I looked through the log again. Still looks like it's overloaded and not handling the overload very well. 

It looks like a sustained write load of around 280K columns every 5 minutes for about 5 hours. It may be that the CPU is the bottle neck when it comes to GC throughput. You are hitting ParNew issues from the very start, and end up with 20 second CMS. Do you see high CPU load ? 

Can you enable the GC logging options in cassandra-env.sh ? 
Can you throttle back the test and to a level where the server does not fail ? 

Alternatively can you dump the heap when it get's full and see what it taking up all the space ?


Aaron Morton
Freelance Developer

On 6/06/2012, at 2:12 PM, Poziombka, Wade L wrote:

Ok, so I have completely refactored to remove deletes and it still fails. So it is completely unrelated to deletes.

I guess I need to go back to 1.0.10?  When I originally evaluated I ran 1.0.8... perhaps I went a bridge too far with 1.1.

I don't think I am doing anything exotic here.

Here is my column family.  

KsDef(name:TB_UNIT, strategy_class:org.apache.cassandra.locator.SimpleStrategy, strategy_options:{replication_factor=3},

CfDef(keyspace:TB_UNIT, name:token, column_type:Standard, comparator_type:BytesType, column_metadata:[ColumnDef(name:70 61 6E 45 6E 63, validation_class:BytesType), ColumnDef(name:63 72 65 61 74 65 54 73, validation_class:DateType), ColumnDef(name:63 72 65 61 74 65 44 61 74 65, validation_class:DateType, index_type:KEYS, index_name:TokenCreateDate), ColumnDef(name:65 6E 63 72 79 70 74 69 6F 6E 53 65 74 74 69 6E 67 73 49 44, validation_class:UTF8Type, index_type:KEYS, index_name:EncryptionSettingsID)], caching:keys_only),

CfDef(keyspace:TB_UNIT, name:pan_d721fd40fd9443aa81cc6f59c8e047c6, column_type:Standard, comparator_type:BytesType, caching:keys_only),

CfDef(keyspace:TB_UNIT, name:counters, column_type:Standard, comparator_type:BytesType, column_metadata:[ColumnDef(name:75 73 65 43 6F 75 6E 74, validation_class:CounterColumnType)], default_validation_class:CounterColumnType, caching:keys_only)


-----Original Message-----
From: Poziombka, Wade L [mailto:wade.l.poziombka@intel.com]
Sent: Tuesday, June 05, 2012 3:09 PM
To: user@cassandra.apache.org
Subject: RE: memory issue on 1.1.0

Thank you.  I do have some of the same observations.  Do you do deletes?

My observation is that without deletes (or column updates I guess) I can run forever happy.  but when I run (what for me is a batch process) operations that delete and modify column values I run into this.

Reading bug https://issues.apache.org/jira/browse/CASSANDRA-3741 the advice is to NOT do deletes individually and to truncate.  I am scrambling to try to do this but curious if it will be worth the effort.


-----Original Message-----
From: Mina Naguib [mailto:mina.naguib@bloomdigital.com]
Sent: Tuesday, June 05, 2012 2:24 PM
To: user@cassandra.apache.org
Subject: Re: memory issue on 1.1.0

Hi Wade

I don't know if your scenario matches mine, but I've been struggling with memory pressure in 1.x as well.  I made the jump from 0.7.9 to 1.1.0, along with enabling compression and levelled compactions, so I don't know which specifically is the main culprit.

Specifically, all my nodes seem to "lose" heap memory.  As parnew and CMS do their job, over any reasonable period of time, the "floor" of memory after a GC keeps rising.  This is quite visible if you leave jconsole connected for a day or so, and manifests itself as a funny-looking cone like so: http://mina.naguib.ca/images/cassandra_jconsole.png

Once memory pressure reaches a point where the heap can't be maintained reliably below 75%, cassandra goes into survival mode - via a bunch of tunables in cassandra.conf it'll do things like flush memtables, drop caches, etc - all of which, in my experience, especially with the recent off-heap data structures, exasperate the problem.

I've been meaning, of course, to collect enough technical data to file a bug report, but haven't had the time.  I have not yet tested 1.1.1 to see if it improves the situation.

What I have found however, is a band-aid which you see at the rightmost section of the graph in the screenshot I posted.  That is simply to hit "Perform GC" button in jconsole.  It seems that a full System.gc() *DOES* reclaim heap memory that parnew and CMS fail to reclaim.

On my production cluster I have a full-GC via JMX scheduled in a rolling fashion every 4 hours.  It's extremely expensive (20-40 seconds of unresponsiveness) but is a necessary evil in my situation.  Without it, my nodes enter a nasty spiral of constant flushing, constant compactions, high heap usage, instability and high latency.

On 2012-06-05, at 2:56 PM, Poziombka, Wade L wrote:

Alas, upgrading to 1.1.1 did not solve my issue.

-----Original Message-----
From: Brandon Williams [mailto:driftx@gmail.com]
Sent: Monday, June 04, 2012 11:24 PM
To: user@cassandra.apache.org
Subject: Re: memory issue on 1.1.0

Perhaps the deletes:


On Sun, Jun 3, 2012 at 6:12 PM, Poziombka, Wade L <wade.l.poziombka@intel.com> wrote:
Running a very write intensive (new column, delete old column etc.) process and failing on memory.  Log file attached.

Curiously when I add new data I have never seen this have in past
sent hundreds of millions "new" transactions.  It seems to be when I
modify.  my process is as follows

key slice to get columns to modify in batches of 100, in separate threads modify those columns.  I advance the slice with the start key each with last key in previous batch.  Mutations done are update a column value in one column family(token), delete column and add new column in another (pan).

Runs well until after about 5 million rows then it seems to run out of memory.  Note that these column families are quite small.

WARN [ScheduledTasks:1] 2012-06-03 17:49:01,558 GCInspector.java
145) Heap is 0.7967470834946492 full.  You may need to reduce
memtable and/or cache sizes.  Cassandra will now flush up to the two
largest memtables to free up memory.  Adjust
flush_largest_memtables_at threshold in cassandra.yaml if you don't
want Cassandra to do this automatically  INFO [ScheduledTasks:1]
2012-06-03 17:49:01,559 StorageService.java (line 2772) Unable to
reduce heap usage since there are no dirty column families  INFO
[GossipStage:1] 2012-06-03 17:49:01,999 Gossiper.java (line 797)
InetAddress / is now UP  INFO [ScheduledTasks:1]
2012-06-03 17:49:10,048 GCInspector.java (line 122) GC for ParNew:
206 ms for 1 collections, 7345969520 used; max is 8506048512  INFO
[ScheduledTasks:1] 2012-06-03 17:49:53,187 GCInspector.java (line
122) GC for ConcurrentMarkSweep: 12770 ms for 1 collections,
5714800208 used; max is 8506048512

Keyspace: keyspace
      Read Count: 50042632
      Read Latency: 0.23157864418482224 ms.
      Write Count: 44948323
      Write Latency: 0.019460829472992797 ms.
      Pending Tasks: 0
              Column Family: pan
              SSTable count: 5
              Space used (live): 1977467326
              Space used (total): 1977467326
              Number of Keys (estimate): 16334848
              Memtable Columns Count: 0
              Memtable Data Size: 0
              Memtable Switch Count: 74
              Read Count: 14985122
              Read Latency: 0.408 ms.
              Write Count: 19972441
              Write Latency: 0.022 ms.
              Pending Tasks: 0
              Bloom Filter False Postives: 829
              Bloom Filter False Ratio: 0.00073
              Bloom Filter Space Used: 37048400
              Compacted row minimum size: 125
              Compacted row maximum size: 149
              Compacted row mean size: 149

              Column Family: token
              SSTable count: 4
              Space used (live): 1250973873
              Space used (total): 1250973873
              Number of Keys (estimate): 14217216
              Memtable Columns Count: 0
              Memtable Data Size: 0
              Memtable Switch Count: 49
              Read Count: 30059563
              Read Latency: 0.167 ms.
              Write Count: 14985488
              Write Latency: 0.014 ms.
              Pending Tasks: 0
              Bloom Filter False Postives: 13642
              Bloom Filter False Ratio: 0.00322
              Bloom Filter Space Used: 28002984
              Compacted row minimum size: 150
              Compacted row maximum size: 258
              Compacted row mean size: 224

              Column Family: counters
              SSTable count: 2
              Space used (live): 561549994
              Space used (total): 561549994
              Number of Keys (estimate): 9985024
              Memtable Columns Count: 0
              Memtable Data Size: 0
              Memtable Switch Count: 38
              Read Count: 4997947
              Read Latency: 0.092 ms.
              Write Count: 9990394
              Write Latency: 0.023 ms.
              Pending Tasks: 0
              Bloom Filter False Postives: 191
              Bloom Filter False Ratio: 0.37525
              Bloom Filter Space Used: 18741152
              Compacted row minimum size: 125
              Compacted row maximum size: 179
              Compacted row mean size: 150