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From Keith Turner <ke...@deenlo.com>
Subject Re: BatchWriter performance on 1.4
Date Thu, 19 Sep 2013 23:01:24 GMT
On Thu, Sep 19, 2013 at 5:08 PM, Slater, David M.
<David.Slater@jhuapl.edu>wrote:

> Thanks Keith, I’m looking at it now. It appears like what I would want. As
> for the proper usage…****
>
> ** **
>
> Would I create one using the Connector, ****
>
> then .getBatchWriter() for each of the tables I’m interested in,****
>
> add data to each of BatchWriters returned,
>

yes.


> ****
>
> and then hit flush() when I want to write all of that to get written?
>

Why are you calling flush() ?   Doing this frequently will increase rpc
overhead and lower throughput.


> ****
>
> ** **
>
> Would the individual batch writers spawned by the multiTableBatchWriter
> still have synchronized addMutations() methods so I would have to worry
> about blocking still, or would that all happen at the flush() method?
>

The returned batch writers are thread safe. They all add to the same
queue/buffer in a synchronized manner.   Calling flush() on any of the
batch writers returned from getBatchWriter() will block the others.

If you enable set the log4j log level to TRACE for
org.apache.accumulo.client.impl you can see output like the following.
 Binning is the process of taking each mutation and deciding which tablet
and tablet server it goes to.

  2013-09-19 18:43:37,261 [impl.ThriftTransportPool] TRACE: Using existing
connection to 127.0.0.1:9997
  2013-09-19 18:43:37,393 [impl.TabletLocatorImpl] TRACE: tid=12 oid=13
 Binning 80909 mutations for table 3
  2013-09-19 18:43:37,402 [impl.TabletLocatorImpl] TRACE: tid=12 oid=13
 Binned 80909 mutations for table 3 to 1 tservers in 0.009 secs
  2013-09-19 18:43:37,402 [impl.TabletServerBatchWriter] TRACE: Started
sending 80,909 mutations to 1 tablet servers
  2013-09-19 18:43:37,656 [impl.ThriftTransportPool] TRACE: Returned
connection 127.0.0.1:9997 (120000) ioCount : 1459116
  2013-09-19 18:43:37,657 [impl.TabletServerBatchWriter] TRACE: sent 80,909
mutations to 127.0.0.1:9997 in 0.40 secs (204,832.91 mutations/sec) with 0
failures

When you close the batch writer, it will log some summary stats like the
following.


  2013-09-19 18:43:39,149 [impl.TabletServerBatchWriter] TRACE:
  2013-09-19 18:43:39,149 [impl.TabletServerBatchWriter] TRACE: TABLET
SERVER BATCH WRITER STATISTICS
  2013-09-19 18:43:39,149 [impl.TabletServerBatchWriter] TRACE: Added
         :  1,000,000 mutations
  2013-09-19 18:43:39,149 [impl.TabletServerBatchWriter] TRACE: Sent
          :  1,000,000 mutations
  2013-09-19 18:43:39,149 [impl.TabletServerBatchWriter] TRACE: Resent
percentage   :       0.00%
  2013-09-19 18:43:39,150 [impl.TabletServerBatchWriter] TRACE: Overall
time         :       5.94 secs
  2013-09-19 18:43:39,150 [impl.TabletServerBatchWriter] TRACE: Overall
send rate    : 168,406.87 mutations/sec
  2013-09-19 18:43:39,150 [impl.TabletServerBatchWriter] TRACE: Send
efficiency      :      86.91%
  2013-09-19 18:43:39,150 [impl.TabletServerBatchWriter] TRACE:
  2013-09-19 18:43:39,150 [impl.TabletServerBatchWriter] TRACE: BACKGROUND
WRITER PROCESS STATISTICS
  2013-09-19 18:43:39,150 [impl.TabletServerBatchWriter] TRACE: Total send
time      :       5.16 secs  86.91%
  2013-09-19 18:43:39,150 [impl.TabletServerBatchWriter] TRACE: Average
send rate    : 193,760.90 mutations/sec
  2013-09-19 18:43:39,151 [impl.TabletServerBatchWriter] TRACE: Total bin
time       :       0.46 secs   7.81%
  2013-09-19 18:43:39,151 [impl.TabletServerBatchWriter] TRACE: Average bin
rate     : 2,155,172.41 mutations/sec
  2013-09-19 18:43:39,151 [impl.TabletServerBatchWriter] TRACE: tservers
per batch   :     1.00 avg       1 min      1 max
  2013-09-19 18:43:39,151 [impl.TabletServerBatchWriter] TRACE: tablets per
batch    :     1.00 avg       1 min      1 max
  2013-09-19 18:43:39,151 [impl.TabletServerBatchWriter] TRACE:
  2013-09-19 18:43:39,151 [impl.TabletServerBatchWriter] TRACE: SYSTEM
STATISTICS
  2013-09-19 18:43:39,151 [impl.TabletServerBatchWriter] TRACE: JVM GC Time
         :       0.53 secs
  2013-09-19 18:43:39,152 [impl.TabletServerBatchWriter] TRACE: JVM Compile
Time     :       1.60 secs
  2013-09-19 18:43:39,152 [impl.TabletServerBatchWriter] TRACE: System load
average : initial=  0.22 final=  0.20

What do these numbers look like for you?

Keith

****
>
> ** **
>
> *From:* Keith Turner [mailto:keith@deenlo.com]
> *Sent:* Thursday, September 19, 2013 12:39 PM
> *To:* user@accumulo.apache.org
>
> *Subject:* Re: BatchWriter performance on 1.4****
>
> ** **
>
> Are you aware of the multi table batch writer?  I am not sure if it would
> be useful, but wanted to make sure you knew about it.   It will use the
> same thread pool to process mutations for multiple tables.  Also it will
> batch mutations for multiple tablets into the same rpc calls.****
>
> ** **
>
> On Wed, Sep 18, 2013 at 5:07 PM, Slater, David M. <David.Slater@jhuapl.edu>
> wrote:****
>
> Hi, I’m running a single-threaded ingestion program that takes data from
> an input source, parses it into mutations, and then writes those mutations
> (sequentially) to four different BatchWriters (all on different tables).
> Most of the time (95%) taken is on adding mutations, e.g.
> batchWriter.addMutations(mutations); I am wondering how to reduce the time
> taken by these methods. ****
>
>  ****
>
> 1) For the method batchWriter.addMutations(Iterable<Mutation>), does it
> matter for performance whether the mutations returned by the iterator are
> sorted in lexicographic order? ****
>
>  ****
>
> 2) If the Iterable<Mutation> that I pass to the BatchWriter is very large,
> will I need to wait for a number of Batches to be written and flushed
> before it will finish iterating, or does it transfer the elements of the
> Iterable to a different intermediate list?****
>
>  ****
>
> 3) If that is the case, would it then make sense to spawn off short
> threads for each time I make use of addMutations?****
>
>  ****
>
> At a high level, my code looks like this:****
>
>  ****
>
> BatchWriter bw1 = connector.createBatchWriter(…)****
>
> BatchWriter bw2 = …****
>
> …****
>
> while(true) {****
>
> String[] data = input.getData();****
>
> List<Mutation> mutations1 = parseData1(data);****
>
>                 List<Mutation> mutations2 = parseData2(data);****
>
>                 …****
>
>                 bw1.addMutations(mutations1);****
>
>                 bw2.addMutations(mutations2);****
>
>                 …****
>
> }****
>
> Thanks,
> David****
>
> ** **
>

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