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From "R. Verlangen" <ro...@us2.nl>
Subject Re: Restart cassandra every X days?
Date Thu, 02 Feb 2012 08:55:05 GMT
Yes, I already did a repair and cleanup. Currently my ring looks like this:

Address         DC          Rack        Status State   Load            Owns
   Token
***.89    datacenter1 rack1       Up     Normal  2.44 GB         50.00%  0
***.135    datacenter1 rack1       Up     Normal  6.99 GB         50.00%
 85070591730234615865843651857942052864

It's not really a problem, but I'm still wondering why this happens.

2012/2/1 aaron morton <aaron@thelastpickle.com>

> Do you mean the load in nodetool ring is not even, despite the tokens been
> evenly distributed ?
>
> I would assume this is not the case given the difference, but it may be
> hints given you have just done an upgrade. Check the system using nodetool
> cfstats to see. They will eventually be delivered and deleted.
>
> More likely you will want to:
> 1) nodetool repair to make sure all data is distributed then
> 2) nodetool cleanup if you have changed the tokens at any point finally
>
> Cheers
>
> -----------------
> Aaron Morton
> Freelance Developer
> @aaronmorton
> http://www.thelastpickle.com
>
> On 31/01/2012, at 11:56 PM, R. Verlangen wrote:
>
> After running 3 days on Cassandra 1.0.7 it seems the problem has been
> solved. One weird thing remains, on our 2 nodes (both 50% of the ring), the
> first's usage is just over 25% of the second.
>
> Anyone got an explanation for that?
>
> 2012/1/29 aaron morton <aaron@thelastpickle.com>
>
>> Yes but…
>>
>> For every upgrade read the NEWS.TXT it will go through the upgrade
>> procedure in detail. If you want to feel extra smart scan through the
>> CHANGES.txt to get an idea of whats going on.
>>
>> Cheers
>>
>>   -----------------
>> Aaron Morton
>> Freelance Developer
>> @aaronmorton
>> http://www.thelastpickle.com
>>
>> On 29/01/2012, at 4:14 AM, Maxim Potekhin wrote:
>>
>>  Sorry if this has been covered, I was concentrating solely on 0.8x --
>> can I just d/l 1.0.x and continue using same data on same cluster?
>>
>> Maxim
>>
>>
>> On 1/28/2012 7:53 AM, R. Verlangen wrote:
>>
>> Ok, seems that it's clear what I should do next ;-)
>>
>> 2012/1/28 aaron morton <aaron@thelastpickle.com>
>>
>>> There are no blockers to upgrading to 1.0.X.
>>>
>>>  A
>>>      -----------------
>>> Aaron Morton
>>> Freelance Developer
>>> @aaronmorton
>>> http://www.thelastpickle.com
>>>
>>>   On 28/01/2012, at 7:48 AM, R. Verlangen wrote:
>>>
>>> Ok. Seems that an upgrade might fix these problems. Is Cassandra 1.x.x
>>> stable enough to upgrade for, or should we wait for a couple of weeks?
>>>
>>> 2012/1/27 Edward Capriolo <edlinuxguru@gmail.com>
>>>
>>>> I would not say that issuing restart after x days is a good idea. You
>>>> are mostly developing a superstition. You should find the source of the
>>>> problem. It could be jmx or thrift clients not closing connections. We
>>>> don't restart nodes on a regiment they work fine.
>>>>
>>>>
>>>> On Thursday, January 26, 2012, Mike Panchenko <m@mihasya.com> wrote:
>>>> > There are two relevant bugs (that I know of), both resolved in
>>>> somewhat recent versions, which make somewhat regular restarts beneficial
>>>> > https://issues.apache.org/jira/browse/CASSANDRA-2868 (memory leak in
>>>> GCInspector, fixed in 0.7.9/0.8.5)
>>>> > https://issues.apache.org/jira/browse/CASSANDRA-2252 (heap
>>>> fragmentation due to the way memtables used to be allocated, refactored in
>>>> 1.0.0)
>>>> > Restarting daily is probably too frequent for either one of those
>>>> problems. We usually notice degraded performance in our ancient cluster
>>>> after ~2 weeks w/o a restart.
>>>> > As Aaron mentioned, if you have plenty of disk space, there's no
>>>> reason to worry about "cruft" sstables. The size of your active set is what
>>>> matters, and you can determine if that's getting too big by watching for
>>>> iowait (due to reads from the data partition) and/or paging activity of the
>>>> java process. When you hit that problem, the solution is to 1. try to tune
>>>> your caches and 2. add more nodes to spread the load. I'll reiterate -
>>>> looking at raw disk space usage should not be your guide for that.
>>>> > "Forcing" a gc generally works, but should not be relied upon (note
>>>> "suggest" in
>>>> http://docs.oracle.com/javase/6/docs/api/java/lang/System.html#gc()).
>>>> It's great news that 1.0 uses a better mechanism for releasing unused
>>>> sstables.
>>>> > nodetool compact triggers a "major" compaction and is no longer a
>>>> recommended by datastax (details here
>>>> http://www.datastax.com/docs/1.0/operations/tuning#tuning-compactionbottom
of the page).
>>>> > Hope this helps.
>>>> > Mike.
>>>> > On Wed, Jan 25, 2012 at 5:14 PM, aaron morton <
>>>> aaron@thelastpickle.com> wrote:
>>>> >
>>>> > That disk usage pattern is to be expected in pre 1.0 versions. Disk
>>>> usage is far less interesting than disk free space, if it's using 60 GB and
>>>> there is 200GB thats ok. If it's using 60Gb and there is 6MB free thats a
>>>> problem.
>>>> > In pre 1.0 the compacted files are deleted on disk by waiting for the
>>>> JVM do decide to GC all remaining references. If there is not enough space
>>>> (to store the total size of the files it is about to write or compact) on
>>>> disk GC is forced and the files are deleted. Otherwise they will get
>>>> deleted at some point in the future.
>>>> > In 1.0 files are reference counted and space is freed much sooner.
>>>> > With regard to regular maintenance, node tool cleanup remvos data
>>>> from a node that it is no longer a replica for. This is only of use when
>>>> you have done a token move.
>>>> > I would not recommend a daily restart of the cassandra process. You
>>>> will lose all the run time optimizations the JVM has made (i think the
>>>> mapped files pages will stay resident). As well as adding additional
>>>> entropy to the system which must be repaired via HH, RR or nodetool repair.
>>>> > If you want to see compacted files purged faster the best approach
>>>> would be to upgrade to 1.0.
>>>> > Hope that helps.
>>>> > -----------------
>>>> > Aaron Morton
>>>> > Freelance Developer
>>>> > @aaronmorton
>>>> > http://www.thelastpickle.com
>>>> > On 26/01/2012, at 9:51 AM, R. Verlangen wrote:
>>>> >
>>>> > In his message he explains that it's for " Forcing a GC ". GC stands
>>>> for garbage collection. For some more background see:
>>>> http://en.wikipedia.org/wiki/Garbage_collection_(computer_science)
>>>> > Cheers!
>>>> >
>>>> > 2012/1/25 <mike.li@thomsonreuters.com>
>>>> >
>>>> > Karl,
>>>> >
>>>> > Can you give a little more details on these 2 lines, what do they do?
>>>> >
>>>> > java -jar cmdline-jmxclient-0.10.3.jar - localhost:8080
>>>> > java.lang:type=Memory gc
>>>> >
>>>> > Thank you,
>>>> > Mike
>>>> >
>>>> > -----Original Message-----
>>>> > From: Karl Hiramoto [mailto:karl@hiramoto.org]
>>>> > Sent: Wednesday, January 25, 2012 12:26 PM
>>>> > To: user@cassandra.apache.org
>>>> > Subject: Re: Restart cassandra every X days?
>>>> >
>>>> >
>>>> > On 01/25/12 19:18, R. Verlangen wrote:
>>>> >> Ok thank you for your feedback. I'll add these tasks to our daily
>>>> >> cassandra maintenance cronjob. Hopefully this will keep things under
>>>> >> controll.
>>>> >
>>>> > I forgot to mention that we found that Forcing a GC also cleans up
>>>> some
>>>> > space.
>>>> >
>>>> >
>>>> > in a cronjob you can do this with
>>>> > http://crawler.archive.org/cmdline-jmxclient/
>>>> >
>>>> >
>>>> > my cron
>>>>
>>>
>>>
>>>
>>
>>
>>
>
>

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