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Configuring Databases

3 months ago3 min read
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This document describes how to use the official CircleCI pre-built Docker container images for a database service in CircleCI.

Overview

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 .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 service image gives access to additional services 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: cimg/postgres:14.0
        auth:
          username: mydockerhub-user
          password: $DOCKERHUB_PASSWORD  # context / project UI env-var reference
        environment:
          POSTGRES_USER: postgres
version: 2.1

jobs:
  build:

    # Primary container image where all commands run
    docker:
      - image: cimg/python:3.10
        environment:
          TEST_DATABASE_URL: postgresql://postgres@localhost/circle_test
        auth:
          username: mydockerhub-user
          password: $DOCKERHUB_PASSWORD  # context / project UI env-var reference

    # Service container image
      - image: cimg/postgres:14.0
        environment:
          POSTGRES_USER: postgres
        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
      - 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');"

The steps run checkout first, then install the Postgres client tools. The cimg/postgres:14.0 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.

In this example, the config installs the PostgreSQL client tools, postgresql-client via apt-get, to get access to psql. Installing packages in images requires administrator privileges, therefore sudo is used - a password is not required.

Two commands follow the postgresql-client installation that interact with the database service. These are SQL commands that create a table called test and insert a value into that table. After committing changes and pushing them, 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 execution environments. See the Build Specific Environment Variables document for details.

When the database service spins up, it automatically creates the database circle_test and the postgres role that you can use to log in and run your tests. Then the database tests run to create a table and insert a value into it.

Optional customization

This section describes additional optional configuration for further customizing your build and avoiding race conditions.

Optimizing PostgreSQL images

The cimg/postgres Docker image uses regular persistent storage on disk. Storing the database in a ramdisk may improve performance. This can be done by setting the PGDATA: /dev/shm/pgdata/data environment variable in the service container image config.

Using binaries

To use pg_dump, 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 12.0 binaries to the path.
       - run: echo 'export PATH=/usr/lib/postgresql/12.0/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 config.yml file:

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: cimg/postgres:14.0
        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: v0.6.1
      - 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:

  • MySQL:

dockerize -wait tcp://localhost:3306 -timeout 1m

  • Redis:

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

See also

Refer to the Database Configuration Examples document for additional configuration file examples.


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