This document describes how to use the official CircleCI pre-built Docker container images for a database service in CircleCI 2.0.
CircleCI provides pre-built images for languages and services like databases with a lot of conveniences added into the images on CircleCI Docker Hub.
The following example shows a 2.0
.circleci/config.yml file with one job called
build. Docker is selected for the executor and the first image is the primary container where all execution occurs. This example has a second image and this will be used as the service image. The first image is the programming language Python. The Python image has
pip installed and
-browsers for browser testing. The secondary image gives access to things like databases.
PostgreSQL database testing example
In the primary image the config defines an environment variable with the
environment key, giving it a URL. The URL tells it that it is a PostgreSQL database, so it will default to the PostgreSQL default port. This pre-built circleci image includes a database and a user already. The username is
postgres and database is
circle_test. So, you can begin with using that user and database without having to set it up yourself.
Set the POSTGRES_USER environment variable in your CircleCI config to
postgres to add the role to the image as follows:
- image: circleci/postgres:9.6-alpine auth: username: mydockerhub-user password: $DOCKERHUB_PASSWORD # context / project UI env-var reference environment: POSTGRES_USER: postgres
This Postgres image in the example is slightly modified already with
-ram at the end. It runs in-memory so it does not hit the disk and that will significantly improve the testing performance on this PostgreSQL database by using this image.
version: 2 jobs: build: # Primary container image where all commands run docker: - image: circleci/python:3.6.2-stretch-browsers auth: username: mydockerhub-user password: $DOCKERHUB_PASSWORD # context / project UI env-var reference environment: TEST_DATABASE_URL: postgresql://root@localhost/circle_test # Service container image - image: circleci/postgres:9.6.5-alpine-ram auth: username: mydockerhub-user password: $DOCKERHUB_PASSWORD # context / project UI env-var reference steps: - checkout - run: sudo apt-get update - run: sudo apt-get install postgresql-client-9.6 - run: whoami - run: | psql \ -d $TEST_DATABASE_URL \ -c "CREATE TABLE test (name char(25));" - run: | psql \ -d $TEST_DATABASE_URL \ -c "INSERT INTO test VALUES ('John'), ('Joanna'), ('Jennifer');" - run: | psql \ -d $TEST_DATABASE_URL \ -c "SELECT * from test"
checkout first, then install the Postgres client tools. The
postgres:9.6.5-alpine-ram image doesn’t install any client-specific database adapters. For example, for Python, you might install
psycopg2 so that you can interface with the PostgreSQL database. See Pre-Built CircleCI Services Images for the list of images and for a video of this build configuration.
In this example, the config installs the PostgreSQL client tools to get access to
psql. Note: that
sudo is run because the images do not run under the root account like most containers do by default. CircleCI has a circle account that runs commands by default, so if you want to do admin privileges or root privileges, you need to add
sudo in front of your commands.
Three commands follow the
postgresql-client-9.6 installation that interact with the database service. These are SQL commands that create a table called test, insert a value into that table, and select from the table. After committing changes and pushing them to GitHub, the build is automatically triggered on CircleCI and spins up the primary container.
Note: CircleCI injects a number of convenience environment variables into the primary container that you can use in conditionals throughout the rest of your build. For example, CIRCLE_NODE_INDEX and CIRCLE_NODE_TOTAL are related to concurrent build environments. See the Build Specific Environment Variables document for details.
When the database service spins up, it automatically creates the database
circlecitest and the
root role that you can use to log in and run your tests. It isn’t running as
root, it is using the
circle account. Then the database tests run to create a table, insert value into the table, and when SELECT is run on the table, the value comes out.
This section describes additional optional configuration for further customizing your build and avoiding race conditions.
Optimizing Postgres images
circleci/postgres Docker image uses regular persistent storage on disk.
tmpfs may make tests run faster and may use fewer resources. To use a variant
tmpfs storage, just append
-ram to the
circleci/postgres tag (i.e.,
PostGIS is also available and can be combined with the previous example:
pg_restore and similar utilities requires some extra configuration to ensure that
pg_dump invocations will also use the correct version. Add the following to your
config.yml file to enable
pg_* or equivalent database utilities:
steps: # Add the Postgres 9.6 binaries to the path. - run: echo 'export PATH=/usr/lib/postgresql/9.6/bin/:$PATH' >> $BASH_ENV
Using Dockerize to wait for dependencies
Using multiple Docker containers for your jobs may cause race conditions if the service in a container does not start before the job tries to use it. For example, your PostgreSQL container might be running, but might not be ready to accept connections. Work around this problem by using
dockerize to wait for dependencies.
Following is an example of how to do this in your CircleCI
version: 2.0 jobs: build: working_directory: /your/workdir docker: - image: your/image_for_primary_container auth: username: mydockerhub-user password: $DOCKERHUB_PASSWORD # context / project UI env-var reference - image: postgres:9.6.2-alpine auth: username: mydockerhub-user password: $DOCKERHUB_PASSWORD # context / project UI env-var reference environment: POSTGRES_USER: your_postgres_user POSTGRES_DB: your_postgres_test steps: - checkout - run: name: install dockerize command: wget https://github.com/jwilder/dockerize/releases/download/$DOCKERIZE_VERSION/dockerize-linux-amd64-$DOCKERIZE_VERSION.tar.gz && sudo tar -C /usr/local/bin -xzvf dockerize-linux-amd64-$DOCKERIZE_VERSION.tar.gz && rm dockerize-linux-amd64-$DOCKERIZE_VERSION.tar.gz environment: DOCKERIZE_VERSION: v0.3.0 - run: name: Wait for db command: dockerize -wait tcp://localhost:5432 -timeout 1m
It is possible to apply the same principle for the following databases:
dockerize -wait tcp://localhost:3306 -timeout 1m
dockerize -wait tcp://localhost:6379 -timeout 1m
Redis also has a CLI available:
sudo apt-get install redis-tools ; while ! redis-cli ping 2>/dev/null ; do sleep 1 ; done
- Other services such as web servers:
dockerize -wait http://localhost:80 -timeout 1m
Refer to the Database Configuration Examples document for additional configuration file examples.
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