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elsy (also known as lc, which is what the binary is called) is an opinionated, multi-language, build-tool based on Docker and Docker Compose. It allows organizations to implement a consistent build workflow across many different repos, spanning a wide array of programming languages.

elsy will not replace your favorite build tool, it is simply a thin wrapper that:

  • provides a consistent development workflow across all repos using elsy
  • provides the ability to fully test Docker images from a blackbox perspective
  • reduces local-dev tool requirements to the bare minimum, regardless of programming language (i.e., you only need to install Docker, Compose, and elsy)
  • ensures consistent builds regardless of environment (i.e., fixes the "works on my machine" problem since the repo defines its exact dependency requirements)

With elsy, it is possible to build, test, and publish a repo from scratch with just:

git clone <repo>
cd repo
lc ci

Getting Started

Prerequisites: elsy requires both Docker and Docker Compose.

Follow the below steps to install elsy:

## choose platform (darwin or linux) and versions (see releases page)

## install binary for your system
curl -fL -o /usr/local/bin/lc$VERSION/lc-$PLATFORM-amd64-v$VERSION
chmod +x /usr/local/bin/lc

As of version v2.1.0 of Elsy, you can upgrade to the latest verison by running

lc system upgrade

Previous versions require repeating the installation steps to manually download and install the binary.

See the Using elsy in a Project document for info on how to setup a repo to use elsy.

The Lifecycle

At its core, elsy is an implementation of a build lifecycle that generalizes to any repo producing a software artifact. Running lc ci will execute the full build lifecycle inside a repo, it is made up of the stages defined in the following sub-sections. lc ci operates in a fail-fast mode, so if any stage fails, the following stage will not be run.

See the examples folder for concrete examples of this lifecycle in action.

See elsy Best Practices for guidance on how to use elsy for typical development workflows.

lc teardown

Running lc teardown simply tells elsy to clean up any state that might be left over from a previous build.

lc bootstrap

Running lc bootstrap will setup a new repo and make sure all dependencies (e.g., docker images, external software libs) are downloaded and built. Thanks to Docker caching, this step is only time-intensive the first time it is run.

If present, bootstrap will call the repo's docker-compose installdependencies service that will execute repo-specific command(s) to install external libraries. See the docker-compose.yml file inside the elsy repo itself for an example of this.

lc clean

Running lc clean will ensure artifacts from previous builds are removed. Typically, this service is used before starting a new build. This is analogous to running mvn clean before running mvn package, for example. The mvn, lein, make, and sbt templates all define clean services, so if the project uses one of those, no additional work is required.

The difference between clean and teardown, which both perform similar actions, is that teardown only disposes of containers, whereas clean can remove artifacts from the local disk.

lc test

Running lc test will execute the repo's docker-compose test service, which will execute repo-specific command(s) to run all unit and integration tests for the code in that repo.

lc package

Running lc package will do two things. First it will execute the repo's (optional) docker-compose package service, which will execute repo-specific command(s) for packaging the repo's code into the final artifact. Second, if a Dockerfile is found in the root of the repo, elsy will build that Dockerfile into a new Docker image that is ready for final testing and publishing.

Note, when run on its own, lc package will also run lc test to ensure you are packaging working code, you can prevent this by using the --skip-tests flag.

When using elsy with Docker 1.11.1 and higher, lc package will apply the following image labels during build time:

  • com.elsy.metadata.git-commit=<git-commit> - The git commit that the image was built from. The value of <git-commit> is taken from the GIT_COMMIT env var (it is up to your build system to populate this env var).

lc blackbox-test

This is where the real power of docker-based development comes into play.

Running lc blackbox-test will execute the repo's docker-compose blackbox-test service to run repo-specifc logic for testing the final artifact of the repo. This means that it is possible to test the real container before releasing it to production.

For example, if the repo is producing a Docker-based microservice that uses a Mysql database, the blackbox-test service will:

  1. stand up the microservice container that was just packaged during lc package
  2. stand up a mysql container (and initialize the schema) for the microservice to use
  3. execute API-level tests against the microservice container to ensure it is functioning correctly with the database

Note, when run on its own, lc blackbox-test will also run lc package to ensure you are testing the latest code, you can prevent this by using the --skip-package flag.

You can also run the blackbox tests by running lc bbtest.

At the end of the blackbox-test run, regardless of the outcome, all associated containers will be torn down. If you wish to leave them up, pass the --keep-containers option.

lc publish

Running lc publish does two things: First it will execute the repo's (optional) docker-compose publish service that will run repo-specific command(s) for publishing an artifact. This custom service is typically used for repos that do not produce Docker images.

Second, if a Docker image was created during the lc package phase, elsy will correctly tag and publish that image to the registry defined in the lc.yml file.

lc publish uses the following rules when deciding what to publish:

For running the custom publish service:

  • elsy will only run the custom publish service on branches with the pattern of: origin/master or origin/release/<name>, or on a valid elsy release git tag.

For tagging Docker images:

  • If the git branch is origin/master, elsy will apply the tag latest to the docker image.
  • If the git branch is origin/release/<name> elsy will apply the tag <name>
  • If the git branch is origin/feature/<name>, elsy will apply the tag snapshot.feature.<name> to the docker image.
  • If the git branch is origin/<name>, elsy will apply the tag snapshot.<name>
  • If a git tag exists and it is a valid elsy release tag, elsy will use that tag as the docker image tag.

If you have defined a custom publish service in your docker-compose.yml, elsy will pass the service an env var called LC_PUBLISH_DOCKER_TAG that contains the tag elsy will use for the docker image, you just need to delcare the env var like so:

  image: busybox
  command: echo custom publish of tag $LC_PUBLISH_DOCKER_TAG

Valid Git Relase Tag:

elsy currently considers a valid git release tag to be any tag following the schema:


Where X, Y and Z are integers representing the Major, Minor, and Patch version (respectively) and Q is an optional string qualifier. In the future we plan to make this schema configurable.

lc run

Running lc run will run a specific service that is contained in the docker-compose.yml file. This is equivalent to lc dc run ....

elsy Templates

The elsy lifecycle manifests itself in subtly different ways depending on the underlying build tool. elsy ships with a small set of pre-baked templates (e.g., mvn, sbt) that define a sensible default lifecycle for the build tool encapsulated by the template.

See the elsy templates documentation for more information on using templates.

Improving elsy Performance

See the Improving Performance doc.


See the Contributing to elsy document.


An opinionated, multi-language, build tool based on Docker and Docker Compose







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