Home » Archives for Jakub Holy

Author Archives: Jakub Holy

Jakub is an experienced Java[EE] developer working for a lean & agile consultancy in Norway. He is interested in code quality, developer productivity, testing, and in how to make projects succeed.

Java: Simulating various connection problems with Toxiproxy

Simulate various connection problems with Toxiproxy and Java’s HttpURLConnection to see what kind of errors get produced: connect timed out vs. read timed out vs. connection refused … . Results: System: openjdk 11.0.1 2018-10-16 (.setConnectTimeout 1) => java.net.SocketTimeoutException: connect timed out (.setReadTimeout 1) => javax.net.ssl.SSLProtocolException: Read timed out on HTTPS, java.net.SocketTimeoutException: Read timed out on HTTP (or Toxiproxy with 5s latency or timeout ) Nothing listening at the port => ...

Read More »

Clojure – comparison of gnuplot, Incanter, oz/vega-lite for plotting usage data

What is the best way to plot memory and CPU usage data (mainly) in Clojure? I will compare gnuplot, Incanter with JFreeChart, and vega-lite (via Oz). (Spoiler: I like Oz/vega-lite most but still use Incanter to prepare the data.) The data looks like this: ;; sec.ns | memory | CPU % 1541052937.882172509 59m 0.0 1541052981.122419892 78m 58.0 1541052981.625876498 199m 85.9 ...

Read More »

An answer to CircleCI’s Why we’re no longer using Core.typed

CircleCI has recently published a very useful post “Why we’re no longer using Core.typed” that raises some important concerns w.r.t. Typed Clojure that in their particular case led to the cost overweighting the benefits. CircleCI has a long and positive relation to Ambrose Bonnaire-Sergeant, the main author of core.typed, that has addressed their concerns in his recent Strange Loop talk “Typed ...

Read More »

There will be failures – On systems that live through difficulties instead of turning them into a catastrophy

Our systems always depend on other systems and services and thus may and will be subject to failures – network glitches, dropped connections, load spikes, deadlocks, slow or crashed subsystems. We will explore how to create robust systems that can sustain blows from its users, interconnecting networks, and supposedly allied systems yet carry on as well as possible, recovering quickly ...

Read More »

Challenging Myself With Coplien’s Why Most Unit Testing is Waste

James O. Coplien has written in 2014 the thought-provoking essay Why Most Unit Testing is Waste and further elaborates the topic in his Segue. I love testing but I also value challenging my views to expand my understanding so it was a valuable read. When encountering something so controversial, it’s crucial to set aside one’s emotions and opinions and ask: “Provided ...

Read More »