Chaotic Java

It’s called garbage collection, not resource collection!

Java’s garbage collector has made life so easy for us developers that we sometimes confuse between deleting a reference, i.e. a task the GC does, and releasing a resource – a task the GC doesn’t do. That’s because the GC does something else for us called object finalization, where resources usually clean themselves up.

When I say resources, just think of input/output streams, readers/writers, channels, JDBC, JMS.. the list could go on and on. I almost expect to see code such as: Continue reading »

One of the most classic patterns in software is the producer-consumer pattern. There is a module producing data, and a module reading it for further processing. Moreover, in order to achieve better performance, usually there are many consumer modules running on many different threads while the producer (or several producers) run on its own thread. This allows to distribute processing work between threads, and in the multi-core, multi-processor environment of today, between physical processors as well. Concurrent frameworks (such as java.util.concurrent) provide out-of-the-box solutions for these kind of problems.

Same pattern, multiple machines

This pattern also works well when wanting to distribute tasks between different physical machines as well. The producer machine somehow creates information, and offloads the task of processing that information to other machines. Since we want to distribute the work between different machines without coupling issues, the data is written to a physical disk and using some sort of a distribution system (e.g. JMS queues), a notification containing the full path to the data is sent. An available consumer receiving the notification can then read the data from the physical disk and process it. The following diagram illustrates this simple idea:

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