[Glass] Garbage Collection , maintenance gem and typical seaside app

[Norm Green]

Well, it all depends on the usage pattern of the database.  Epoch GC is 
designed to cleanup short lived objects.  MFC is the global cleanup.

Running epochs hourly or daily and running MFC during low times 
(weekends or middle of the night) are common practices.

Norm

On 5/8/14, 9:32, Otto Behrens wrote:
> Thanks, so the MFC have become quite fancy. Very interesting.
>
> So when do I use the MFC (eg from cron / maintenance process) and when
> do I use the epoch GC?
>
> On Thu, May 8, 2014 at 6:19 PM, Norm Green
> <norm.green at gemtalksystems.com> wrote:
>> The MFC can be heavy-weight but is designed to be tunable so that it can
>> also be very light-weight at the expense of taking more time to complete.
>> This is done by tuning the number of threads used by the MFC and how much
>> CPU those threads are allowed to consume.
>>
>> For example, in 3.x, running the MFC with 1 thread and a cpu limit of 10%
>> should have minimal impact on the system:
>>
>> SystemRepository markForCollectionWithMaxThreads: 1 waitForLock: 60
>> percentCpuActiveLimit: 10
>>
>> Of course you have to be careful not to limit resources too much else the
>> MFC may never finish.
>>
>> Norm
>>
>>
>>
>>
>> On 5/8/14, 9:08, Otto Behrens wrote:
>>>> GLASS comes with nice seaside scripts to start/stop gems and also a
>>>> maintenance gem which calls WAGemStoneMaintenanceTask. This class, from
>>>> what
>>>> I can see, it does seaside session expiration and MFC. So....second
>>>> question... if I have this VM running...then I wouldn't need to
>>>> explicitly
>>>> run a MFC as part of a cron job, right?
>>>>
>>>>
>>>> Right.
>>> Sorry, I lied. The default maintenance30 implementation does an MFC
>>> every hour. We disabled that in our apps and switched the epoch GC on.
>>> I think the MFC is *extremely* heavyweight and will influence your
>>> application when it runs on a DB with some data. I can't really give a
>>> measure of how much "some" is, in other words when the DB is small
>>> enough where the MGC will not influence it that much.
>>>
>>> I understand that the purpose of the epoch GC is to be a process that
>>> runs in the background with loads of fancy parameters to throttle it.
>>> A seaside app in my understanding is an ideal candidate app for the
>>> epoch GC. We bypassed WAGemStoneMaintenanceTask >>
>>> maintenanceTaskMarkForCollect such a long time ago that I forgot about
>>> it. To me, it does not make sense to implement that complexity in
>>> maintenanceTaskMarkForCollect if there is a much more sophisticated
>>> and efficient tool around (epoch GC).
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