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From aaron morton <aa...@thelastpickle.com>
Subject Re: Restart cassandra every X days?
Date Thu, 02 Feb 2012 19:44:52 GMT
Speaking technically, that ain't right.

I would:
* Check if node .135 is holding a lot of hints. 
* Take a look on disk and see what is there.
* Go through a repair and compact on each node.    

Cheers

-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 2/02/2012, at 9:55 PM, R. Verlangen wrote:

> 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-compaction
bottom 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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