I was thinking about that (increment/decrement)...
But, first, if the tasks read the value of the variable that needs to be
incremented, isn't there a posibility that all tasks will read the same
value at the same time and then increment it in the same time ?
On 14 December 2010 11:59, Simon <qila...@gmail.com> wrote:
> The synchronized block won't work at all, since it's not guaranteed
> that you only have a single instance of your application running at
> any point in time. As soon as you have multiple instances then you
> will be synchronizing in different JVMs and hence you'll get multiple
> threads accessing the cache, and hence the same problem will occur.
>
> You could probably use the Memcache increment/decrement functionality
> to hook together a rough cross-instance synchronization, since they
> increment and decrement atomically.
>
> On Dec 14, 5:22 am, Michael Weinberg <weinbe...@gmail.com> wrote:
> > You can use the standard Java synchronization to synchronize the task
> > threads, e.g.
> >
> > synchronized (YourMemcachedDataClass.class) {
> > YourMemcachedDataClass cachedData =
> > (YourMemcachedDataClass)cache.get(CACHE_KEY);
> >
> > if (cachedData == null)
> > cachedData = new YourMemcachedDataClass ();
> >
> > cachedData.add(...);
> > cachedData.set(...);
> >
> > cache.put(CACHE_KEY, cachedData);
> >
> > }
> >
> > this way only 1 thread at a time will get into the synchronized block.
> >
> > Hope it helps..
> >
> > Michael Weinberg
> >
> > On Dec 13, 11:41 am, Ice13ill <andrei.fifi...@gmail.com> wrote:
> >
> > > Maybe there's something that i don't know very well about the memcache
> > > service and this problem is simpler then i thing it is... If so,
> > > please advice :)
> >
> > > On Dec 13, 6:38 pm, Ice13ill <andrei.fifi...@gmail.com> wrote:
> >
> > > > I need advice for implementing concurrent access to a memcache
> > > > variable, when used by multiple running tasks.
> > > > The problem is this: I have a number of tasks reading from datastore
> > > > and doing some processing.
> > > > When the processing is complete, i add a String to a List stored in
> > > > memcache. So i need to get the List from memcache, add a new element,
> > > > and put it back. The pb is that if 2 tasks write on that variable, i
> > > > get an exception (I understand that the memcache service gives me a
> > > > "clone" of the object, not the object itself, or am I wrong ?)
> > > > So how can i avoid more than one tasks writing in the same object ?
>
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