Jeroen Reijn


on Tech, Open Source and software development

Useful tools for local development with AWS services

Over the last 2.5 years, I’ve been working with AWS and a wide range of its services. During this time I noticed that for most projects it’s useful to be able to test your application against AWS services without having to deploy or move your code into the cloud. There are several free solutions available for you to use depending on the services required by your project. In this post, I’ll describe some of the tools that I use. DynamoDB local At one of my previous projects, we made extensive use of the combination of DynamoDB and Elasticsearch for storing and querying data. The fact that DynamoDB is a managed database service with immense scale and performance benefits, makes DynamoDB a great fit for high traffic applications.

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Heap dump with lots of 'Unresolved Name' objects

If you’re familiar with Java as a programming language you might have come across the following message: java.lang.OutOfMemoryError: Java heap space. We recently got that message in of the services that we’re currently working on. To better understand why this happens, it’s good to get a Java memory heap dump for further analysis.

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Migrating a Spring Boot service from Java 11 to Kotlin

At my current project we’ve just finished migrating a Spring Boot 2.1.x service from Java 11 to Kotlin. While doing so we’ve learned quite a few things along the way and I created some notes that I wanted to share in case somebody else runs into the same issues. It was our first Kotlin migration and getting to know the Kotlin language better was/is a lot of fun, but also confusing at times.

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Looking back at 2018

It’s the second day of the new year and I think my body is still trying to digest some of the Dutch traditional ‘oliebollen’ which I ate on new years eve. The last days of 2018 were mostly about family and friends, food and having some time off. I hope you also had some wonderful days with friends and family. For those of you who’ve been reading this blog over the last couple of years, you’ve probably noticed that this yearly review post always gets published somewhere in February or March, so this time I tried something different and started early 😉. If you don’t want to read the entire post here is a short summary: 2018 was a great year with lots of highs and very few lows.

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Monitoring Spring Boot applications with Prometheus and Grafana

At my current project we’ve been building three different applications. All three applications are based on Spring Boot, but have very different workloads. They’ve all reached their way to the production environment and have been running steadily for quite some time now. We do regular (weekly basis) deployments of our applications to production with bug fixes, new features and technical improvements. The organisation has a traditional infrastructure workflow in the sense that deployments to the VM instances on acceptance and production happen via the (remote hosting) provider.

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