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From Tamar Fraenkel <ta...@tok-media.com>
Subject Re: GCInspector info messages in cassandra log
Date Thu, 16 Aug 2012 07:17:13 GMT
Thank you very much!
*Tamar Fraenkel *
Senior Software Engineer, TOK Media

[image: Inline image 1]

tamar@tok-media.com
Tel:   +972 2 6409736
Mob:  +972 54 8356490
Fax:   +972 2 5612956





On Thu, Aug 16, 2012 at 12:11 AM, aaron morton <aaron@thelastpickle.com>wrote:

> Is there anything to do before that? like drain or flush?
>
> For a clean shutdown I do
>
> nodetool -h localhost disablethrift
> nodetool -h localhost disablegossip && sleep 10
> nodetool -h localhost drain
> then kill
>
> Would you recommend that? If I do it, how often should I do a full
> snapshot, and how often should I backup the backup directory?
>
> Sounds like you could use Priam and be happier...
> http://techblog.netflix.com/2012/02/announcing-priam.html
>
>  I just saw that there is an option global_snapshot, is it still supported?
>
> I cannot find it.
>
> Try Piram or the instructions here, which are pretty much what you have
> described http://www.datastax.com/docs/1.0/operations/backup_restore
>
> Cheers
>
>   -----------------
> Aaron Morton
> Freelance Developer
> @aaronmorton
> http://www.thelastpickle.com
>
> On 15/08/2012, at 4:57 PM, Tamar Fraenkel <tamar@tok-media.com> wrote:
>
> Aaron,
> Thank you very much. I will do as you suggested.
>
> One last question regarding restart:
> I assume, I should do it node by node.
> Is there anything to do before that? like drain or flush?
>
> I am also considering enabling incremental backups on my cluster.
> Currently I take a daily full snapshot of the cluster, tar it and load it
> to S3 (size now is 3.1GB). Would you recommend that? If I do it, how often
> should I do a full snapshot, and how often should I backup the backup
> directory?
>
> Another snapshot related question, currently I snapshot on each node and
> use parallel-slurp to copy the snapshot to one node where I tar them. I
> just saw that there is an option global_snapshot, is it still supported?
> Does that mean that if I run it on one node the snapshot will contain data
> from all cluster? How does it work in restore? Is it better than my current
> backup system?
>
> *Tamar Fraenkel *
> Senior Software Engineer, TOK Media
>
> [image: Inline image 1]
>
> tamar@tok-media.com
> Tel:   +972 2 6409736
> Mob:  +972 54 8356490
> Fax:   +972 2 5612956
>
>
>
>
>
> On Tue, Aug 14, 2012 at 11:51 PM, aaron morton <aaron@thelastpickle.com>wrote:
>
>>
>>    1. According to cfstats there are the some CF with high Comacted row
>>    maximum sizes (1131752, 4866323 and 25109160). Others max sizes are <
>>    1000000. Are these considered to be problematic, what can I do to solve
>>    that?
>>    2.
>>
>> They are only 1, 4 and 25 MB. Not too big.
>>
>> What should be the values of  in_memory_compaction_limit_in_mb
>>  and concurrent_compactors and how do I change them?
>>
>> Sounds like you dont have very big CF's, so changing the
>> in_memory_compaction_limit_in_mb may not make too much difference.
>>
>> Try changing concurrent_compactors to 2 in the yaml file. This change
>> will let you know if GC and compaction are related.
>>
>>
>>  change yaml file and restart,
>>
>> yes
>>
>> What do I do about the long rows? What value is considered too big.
>>
>> They churn more memory during compaction. If you have a lot of rows +32
>> MB I would think about it, does not look that way.
>>
>> Cheers
>>
>>
>>   -----------------
>> Aaron Morton
>> Freelance Developer
>> @aaronmorton
>> http://www.thelastpickle.com
>>
>> On 15/08/2012, at 3:15 AM, Tamar Fraenkel <tamar@tok-media.com> wrote:
>>
>> Hi!
>> It helps, but before I do more actions I want to give you some more info,
>> and ask some questions:
>>
>> *Related Info*
>>
>>    1. According to my yaml file (where do I see these parameters in the
>>    jmx? I couldn't find them):
>>    in_memory_compaction_limit_in_mb: 64
>>    concurrent_compactors: 1, but it is commented out, so I guess it is
>>    the default value
>>    multithreaded_compaction: false
>>    compaction_throughput_mb_per_sec: 16
>>    compaction_preheat_key_cache: true
>>    2. According to cfstats there are the some CF with high Comacted row
>>    maximum sizes (1131752, 4866323 and 25109160). Others max sizes are <
>>    1000000. Are these considered to be problematic, what can I do to solve
>>    that?
>>    3. During compactions Cassandra is slower
>>    4. Running Cassandra Version 1.0.8
>>
>> *Questions*
>> What should be the values of  in_memory_compaction_limit_in_mb
>>  and concurrent_compactors and how do I change them? change yaml file
>> and restart, or can it be done using jmx without restarting Cassandra?
>> What do I do about the long rows? What value is considered too big.
>>
>> I appreciate your help! Thanks,
>>
>>
>>
>> *Tamar Fraenkel *
>> Senior Software Engineer, TOK Media
>>
>> <tokLogo.png>
>>
>> tamar@tok-media.com
>> Tel:   +972 2 6409736
>> Mob:  +972 54 8356490
>> Fax:   +972 2 5612956
>>
>>
>>
>>
>>
>> On Tue, Aug 14, 2012 at 1:22 PM, aaron morton <aaron@thelastpickle.com>wrote:
>>
>>> There are a couple of steps you can take if compaction is causing GC.
>>>
>>> - if you have a lot of wide rows consider reducing
>>> the in_memory_compaction_limit_in_mb yaml setting. This will slow down
>>> compaction but will reduce the memory usage.
>>>
>>> - reduce concurrent_compactors
>>>
>>> Both of these may slow down compaction. Once you have GC under control
>>> you may want to play with memory settings.
>>>
>>> Hope that helps.
>>>   -----------------
>>> Aaron Morton
>>> Freelance Developer
>>> @aaronmorton
>>> http://www.thelastpickle.com
>>>
>>> On 14/08/2012, at 4:45 PM, Tamar Fraenkel <tamar@tok-media.com> wrote:
>>>
>>> Hi!
>>> I have 3 nodes ring running on Amazon EC2.
>>> About once a week I see in the logs compaction messages and around the
>>> same time info messages about GC (see below) that I think means it is
>>> taking too long and happening too often.
>>>
>>> Does it mean I have to reduce my cache size?
>>> Thanks,
>>> Tamar
>>>
>>>  INFO [ScheduledTasks:1] 2012-08-13 12:50:57,593 GCInspector.java (line
>>> 122) GC for ParNew: 242 ms for 1 collections, 1541590352 used; max is
>>> 1937768448
>>>  INFO [ScheduledTasks:1] 2012-08-13 12:51:27,740 GCInspector.java (line
>>> 122) GC for ParNew: 291 ms for 1 collections, 1458227032 used; max is
>>> 1937768448
>>>  INFO [ScheduledTasks:1] 2012-08-13 12:51:29,741 GCInspector.java (line
>>> 122) GC for ParNew: 261 ms for 1 collections, 1228861368 used; max is
>>> 1937768448
>>>  INFO [ScheduledTasks:1] 2012-08-13 12:51:30,833 GCInspector.java (line
>>> 122) GC for ParNew: 319 ms for 1 collections, 1120131360 used; max is
>>> 1937768448
>>>  INFO [ScheduledTasks:1] 2012-08-13 12:51:32,863 GCInspector.java (line
>>> 122) GC for ParNew: 241 ms for 1 collections, 983144216 used; max is
>>> 1937768448
>>>  INFO [ScheduledTasks:1] 2012-08-13 12:51:33,864 GCInspector.java (line
>>> 122) GC for ParNew: 215 ms for 1 collections, 967702720 used; max is
>>> 1937768448
>>>  INFO [ScheduledTasks:1] 2012-08-13 12:51:34,964 GCInspector.java (line
>>> 122) GC for ParNew: 248 ms for 1 collections, 973803344 used; max is
>>> 1937768448
>>>  INFO [ScheduledTasks:1] 2012-08-13 12:51:41,211 GCInspector.java (line
>>> 122) GC for ParNew: 265 ms for 1 collections, 1071933560 used; max is
>>> 1937768448
>>>  INFO [ScheduledTasks:1] 2012-08-13 12:51:43,212 GCInspector.java (line
>>> 122) GC for ParNew: 326 ms for 1 collections, 1217367792 used; max is
>>> 1937768448
>>>  INFO [ScheduledTasks:1] 2012-08-13 12:51:44,212 GCInspector.java (line
>>> 122) GC for ParNew: 245 ms for 1 collections, 1203481536 used; max is
>>> 1937768448
>>>  INFO [ScheduledTasks:1] 2012-08-13 12:51:45,213 GCInspector.java (line
>>> 122) GC for ParNew: 209 ms for 1 collections, 1208819416 used; max is
>>> 1937768448
>>>  INFO [ScheduledTasks:1] 2012-08-13 12:51:46,237 GCInspector.java (line
>>> 122) GC for ParNew: 248 ms for 1 collections, 1338361648 used; max is
>>> 1937768448
>>>
>>>
>>>  *Tamar Fraenkel *
>>> Senior Software Engineer, TOK Media
>>>
>>> <tokLogo.png>
>>>
>>>
>>> tamar@tok-media.com
>>> Tel:   +972 2 6409736
>>> Mob:  +972 54 8356490
>>> Fax:   +972 2 5612956
>>>
>>>
>>>
>>>
>>>
>>
>>
>
>

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