In my previous post on Morphia, I went through some typical usages and mentioned some caveats and workarounds for known problems. I showed how easy it is to work with Morphia and how cleanly it interacts with the Java world. To follow up on that post, I’m going to discuss how to deal with some … Read more
A lot of developers end up in the Java “enterprise” world at some point in their careers. I know the term alone conjures up all kinds of reactions, and rightly so. Often environments where lots of interesting technical challenges exist end up being those that nobody wants to work on because they are brittle, difficult … Read more
When we began development on Obsidian Scheduler, one of its key objectives was transparency. Quoting my own post, transparent means letting us know what is going on. We want to have available to us information such as when was the job scheduled to run, when did it start, when did it complete, which host ran … Read more
Job scheduling is used on many software projects to enable both internal jobs and third-party integration. Clustering can provide a huge boost to reliability by providing fail-over and load-sharing. I believe that clustering should be implemented for reliability on just about all software projects, so I’ve decided to outline how to go about doing that … Read more
When dealing with data sets retrieved from a database, if we want them ordered, we usually will want to order them right in the SQL, rather than order them after retrieval. Our database will typically be more efficient due to available processing power, potential use of available indexes and overall algorithm efficiency in modern RDBMSes. … Read more
In my previous post on Object-Relational Mapping tools (ORMs), I discussed various issues that I’ve faced dealing with the common ORMs out there today, including Hibernate. This included issues related to generating a schema from POJOs, real-world performance and maintenance problems that crop up. Essentially, the conclusion is that ORMs get you most of the … Read more
Object Relational Mapping tools like Hibernate have helped developers make huge productivity gains in dealing with relational databases in the past several years. ORMs free developers to focus on application logic and avoid writing a lot of boilerplate SQL for simple tasks like inserts or queries. However, the well-documented problems with object-relational impedance mismatch inevitably … Read more
In the past few years, NoSQL databases like CouchDB, Cassandra and MongoDB have gained some popularity for applications that don’t require the semantics and overhead of running a traditional RDBMS. I won’t get into the design decisions to go into choosing a NoSQL database as others have done a good enough job already, but I … Read more
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
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