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From aaron morton <aa...@thelastpickle.com>
Subject Re: Restart cassandra every X days?
Date Sun, 29 Jan 2012 10:38:22 GMT
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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