Hi, Yeah I was exploring a more complex functionality in memcached which I believe is not there. And I may have to write some engine for my work as suggested. Thanks for your replies.
Yours sincerely, Vishal Garg Undergraduate IIIT-Hyderabad India On Sun, Jun 5, 2011 at 1:00 AM, Dustin <dsalli...@gmail.com> wrote: > > On Jun 4, 12:25 pm, vishal garg <vishal17g...@gmail.com> wrote: > >> Thanks for the solution. But I was looking for something more >> efficient. Suppose you have an object which you need very frequently, >> so you store it into memcached. But that object may change, so you may >> need to update. Now there are two possible approaches: >> >> 1)You update the database accordingly and store the newly formed >> object in the memcached.//I think this has been suggested >> >> 2)You update the object in the cache and leave the database untouched. >> But here you update the database whenever the object is removed from >> cache incase the object changed. //you may require flags here >> >> The (2) is more efficient to implement which I perceive since the >> database is seldom touched. And infact is the core of the dirty bit in >> cache of OS as I mentioned before. >> I rephrase my question to - is there any way we can set flags to the >> key:value pair which can be detected by the memcached when it removes >> data from memory? Please reply incase you find something related. > > If you update the cache, but not the primary store, you lose data. > Memcached doesn't know *why* you gave it data and has no way to decide > what's important. > > *or* > > If you update the cache and have cache operations block on writing > data out the other side, you lose absolute predictability of cache > behavior. This is exactly what membase does. If you write fast > enough, you can't update the underlying store and you hit memory > limits and have to slow down (or add nodes to compensate for the > increased write volume). > > You can, of course, write another engine that fits your semantics > better, but the core engine is designed to add speed to unobtrusively > add speed to something that's already working. At the point where you > need reliability of the data you're storing in it, you're doing > something else.
