Wednesday, December 20, 2017

Java Jigsaw Puzzles DevOps

Oh man that's a catchy blog title.

For the past couple o' weeks, my after-hours project has been trying out building webapps and batch jobs using the combo of Java 9, Spring Boot 2 milestone releases, Elasticsearch 6.1 and Docker Edge with Docker Compose. Just because I was in a WAF frame of mind I added modsecurity as a web application firewall in front of the app so I could learn a bit more about building WAF rules with Apache 2.

It was a fun lil' exercise, but in the end I found that all the cutting edge releases simply wouldn't play nicely with each other.

One painful exercise was trying to get Java 9 distributions to work within a Docker container just as it would within my desktop environment. Project Jigsaw is an oft-cited future feature of Java that build engineers have been asking for to end the myriad of JavaEE / Java ME / Java Desktop / Java Server distributions. It should help containerization by allowing svelte JRE installations to bootstrap within a minimal OS. However... this new way of distributing JREs with modular components creates yet another dependency management headache for builds. Once you begin writing manifest elements for Jigsaw + Java 9, every library and its mother now needs to be managed by your manifest as well. Its enough to drive you nuts.

Let's say you don't want to jump into building modular JARs yet and just build traditional JARs that don't use Jigsaw dependency management. Well... Ubuntu's OpenJRE 9 distribution doesn't automatically inject some Java 9 foundation libraries (such as javax.image), while Oracle's JDK does. If you use an Oracle JDK locally to develop things may appear just fine, but then you need to perform some command-line overrides for things to work on an OpenJRE 9 build. To make things more hairy, it seems that OpenJDK and Oracle have built implementations that might be runtime compatible but are NOT compatible from a build & deployment standpoint. Command-line arguments are vastly different, even though manifest formats are the same. That makes building standard build & deployment scripts a pain, as well as local testing. Distributing Oracle's JRE within a container is just to fraught for me to attempt - so I stick to distribution with OpenJDK instead.

I ended up burning too much time trying to get a consistent build between my streamlined Ubuntu-powered Docker container and my local MacOS development environment, so I punted back to Java 8. While Java 9 had some nice memory management features and some syntactic sugar, what I really needed was Lambda and Stream support. Java 8 was sufficient for this in both Oracle and OpenJDK-land.

The combo of Spring Boot 2 (milestone 7) and Elasticsearch 6.1.0 was another mix that simply didn't pan out. The Java libraries for Elasticsearch 6 had a few signature changes across the API which were entirely incompatible with Spring Data Elasticsearch, and the protocol between ES 5 and 6 did not appear to be compatible. I'm sure this will get patched up in short order within the Spring project, however until then I had to fall back to Elasticsearch 5.6.4. I wanted to stick with Spring Boot conventions as closely as possible, so I did not go native just for ES 6 support.

In the end... I do have a fully containerized solution using Spring Boot 2, Java 8, Elasticsearch 5.6.4, and modsecurity. Getting WAF protection, a single-node ES cluster, a web front-end and a indexing batch process running in the background all happens with:

export DOCUMENT_HOST_DIR=/mnt/documents && docker-compose up -d

...and that's it! Containers are also available at Docker Hub and require thankfully LITTLE dependency management.

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