clojureEstimated reading time: 6 minutes
Clojure is a dialect of Lisp that runs on the JVM.
GitHub repo: https://github.com/Quantisan/docker-clojure
Supported tags and respective
Where to file issues:
the Docker Community
Supported Docker versions:
the latest release (down to 1.6 on a best-effort basis)
What is Clojure?
How to use this image
Start a Lein/Clojure instance in your app
Since the most common way to use Clojure is in conjunction with Leiningen (
lein), this image assumes that’s how you’ll be working. The most straightforward way to use this image is to add a
Dockerfile to an existing Leiningen/Clojure project:
FROM clojure COPY . /usr/src/app WORKDIR /usr/src/app CMD ["lein", "run"]
Then, run these commands to build and run the image:
$ docker build -t my-clojure-app . $ docker run -it --rm --name my-running-app my-clojure-app
While the above is the most straightforward example of a
Dockerfile, it does have some drawbacks. The
lein run command will download your dependencies, compile the project, and then run it. That’s a lot of work, all of which you may not want done every time you run the image. To get around this, you can download the dependencies and compile the project ahead of time. This will significantly reduce startup time when you run your image.
FROM clojure RUN mkdir -p /usr/src/app WORKDIR /usr/src/app COPY project.clj /usr/src/app/ RUN lein deps COPY . /usr/src/app RUN mv "$(lein uberjar | sed -n 's/^Created \(.*standalone\.jar\)/\1/p')" app-standalone.jar CMD ["java", "-jar", "app-standalone.jar"]
Dockerfile this way will download the dependencies (and cache them, so they are only re-downloaded when the dependencies change) and then compile them into a standalone jar ahead of time rather than each time the image is run.
You can then build and run the image as above.
Compile your Lein/Clojure project into a jar from within the container
If you have an existing Lein/Clojure project, it’s fairly straightforward to compile your project into a jar from a container:
$ docker run -it --rm -v "$PWD":/usr/src/app -w /usr/src/app clojure lein uberjar
This will build your project into a jar file located in your project’s
clojure images come in many flavors, each designed for a specific use case.
This is the defacto image. If you are unsure about what your needs are, you probably want to use this one. It is designed to be used both as a throw away container (mount your source code and start the container to start your app), as well as the base to build other images off of.
ONBUILD image variants are deprecated, and their usage is discouraged. For more details, see docker-library/official-images#2076.
onbuild variant is really useful for “getting off the ground running” (zero to Dockerized in a short period of time), it’s not recommended for long-term usage within a project due to the lack of control over when the
ONBUILD triggers fire (see also
Once you’ve got a handle on how your project functions within Docker, you’ll probably want to adjust your
Dockerfile to inherit from a non-
onbuild variant and copy the commands from the
Dockerfile (moving the
ONBUILD lines to the end and removing the
ONBUILD keywords) into your own file so that you have tighter control over them and more transparency for yourself and others looking at your
Dockerfile as to what it does. This also makes it easier to add additional requirements as time goes on (such as installing more packages before performing the previously-
This image is based on the popular Alpine Linux project, available in the
alpine official image. Alpine Linux is much smaller than most distribution base images (~5MB), and thus leads to much slimmer images in general.
This variant is highly recommended when final image size being as small as possible is desired. The main caveat to note is that it does use musl libc instead of glibc and friends, so certain software might run into issues depending on the depth of their libc requirements. However, most software doesn’t have an issue with this, so this variant is usually a very safe choice. See this Hacker News comment thread for more discussion of the issues that might arise and some pro/con comparisons of using Alpine-based images.
To minimize image size, it’s uncommon for additional related tools (such as
bash) to be included in Alpine-based images. Using this image as a base, add the things you need in your own Dockerfile (see the
alpine image description for examples of how to install packages if you are unfamiliar).
View license information for the software contained in this image.library, sample, clojure