That sounds a lot like death by paging.
On 27 February 2014 16:29, Frank Ng <fnt...@gmail.com> wrote: > I just caught that a node was down based on running nodetool status on a > different node. I tried to ssh into the downed node at that time and it > was very slow logging on. Looking at the gc.log file, there was a ParNew > that only took 0.09 secs. Yet the overall application threads stop time is > 315 seconds (5 minutes). Our cluster is handling alot of read requests. > > If there were network hiccups, would that cause a delay in the Cassandra > process when it tries to get to a safepoint? I assume Cassandra has > threads running with lots of network activity and maybe taking a long time > to reach a safepoint. > > thanks, > Frank > > > On Fri, Feb 21, 2014 at 4:24 AM, Joel Samuelsson < > samuelsson.j...@gmail.com> wrote: > >> What happens if a ParNew is triggered while CMS is running? Will it wait >> for the CMS to finish? If so, that would be the eplanation of our long >> ParNew above. >> >> Regards, >> Joel >> >> >> 2014-02-20 16:29 GMT+01:00 Joel Samuelsson <samuelsson.j...@gmail.com>: >> >> Hi Frank, >>> >>> We got a (quite) long GC pause today on 2.0.5: >>> INFO [ScheduledTasks:1] 2014-02-20 13:51:14,528 GCInspector.java (line >>> 116) GC for ParNew: 1627 ms for 1 collections, 425562984 used; max is >>> 4253024256 >>> INFO [ScheduledTasks:1] 2014-02-20 13:51:14,542 GCInspector.java (line >>> 116) GC for ConcurrentMarkSweep: 3703 ms for 2 collections, 434394920 used; >>> max is 4253024256 >>> >>> Unfortunately it's a production cluster so I have no additional >>> GC-logging enabled. This may be an indication that upgrading is not the >>> (complete) solution. >>> >>> Regards, >>> Joel >>> >>> >>> 2014-02-17 13:41 GMT+01:00 Benedict Elliott Smith < >>> belliottsm...@datastax.com>: >>> >>> Hi Ondrej, >>>> >>>> It's possible you were hit by the problems in this thread before, but >>>> it looks potentially like you may have other issues. Of course it may be >>>> that on G1 you have one issue and CMS another, but 27s is extreme even for >>>> G1, so it seems unlikely. If you're hitting these pause times in CMS and >>>> you get some more output from the safepoint tracing, please do contribute >>>> as I would love to get to the bottom of that, however is it possible you're >>>> experiencing paging activity? Have you made certain the VM memory is locked >>>> (and preferably that paging is entirely disabled, as the bloom filters and >>>> other memory won't be locked, although that shouldn't cause pauses during >>>> GC) >>>> >>>> Note that mmapped file accesses and other native work shouldn't in >>>> anyway inhibit GC activity or other safepoint pause times, unless there's a >>>> bug in the VM. These threads will simply enter a safepoint as they return >>>> to the VM execution context, and are considered safe for the duration they >>>> are outside. >>>> >>>> >>>> >>>> >>>> On 17 February 2014 12:30, Ondřej Černoš <cern...@gmail.com> wrote: >>>> >>>>> Hi, >>>>> >>>>> we tried to switch to G1 because we observed this behaviour on CMS too >>>>> (27 seconds pause in G1 is quite an advise not to use it). Pauses with CMS >>>>> were not easily traceable - JVM stopped even without stop-the-world pause >>>>> scheduled (defragmentation, remarking). We thought the go-to-safepoint >>>>> waiting time might have been involved (we saw waiting for safepoint >>>>> resolution) - especially because access to mmpaped files is not >>>>> preemptive, >>>>> afaik, but it doesn't explain tens of seconds waiting times, even slow IO >>>>> should read our sstables into memory in much less time. We switched to G1 >>>>> out of desperation - and to try different code paths - not that we'd >>>>> thought it was a great idea. So I think we were hit by the problem >>>>> discussed in this thread, just the G1 report wasn't very clear, sorry. >>>>> >>>>> regards, >>>>> ondrej >>>>> >>>>> >>>>> >>>>> On Mon, Feb 17, 2014 at 11:45 AM, Benedict Elliott Smith < >>>>> belliottsm...@datastax.com> wrote: >>>>> >>>>>> Ondrej, >>>>>> >>>>>> It seems like your issue is much less difficult to diagnose: your >>>>>> collection times are long. At least, the pause you printed the time for >>>>>> is >>>>>> all attributable to the G1 pause. >>>>>> >>>>>> Note that G1 has not generally performed well with Cassandra in our >>>>>> testing. There are a number of changes going in soon that may change >>>>>> that, >>>>>> but for the time being it is advisable to stick with CMS. With tuning you >>>>>> can no doubt bring your pauses down considerably. >>>>>> >>>>>> >>>>>> On 17 February 2014 10:17, Ondřej Černoš <cern...@gmail.com> wrote: >>>>>> >>>>>>> Hi all, >>>>>>> >>>>>>> we are seeing the same kind of long pauses in Cassandra. We tried to >>>>>>> switch CMS to G1 without positive result. The stress test is read >>>>>>> heavy, 2 >>>>>>> datacenters, 6 nodes, 400reqs/sec on one datacenter. We see spikes in >>>>>>> latency on 99.99 percentil and higher, caused by threads being stopped >>>>>>> in >>>>>>> JVM. >>>>>>> >>>>>>> The GC in G1 looks like this: >>>>>>> >>>>>>> {Heap before GC invocations=4073 (full 1): >>>>>>> garbage-first heap total 8388608K, used 3602914K >>>>>>> [0x00000005f5c00000, 0x00000007f5c00000, 0x00000007f5c00000) >>>>>>> region size 4096K, 142 young (581632K), 11 survivors (45056K) >>>>>>> compacting perm gen total 28672K, used 27428K [0x00000007f5c00000, >>>>>>> 0x00000007f7800000, 0x0000000800000000) >>>>>>> the space 28672K, 95% used [0x00000007f5c00000, >>>>>>> 0x00000007f76c9108, 0x00000007f76c9200, 0x00000007f7800000) >>>>>>> No shared spaces configured. >>>>>>> 2014-02-17T04:44:16.385+0100: 222346.218: [GC pause (G1 Evacuation >>>>>>> Pause) (young) >>>>>>> Desired survivor size 37748736 bytes, new threshold 15 (max 15) >>>>>>> - age 1: 17213632 bytes, 17213632 total >>>>>>> - age 2: 19391208 bytes, 36604840 total >>>>>>> , 0.1664300 secs] >>>>>>> [Parallel Time: 163.9 ms, GC Workers: 2] >>>>>>> [GC Worker Start (ms): Min: 222346218.3, Avg: 222346218.3, Max: >>>>>>> 222346218.3, Diff: 0.0] >>>>>>> [Ext Root Scanning (ms): Min: 6.0, Avg: 6.9, Max: 7.7, Diff: >>>>>>> 1.7, Sum: 13.7] >>>>>>> [Update RS (ms): Min: 20.4, Avg: 21.3, Max: 22.1, Diff: 1.7, >>>>>>> Sum: 42.6] >>>>>>> [Processed Buffers: Min: 49, Avg: 60.0, Max: 71, Diff: 22, >>>>>>> Sum: 120] >>>>>>> [Scan RS (ms): Min: 23.2, Avg: 23.2, Max: 23.3, Diff: 0.1, Sum: >>>>>>> 46.5] >>>>>>> [Object Copy (ms): Min: 112.3, Avg: 112.3, Max: 112.4, Diff: >>>>>>> 0.1, Sum: 224.6] >>>>>>> [Termination (ms): Min: 0.0, Avg: 0.0, Max: 0.1, Diff: 0.0, >>>>>>> Sum: 0.1] >>>>>>> [GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, >>>>>>> Sum: 0.1] >>>>>>> [GC Worker Total (ms): Min: 163.8, Avg: 163.8, Max: 163.8, >>>>>>> Diff: 0.0, Sum: 327.6] >>>>>>> [GC Worker End (ms): Min: 222346382.1, Avg: 222346382.1, Max: >>>>>>> 222346382.1, Diff: 0.0] >>>>>>> [Code Root Fixup: 0.0 ms] >>>>>>> [Clear CT: 0.4 ms] >>>>>>> [Other: 2.1 ms] >>>>>>> [Choose CSet: 0.0 ms] >>>>>>> [Ref Proc: 1.1 ms] >>>>>>> [Ref Enq: 0.0 ms] >>>>>>> [Free CSet: 0.4 ms] >>>>>>> [Eden: 524.0M(524.0M)->0.0B(476.0M) Survivors: 44.0M->68.0M Heap: >>>>>>> 3518.5M(8192.0M)->3018.5M(8192.0M)] >>>>>>> Heap after GC invocations=4074 (full 1): >>>>>>> garbage-first heap total 8388608K, used 3090914K [0x00000005f5c00000, >>>>>>> 0x00000007f5c00000, 0x00000007f5c00000) >>>>>>> region size 4096K, 17 young (69632K), 17 survivors (69632K) >>>>>>> compacting perm gen total 28672K, used 27428K [0x00000007f5c00000, >>>>>>> 0x00000007f7800000, 0x0000000800000000) >>>>>>> the space 28672K, 95% used [0x00000007f5c00000, 0x00000007f76c9108, >>>>>>> 0x00000007f76c9200, 0x00000007f7800000) >>>>>>> No shared spaces configured. >>>>>>> } >>>>>>> [Times: user=0.35 sys=0.00, real=27.58 secs] >>>>>>> 222346.219: G1IncCollectionPause [ 111 0 >>>>>>> 0 ] [ 0 0 0 0 27586 ] 0 >>>>>>> >>>>>>> And the total thime for which application threads were stopped is >>>>>>> 27.58 seconds. >>>>>>> >>>>>>> CMS behaves in a similar manner. We thought it would be GC, waiting >>>>>>> for mmaped files being read from disk (the thread cannot reach safepoint >>>>>>> during this operation), but it doesn't explain the huge time. >>>>>>> >>>>>>> We'll try jhiccup to see if it provides any additional information. >>>>>>> The test was done on mixed aws/openstack environment, openjdk 1.7.0_45, >>>>>>> cassandra 1.2.11. Upgrading to 2.0.x is no option for us. >>>>>>> >>>>>>> regards, >>>>>>> >>>>>>> ondrej cernos >>>>>>> >>>>>>> >>>>>>> On Fri, Feb 14, 2014 at 8:53 PM, Frank Ng <fnt...@gmail.com> wrote: >>>>>>> >>>>>>>> Sorry, I have not had a chance to file a JIRA ticket. We have not >>>>>>>> been able to resolve the issue. But since Joel mentioned that >>>>>>>> upgrading to >>>>>>>> Cassandra 2.0.X solved it for them, we may need to upgrade. We are >>>>>>>> currently on Java 1.7 and Cassandra 1.2.8 >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> On Thu, Feb 13, 2014 at 12:40 PM, Keith Wright < >>>>>>>> kwri...@nanigans.com> wrote: >>>>>>>> >>>>>>>>> You’re running 2.0.* in production? May I ask what C* version and >>>>>>>>> OS? Any hardware details would be appreciated as well. Thx! >>>>>>>>> >>>>>>>>> From: Joel Samuelsson <samuelsson.j...@gmail.com> >>>>>>>>> Reply-To: "user@cassandra.apache.org" <user@cassandra.apache.org> >>>>>>>>> Date: Thursday, February 13, 2014 at 11:39 AM >>>>>>>>> >>>>>>>>> To: "user@cassandra.apache.org" <user@cassandra.apache.org> >>>>>>>>> Subject: Re: Intermittent long application pauses on nodes >>>>>>>>> >>>>>>>>> We have had similar issues and upgrading C* to 2.0.x and Java to >>>>>>>>> 1.7 seems to have helped our issues. >>>>>>>>> >>>>>>>>> >>>>>>>>> 2014-02-13 Keith Wright <kwri...@nanigans.com>: >>>>>>>>> >>>>>>>>>> Frank did you ever file a ticket for this issue or find the root >>>>>>>>>> cause? I believe we are seeing the same issues when attempting to >>>>>>>>>> bootstrap. >>>>>>>>>> >>>>>>>>>> Thanks >>>>>>>>>> >>>>>>>>>> From: Robert Coli <rc...@eventbrite.com> >>>>>>>>>> Reply-To: "user@cassandra.apache.org" <user@cassandra.apache.org> >>>>>>>>>> Date: Monday, February 3, 2014 at 6:10 PM >>>>>>>>>> To: "user@cassandra.apache.org" <user@cassandra.apache.org> >>>>>>>>>> Subject: Re: Intermittent long application pauses on nodes >>>>>>>>>> >>>>>>>>>> On Mon, Feb 3, 2014 at 8:52 AM, Benedict Elliott Smith < >>>>>>>>>> belliottsm...@datastax.com> wrote: >>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> It's possible that this is a JVM issue, but if so there may be >>>>>>>>>>> some remedial action we can take anyway. There are some more flags >>>>>>>>>>> we >>>>>>>>>>> should add, but we can discuss that once you open a ticket. If you >>>>>>>>>>> could >>>>>>>>>>> include the strange JMX error as well, that might be helpful. >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> It would be appreciated if you could inform this thread of the >>>>>>>>>> JIRA ticket number, for the benefit of the community and google >>>>>>>>>> searchers. >>>>>>>>>> :) >>>>>>>>>> >>>>>>>>>> =Rob >>>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>> >>>>>>> >>>>>> >>>>> >>>> >>> >> >