Yes. On Thu, Nov 5, 2009 at 6:07 PM, Bassil Karam <[email protected]> wrote: > If there is no memcached guarantee, and we need to assume that it could > disappear at any time - even between 2 requests - is it safe to say then > that we must code in a check on the state of memcached on every request? > Baz > > On Thu, Nov 5, 2009 at 3:03 PM, Vince Bonfanti <[email protected]> wrote: >> >> > Interacting with memcached is faster and cheaper than the datastore, but >> > it >> > still costs something both in terms of performance and money. Is it >> > recommended to load commonly used data into the app scope (of every new >> > server that spins up) and use it from there rather than pulling it >> > directly >> > from memcached on every request? >> >> I don't know that we have enough experience yet to recommend a best >> practice. The trade-off will be application instance start-up time >> (for using the app scope) versus memcache accesses. If you know your >> application scope will be initialized with the same values every time, >> and those values don't change over the life of the application, and >> the initialization is relatively lightweight, then you might be better >> off using the application scope. Otherwise, memcache might be better. >> >> > If data in memcached changes, is there a >> > way to ensure that all the app scopes are synchronized with those >> > changes? >> >> Nope. You'll need to figure out a way to manage this yourself--GAE >> does not provide any support for doing this. >> >> > Also, how permanent is memcached? Does it have to be rebuilt from the >> > datastore at times? Are there predictable events to watch out for? >> >> I've noticed that memcache values can remain for weeks. However, >> there's no guarantee at all regarding the longevity (or lack thereof) >> of memcache values. Also, memcache is *not* automatically backed by >> the datastore. Once evicted, memcache values are gone forever. No, >> there are no events to tell you when memcache values have been evicted >> or changed. >> >> Vince >> >> > > > > >
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