Its interesting that you are running into this issue Ted on a
'non-hdfs append-enabled substrate'. This would seem to rule out
'slow hdfs' as culprit.
St.Ack
On Tue, Jan 11, 2011 at 2:51 PM, Ted Dunning <tdunn...@maprtech.com> wrote:
> I am running YCSB to load a modest amount of data (2 M rows) and see
> something similar.
>
> For example:
>
> 10 sec: 135327 operations; 13505.69 current ops/sec; [INSERT
> AverageLatency(ms)=0.84]
> 20 sec: 204440 operations; 6883.08 current ops/sec; [INSERT
> AverageLatency(ms)=3.51]
> 30 sec: 250166 operations; 4572.14 current ops/sec; [INSERT
> AverageLatency(ms)=0.25]
> 40 sec: 348603 operations; 9843.7 current ops/sec; [INSERT
> AverageLatency(ms)=3.02]
> * 50 sec: 348603 operations; 0 current ops/sec; *
> 60 sec: 447040 operations; 9821.11 current ops/sec; [INSERT
> AverageLatency(ms)=3.59]
> 70 sec: 504461 operations; 5741.53 current ops/sec; [INSERT
> AverageLatency(ms)=1.88]
> 80 sec: 598797 operations; 9433.6 current ops/sec; [INSERT
> AverageLatency(ms)=2.53]
> 90 sec: 676724 operations; 7791.92 current ops/sec; [INSERT
> AverageLatency(ms)=1.49]
> 100 sec: 758754 operations; 8202.18 current ops/sec; [INSERT
> AverageLatency(ms)=2.71]
> 110 sec: 779263 operations; 2050.9 current ops/sec; [INSERT
> AverageLatency(ms)=2.26]
> 120 sec: 890004 operations; 11060.83 current ops/sec; [INSERT
> AverageLatency(ms)=2.48]
> 130 sec: 996641 operations; 10662.63 current ops/sec; [INSERT
> AverageLatency(ms)=1.56]
> * 140 sec: 996641 operations; 0 current ops/sec; *
> 150 sec: 1111600 operations; 11494.75 current ops/sec; [INSERT
> AverageLatency(ms)=3.81]
> 160 sec: 1175494 operations; 6371.56 current ops/sec; [INSERT
> AverageLatency(ms)=3.08]
> 170 sec: 1209919 operations; 3442.16 current ops/sec; [INSERT
> AverageLatency(ms)=0.04]
> * 180 sec: 1209919 operations; 0 current ops/sec; *
> 190 sec: 1265127 operations; 5515.84 current ops/sec; [INSERT
> AverageLatency(ms)=10.25]
> 200 sec: 1382184 operations; 11705.7 current ops/sec; [INSERT
> AverageLatency(ms)=0.43]
> 210 sec: 1431400 operations; 4921.11 current ops/sec; [INSERT
> AverageLatency(ms)=2.39]
> * 220 sec: 1431400 operations; 0 current ops/sec; *
> 230 sec: 1490315 operations; 5869.2 current ops/sec; [INSERT
> AverageLatency(ms)=9.58]
> 240 sec: 1513430 operations; 2311.27 current ops/sec; [INSERT
> AverageLatency(ms)=0.29]
> 250 sec: 1599562 operations; 8613.2 current ops/sec; [INSERT
> AverageLatency(ms)=3.86]
> 260 sec: 1725739 operations; 12616.44 current ops/sec; [INSERT
> AverageLatency(ms)=1.35]
> 270 sec: 1823203 operations; 9746.4 current ops/sec; [INSERT
> AverageLatency(ms)=1.39]
> 280 sec: 1911486 operations; 8827.42 current ops/sec; [INSERT
> AverageLatency(ms)=1.25]
> 290 sec: 2000000 operations; 8850.51 current ops/sec; [INSERT
> AverageLatency(ms)=1.41]
>
>
> This is with 0.89 running on 5 region servers on a non-hdfs append-enabled
> substrate.
>
> I am logging GC's on both master and regions and I don't see a correlation
> between either. I am still verifying that, so it could be wrong, but I am
> pretty sure not. What I do see is lots of small compactions that look
> roughly like this:
>
> {Heap before GC invocations=181 (full 23):
> par new generation total 19136K, used 17895K [0x00007f9aa40a0000,
> 0x00007f9aa5560000, 0x00007f9aabda0000)
> eden space 17024K, 99% used [0x00007f9aa40a0000, 0x00007f9aa513b058,
> 0x00007f9aa5140000)
> from space 2112K, 42% used [0x00007f9aa5350000, 0x00007f9aa542ef38,
> 0x00007f9aa5560000)
> to space 2112K, 0% used [0x00007f9aa5140000, 0x00007f9aa5140000,
> 0x00007f9aa5350000)
> concurrent mark-sweep generation total 252700K, used 83769K
> [0x00007f9aabda0000, 0x00007f9abb467000, 0x00007f9ae28a0000)
> concurrent-mark-sweep perm gen total 29120K, used 17377K
> [0x00007f9ae28a0000, 0x00007f9ae4510000, 0x00007f9ae7ca0000)
> 542.472: [GC 542.472: [ParNew
> Desired survivor size 1081344 bytes, new threshold 4 (max 4)
> - age 1: 274408 bytes, 274408 total
> - age 2: 47352 bytes, 321760 total
> - age 3: 10304 bytes, 332064 total
> - age 4: 10472 bytes, 342536 total
> : 17895K->510K(19136K), 0.0586100 secs] 101665K->84784K(271836K) icms_dc=1 ,
> 0.0586740 secs] [Times: user=0.36 sys=0.00, real=0.06 secs]
> Heap after GC invocations=182 (full 23):
> par new generation total 19136K, used 510K [0x00007f9aa40a0000,
> 0x00007f9aa5560000, 0x00007f9aabda0000)
> eden space 17024K, 0% used [0x00007f9aa40a0000, 0x00007f9aa40a0000,
> 0x00007f9aa5140000)
> from space 2112K, 24% used [0x00007f9aa5140000, 0x00007f9aa51bfa98,
> 0x00007f9aa5350000)
> to space 2112K, 0% used [0x00007f9aa5350000, 0x00007f9aa5350000,
> 0x00007f9aa5560000)
> concurrent mark-sweep generation total 252700K, used 84274K
> [0x00007f9aabda0000, 0x00007f9abb467000, 0x00007f9ae28a0000)
> concurrent-mark-sweep perm gen total 29120K, used 17377K
> [0x00007f9ae28a0000, 0x00007f9ae4510000, 0x00007f9ae7ca0000)
> }
> 542.730: [CMS-concurrent-mark: 0.060/2.344 secs] [Times: user=1.48 sys=0.05,
> real=2.35 secs]
> 542.730: [CMS-concurrent-preclean-start]
> 542.744: [CMS-concurrent-preclean: 0.014/0.014 secs] [Times: user=0.01
> sys=0.00, real=0.01 secs]
> 542.744: [CMS-concurrent-abortable-preclean-start]
>
>
> It is unusual to see things last 4 generations. There are clearly full
> collections going on, but not a lot of them and the heap is small enough on
> this system that it should be fast.
>
> I will be gather more information.
>
> On Tue, Jan 11, 2011 at 2:34 PM, Wayne <wav...@gmail.com> wrote:
>
>> We have very frequent cluster wide pauses that stop all reads and writes
>> for seconds. We are constantly loading data to this cluster of 10 nodes.
>> These pauses can happen as frequently as every minute but sometimes are not
>> seen for 15+ minutes. Basically watching the Region server list with
>> request
>> counts is the only evidence of what is going on. All reads and writes
>> totally stop and if there is ever any activity it is on the node hosting
>> the
>> .META. table with a request count of region count + 1. This problem seems
>> to
>> be worse with a larger region size. We tried a 1GB region size and saw this
>> more than we saw actual activity (and stopped using a larger region size
>> because of it). We went back to the default region size and it was better,
>> but we had too many regions so now we are up to 512M for a region size and
>> we are seeing it more again.
>>
>> Does anyone know what this is? We have dug into all of the logs to find
>> some
>> sort of pause but are not able to find anything. Is this an wal hlog roll?
>> Is this a region split or compaction? Of course our biggest fear is a GC
>> pause on the master but we do not have java logging turned on with the
>> master to tell. What could possibly stop the entire cluster from working
>> for
>> seconds at a time very frequently?
>>
>> Thanks in advance for any ideas of what could be causing this.
>>
>
