I was using flush() after sending a bunch of mutations to the batchwriters to limit their latency. I thought it would normally flush the buffer to ensure that the maxLatency is not violated. If the maxLatency is quite large, how do I ensure that it doesn't wait a long time before writing?
If the returned batchscanners are all thread safe, then I'm still going to have the bottleneck of their synchronized addMutations method, correct? I'm looking for "org.apache.accumulo.client.impl" in the log4j.properties, generic_logger.xml the and other config files, but can't locate it. Do I need to create a new entry for it there? Thanks, David From: Keith Turner [mailto:[email protected]] Sent: Thursday, September 19, 2013 7:01 PM To: [email protected] Subject: Re: BatchWriter performance on 1.4 On Thu, Sep 19, 2013 at 5:08 PM, Slater, David M. <[email protected]<mailto:[email protected]>> 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<http://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<http://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<http://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:[email protected]<mailto:[email protected]>] Sent: Thursday, September 19, 2013 12:39 PM To: [email protected]<mailto:[email protected]> 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. <[email protected]<mailto:[email protected]>> 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
