Menu
What is the best strategy to refactor a Singleton object to a cluster environment?
We use Singleton to cache some custom information from Database. Its mostly read-only but gets refreshed when some particular event occurs.
Now our application needs to be deployed in a Clustered environment. By definition, each JVM will have its own Singleton instance. So the cache may be out-of-sync between the JVM's when a refresh event occurs on a single node and its cache is refreshed.
What is the best way to keep the cache's in sync?
Thanks.
Edit: The cache is mainly used to provide an autocomplete list (performance reasons) to UI and we use Websphere. So any Websphere related tips welcome.
308
A clustered singleton service (also known as an HA singleton) is a service that is deployed on multiple nodes in a cluster, but is providing its service on only one of the nodes. The node running the singleton service is typically called the master node.
The Singleton's purpose is to control object creation, limiting the number to one but allowing the flexibility to create more objects if the situation changes. Since there is only one Singleton instance, any instance fields of a Singleton will occur only once per class, just like static fields.
The truth is that singletons aren't inherently bad if they're used correctly. The goal of the singleton pattern is to ensure only one instance of a class is alive at any one time. That, however, is not the goal many developers have in mind when using singletons.
Replace your singleton cache with a distributed cache.
One such cache could be JBoss Infinispan but I'm sure that other distributed cache and grid technologies exist, including commercial ones which are probably more mature at this point.
For singleton objects in general, I'm not sure. I think I'd try to not have singletons in the first place.
174
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
