I haven't used dtrace, but is it possible to have it running and recording the ftruncate64 times? Then when you see one of these long roll times look at the dtrace log to see if it was that call?
-Dave -----Original Message----- From: Stephen Powis [mailto:spo...@salesforce.com] Sent: Friday, January 13, 2017 9:25 AM To: users@kafka.apache.org Subject: Re: Taking a long time to roll a new log segment (~1 min) So the underlying system call is ftruncate64, logged using dtrace. # BEGIN stack trace for ftruncate, call took 34160541200ns: > args== > 0x7f5f9a1134d7 : ftruncate64+0x7/0x30 [/lib64/libc-2.12.so] > 0x7f5f987b80c3 : 0x7f5f987b80c3 > [/usr/lib/jvm/jdk1.8.0_51/jre/lib/amd64/libjava.so+0x180c3/0x22c000] > # END stack trace for ftruncate > These index files seem to be typically around 10MB for open log segments, and get truncated down to ~1MB after being closed. I'd imagine truncating off ~9MB shouldn't be that heavy of an operation. ZFS options: > data/kafka type filesystem - > data/kafka creation Tue Feb 9 22:45 2016 - > data/kafka used 196G - > data/kafka available 6.65T - > data/kafka referenced 196G - > data/kafka compressratio 4.59x - > data/kafka mounted yes - > data/kafka quota none default > data/kafka reservation none default > data/kafka recordsize 128K default > data/kafka mountpoint /kafka local > data/kafka sharenfs off default > data/kafka checksum on default > data/kafka compression lz4 inherited > from data > data/kafka atime off inherited > from data > data/kafka devices on default > data/kafka exec on default > data/kafka setuid on default > data/kafka readonly off default > data/kafka zoned off default > data/kafka snapdir hidden default > data/kafka aclinherit restricted default > data/kafka canmount on default > data/kafka xattr on default data/kafka copies 1 default > data/kafka version 5 - > data/kafka utf8only off - > data/kafka normalization none - > data/kafka casesensitivity sensitive - > data/kafka vscan off default > data/kafka nbmand off default > data/kafka sharesmb off default > data/kafka refquota none default > data/kafka refreservation none default > data/kafka primarycache all default > data/kafka secondarycache all default > data/kafka usedbysnapshots 0 - > data/kafka usedbydataset 196G - > data/kafka usedbychildren 0 - > data/kafka usedbyrefreservation 0 - > data/kafka logbias throughput local > data/kafka dedup off default > data/kafka mlslabel none default > data/kafka sync standard default > data/kafka refcompressratio 4.59x - > data/kafka written 196G - > data/kafka logicalused 900G - > data/kafka logicalreferenced 900G - > data/kafka filesystem_limit none default > data/kafka snapshot_limit none default > data/kafka filesystem_count none default > data/kafka snapshot_count none default > data/kafka snapdev hidden default > data/kafka acltype off default > data/kafka context none default > data/kafka fscontext none default > data/kafka defcontext none default > data/kafka rootcontext none default > data/kafka relatime off default > data/kafka redundant_metadata all default > data/kafka overlay off default > CPU IO Wait is extremely low (below 0.01%) with no recorded spikes. On Fri, Jan 13, 2017 at 6:57 AM, Ismael Juma <ism...@juma.me.uk> wrote: > Hi Stephen, > > I think it's worth capturing this in a JIRA so that it doesn't get lost. > > Ismael > > On Thu, Jan 12, 2017 at 7:22 PM, Stephen Powis <spo...@salesforce.com> > wrote: > > > I've further narrowed it down to this particular line: > > https://github.com/apache/kafka/blob/0.10.0/core/src/ > main/scala/kafka/log/ > > OffsetIndex.scala#L294 > > > > But I'm still at a loss to why this would be slow sometimes and not > others. > > > > On Thu, Jan 12, 2017 at 10:56 AM, Stephen Powis > > <spo...@salesforce.com> > > wrote: > > > > > Using the little bash script in that JIRA ticket to go thru the GC > > > log > > and > > > sum up the total pause times I come up with the following. I > > > don't see anything that would indicate a ~28 second pause. > > > > > > 2017-01-12T07:00 = 72.2961 > > >> 2017-01-12T07:01 = 59.8112 > > >> 2017-01-12T07:02 = 69.6915 > > >> 2017-01-12T07:03 = 74.4093 > > >> 2017-01-12T07:04 = 73.507 > > >> 2017-01-12T07:05 = 73.7028 > > >> 2017-01-12T07:06 = 72.3392 > > >> 2017-01-12T07:07 = 70.502 > > >> 2017-01-12T07:08 = 71.7471 > > >> 2017-01-12T07:09 = 76.8371 > > >> 2017-01-12T07:10 = 72.3836 > > >> 2017-01-12T07:11 = 74.7462 > > >> 2017-01-12T07:12 = 57.1328 > > >> 2017-01-12T07:13 = 80.005 > > >> 2017-01-12T07:14 = 76.0012 > > >> 2017-01-12T07:15 = 79.2221 > > >> 2017-01-12T07:16 = 57.5385 > > >> 2017-01-12T07:17 = 58.1185 > > >> 2017-01-12T07:18 = 72.0524 > > >> 2017-01-12T07:19 = 110.6736 > > >> 2017-01-12T07:20 = 64.9808 > > >> 2017-01-12T07:21 = 66.8767 > > >> 2017-01-12T07:22 = 32.409 > > >> 2017-01-12T07:23 = 85.3671 > > >> 2017-01-12T07:24 = 123.9212 > > >> 2017-01-12T07:25 = 70.3219 > > >> > > > > > > > > > > > > > > > > > > On Thu, Jan 12, 2017 at 10:49 AM, Stephen Powis > > > <spo...@salesforce.com > > > > > wrote: > > > > > >> Just realized that GCEasy doesn't keep reports around for very > > >> long anymore, here is a screencap of the report: > > >> http://imgur.com/a/MEubD > > >> > > >> The longest reported GC pause was 30ms, tho they happen somewhat > > >> frequently at an average of once per 12 seconds. KAFKA-4616 > > >> certainly sounds just like my scenario, but I'm having trouble > > >> finding the long > GC > > >> pauses described in that ticket in my own logs. > > >> > > >> On Thu, Jan 12, 2017 at 10:42 AM, tao xiao <xiaotao...@gmail.com> > > wrote: > > >> > > >>> You may run into this bug https://issues.apache.org/jira > > >>> /browse/KAFKA-4614 > > >>> > > >>> On Thu, 12 Jan 2017 at 23:38 Stephen Powis > > >>> <spo...@salesforce.com> > > >>> wrote: > > >>> > > >>> > Per my email to the list in Sept, when I reviewed GC logs > > >>> > then, I > > >>> didn't > > >>> > see anything out of the ordinary. ( > > >>> > > > >>> > http://mail-archives.apache.org/mod_mbox/kafka-users/201609. > > >>> mbox/%3CCABQB-gS7h4Nuq3TKgHoAVeRHPWnBNs2B0Tz0kCjmdB9c0SDcLQ% > > >>> 40mail.gmail.com%3E > > >>> > ) > > >>> > > > >>> > Reviewing the GC logs from this morning around the timestamp > > >>> > in my > > >>> previous > > >>> > email, I see GC running roughly every 10-12 seconds, with > > >>> > total > times > > >>> > similar to the following: > > >>> > > > >>> > 2017-01-12T07:16:46.867-0500: 46891.844: Total time for which > > >>> application > > >>> > > threads were stopped: 0.0141281 seconds, Stopping threads took: > > >>> 0.0002171 > > >>> > > seconds > > >>> > > > > >>> > > > > >>> > Here is a link to a GCEasy report: > > >>> > > > >>> > http://gceasy.io/my-gc-report.jsp?p=c2hhcmVkLzIwMTcvMDEvMTIv > > >>> LS10b3RhbEdDLWthZmthMS00LmxvZy5nei0tMTUtMzQtNTk= > > >>> > > > >>> > > > >>> > Currently using G1 gc with the following settings: > > >>> > > > >>> > -Xmx12G -Xms12G -server -XX:MaxPermSize=48M -verbose:gc > > >>> > -Xloggc:/var/log/kafka/gc.log -XX:+PrintGCDateStamps > > >>> -XX:+PrintGCDetails > > >>> > -XX:+PrintTenuringDistribution > > >>> > -XX:+PrintGCApplicationStoppedTime > > >>> > -XX:+PrintTLAB -XX:+DisableExplicitGC > > >>> > -XX:+UseGCLogFileRotation > > >>> > -XX:NumberOfGCLogFiles=10 -XX:GCLogFileSize=100M > > -XX:+UseCompressedOops > > >>> > -XX:+AlwaysPreTouch -XX:+UseG1GC -XX:MaxGCPauseMillis=20 > > >>> > -XX:+HeapDumpOnOutOfMemoryError > > >>> > -XX:HeapDumpPath=/var/log/kafka/heapDump.log > > >>> > -Xloggc:/opt/kafka/current/bin/../logs/kafkaServer-gc.log > > -verbose:gc > > >>> > -XX:+PrintGCDetails -XX:+PrintGCDateStamps > > >>> > -XX:+PrintGCTimeStamps > > >>> > > > >>> > > > >>> > > > >>> > On Thu, Jan 12, 2017 at 9:55 AM, Tauzell, Dave < > > >>> > dave.tauz...@surescripts.com > > >>> > > wrote: > > >>> > > > >>> > > Can you collect garbage collection stats and verify there > > >>> > > isn't a > > >>> long GC > > >>> > > happening at the same time? > > >>> > > > > >>> > > -Dave > > >>> > > > > >>> > > -----Original Message----- > > >>> > > From: Stephen Powis [mailto:spo...@salesforce.com] > > >>> > > Sent: Thursday, January 12, 2017 8:34 AM > > >>> > > To: users@kafka.apache.org > > >>> > > Subject: Re: Taking a long time to roll a new log segment > > >>> > > (~1 > min) > > >>> > > > > >>> > > So per the kafka docs I up'd our FD limit to 100k, and we > > >>> > > are no > > >>> longer > > >>> > > seeing the process die, which is good. > > >>> > > > > >>> > > Unfortunately we're still seeing very high log segment roll > times, > > >>> and > > >>> > I'm > > >>> > > unsure if this is considered 'normal', as it tends to block > > producers > > >>> > > during this period. > > >>> > > > > >>> > > We are running kafka 0.10.0.1, but I patched in some > > >>> > > additionally > > >>> timing > > >>> > > statements into the kafka.log.log roll() method to narrow > > >>> > > down > > >>> exactly > > >>> > > which part of that method is taking so long. > > >>> > > > > >>> > > Again, typically the process to roll a new log file takes > > >>> > > only > > 1-2ms > > >>> > tops, > > >>> > > but several times a day it takes 30-60+ seconds, across all > > >>> > > of > our > > >>> > > brokers. I've narrowed it down to this bit of code causing > > >>> > > the > > >>> issue: > > >>> > > https://github.com/apache/kafka/blob/0.10.0/core/src/ > > >>> > > main/scala/kafka/log/Log.scala#L652-L658 > > >>> > > > > >>> > > Here's an example of output w/ my additional timing log > statements: > > >>> > > > > >>> > > [2017-01-12 07:17:58,199] INFO Rolled new log segment for > > >>> 'MyTopic-4' in > > >>> > > > 28028 ms. (kafka.log.Log) > > >>> > > > > >>> > > [2017-01-12 07:17:58,200] INFO LastEntry match time > 'EventStream-4' > > >>> in > > >>> > > > 28027 ms. (kafka.log.Log) > > >>> > > > > > >>> > > > > >>> > > Any thoughts? Help? This considered normal? > > >>> > > > > >>> > > Thanks > > >>> > > Stephen > > >>> > > > > >>> > > > > >>> > > On Tue, Jan 10, 2017 at 2:37 AM, Ewen Cheslack-Postava < > > >>> > e...@confluent.io> > > >>> > > wrote: > > >>> > > > > >>> > > > I can't speak to the exact details of why fds would be > > >>> > > > kept > open > > >>> > > > longer in that specific case, but are you aware that the > > >>> > > > recommendation for production clusters for open fd limits > > >>> > > > is > much > > >>> > > > higher? It's been suggested to be 100,000 as a starting > > >>> > > > point > for > > >>> quite > > >>> > > awhile: > > >>> > > > http://kafka.apache.org/documentation.html#os > > >>> > > > > > >>> > > > -Ewen > > >>> > > > > > >>> > > > On Mon, Jan 9, 2017 at 12:45 PM, Stephen Powis < > > >>> spo...@salesforce.com> > > >>> > > > wrote: > > >>> > > > > > >>> > > > > Hey! > > >>> > > > > > > >>> > > > > I've run into something concerning in our production > > cluster....I > > >>> > > > > believe I've posted this question to the mailing list > > previously > > >>> ( > > >>> > > > > http://mail-archives.apache.org/mod_mbox/kafka-users/201609. > > >>> mbox/bro > > >>> > > > > wser > > >>> > > > ) > > >>> > > > > but the problem has become considerably more serious. > > >>> > > > > > > >>> > > > > We've been fighting issues where Kafka 0.10.0.1 hits its > > >>> > > > > max > > file > > >>> > > > > descriptor limit. Our limit is set to ~16k, and under > > >>> > > > > normal operation > > >>> > > > it > > >>> > > > > holds steady around 4k open files. > > >>> > > > > > > >>> > > > > But occasionally Kafka will roll a new log segment, > > >>> > > > > which > > >>> typically > > >>> > > > > takes on the order of magnitude of a few milliseconds. > > >>> > > > > However...sometimes it will take a considerable amount > > >>> > > > > of > time, > > >>> any > > >>> > > > > where from 40 seconds up to over a minute. When this > happens, > > it > > >>> > > > > seems like connections are not released by kafka, and we > > >>> > > > > end > up > > >>> with > > >>> > > > > thousands of client connections > > >>> > > > stuck > > >>> > > > > in CLOSE_WAIT, which pile up and exceed our max file > descriptor > > >>> > limit. > > >>> > > > > This happens all in the span of about a minute. > > >>> > > > > > > >>> > > > > Our logs look like this: > > >>> > > > > > > >>> > > > > [2017-01-08 01:10:17,117] INFO Rolled new log segment > > >>> > > > > for 'MyTopic-8' in > > >>> > > > > > 41122 ms. (kafka.log.Log) > > >>> > > > > > [2017-01-08 01:10:32,550] INFO Rolled new log segment > > >>> > > > > > for > > >>> > 'MyTopic-4' > > >>> > > > in > > >>> > > > > 1 > > >>> > > > > > ms. (kafka.log.Log) > > >>> > > > > > [2017-01-08 01:11:10,039] INFO [Group Metadata Manager > > >>> > > > > > on > > >>> Broker > > >>> > 4]: > > >>> > > > > > Removed 0 expired offsets in 0 milliseconds. > > >>> > > > > > (kafka.coordinator.GroupMetadataManager) > > >>> > > > > > [2017-01-08 01:19:02,877] ERROR Error while accepting > > >>> connection > > >>> > > > > > (kafka.network.Acceptor) > > >>> > > > > > java.io.IOException: Too many open files at > > >>> > > > > > sun.nio.ch.ServerSocketChannelImpl.accept0(Native > > >>> > > > > > Method) > > >>> > > > > > > > >>> > > > > at > > >>> > > > > > sun.nio.ch.ServerSocketChannelImpl.accept( > > >>> > > > ServerSocketChannelImpl.java: > > >>> > > > > 422) > > >>> > > > > > at > > >>> > > > > > sun.nio.ch.ServerSocketChannelImpl.accept( > > >>> > > > ServerSocketChannelImpl.java: > > >>> > > > > 250) > > >>> > > > > > at kafka.network.Acceptor.accept( > > >>> SocketServer.scala:323) > > >>> > > > > > at kafka.network.Acceptor.run( > > SocketServer.scala:268) > > >>> > > > > > at java.lang.Thread.run(Thread.java:745) > > >>> > > > > > [2017-01-08 01:19:02,877] ERROR Error while accepting > > >>> connection > > >>> > > > > > (kafka.network.Acceptor) > > >>> > > > > > java.io.IOException: Too many open files > > >>> > > > > > at sun.nio.ch.ServerSocketChannelImpl. > accept0(Native > > >>> > Method) > > >>> > > > > > at > > >>> > > > > > sun.nio.ch.ServerSocketChannelImpl.accept( > > >>> > > > ServerSocketChannelImpl.java: > > >>> > > > > 422) > > >>> > > > > > at > > >>> > > > > > sun.nio.ch.ServerSocketChannelImpl.accept( > > >>> > > > ServerSocketChannelImpl.java: > > >>> > > > > 250) > > >>> > > > > > at kafka.network.Acceptor.accept( > > >>> SocketServer.scala:323) > > >>> > > > > > at kafka.network.Acceptor.run( > > SocketServer.scala:268) > > >>> > > > > > at java.lang.Thread.run(Thread.java:745) > > >>> > > > > > ..... > > >>> > > > > > > > >>> > > > > > > >>> > > > > > > >>> > > > > And then kafka crashes. > > >>> > > > > > > >>> > > > > Has anyone seen this behavior of slow log segmented > > >>> > > > > being > > rolled? > > >>> > > > > Any ideas of how to track down what could be causing this? > > >>> > > > > > > >>> > > > > Thanks! > > >>> > > > > Stephen > > >>> > > > > > > >>> > > > > > >>> > > This e-mail and any files transmitted with it are > > >>> > > confidential, > may > > >>> > > contain sensitive information, and are intended solely for > > >>> > > the > use > > >>> of the > > >>> > > individual or entity to whom they are addressed. If you have > > received > > >>> > this > > >>> > > e-mail in error, please notify the sender by reply e-mail > > >>> immediately and > > >>> > > destroy all copies of the e-mail and any attachments. > > >>> > > > > >>> > > > >>> > > >> > > >> > > > > > > This e-mail and any files transmitted with it are confidential, may contain sensitive information, and are intended solely for the use of the individual or entity to whom they are addressed. If you have received this e-mail in error, please notify the sender by reply e-mail immediately and destroy all copies of the e-mail and any attachments.
