Use built-in Tomcat in Docker deployments

[magnusbaeck]

Description

The project's Dockerfile starts from a Tomcat image and drops the eiffel-remrem-generate war file into the webapps directory, thus running the app via Tomcat. In the Docker case we should use the Spring-provided Tomcat and run it standalone as described in https://eiffel-community.github.io/eiffel-remrem-generate/serviceUsage.html.

I'm not a Java expert so there might be legitimate reasons for the current design, but it strikes me as odd.

Motivation

Main points:

• Smaller Docker image (309 vs. 525 MB).
• Shorter startup time (~6 s vs. ~11 s).
• Less memory consumption?
• Simpler deployment with e.g. only one logging configuration to deal with.
• Reduces environment differences between development and production for sites that deploy with Docker.

I'm sure there are reasons why one would want to run eiffel-remrem-generate in a "real" Tomcat instance, in particular if you want to run multiple apps in the same servlet container, but the reasonable way of doing that would be to run a service-agnostic Tomcat container and drop the war files in its webapps directory, in which case you wouldn't need a Docker image for eiffel-remrem-generate.

[tobiasake]

Hi,
The Eiffel Operation at Ericsson uses Tomcat instances and we have been asked to use and test Eiffel applications as webapps in Tomcat instance, thats why we use Tomcat in the Dockerfile/Docker image. Just to make sure that the application works in Tomcat.

[magnusbaeck]

Shouldn't the contents of the eiffel-community repositories be tailored to general use rather than Ericsson's internal preferences? If you want to run tests based on the tomcat:8-jre image we can have a dockerfile for that but the dockerfile recommended for standalone use (and whose image could be subject to Docker Hub publication) should be tailored to the general use case.

I compared the memory consumption of the current image with one where we won't run a standalone Tomcat and there's no significant difference (550 vs. 650 MB as reported by cAdvisor), but I can confirm that skipping the standalone Tomcat solves eiffel-community/eiffel-remrem-publish#177.

[tobiasake]

I really don't see the general usage view is impacted of which base image Dockerfile is based on, Tomcat image or based on a more pure Java Docker base image. Works more or less the same from a usage view.
I have no problem with not using Tomcat base image and using a more pure Java based Docker image, e.g. fabric8/java-jboss-openjdk8-jdk
As long as Docker image is configured and executed in the same way.

[magnusbaeck]

To be clear, the base image doesn't matter, but it does matter if the container's entrypoint is catalina.sh run or java -jar ...war. Let me summarize the most important problems with the current image:

• It doesn't respond to SIGTERM so shutdowns and therefore restarts take significantly longer and the JVM never gets a chance to do a clean shutdown since it eventually receives a SIGKILL (Docker container doesn't respond correctly to SIGTERM eiffel-remrem-publish#177).
• Logging is configured in two places, logback.xml and logging.properties, which is annoying for anyone who wants to modify the logging format, add additional appenders (like a JSON appender, to make it easier to ship logs to e.g. Elasticsearch), or add rotation.
• Customization and configuration is simpler and requires fewer Tomcat skills. For example, since the war file is invoked directly it's trivial to pass extra properties or other arguments. Maybe that's just as easy via environment variables if you use a Tomcat-based image, but it's not obvious and it's not documented.

I can prepare a PR that renames Dockerfile to Dockerfile.tomcat and adds a new Dockerfile.standalone (or .springboot?) that's based on a JRE-only image and runs java -jar .....war.

[tobiasake]

As I said, its ok to change to java base image, if you ask me.
If you change to the docker image I suggested in my previous comment, then war file only need to be placed under "/deployments" and update the start-service.sh script to start java with command: /deployments/run-java.sh. (I have used this image earlier and it works)
I prefer to only have one Dockerfile, so we don't need to maintain 2 Dockerfiles.
So update the existing Dockerfile.

And, Yes, RemRem documentation is not covering everything and might be outdated. We have github issues for improving documentation.

We have Docker configuration examples in Eiffel-Intelligence documentation:
https://github.com/eiffel-community/eiffel-intelligence/blob/master/wiki/markdown/docker.md
RemRem docker images/container works in same way.
Java/Spring properties for RemRem-Generate can be found under src/main/resources:
https://github.com/eiffel-community/eiffel-remrem-generate/blob/master/service/src/main/resources/application.properties

You can create a PR and then you might get more input from more Eiffel-Community developers, hopefully :)

[magnusbaeck]

PR was merged, closing issue. I'll send a very similar PR for REMReM Publish.