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Showing posts from 2017

Java ExecutorService and Linux Max Process Limit

Here's a little post about the Java ExecutorService, and a problem I ran into on Ubuntu. Consider this Java code
public static void main(String[] args) throws InterruptedException { int tasksSubmitted = 0; int nTasks = 800; int taskDur = 2000; int nThreads = 400; ExecutorService executor = Executors.newFixedThreadPool(nThreads); try { for (int i = 0; i < nTasks; i++) { executor.submit(() -> { try { Thread.sleep(taskDur); } catch (InterruptedException e) { System.out.println(e); } }); tasksSubmitted++; } } catch (Error | Exception e) { System.out.println(e); } System.out.println("Tasks submitted: " + tasksSubmitted); executor.shutdown(); executor.awaitTermination(Long.MAX_VALUE, TimeUnit.MILLISECONDS); if (tasksSubmitted != nTasks) { System.out.println("Only…

Openers vs Closers

I've read an article in the past about the 2 types of developers: openers and closers. I can't remember the exact link, but this distinction is weighing on my mind lately.

In my mind these are roles, not developer types. A developer might be filling either role, depending on the circumstances.

Openers

The openers are the developers that are on the front line, taking feature requests from managers and customers, and turning them into real applications that can be interacted with. The openers are free to use whatever means necessary to get the job done. They aren't concerned with performance or scalability. Their job is to make the app work.

Closers

Once the app features solidify, the closers are the ones who fix the performance and scalability issues. They care deeply about runtime performance, about efficient algorithms, about profiling tools, memory allocation, all all the deep technical issues. While all developers are typically nerds, the closes are typically the uber-ner…

Relationships Between The DevOps Handbook and Systems Thinking

I've recently finished reading The DevOps Handbook, and Thinking in Systems, and have just started reading The Fifth Discipline. Below are a few of my thoughts after reading them.

The DevOps Handbook is a really great book and I highly recommend anyone participating in software development to give it a read. In the book, the authors describe the Three Ways (aka principles):
FlowFeedback Continual Learning and Experimentation
The first way focuses on getting software through the work stream, the second way focuses on getting feedback, and the third way focuses on organization learning. 
The DevOps Handbook's visualization of the 3 ways reminds me of systems diagrams in Thinking in Systems by Donella Meadows. 

Stuart Rimell has a nice 2 part post on systems thinking in software development, that draws on ideas in Thinking in Systems (Part 1, Part 2)
After reading The DevOps Handbook and Thinking in Systems, I got curious about systems thinking, and how that applies to software de…

Java: throws Exception

I have a pet peeve in Java, and it's methods that use the java.lang.Exception class in the throws clause.

For example

public void doSomething() throws Exception {
}

This forces callers of the doSomething method to either catch the raw Exception, or add it to throws clause of the consuming method. I think that this encourages developers to do the wrong thing. If you're going to use checked exceptions, then callers should only be catching specific exceptions that can be handled. Otherwise, the exception should propagate up the call stack, potentially terminating the thread if no one handles the exception.

Throws clauses are part of the specification of your method. If you're going to use checked exceptions, wouldn't it be nice if the caller could see the explicit list of exceptions to be handled? From a contract perspective, there's no value in specifying that your method can throw any Exception. You're better off removing the throws Exception clause, and just th…