What is your development checklist for Java low-latency application?
I would like to create comprehensive checklist for Java low latency application. Can you add your checklist here?
Here is my list
1. Make your objects immutable
2. Try to reduce synchronized method
3. Locking order should be well documented, and handled carefully
4. Use profiler
5. Use Amdhal's law, and find the sequential execution path
6. Use Java 5 concurrency utilities, and locks
7. Avoid Thread priorities as they are platform dependent
8. JVM warmup can be used
9. Prefer unfair locking strategy
10. Avoid context-switching (many threads lead to counter productive)
11. Avoid boxing, un-boxing
12. Give attention to compiler warnings
13. Number of threads should be equal or lesser than the number of core
Low-latency application is tuned for every milli-seconds.
Answer
Although immutability is good, it is not necessarily going to improve latency. Ensuring low-latency is likely to be platform dependent.
Other than general performance, GC tuning is very important. Reducing memory usage will help GC. In particular if you can reduce the number of middle-aged objects that need to get moved about - keep it object either long lived or short lived. Also avoid anything touching the perm gen.