Re: [infinispan-dev] cache loader: purgerThreads and purgeSynchronously
On 14 August 2013 12:27, Radim Vansa <rvansa(a)redhat.com> wrote:
It seems to me that these attributes may not be common to all cache
stores. For some stores, the purging can be executed as part of other
process anyway and it is not desired to purge the store on-demand. Some
stores may not be able to purge in parallel at all (for example some
single-file store where you just can't jump in the middle of file) or
would be highly inefficient. Rather than emitting warning upon improper
configuration, I'd let these parameters to implementation and make the
purging service optional.
Radim
On 08/14/2013 12:59 PM, Mircea Markus wrote:
> Hi,
>
> I'm not sure these config attributes are needed.
>
> - *purgeThreads* configures the number of threads that run the storage purging
(removal of expired entries from the storage). The more threads the faster the purging
processes. Is there a reason for putting effort in making the purging fast (and parallel)
though? The cache store implementations check if an entry is expired before returning it
anyway.
That's not enough.You might have lots of large entries which need to
be cleaned up in the CacheStore which are never hit by a get
operation, you still need to delete them regularly.
On a similar reasoning, multiple threads might be needed if the
cleanup is slower than the amount of garbage the system is able to
store - agreed that's quite an extreme case, but still a possibility
for example on efficient append-only systems.. so I tend to agree with
Radim in saying that these could be CacheStore specific details.
> Actually I'll move the code in CacheLoader interceptor to
make sure this happens for all stores.
> - *purgeSynchronously*. I think the reason for this parameter is that the purging is
invoked by the eviction thread. If the purging takes long then eviction is delayed. This
is false by default (I doubt users change this btw) so there's a different thread than
the eviction thread that runs the purging. I'd rather remove the config option and
always run the purging in its own thread.
>
> Opinions?
>
> Cheers,
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