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Date: Tue, 20 Mar 2012 10:44:23 -0400
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Subject: Re: Best practice for caching configuration
From: Jon Moore <jonm@apache.org>
To: HttpClient User Discussion <httpclient-users@hc.apache.org>
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Hi Alin,

Actually, as it turns out, much of this information is already in the
online docs:

http://hc.apache.org/httpcomponents-client-ga/tutorial/html/caching.html
http://hc.apache.org/httpcomponents-client-ga/tutorial/html/caching.html#storage

Jon

On Tue, Mar 20, 2012 at 8:19 AM, Jon Moore <jonm@apache.org> wrote:

> Hi Alin,
>
> Great suggestion - I'll look into updating the documents for the 4.2
> release.
>
> Jon
>
>
> On Sat, Mar 17, 2012 at 6:51 PM, Vasile Alin <alinachegalati@gmail.com>wrote:
>
>> would be great if http-cache will have these hints in its overview
>> documents.
>>
>> Alin
>>
>> On 17 March 2012 17:50, Jon Moore <jonm@apache.org> wrote:
>>
>> > Hi Robert,
>> >
>> > Naturally, the ultimate answer is: it depends on your scenario!
>> However, I
>> > can perhaps provide some ways of thinking about your cache
>> configuration.
>> >
>> > First, one of your choices will be which HttpCacheStorage
>> implementation(s)
>> > you want to use; there are 3 supported in the distribution:
>> > 1. an in-memory cache; this is the default implementation if you don't
>> > specify an alternative
>> > 2. an EhCache backend; this can be used to build a tiered in-memory and
>> > on-disk cache, and the on-disk can be configured to persist across
>> > application invocations
>> > 3. a memcached backend; this can be used either to keep your JVM heap
>> size
>> > smaller by keeping the cache memory out-of-process, or as a shared
>> > memcached pool for a cluster of application servers, for example
>> >
>> > Now, because the CachingHttpClient is a decorator, you can actually use
>> > multiple of these at the same time by wrapping them one inside the
>> other.
>> > So, for example, you can have a L1 in-memory cache backed by a L2
>> EhCache
>> > that spills to disk.
>> >
>> > In all cases, you will want to be concerned with the total storage
>> > resources you want to allocate to the cache; EhCache and memcached have
>> > their own configuration for this, but you may want to tweak this for the
>> > in-memory cache if that's what you use. One thing to look at is the
>> maximum
>> > response body size that you'll cache, which currently defaults to 8KB;
>> if
>> > you plan on caching responses than that, you'll need to increase this
>> > setting via CacheConfig#setMaxObjectSizeBytes().
>> >
>> > If your server(s) use the 'stale-while-revalidate' Cache-Control
>> directive,
>> > then you may want to play with
>> > CacheConfig#setAsynchronousWorkerIdleLifetimeSecs(),
>> > CacheConfig#setAsynchronousWorkersCore(),
>> > CacheConfig#setAsynchronousWorkersMax(), and
>> > CacheConfig#setRevalidationQueueSize(), all of which basically control
>> an
>> > underlying thread pool configuration to handle the background validation
>> > requests. These have "safe" defaults, so you may not need to tweak these
>> > until you get into performance tuning.
>> >
>> > Finally, if your origin servers don't set proper Cache-Control headers
>> but
>> > you want to cache the responses anyway, you may want to change
>> > CacheConfig#setHeuristicDefaultLifetime(). Another option for this is to
>> > write another decorator to modify Cache-Control headers on specific
>> > responses that come through, wired up between the CachingHttpClient and
>> the
>> > "real" underlying HttpClient.
>> >
>> > That said, if you just drop an unconfigured CachingHttpClient in, for
>> say,
>> > an API client that gets relatively small, but cacheable responses, you
>> > should hopefully see some immediate benefit just from the in-memory
>> cache.
>> >
>> > Hope that helps,
>> > Jon
>> >
>> > On Sat, Mar 17, 2012 at 10:21 AM, Robert Naczinski <
>> > robert.naczinski@googlemail.com> wrote:
>> >
>> > > Hello,
>> > >
>> > > I want my application use cache, as shown below
>> > >
>> http://hc.apache.org/httpcomponents-client-ga/tutorial/html/caching.html
>> > .
>> > >
>> > > Does anyone know the best settings or recommendations for the
>> > > configuration of the cache?
>> > >
>> > > Regards,
>> > >
>> > > Robert
>> > >
>> > > ---------------------------------------------------------------------
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>> > > For additional commands, e-mail: httpclient-users-help@hc.apache.org
>> > >
>> > >
>> >
>>
>
>

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