PECL memcache extension

Don MacAskill don at
Wed Feb 8 21:40:30 UTC 2006

The memcached servers don't need to know about each other - a simple 
wrapper around your memcache calls in your client need to know, that's all.

It's not massive overhead - it's almost negligible.

And I agree that it shouldn't be part of memcached - but it should be 
part of memcache clients that need it, like we do.


Brian Moon wrote:
> The things you are talking about require the memcached servers to know 
> about each other.  This is not the case.  That would add massive 
> overhead that I believe was avoided on purpose.
> Brian Moon
> --------------
> How to go broke saving money.
> Joshua Thijssen wrote:
>>> Yeah, that's an issue.  When you've got, say, 50 memcache servers,
>>> though, and one fails, you're only getting 1/50th of those queries
>>> passed to the DB.  So it's not (at least, for us) that big of a deal.
>>> 49/50 queries to memcache is still nice.
>> Isn't it to prioritize the a key?
>> I'm not sure if memcached knows if a bucket is not available anymore.
>> Suppose machine A breaks and had key X with value 1. Another query would
>>  place the same key X onto server B with a higher priority and a
>> mandatory small timeout. This will trigger the DB more often, but takes
>> care of the key after expiration (I'm not sure of the key expiration is
>> checked on quering, or that an internal process just scans all keys for
>> expiry), even if the key is set not to expire.
>> To take care of coming back online of machine A:
>> Machine A comes back up, and a query is made to key X. Memcache sees
>> that there is a key inside 2 different buckets (is this possible?),
>> collects the one with the highest priority, internally updates all keys
>> inside the other (still online) bucket(s) with the new value.
>> The mandatory timeout could even be left out, since a query known that
>> it's grabbing "slave"-data, and it could delete the complete key after
>> syncing the master key on machine A.
>> I think this would take care of unsynced data and obsolete (slave) data.
>> Gr,
>> Joshua

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