Thread.currentThread().join()

The cache can be loaded at the startup with the hot set o Products or as desired, against loading it at runtime, upon a Cache miss.

Case 2: For an Element Management System, loading all the Managed Devices into cache, available to all nodes in the cluster

For an EMS Device Information for the Devices it is managing is used most often. The Device info can be bulk loaded at the startup. The example show the use of cache by a Poller, which Polls the Device status.

There are other common use cases. Please add comment with your Use case.

Ehcache Bulk Loading with Terracotta

Terracotta Darwin release has optimized bulk loading in Ehcache. In normal scenario, loading elements in Ehcache, would update the cache entry to all the clustered caches, making the bulk loading a bit slower.

Let's see how bulk loading in action

      // Get the Cache to be preloaded
      Cache ehcache = CacheManager.getInstance().getCache("mycache");

      // Set this property before bulk loading
      ehcache.setNodeCoherence(false);

      // Load everything here
      loadCache(); 

      // reset the property
      ehcache.setNodeCoherence(true);

      // Wait for all data to be distributed across cluster
      ehcache.waitUntilClusterCoherent();

What's being done inside the loadCache()?
Here is a glimpse

private void loadCache() {
   // Query the DB get the data and get the result into array
   // or what ever data structure you need

   // iterate over result and put into cache
   for(int i = 0; i < data.length; i++) {
       Element element = new Element(data.getId, data);
       ehcache.put(element);
   }
}

Here is how the cache look when we are bulk loading the data. We are using both nodes to load distinct data to speed up loading process. The loading can be taken care by a single node also.

Once the bulk loading is completed, and Nodes are set to coherent again, the data is replicated across the cluster, and all Nodes have the same data set.

What's Next?
In the next post we shall cover the Write-Behind feature of Ehcache for DB offloading. I will rewrite the code of one my previous post Exploring Terracotta tim-async - Scalable way to off-load DB updates from App Transaction, to use the write-behind feature.