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Lightweight docker images for Java apps

There’s a number of posts (e.g. here) talking about the official Java docker images being on the large side – in Docker terms, the standard images at > 600MB before you even build your image containing you app are … pretty big.

Suggestions are to use a smaller image as a starting point, like Alpine Linux. It looks like at some point the official Java images have been updates to include a number of Alpine based images too.

Pulling down an OpenJDK 8 image, java:openjdk-8-jdk and then java:openjdk-8-alpine, there’s a massive size difference between the size of the two:

If you’re planning on running something lightweight like a Spring Boot app, looks like the provided Alpine images are a good starting point.

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Node.js online courses and self-paced tutorials

I’m always looking for resources for learning something new. I’m currently digging into some Node.js. I’ve been working through a Udemy course, ‘The Complete Node.js Developer Course’, and while the quality of the materials and videos is very good, I’m finding the initial pace of the videos a bit slow for my liking (you can run them at 1.5x and 2x which helps to get through them quicker). If you were starting from zero background in JavaScript then the initial pace is probably spot on, but if you have some background already, then you might want to skip ahead.

Looking for other sources, I came across http://nodeschool.io/ . The interesting thing with their approach is they have Node.js apps that drive your tutorials and assess your solutions to the puzzles. I’ve been working though learnyounode and so far it’s going pretty well. Install with:

npm install -g learnyounode
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Refreshing a JAX-RS backend with some Node.js and Express?

Over the past few year or so, I’ve been building a web app that visualizes amateur radio spots using a digital mode called JT65. The site is currently up and live here: http://www.spotviz.info/#/home

I started building this as an exercise to learn some AngularJS 1.x (I posted a number of posts along the way too). The backend datastore is MongoDB, and there’s a JAX-RS War deployed to WildFly that provides a REST backend to the AngularJS frontend. The majority of the logic for the webapp is all in the AngularJS app.

Since playing with some Node.JS and Express a couple of weeks ago, I’ve been considering if I should have a go at replacing the JAX-RS code with a Node.js backend too. Since the existing code is mainly building and executing MongoDB queries, this wouldn’t be that hard to do a straight replace. Based on what I’ve seen so far of libraries like Mongoose, the replacement code is likely to be significantly more concise than the existing Java based backend. I’ll queue this up for a project in the coming weeks 🙂

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Raspbian USB disconnects and USB keyboards

I was looking for a solution to a USB soundcard that would randomly disconnect from my Raspberry Pi (it’s a Signalink USB soundcard/radio interface for amateur radio). Turns out, the issue I was seeing was caused by RF getting into somewhere when my radio was keying up – when I moved the HT radio further away from the Pi (only as far as the length of the connecting cable, a few feet) then my problems stopped. This could probably be avoided better with some snap-on ferrite beads.

In this post (and others), there is a suggestion about adding dwc_otg.speed=1 to your /boot/cmdline.txt. I tried this for a while and this didn’t seem to make any difference to my USB disconnects for this particular USB soundcard. It did however stop a USB keyboard from being recognized (a Gear Head Mini USB). Remembering I had added this param and then removing it solved my keyboard issue.

Lesson learnt: if trying out solutions to problems by trial and error, if something doesn’t work, remember to remove it afterwards in case it breaks other stuff 🙂

 

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