Best programming approach/methodology to assure thread safety

Question

When I was learning Java coming from a background of some 20 years of procedural programming with basic, Pascal, COBOL and C, I thought at the time that the hardest thing about

Answer 1

I typically follow an Erlang style approach. I use the Active Object Pattern. It works as follows.

Divide your application into very coarse grained units. In one of my current applications (400.000 LOC) I have appr. 8 of these coarse grained units. These units share no data at all. Every unit keeps its own local data. Every unit runs on its own thread (= Active Object Pattern) and hence is single threaded. You don't need any locks within the units. When the units need to send messages to other units they do it by posting a message to a queue of the other units. The other unit picks the message from the queue and reacts on that message. This might trigger other messages to other units. Consequently the only locks in this type of application are around the queues (one queue and lock per unit). This architecture is deadlock free by definition!

This architecture scales extremely well and is very easy to implement and extend as soon as you understood the basic principle. It like to think of it as a SOA within an application.

By dividing your app into the units remember. The optimum number of long running threads per CPU core is 1.