175.001.patch, HDFS-10175.002.patch,
> HDFS-10175.003.patch, HDFS-10175.004.patch, HDFS-10175.005.patch,
> HDFS-10175.006.patch, TestStatisticsOverhead.java
>
>
> Currently FileSystem.Statistics exposes the following statistics:
> BytesRead
> BytesWritten
> ReadOps
> LargeReadOps
> WriteOps
> These are in-turn exposed as job counters by MapReduce and other frameworks.
> There is logic within DfsClient to map operations to these counters that can
> be confusing, for instance, mkdirs counts as a writeOp.
> Proposed enhancement:
> Add a statistic for each DfsClient operation including create, append,
> createSymlink, delete, exists, mkdirs, rename and expose them as new
> properties on the Statistics object. The operation-specific counters can be
> used for analyzing the load imposed by a particular job on HDFS.
> For example, we can use them to identify jobs that end up creating a large
> number of files.
> Once this information is available in the Statistics object, the app
> frameworks like MapReduce can expose them as additional counters to be
> aggregated and recorded as part of job summary.
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