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https://issues.apache.org/jira/browse/HBASE-13071?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14494748#comment-14494748
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Eshcar Hillel commented on HBASE-13071:
---------------------------------------
I looked into the PerformanceEvaluation tool, the code is easy to read and
maintain.
I believe the changes that are required in the implementation of testRow() in
ScanTest:
* set caching to 100 (or even to DEFAULT_HBASE_CLIENT_SCANNER_CACHING)
instead of 30
* add timeout before calling testScanner.next() [I think you already added
this one]
* make sure setFilter(FilterAllFilter) is not invoked
and optionally, add a scanRange100000 class to do really big scans
[~stack], do you have by any chance the results of the client latency
distribution collected by the tool in your previous experiments?
BTW, 30 is not the default value for prefetch size.
DEFAULT_HBASE_CLIENT_SCANNER_CACHING is set to 100 in 0.98 and to
Integer.MAX_VALUE in master.
> Hbase Streaming Scan Feature
> ----------------------------
>
> Key: HBASE-13071
> URL: https://issues.apache.org/jira/browse/HBASE-13071
> Project: HBase
> Issue Type: New Feature
> Reporter: Eshcar Hillel
> Attachments: 99.eshcar.png, HBASE-13071_98_1.patch,
> HBASE-13071_trunk_1.patch, HBASE-13071_trunk_10.patch,
> HBASE-13071_trunk_2.patch, HBASE-13071_trunk_3.patch,
> HBASE-13071_trunk_4.patch, HBASE-13071_trunk_5.patch,
> HBASE-13071_trunk_6.patch, HBASE-13071_trunk_7.patch,
> HBASE-13071_trunk_8.patch, HBASE-13071_trunk_9.patch,
> HBaseStreamingScanDesign.pdf, HbaseStreamingScanEvaluation.pdf,
> HbaseStreamingScanEvaluationwithMultipleClients.pdf, gc.delay.png,
> gc.eshcar.png, gc.png, hits.delay.png, hits.eshcar.png, hits.png,
> latency.delay.png, latency.png, network.png
>
>
> A scan operation iterates over all rows of a table or a subrange of the
> table. The synchronous nature in which the data is served at the client side
> hinders the speed the application traverses the data: it increases the
> overall processing time, and may cause a great variance in the times the
> application waits for the next piece of data.
> The scanner next() method at the client side invokes an RPC to the
> regionserver and then stores the results in a cache. The application can
> specify how many rows will be transmitted per RPC; by default this is set to
> 100 rows.
> The cache can be considered as a producer-consumer queue, where the hbase
> client pushes the data to the queue and the application consumes it.
> Currently this queue is synchronous, i.e., blocking. More specifically, when
> the application consumed all the data from the cache --- so the cache is
> empty --- the hbase client retrieves additional data from the server and
> re-fills the cache with new data. During this time the application is blocked.
> Under the assumption that the application processing time can be balanced by
> the time it takes to retrieve the data, an asynchronous approach can reduce
> the time the application is waiting for data.
> We attach a design document.
> We also have a patch that is based on a private branch, and some evaluation
> results of this code.
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