Which version? 1.2 or trunk? -- Brock Noland Sent with Sparrow (http://www.sparrowmailapp.com/?sig)
On Monday, October 22, 2012 at 8:18 AM, Jagadish Bihani wrote: > Hi > > This is the simplistic configuration with which I am getting lower > performance. > Even with 2-tier architecture (cat source - avro sinks - avro source- HDFS > sink) > I get the similar performance with file channel. > > Configuration: > ========= > adServerAgent.sources = avro-collection-source > adServerAgent.channels = fileChannel > adServerAgent.sinks = hdfsSink fileSink > > # For each one of the sources, the type is defined > adServerAgent.sources.avro-collection-source.type=exec > adServerAgent.sources.avro-collection-source.command= cat > /home/hadoop/file.tsf > > # The channel can be defined as follows. > adServerAgent.sources.avro-collection-source.channels = fileChannel > > #Define file sink > adServerAgent.sinks.fileSink.type = file_roll > adServerAgent.sinks.fileSink.sink.directory = /home/hadoop/flume_sink > > adServerAgent.sinks.fileSink.channel = fileChannel > adServerAgent.channels.fileChannel.type=file > adServerAgent.channels.fileChannel.dataDirs=/home/hadoop/flume/channel/dataDir5 > adServerAgent.channels.fileChannel.checkpointDir=/home/hadoop/flume/channel/checkpointDir5 > adServerAgent.channels.fileChannel.maxFileSize=4000000000 > > And it is run with : > JAVA_OPTS = -Xms500m -Xmx700m -Dcom.sun.management.jmxremote > -XX:MaxDirectMemorySize=2g > > Regards, > Jagadish > > On 10/22/2012 05:42 PM, Brock Noland wrote: > > Hi, > > > > I'll respond in more depth later, but it would help if you posted your > > configuration file and the version of flume you are using. > > > > Brock > > > > On Mon, Oct 22, 2012 at 6:48 AM, Jagadish Bihani > > <[email protected] (mailto:[email protected])> wrote: > > > Hi > > > > > > I am writing this on top of another thread where there was discussion on > > > "fsync lies" and > > > only file channel used fsync and not file sink. : > > > > > > -- I tested the fsync performance on 2 machines (On 1 machine I was > > > getting very good throughput > > > using file channel and on another almost 100 times slower with almost > > > same hardware configuration.) > > > using following code > > > > > > > > > #define PAGESIZE 4096 > > > > > > int main(int argc, char *argv[]) > > > { > > > > > > char my_write_str[PAGESIZE]; > > > char my_read_str[PAGESIZE]; > > > char *read_filename= argv[1]; > > > int readfd,writefd; > > > > > > readfd = open(read_filename,O_RDONLY); > > > writefd = open("written_file",O_WRONLY|O_CREAT,777); > > > int len=lseek(readfd,0,2); > > > lseek(readfd,0,0); > > > int iterations = len/PAGESIZE; > > > int i; > > > struct timeval t0,t1; > > > > > > for(i=0;i<iterations;i++) > > > { > > > > > > read(readfd,my_read_str,PAGESIZE); > > > write(writefd,my_read_str,PAGESIZE); > > > gettimeofday(&t0,0); > > > fsync(writefd); > > > gettimeofday(&t1,0); > > > long elapsed = (t1.tv_sec-t0.tv_sec)*1000000 + > > > t1.tv_usec-t0.tv_usec; > > > printf("Elapsed time is= %ld \n",elapsed); > > > } > > > close(readfd); > > > close(writefd); > > > } > > > > > > > > > -- As expected it requires typically 50000 microseconds for fsync to > > > complete on one machine and 200 microseconds > > > on another machine it took 290 microseconds to complete on an average. So > > > is machine with higher > > > performance is doing a 'fsync lie'? > > > i > > > -- If I have understood it clearly; "fsync lie" means the data is not > > > actually written to disk and it is in > > > some disk/controller buffer. I) Now if disk loses power due to some > > > shutdown or any other disaster, data will > > > be lost. II) Can data be lost even without it ? (e.g. if it is keeping > > > data in some disk buffer and if fsync is being > > > invoked continuously then will that data can also be lost? If only part > > > -I is true; then it can be acceptable > > > because probability of shutdown is usually less in production > > > environment. But if even II is true then there is a > > > problem. > > > > > > -- But on the machine where disk doesn't lie performance of flume using > > > File channel is very low (I have seen it > > > maximum 100 KB/sec even with sufficient DirectMemory allocation.) Does > > > anybody have stats about throughput > > > of file channel ? Is anybody getting better performance with file channel > > > (without fsync lies). What is the recommended > > > usage of it for an average scenario ? (Transferring files of few MBs to > > > HDFS sink continuously on typical hardware > > > (16 core processors, 16 GB RAM etc.) > > > > > > > > > Regards, > > > Jagadish > > > > > > On 10/10/2012 11:30 PM, Brock Noland wrote: > > > > Hi, On Wed, Oct 10, 2012 at 11:22 AM, Jagadish Bihani > > > > <[email protected]> (mailto:[email protected]) > > > > wrote: > > > > > Hi Brock I will surely look into 'fsync lies'. But as per my > > > > > experiments I think "file channel" is causing the issue. Because on > > > > > those 2 machines (one with higher throughput and other with lower) I > > > > > did following experiment: cat Source -memory channel - file sink. Now > > > > > with this setup I got same throughput on both the machines. (around 3 > > > > > MB/sec) Now as I have used "File sink" it should also do "fsync" at > > > > > some point of time. 'File Sink' and 'File Channel' both do disk > > > > > writes. So if there is differences in disk behaviour then even in the > > > > > 'File Sink' it should be visible. Am I missing something here? > > > > > > > > > > > > > File sink does not call fsync. > > > > > Regards, Jagadish On 10/10/2012 09:35 PM, Brock Noland wrote: > > > > > > OK your disk that is giving you 40KB/second is telling you the > > > > > > truth and the faster disk is lying to you. Look up "fsync lies" to > > > > > > see what I am referring to. A spinning disk can do 100 fsync > > > > > > operations per second (this is done at the end of every batch). > > > > > > That is how I estimated your event size, 40KB/second is doing 40KB > > > > > > / 100 = 409 bytes. Once again, if you want increased performance, > > > > > > you should increase the batch size. Brock On Wed, Oct 10, 2012 at > > > > > > 11:00 AM, Jagadish Bihani <[email protected]> > > > > > > (mailto:[email protected]) wrote: > > > > > > > Hi Yes. It is around 480 - 500 bytes. On 10/10/2012 09:24 PM, > > > > > > > Brock Noland wrote: > > > > > > > > How big are your events? Average about 400 bytes? Brock On Wed, > > > > > > > > Oct 10, 2012 at 5:11 AM, Jagadish Bihani > > > > > > > > <[email protected]> > > > > > > > > (mailto:[email protected]) wrote: > > > > > > > > > Hi Thanks for the inputs Brock. After doing several > > > > > > > > > experiments eventually problem boiled down to disks. -- But I > > > > > > > > > had used the same configuration (so all software components > > > > > > > > > are same in all 3 machines) on all 3 machines. -- In User > > > > > > > > > guide it is written that if multiple file channel instances > > > > > > > > > are active on the same agent then different disks are > > > > > > > > > preferable. But in my case only one file channel is active > > > > > > > > > per agent. -- Only one pattern I observed that on the > > > > > > > > > machines where I got better performance have multiple disks. > > > > > > > > > But I don't understand how that will help if I have only 1 > > > > > > > > > active file channel. -- What is the impact of the type of > > > > > > > > > disk/disk device driver on performance? I mean I don't > > > > > > > > > understand with 1 disk I am getting 40 KB/sec and with other > > > > > > > > > 2 MB/sec. Could you please elaborate on File channel and > > > > > > > > > disks correlation. Regards, Jagadish On 10/09/2012 08:01 PM, > > > > > > > > > Brock Noland wrote: Hi, Using file channel, in terms of > > > > > > > > > performance, the number and type of disks is going to be much more predictive of performance than CPU or RAM. Note that consumer level drives/controllers will give you much "better" performance because they lie to you about when your data is actually written to the drive. If you search for "fsync lies" you'll find more information on this. You probably want to increase the batch size to get better performance. Brock On Tue, Oct 9, 2012 at 2:46 AM, Jagadish Bihani <[email protected]> (mailto:[email protected]) wrote: Hi My flume setup is: Source Agent : cat source - File Channel - Avro Sink Dest Agent : avro source - File Channel - HDFS Sink. There is only 1 source agent and 1 destination agent. I measure throughput as amount of data written to HDFS per second. ( I have rolling interval 30 sec; so If 60 MB file is generated in 30 sec the throughput is : -- 2 MB/sec ). I have run source agent on various machines with different hardware configurations : (In all cases I run flume agent with JAVA OPTIONS as "-DJAVA_OPT S="-Xms500m -Xmx1g -Dcom.sun.management.jmxremote -XX:MaxDirectMemorySize=2g") JDK is 32 bit. Experiment 1: ===== RAM : 16 GB Processor: Intel Xeon E5620 @ 2.40 GHz (16 cores). 64 bit Processor with 64 bit Kernel. Throughput: 2 MB/sec Experiment 2: ====== RAM : 4 GB Processor: Intel Xeon E5504 @ 2.00GHz (4 cores). 32 bit Processor 64 bit Processor with 32 bit Kernel. Throughput : 30 KB/sec Experiment 3: ====== RAM : 8 GB Processor:Intel Xeon E5520 @ 2.27 GHz (16 cores).32 bit Processor 64 bit Processor with 32 bit Kernel. Throughput : 80 KB/sec -- So as can be seen there is huge difference in the throughput with same configuration but different hardware. -- In the first case where throughput is more RES is around 160 MB in other cases it is in the range of 40 MB - 50 MB. Can anybody please give insights that why there is this huge difference in the throughput? What is the correlation between RAM and filechannel/HDFS sink performance and also with 32-bit/64 bit kernel? Regards, Jagadi sh > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > Apache MRUnit - Unit testing MapReduce - http://incubator.apache.org/mrunit/ >
