Commit 05267b64 authored by Achilleas Pipinellis's avatar Achilleas Pipinellis

Clean up using_docker_images.md

parent dcdc49fe
# Using Docker Images # Using Docker Images
GitLab CI can use [Docker Engine](https://www.docker.com/) to build projects.
Docker is an open-source project that allows to use predefined images to run applications GitLab CI can use [Docker Engine](https://www.docker.com/) to build projects.
in independent "containers" that are run within a single Linux instance.
[Docker Hub](https://registry.hub.docker.com/) have rich database of built images that can be used to build applications.
Docker when used with GitLab CI runs each build in separate and isolated container using predefined image and always from scratch. Docker is an open-source project that allows to use predefined images to run
It makes it easier to have simple and reproducible build environment that can also be run on your workstation. applications in independent "containers" that are run within a single Linux
This allows you to test all commands from your shell, rather than having to test them on a CI server. instance. [Docker Hub][hub] has a rich database of prebuilt images that can be
used to test and build your applications.
### Register Docker runner Docker, when used with GitLab CI, runs each build in a separate and isolated
To use GitLab Runner with Docker you need to register new runner to use `docker` executor: container using the predefined image that is set up in `.gitlab-ci.yml`. The
container is always euphemeral which means you get only one container per build.
This makes it easier to have a simple and reproducible build environment that
can also run on your workstation. The added benefit is that you can test all
the commands that we will explore later from your shell, rather than having to
test them on a CI server.
### Register docker runner
To use GitLab Runner with docker you need to register a new runner to use the
`docker` executor:
```bash ```bash
gitlab-ci-multi-runner register \ gitlab-ci-multi-runner register \
...@@ -23,45 +32,70 @@ gitlab-ci-multi-runner register \ ...@@ -23,45 +32,70 @@ gitlab-ci-multi-runner register \
--docker-mysql latest --docker-mysql latest
``` ```
**The registered runner will use `ruby:2.1` image and will run two services (`postgres:latest` and `mysql:latest`) that will be accessible for time of the build.** The registered runner will use the `ruby:2.1` docker image and will run two
services, `postgres:latest` and `mysql:latest`, both of which will be
accessible during the build process.
### What is image
The `image` keyword is the name of the docker image that is present in the
local Docker Engine (list all images with `docker images`) or any image that
can be found at [Docker Hub][hub]. For more information about images and Docker
Hub please read the [Docker Fundamentals][] documentation.
In short, with `image` we refer to the docker image, which will be used to
create a container on which your build will run.
### What is service
### What is image? The `service` keyword defines just another docker image that is run during
The image is the name of any repository that is present in local Docker Engine or any repository that can be found at [Docker Hub](https://registry.hub.docker.com/). your build and is linked to the docker image that the `image` keyword defines.
For more information about the image and Docker Hub please read the [Docker Fundamentals](https://docs.docker.com/introduction/understanding-docker/). This allows you to access the service image during build time.
### What is service? The service image can run any application, but the most common use case is to
Service is just another image that is run for time of your build and is linked to your build. This allows you to access the service image during build time. run a database container, eg. `mysql`. It's easier and faster to use an
The service image can run any application, but most common use case is to run some database container, ie.: `mysql`. existing image and run it as an additional container than install `mysql` every
It's easier and faster to use existing image, run it as additional container than install `mysql` every time project is built. time the project is built.
#### How is service linked to the build? #### How is service linked to the build
There's good document that describes how Docker linking works: [Linking containers together](https://docs.docker.com/userguide/dockerlinks/).
To summarize: if you add `mysql` as service to your application, the image will be used to create container that is linked to build container.
The service container for MySQL will be accessible under hostname `mysql`.
So, **to access your database service you have to connect to host: `mysql` instead of socket or `localhost`**.
### How to use other images as services? To better undestand how the container linking works, read
You are not limited to have only database services. [Linking containers together](https://docs.docker.com/userguide/dockerlinks/).
You can add the services to `.gitlab-ci.yml` or hand modify the `config.toml`.
You can use any image as service found at [Docker Hub](https://registry.hub.docker.com/). To summarize, if you add `mysql` as service to your application, the image will
then be used to create a container that is linked to the build container.
The service container for MySQL will be accessible under the hostname `mysql`.
So, in order to access your database service you have to connect to the host
named `mysql` instead of a socket or `localhost`.
### How to use other images as services
You are not limited to have only database services. You can add as many
services you need to `.gitlab-ci.yml` or manually modify `config.toml`.
Any image found at [Docker Hub][hub] can be used as a service.
### Define image and services from `.gitlab-ci.yml` ### Define image and services from `.gitlab-ci.yml`
You can simply define image or list services that you want to use for the build time.
``` You can simply define an image that will be used for all jobs and a list of
services that you want to use during build time.
```yaml
image: ruby:2.2 image: ruby:2.2
services: services:
- postgres:9.3 - postgres:9.3
before_install: before_script:
- bundle install - bundle install
test: test:
script: script:
- bundle exec rake spec - bundle exec rake spec
``` ```
It's possible to define image and service per-job: It is also possible to define different images and services per job:
```
before_install: ```yaml
before_script:
- bundle install - bundle install
test:2.1: test:2.1:
...@@ -80,68 +114,106 @@ test:2.2: ...@@ -80,68 +114,106 @@ test:2.2:
``` ```
### Define image and services in `config.toml` ### Define image and services in `config.toml`
Look for `[runners.docker]` section:
Look for the `[runners.docker]` section:
``` ```
...
[runners.docker] [runners.docker]
image = "ruby:2.1" image = "ruby:2.1"
services = ["mysql:latest", "postgres:latest"] services = ["mysql:latest", "postgres:latest"]
...
``` ```
The image and services defined these way will be added to all builds run by that runner. The image and services defined this way will be added to all builds run by
that runner.
### Accessing the services ### Accessing the services
For example you need `wordpress` instance to test some API integration with `Wordpress`.
You can for example use this image: [tutum/wordpress](https://registry.hub.docker.com/u/tutum/wordpress/).
``` Let's say that you need a Wordpress instance to test some API integration with
# .gitlab-ci.yml your application.
You can then use for example the [tutum/wordpress][] image in your
`.gitlab-ci.yml`:
```yaml
...
services: services:
- tutum/wordpress:latest - tutum/wordpress:latest
...
``` ```
Next time when you run your application the `tutum/wordpress` will be started When the build is run, `tutum/wordpress` will be started and you will have
and you will have access to it from your build container under hostname: `tutum__wordpress`. access to it from your build container under the hostname `tutum_wordpress`.
The alias hostname for the service is made from the image name following these
rules:
Alias hostname for the service is made from the image name: 1. Everything after `:` is stripped
1. Everything after `:` is stripped, 2. Backslash (`/`) is replaced with double underscores (`__`)
2. '/' is replaced to `__`.
### Configuring services ### Configuring services
Many services accept environment variables, which allow you to easily change database names or set account names depending on the environment.
GitLab Runner 0.5.0 and up passes all YAML-defined variables to created service containers. Many services accept environment variables which allow you to easily change
database names or set account names depending on the environment.
1. To configure database name for [postgres](https://registry.hub.docker.com/u/library/postgres/) service, GitLab Runner 0.5.0 and up passes all YAML-defined variables to the created
you need to set POSTGRES_DB. service containers.
```yaml For all possible configuration variables check the documentation of each image
services: provided in their corresponding Docker hub page.
- postgres
variables:
POSTGRES_DB: gitlab
```
1. To use [mysql](https://registry.hub.docker.com/u/library/mysql/) service with empty password for time of build, *Note: All variables will be passed to all service containers. It's not designed
you need to set MYSQL_ALLOW_EMPTY_PASSWORD. to distinguish which variable should go where.*
```yaml #### PostgreSQL service example
services:
- mysql
variables:
MYSQL_ALLOW_EMPTY_PASSWORD: "yes"
```
For other possible configuration variables check the To configure the database name for [postgres][postgres-hub] service, you need
https://registry.hub.docker.com/u/library/mysql/ or https://registry.hub.docker.com/u/library/postgres/ to set the `POSTGRES_DB` variable:
or README page for any other Docker image.
**Note: All variables will passed to all service containers. It's not designed to distinguish which variable should go where.** ```yaml
...
services:
- postgres
variables:
POSTGRES_DB: gitlab
...
```
For a real example visit <https://gitlab.com/gitlab-examples/postgres>.
#### MySQL service example
To use the [mysql][mysql-hub] service with an empty password during the time of
build, you need to set the `MYSQL_ALLOW_EMPTY_PASSWORD` variable:
```yaml
...
services:
- mysql
variables:
MYSQL_ALLOW_EMPTY_PASSWORD: "yes"
...
```
### How Docker integration works ### How Docker integration works
Below is a high level overview of the steps performed by docker during build
time.
1. Create any service container: `mysql`, `postgresql`, `mongodb`, `redis`. 1. Create any service container: `mysql`, `postgresql`, `mongodb`, `redis`.
1. Create cache container to store all volumes as defined in `config.toml` and `Dockerfile` of build image (`ruby:2.1` as in above example). 1. Create cache container to store all volumes as defined in `config.toml` and
`Dockerfile` of build image (`ruby:2.1` as in above example).
1. Create build container and link any service container to build container. 1. Create build container and link any service container to build container.
1. Start build container and send build script to the container. 1. Start build container and send build script to the container.
1. Run build script. 1. Run build script.
...@@ -151,32 +223,62 @@ or README page for any other Docker image. ...@@ -151,32 +223,62 @@ or README page for any other Docker image.
1. Remove build container and all created service containers. 1. Remove build container and all created service containers.
### How to debug a build locally ### How to debug a build locally
1. Create a file with build script:
*Note: The following commands are run without root privileges. You should be
able to run docker with your regular user account.*
First start with creating a file named `build script`:
```bash ```bash
$ cat <<EOF > build_script cat <<EOF > build_script
git clone https://gitlab.com/gitlab-org/gitlab-ci-multi-runner.git /builds/gitlab-org/gitlab-ci-multi-runner git clone https://gitlab.com/gitlab-org/gitlab-ci-multi-runner.git /builds/gitlab-org/gitlab-ci-multi-runner
cd /builds/gitlab-org/gitlab-ci-multi-runner cd /builds/gitlab-org/gitlab-ci-multi-runner
make <- or any other build step make
EOF EOF
``` ```
1. Create service containers: Here we use as an example the GitLab Runner repository which contains a
Makefile, so running `make` will execute the commands defined in the Makefile.
Your mileage may vary, so instead of `make` you could run the command which
is specific to your project.
Then create some service containers:
``` ```
$ docker run -d -n service-mysql mysql:latest docker run -d -n service-mysql mysql:latest
$ docker run -d -n service-postgres postgres:latest docker run -d -n service-postgres postgres:latest
``` ```
This will create two service containers (MySQL and PostgreSQL).
1. Create a build container and execute script in its context: This will create two service containers, named `service-mysql` and
`service-postgres` which use the latest MySQL and PostgreSQL images
respectively. They will both run in the background (`-d`).
Finally, create a build container by executing the `build_script` file we
created earlier:
``` ```
$ docker run --name build -i --link=service-mysql:mysql --link=service-postgres:postgres ruby:2.1 /bin/bash < build_script docker run --name build -i --link=service-mysql:mysql --link=service-postgres:postgres ruby:2.1 /bin/bash < build_script
``` ```
This will create build container that has two service containers linked.
The build_script is piped using STDIN to bash interpreter which executes the build script in container.
1. At the end remove all containers: The above command will create a container named `build` that is spawned from
the `ruby:2.1` image and has two services linked to it. The `build_script` is
piped using STDIN to the bash interpreter which in turn executes the
`build_script` in the `build` container.
When you finish testing and no longer need the containers, you can remove them
with:
``` ```
docker rm -f -v build service-mysql service-postgres docker rm -f -v build service-mysql service-postgres
``` ```
This will forcefully (the `-f` switch) remove build container and service containers
and all volumes (the `-v` switch) that were created with the container creation. This will forcefully (`-f`) remove the `build` container, the two service
containers as well as all volumes (`-v`) that were created with the container
creation.
[Docker Fundamentals]: https://docs.docker.com/engine/introduction/understanding-docker/
[hub]: https://hub.docker.com/
[linking-containers]: https://docs.docker.com/engine/userguide/networking/default_network/dockerlinks/
[tutum/wordpress]: https://registry.hub.docker.com/u/tutum/wordpress/
[postgres-hub]: https://registry.hub.docker.com/u/library/postgres/
[mysql-hub]: https://registry.hub.docker.com/u/library/mysql/
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment