Language Guide: Elixir
This is an annotated config.yml for a simple Phoenix web application, which you can access at https://github.com/CircleCI-Public/circleci-demo-elixir-phoenix.
If you’re in a rush, just copy the configuration below into .circleci/config.yml in your project’s root directory. Otherwise, we recommend reading through the whole configuration for better understanding.
Sample Configuration
version: 2 # use CircleCI 2.0 instead of CircleCI Classic
jobs: # basic units of work in a run
build: # runs not using Workflows must have a `build` job as entry point
parallelism: 1 # run only one instance of this job
docker: # run the steps with Docker
- image: circleci/elixir:1.7.3 # ...with this image as the primary container; this is where all `steps` will run
environment: # environment variables for primary container
MIX_ENV: test
- image: circleci/postgres:10.1-alpine # database image
environment: # environment variables for database
POSTGRES_USER: postgres
POSTGRES_DB: app_test
POSTGRES_PASSWORD:
working_directory: ~/app # directory where steps will run
steps: # commands that comprise the `build` job
- checkout # check out source code to working directory
- run: mix local.hex --force # install Hex locally (without prompt)
- run: mix local.rebar --force # fetch a copy of rebar (without prompt)
- restore_cache: # restores saved mix cache
# Read about caching dependencies: https://circleci.com/docs/2.0/caching/
keys: # list of cache keys, in decreasing specificity
- v1-mix-cache-{{ .Branch }}-{{ checksum "mix.lock" }}
- v1-mix-cache-{{ .Branch }}
- v1-mix-cache
- restore_cache: # restores saved build cache
keys:
- v1-build-cache-{{ .Branch }}
- v1-build-cache
- run: mix do deps.get, compile # get updated dependencies & compile them
- save_cache: # generate and store mix cache
key: v1-mix-cache-{{ .Branch }}-{{ checksum "mix.lock" }}
paths: "deps"
- save_cache: # don't forget to save a *build* cache, too
key: v1-build-cache-{{ .Branch }}
paths: "_build"
- run: # special utility that stalls main process until DB is ready
name: Wait for DB
command: dockerize -wait tcp://localhost:5432 -timeout 1m
- run: mix test # run all tests in project
- store_test_results: # upload junit test results for display in Test Summary
# Read more: https://circleci.com/docs/2.0/collect-test-data/
path: _build/test/lib/REPLACE_WITH_YOUR_APP_NAME # Replace with the name of your :app
Config Walkthrough
Every config.yml starts with the version key.
This key is used to issue warnings about breaking changes.
version: 2
A run is comprised of one or more jobs.
Because this run does not use workflows,
it must have a build job.
Use the working_directory key
to specify where a job’s steps run.
By default, the value of working_directory is ~/project, where project is a literal string.
The steps of a job occur in a virtual environment called an executor.
In this example, the docker executor is used
to specify a custom Docker image. We use the CircleCI-provided Elixir docker image.
jobs:
build:
parallelism: 1
docker:
- image: circleci/elixir:1.7.3
environment:
MIX_ENV: test
- image: circleci/postgres:10.1-alpine
environment:
POSTGRES_USER: postgres
POSTGRES_DB: app_test
POSTGRES_PASSWORD:
working_directory: ~/app
After choosing containers for a job, create steps to run specific commands.
Use the checkout step
to check out source code. By default, source code is checked out to the path specified by working_directory.
Use the run step
to execute commands. In this example, mix is used
to install Elixir tooling.
steps:
- checkout
- run: mix local.hex --force
- run: mix local.rebar --force
To save time between runs, consider caching dependencies or source code.
Use the save_cache step
to cache certain files or directories. In this example, the virtual environment and installed packages are cached.
Use the restore_cache step
to restore cached files or directories.
- restore_cache:
keys:
- v1-mix-cache-{{ .Branch }}-{{ checksum "mix.lock" }}
- v1-mix-cache-{{ .Branch }}
- v1-mix-cache
- restore_cache:
keys:
- v1-build-cache-{{ .Branch }}
- v1-build-cache
- run: mix do deps.get, compile
- save_cache:
key: v1-mix-cache-{{ .Branch }}-{{ checksum "mix.lock" }}
paths: "deps"
- save_cache:
key: v1-build-cache-{{ .Branch }}
paths: "_build"
Finally, we wait for the database to come online so that we can run the test suite. Following running the tests, we upload our test results to be made available in the CircleCI web app.
- run:
name: Wait for DB
command: dockerize -wait tcp://localhost:5432 -timeout 1m
- run: mix test
- store_test_results:
path: _build/test/lib/REPLACE_WITH_YOUR_APP_NAME
Parallelism
Splitting by Timings
As of version 2.0, CircleCI requires users to upload their own JUnit XML test output. Currently the main/only Elixir library that produces that output is JUnitFormatter.
In order to allow CircleCI’s parallelization to use the --split-by=timings strategy with the XML output, you need to configure JUnitFormatter with the include_filename?: true option which will add the filename to the XML.
By default, JUnitFormatter saves the output to the _build/test/lib/<application name> directory, so in your .circleci/config.yml you will want to configure the store_test_results step to point to that same directory:
- store_test_results:
path: _build/test/lib/<application name>
However, JUnitFormatter also allows you to configure the directory where the results are saved via the report_dir setting, in which case, the path value in your CircleCI config should match the relative path of wherever you’re storing the output.