The BlackholeStore is not something you would actually deploy to a production site. The BlackholeStore is a development tool that simulates caching but never actually caches anything. This store can be useful to help tune an application as it can provide a solid baseline for how things would behave without caching. Anything set into a cache powered by the blackhole store will vanish into a blackhole. Anytime a lookup is performed it will appear is if that object has expired. Finally, if you actually try to get and object you will receive a null.

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The ConcurrentStore is an object store that uses concurrent hash maps provided by the Sun JDK. Concurrent maps are better suited for caching algorithms as they do not lock the entire map in order to access elements. They work on the concept of row locking. Therefore, the increased performance and increase in throughput is observable by using concurrency maps. Here is a quote from the Java Docs:

"However, even though all operations are thread-safe, retrieval operations do not entail locking, and there is not any support for locking the entire table in a way that prevents all access. Retrieval operations (including get) generally do not block, so may overlap with update operations (including put and remove). Retrievals reflect the results of the most recently completed update operations holding upon their onset." Java Docs

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You can also find some great research out there about concurrency maps:

• http://www.ibm.com/developerworks/java/library/j-jtp07233.html

• http://www.ehcache.org

CacheBox offers the capability of object stores that can be used to store cached objects. If you look at the following figure you will understand our object model for our object stores:

Each object store is composed into a CacheBox provider for usage of storing and retrieving cached objects. The design principle behind each object store is that each object store implements its own locking, serialization, reading and writing mechanisms that are fronted by a nice API via the CacheBoxProvider object. Also, it is very important to note that the CacheBox eviction policies talk to the object stores in order to get ordered data structures for eviction purposes.

So if you will be creating your own object stores, make sure they implement the right data methods the eviction policies can use for evictions. The CacheBox provider's reaping methods use the object stores in order to get metadata out of the object stores in order to take care of cleanup, expirations and evictions. We definitely encourage you to take a look at the written object store implementations in order to learn how this works.

So let's start investigating each of the object stores that are shipped with CacheBox.

Caution Please note that each object store can have extra properties that need to be set in your cache configuration file.

The JDBCStore is a nice object storage that leverages a single database table to keep track of its objects. This is great for simple or small scale clusters that need centralized caching. It also follows suit that complex objects are serialized into the tables and simple objects are just saved. The object store can even create the database table for you if need be via its own object store custom properties.

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Adobe ColdFusion + CFTransaction Notes

Adobe ColdFusion (ACF) engines require all queryExecute() statements running within a transaction to have identical datasource, username, and password options. If your application uses the JDBCStore within a <cftransaction> block you may receive the following error message "Usernames and Passwords for all the database tags within the cftransaction tag must be the same". If your application sets the default DSN using this.datasource in your Application.cfc file, you may be able to work around the issue by omitting the dsn, dsnUsername, and dsnPassword properties from the JDBCStore.

The ConcurrentSoftReferenceStore uses a combination of concurrency maps and java soft references. In our introductory sections we introduced java soft references and how it allows us to create placeholders in memory for objects and when the JVM needs memory it has permission to collect these placeholders and thus release memory. This is truly a great combination to have and ColdBox leverages this for its template, event and view fragment caching.

Just remember that when you use this object storage, the time spans are never guaranteed as the JVM has permission to cleanup objects when it sees fit. To get much better performance on the JVM memory heap space and a more active memory, we recommend using this object storage. Research has also indicated that a combination of memory sensitive structures in combination with limits in a cache, can increase performance and optimize its usage. So please make sure limits are set in the cache.

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You can also find some great research out there about concurrency maps and soft references:

• http://www.ibm.com/developerworks/java/library/j-jtp07233.html

• http://www.ibm.com/developerworks/java/library/j-jtp01246.html

The DiskStore as its name implies, uses a disk to store cached objects under. This can be any location that can be accessible via cffile and cfdirectory. Therefore, you can use Adobe ColdFusion/Lucee resources or virtual RAM locations or even Amazon S3. You can get funky my friends!

Anyways, this storage will look at the incoming target object to cache and if it is a complex object it will serialize to binary and store it on disk. If it is a simple value, it just saves it. This is a great way to provide a centralized template/view caching mechanisms as views are simple strings. You can even connect a farm of servers to talk to a centralized network drive that has centralized view/event template storage. Anyways, you can get funky!

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