On 2/4/2011 9:34 AM, Roberto Spadim wrote:
What happens when the server holding the lock value is rebooted? Or needs to evict
values from memory? For memcache's real>purpose those things don't affect
operation because the client will reload the correct values on the next access.
Where is the>persistent backing store for this value?
if elockd/lockd/any other lock server die, what happen? (non vollatile
or vollatile? it's a app problem not memcache problem, app must know
what happen, just it.
If they are designed to be reliable, the value will be stored
redundantly and the system will know how to retrieve the copy that is
still valid or an error if that is impossible. It is an application
problem. It is not an error if a cache cannot return data. For a lock
you must have the correct value or an error condition. And it doesn't
make sense to have the memcache server check for the difference on every
request when the client could just call an application designed for the
more complex operation you need when it knows it needs a lock.
with memcache we have volllatile, with memcachedb we have non
vollatile, put at main memcache and i will work with memcachedb and
repcache to sync this new feature at others memcache forks
It probably can be done with membase. I don't think memcachedb is
intended to be reliable.
who will use memcache for lock and don't want loose keys change
memcache command line to don't delete cache keys if cache is full
non volatille?
That still doesn't work in the usual scenario where you have many
memcache servers and expect them to keep working even if some are down.
timeout could work too (it's key-value based)
Memcache is a cache, not a key-value store.
nice, it's a cache (can loose information) it's a key-value store with
timeout and volatille data, right? define cache! (volatile memory? how
to cache? based on key-value? based on memory address? it's a
key-value store! working as a cache! it could be a address-value store
too, but it's a key-value store... and can loose information, app must
know this!)
A cache must have a method where the correct value can be retrieved when
it is empty. How can either the clients or server replenish the value
of the lock when it is gone for any reason?
i use memcache for store some values with pic18f4550 and it's very
good, since my pic have low memory and my server have a lot of memory
Yes, it is very good for holding values for quick access that you are
able to retrieve in some slower way.
--
Les Mikesell
[email protected]
