Java Concurrency Part 1 – Semaphores

This is the first part in a series that we’re going to be doing on Java concurrency. Specifically, we are going to dive into the concurrency tools built into Java 1.5 and beyond. We’re going to assume you have a basic understanding of synchronization and volatile keywords. The first post will cover semaphores - specifically counting semaphores. … Read more

When to use Pessimistic Locking

There are cases where we need to use a pessimistic locking strategy. While optimistic updates are an absolute minimum, we deploy a pessimistic locking strategy into a carefully thought out design. We use pessimistic locking strategies in two primary cases: As a semaphore to ensure only a single process executes a certain block of code … Read more

Optimistic Updates and Transaction Isolation

While we at Carfey Software prefer to run our transactions using READ COMMITTED isolation level, we have taken steps to ensure that our optimistic updates using a version column will work even with READ UNCOMMITTED. How does READ UNCOMMITTED impact optimistic updates? You might start to see that it is the dirty reads, or reads … Read more

Database Concurrency

As previously discussed, the database is a crucial component of our new scheduler and for most business systems. With an appropriately designed data model, well written SQL and well-thought out transaction lifecycles and their makeup, most database implementations will provide little cause for complaint, even with many concurrent requests. But you need to think carefully … Read more

Integrating Java with Scripting Languages

Here at Carfey, we’ve used Java’s native scripting API in our upcoming job scheduler to allow our clients to deploy new scripts at any time they wish, without redeploying their applications. Combined with our advanced configuration support, we think we’ve found a killer combination of flexibility and power. The scripting API was outlined in JSR … Read more


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Getting Licensing Right

A challenge that many software organizations face is how to license your software, and the corresponding controls to make sure it is not abused. The vendor wants a solution that protects their product and gives them multiple ways to sell it. Users want something that just works and doesn’t interfere with up-time or reliability of … Read more