When processing SQL data in Spark, sometimes single rows are not the right unit — your calculation may need a collection or group of records as input.
This post shows how to group SQL data for use in Spark. Continue reading
Conditional breakpoints on multi-threaded code failing in Eclipse?
Today I got a very unusual error while trying to debug the DeepLearning4J framework.
Conditional breakpoint encountered runtime exception. Reason: java.lang.InternalError: Got MethodID of ReferenceType that is not a member of the ReferenceType occured retrieving stack frames.
How to find the Git commit introducing a given change into a file
Continuing last month’s theme of searching Git history — here we look at how to find the source of changes, even after other people have worked on (or reformatted) the area in question.
The question: which commit actually introduced a given string into the file? Continue reading
Why inheritance never made any sense
Great post on inheritance from the Sicpers blog, and why — as a concept — it often fails in OO languages such as Java.
This blog post can help you understand why:
- “Cat and Dog extend Animal” is poor use of OO.
- “Square extends Rectangle” is poor use of OO.
From my own experience, I’ve moved to primarily using inheritance in only two ways: Continue reading
How to find a Git branch containing changes to a given file
Working on many separate enhancements.. How to find which branch my changes to a particular file are on? And if a file was deleted, how can I find that?
Luckily, Git can help us! Continue reading
How to Debug Tests Run Externally
Last week I had to debug some unstable tests, which were only launched externally from Ant (launched from Maven). The tests were largely not directly runnable from the IDE, and did not run equivalently.
Obviously this is outdated practice and not good TDD, but sometimes we need to work with such assets anyway 🙂
Given that, how could I debug & fix these tests? Continue reading
Command-line: How to redirect Windows stdout and stderr to a single file
When investigating complex issues with Maven or command-line tools, it is often helpful to capture the output to a file for further analysis.
This tip shows how to capture both ‘stdout’ and ‘stderr’ to capture a complete authoritative output. Continue reading
How to Crash the JVM in Three Lines of Code
This is a confirmed JDK bug. Just three lines of code to crash the Windows JVM.
Continue reading
Operations and Developers agreeing on Git workflow
From the Classic Programmer Paintings blog. Enjoy!
“Operations and Developers agreeing on Git workflow”
Jacques-Louis David, 1796-1799, Oil on Canvas
(collaboration from @rpiaggio )
Production Troubleshooting Methodology
Software issues in Production can be some of the most demanding challenges a team can face, especially when occurring on a system outside of your control.
Adapted from the OODA loop — a military strategy used to describe the decision cycle of observe, orient, decide and act — this process formalizes an approach to take control, establish facts, and progress towards a resolution for even the most difficult problems.