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 <[email protected]> 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 <[email protected]> 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 <[email protected]> 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 ? -- You received this message because you are subscribed to the Google Groups "Google App Engine for Java" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en.
