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 > > > > --~--~---------~--~----~------------~-------~--~----~ Open BlueDragon Public Mailing List http://groups.google.com/group/openbd?hl=en official site @ http://www.openbluedragon.org/ !! save a network - trim replies before posting !! -~----------~----~----~----~------~----~------~--~---
