Matthias Nehlsen

Software, Data and Stuff

Inspect - println no more

TL;DR: I realized how much I disliked the process of logging data structures to the console and then trying to find them and repeatedly commenting out and uncommenting println statements. So I decided to fix that.

Building a System in #Clojure Part 4 - Inter-process communication with Redis

Last week, I drew a picture of how I wanted to break apart a monolithic application and instead run different parts of the application in separate processes / separate JVMs. The idea was to have a single client for the connection to the Twitter Streaming API and the persistence of the received Tweets in ElasticSearch, plus multiple machines to serve WebSocket connections to the client. For the communication between the processes, I picked Redis Pub/Sub because its model of communication appears to suit the requirements really well. As cute as the drawing may be, I prefer code (plus drawing), so I took the previous monolith apart over the weekend and put Redis in between for communication. It worked really well and here’s how.

Building a System in #Clojure Part 3 - Redesign

I recently did a lot of transcript proofreading concerning enlightening talk for my talk-transcripts project. The most recent one was Design, Composition and Performance, the tenth transcript of a talk by Rich Hickey. That one in particular got me thinking that there are quite a few ideas I want to adopt in BirdWatch, the application about which I started writing this series of articles. That calls for some redesign, so it’s probably time to make up my mind what exactly it is that I am trying to solve with this application.

Weekly Update: Talk Transcripts, Clojure Architecture, OS X Yosemite

As I have no other article to publish this week, I thought a weekly update would be in order. Last week I wrote about making relevant and interesting talks more accessible. In the course of that project, I had eleven talks transcribed so far, four more than when I announced the project last week. Not only have I received great feedback about how appreciated this is, I have also learned a lot myself while proofreading the transcripts.

Talk Transcripts: Rich Hickey, David Nolen & more

TL;DR: I wanted to study the content of some talks in written form but there were no transcripts available. However, I believe that the valuable and relevant content of these talks should be accessible to everyone, including those for whom ‘sit back and listen’ might not be the most viable option. To make that a reality, I had transcripts made. So far, I have compiled five talks by Rich Hickey, one talk by David Nolen and another talk by Guy Steele. The transcripts are available on GitHub.

Building a System in #Clojure 2 - Transducers

TL;DR: This article covers the usage of Transducers in Clojure, spiced up with some core.async. Here’s an animation that shows the information flow of the composed transducer that we are going to build in this article:



If any of that is of interest to you at all (or if you want to see more animations like the one above), you may want to read the following article.

Building a System in #Clojure 1 - Overview

This is the first of n articles about building systems in Clojure. Clojure is a beautiful language and I have been fascinated from the first moment I laid eyes on it last summer. However, what remained a mystery to me for most of the time was how to build more complex systems. I started researching the options that would allow me to structure an arbitrarily complex application in a way that is easy to understand and maintain. Here is what I found.