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stage | group | info | type |
---|---|---|---|
Verify | Runner | To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers | concepts, howto |
Using Docker images
GitLab CI/CD in conjunction with GitLab Runner can use Docker Engine to test and build any application.
Docker is an open-source project that allows you to use predefined images to run applications in independent "containers" that are run within a single Linux instance. Docker Hub has a rich database of pre-built images that can be used to test and build your applications.
When used with GitLab CI/CD, Docker runs each job in a separate and isolated
container using the predefined image that is set up in
.gitlab-ci.yml
.
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 dedicated CI server.
Register Docker Runner
To use GitLab Runner with Docker you need to register a new Runner
to use the docker
executor.
An example can be seen below. First we set up a temporary template to supply the services:
cat > /tmp/test-config.template.toml << EOF
[[runners]]
[runners.docker]
[[runners.docker.services]]
name = "postgres:latest"
[[runners.docker.services]]
name = "mysql:latest"
EOF
Then we register the runner using the template that was just created:
sudo gitlab-runner register \
--url "https://gitlab.example.com/" \
--registration-token "PROJECT_REGISTRATION_TOKEN" \
--description "docker-ruby:2.6" \
--executor "docker" \
--template-config /tmp/test-config.template.toml \
--docker-image ruby:2.6
The registered runner will use the ruby:2.6
Docker image and will run two
services, postgres:latest
and mysql:latest
, both of which will be
accessible during the build process.
What is an image
The image
keyword is the name of the Docker image the Docker executor
will run to perform the CI tasks.
By default, the executor will only pull images from Docker Hub,
however this can be configured in the gitlab-runner/config.toml
by setting
the Docker pull policy to allow using local images.
For more information about images and Docker Hub, please read the Docker Fundamentals documentation.
What is a service
The services
keyword defines just another Docker image that is run during
your job and is linked to the Docker image that the image
keyword defines.
This allows you to access the service image during build time.
The service image can run any application, but the most common use case is to
run a database container, e.g., mysql
. It's easier and faster to use an
existing image and run it as an additional container than install mysql
every
time the project is built.
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 or your private Container Registry can be
used as a service.
Services inherit the same DNS servers, search domains, and additional hosts as the CI container itself.
You can see some widely used services examples in the relevant documentation of CI services examples.
How services are linked to the job
To better understand how the container linking works, read Linking containers together.
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 job 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
. Read more in accessing the
services.
How the health check of services works
Services are designed to provide additional functionality which is network accessible.
It may be a database like MySQL, or Redis, and even docker:stable-dind
which
allows you to use Docker in Docker. It can be practically anything that is
required for the CI/CD job to proceed and is accessed by network.
To make sure this works, the Runner:
- Checks which ports are exposed from the container by default.
- Starts a special container that waits for these ports to be accessible.
When the second stage of the check fails, either because there is no opened port in the
service, or the service was not started properly before the timeout and the port is not
responding, it prints the warning: *** WARNING: Service XYZ probably didn't start properly
.
In most cases it will affect the job, but there may be situations when the job will still succeed even if that warning was printed. For example:
- The service was started a little after the warning was raised, and the job is not using the linked service from the beginning. In that case, when the job needed to access the service, it may have been already there waiting for connections.
- The service container is not providing any networking service, but it's doing
something with the job's directory (all services have the job directory mounted
as a volume under
/builds
). In that case, the service will do its job, and since the job is not trying to connect to it, it won't fail.
What services are not for
As it was mentioned before, this feature is designed to provide network accessible services. A database is the simplest example of such a service.
NOTE: Note:
The services feature is not designed to, and will not add any software from the
defined services
image(s) to the job's container.
For example, if you have the following services
defined in your job, the php
,
node
or go
commands will not be available for your script, and thus
the job will fail:
job:
services:
- php:7
- node:latest
- golang:1.10
image: alpine:3.7
script:
- php -v
- node -v
- go version
If you need to have php
, node
and go
available for your script, you should
either:
- Choose an existing Docker image that contains all required tools.
- Create your own Docker image, which will have all the required tools included and use that in your job.
Accessing the services
Let's say that you need a Wordpress instance to test some API integration with your application.
You can then use for example the tutum/wordpress image in your
.gitlab-ci.yml
:
services:
- tutum/wordpress:latest
If you don't specify a service alias,
when the job is run, tutum/wordpress
will be started and you will have
access to it from your build container under two hostnames to choose from:
tutum-wordpress
tutum__wordpress
NOTE: Note: Hostnames with underscores are not RFC valid and may cause problems in 3rd party applications.
The default aliases for the service's hostname are created from its image name following these rules:
- Everything after the colon (
:
) is stripped. - Slash (
/
) is replaced with double underscores (__
) and the primary alias is created. - Slash (
/
) is replaced with a single dash (-
) and the secondary alias is created (requires GitLab Runner v1.1.0 or higher).
To override the default behavior, you can specify a service alias.
Define image
and services
from .gitlab-ci.yml
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:
default:
image: ruby:2.6
services:
- postgres:11.7
before_script:
- bundle install
test:
script:
- bundle exec rake spec
The image name must be in one of the following formats:
image: <image-name>
(Same as using<image-name>
with thelatest
tag)image: <image-name>:<tag>
image: <image-name>@<digest>
It is also possible to define different images and services per job:
default:
before_script:
- bundle install
test:2.6:
image: ruby:2.6
services:
- postgres:11.7
script:
- bundle exec rake spec
test:2.7:
image: ruby:2.7
services:
- postgres:12.2
script:
- bundle exec rake spec
Or you can pass some extended configuration options
for image
and services
:
default:
image:
name: ruby:2.6
entrypoint: ["/bin/bash"]
services:
- name: my-postgres:11.7
alias: db-postgres
entrypoint: ["/usr/local/bin/db-postgres"]
command: ["start"]
before_script:
- bundle install
test:
script:
- bundle exec rake spec
Passing environment variables to services
You can also pass custom environment variables
to fine tune your Docker images
and services
directly in the .gitlab-ci.yml
file.
For more information, see custom environment variables
# The following variables will automatically be passed down to the Postgres container
# as well as the Ruby container and available within each.
variables:
HTTPS_PROXY: "https://10.1.1.1:8090"
HTTP_PROXY: "https://10.1.1.1:8090"
POSTGRES_DB: "my_custom_db"
POSTGRES_USER: "postgres"
POSTGRES_PASSWORD: "example"
PGDATA: "/var/lib/postgresql/data"
POSTGRES_INITDB_ARGS: "--encoding=UTF8 --data-checksums"
services:
- name: postgres:11.7
alias: db
entrypoint: ["docker-entrypoint.sh"]
command: ["postgres"]
image:
name: ruby:2.6
entrypoint: ["/bin/bash"]
before_script:
- bundle install
test:
script:
- bundle exec rake spec
Extended Docker configuration options
Introduced in GitLab and GitLab Runner 9.4.
When configuring the image
or services
entries, you can use a string or a map as
options:
- when using a string as an option, it must be the full name of the image to use (including the Registry part if you want to download the image from a Registry other than Docker Hub)
- when using a map as an option, then it must contain at least the
name
option, which is the same name of the image as used for the string setting
For example, the following two definitions are equal:
-
Using a string as an option to
image
andservices
:image: "registry.example.com/my/image:latest" services: - postgresql:9.4 - redis:latest
-
Using a map as an option to
image
andservices
. The use ofimage:name
is required:image: name: "registry.example.com/my/image:latest" services: - name: postgresql:9.4 - name: redis:latest
Available settings for image
Introduced in GitLab and GitLab Runner 9.4.
Setting | Required | GitLab version | Description |
---|---|---|---|
name |
yes, when used with any other option | 9.4 | Full name of the image that should be used. It should contain the Registry part if needed. |
entrypoint |
no | 9.4 | Command or script that should be executed as the container's entrypoint. It will be translated to Docker's --entrypoint option while creating the container. The syntax is similar to Dockerfile 's ENTRYPOINT directive, where each shell token is a separate string in the array. |
Available settings for services
Introduced in GitLab and GitLab Runner 9.4.
Setting | Required | GitLab version | Description |
---|---|---|---|
name |
yes, when used with any other option | 9.4 | Full name of the image that should be used. It should contain the Registry part if needed. |
entrypoint |
no | 9.4 | Command or script that should be executed as the container's entrypoint. It will be translated to Docker's --entrypoint option while creating the container. The syntax is similar to Dockerfile 's ENTRYPOINT directive, where each shell token is a separate string in the array. |
command |
no | 9.4 | Command or script that should be used as the container's command. It will be translated to arguments passed to Docker after the image's name. The syntax is similar to Dockerfile 's CMD directive, where each shell token is a separate string in the array. |
alias |
no | 9.4 | Additional alias that can be used to access the service from the job's container. Read Accessing the services for more information. |
NOTE: Note: Alias support for the Kubernetes executor was introduced in GitLab Runner 12.8, and is only available for Kubernetes version 1.7 or later.
Starting multiple services from the same image
Introduced in GitLab and GitLab Runner 9.4. Read more about the extended configuration options.
Before the new extended Docker configuration options, the following configuration would not work properly:
services:
- mysql:latest
- mysql:latest
The Runner would start two containers using the mysql:latest
image, but both
of them would be added to the job's container with the mysql
alias based on
the default hostname naming. This would end with one
of the services not being accessible.
After the new extended Docker configuration options, the above example would look like:
services:
- name: mysql:latest
alias: mysql-1
- name: mysql:latest
alias: mysql-2
The Runner will still start two containers using the mysql:latest
image,
however now each of them will also be accessible with the alias configured
in .gitlab-ci.yml
file.
Setting a command for the service
Introduced in GitLab and GitLab Runner 9.4. Read more about the extended configuration options.
Let's assume you have a super/sql:latest
image with some SQL database
inside it and you would like to use it as a service for your job. Let's also
assume that this image doesn't start the database process while starting
the container and the user needs to manually use /usr/bin/super-sql run
as
a command to start the database.
Before the new extended Docker configuration options, you would need to create
your own image based on the super/sql:latest
image, add the default command,
and then use it in job's configuration, like:
# my-super-sql:latest image's Dockerfile
FROM super/sql:latest
CMD ["/usr/bin/super-sql", "run"]
# .gitlab-ci.yml
services:
- my-super-sql:latest
After the new extended Docker configuration options, you can now simply
set a command
in .gitlab-ci.yml
, like:
# .gitlab-ci.yml
services:
- name: super/sql:latest
command: ["/usr/bin/super-sql", "run"]
As you can see, the syntax of command
is similar to Dockerfile's CMD
.
Overriding the entrypoint of an image
Introduced in GitLab and GitLab Runner 9.4. Read more about the extended configuration options.
Before showing the available entrypoint override methods, let's describe shortly how the Runner starts and uses a Docker image for the containers used in the CI jobs:
- The Runner starts a Docker container using the defined entrypoint (default
from
Dockerfile
that may be overridden in.gitlab-ci.yml
) - The Runner attaches itself to a running container.
- The Runner prepares a script (the combination of
before_script
,script
, andafter_script
). - The Runner sends the script to the container's shell STDIN and receives the output.
To override the entrypoint of a Docker image, the recommended solution is to
define an empty entrypoint
in .gitlab-ci.yml
, so the Runner doesn't start
a useless shell layer. However, that will not work for all Docker versions, and
you should check which one your Runner is using. Specifically:
- If Docker 17.06 or later is used, the
entrypoint
can be set to an empty value. - If Docker 17.03 or previous versions are used, the
entrypoint
can be set to/bin/sh -c
,/bin/bash -c
or an equivalent shell available in the image.
The syntax of image:entrypoint
is similar to Dockerfile's ENTRYPOINT
.
Let's assume you have a super/sql:experimental
image with some SQL database
inside it and you would like to use it as a base image for your job because you
want to execute some tests with this database binary. Let's also assume that
this image is configured with /usr/bin/super-sql run
as an entrypoint. That
means that when starting the container without additional options, it will run
the database's process, while Runner expects that the image will have no
entrypoint or that the entrypoint is prepared to start a shell command.
With the extended Docker configuration options, instead of creating your
own image based on super/sql:experimental
, setting the ENTRYPOINT
to a shell, and then using the new image in your CI job, you can now simply
define an entrypoint
in .gitlab-ci.yml
.
For Docker 17.06+:
image:
name: super/sql:experimental
entrypoint: [""]
For Docker =< 17.03:
image:
name: super/sql:experimental
entrypoint: ["/bin/sh", "-c"]
Define image and services in config.toml
Look for the [runners.docker]
section:
[runners.docker]
image = "ruby:latest"
services = ["mysql:latest", "postgres:latest"]
The image and services defined this way will be added to all job run by that runner.
Define an image from a private Container Registry
To access private container registries, the GitLab Runner process can use:
- Statically defined credentials. That is, a username and password for a specific registry.
- Credentials Store. For more information, see the relevant Docker documentation.
- Credential Helpers. For more information, see the relevant Docker documentation.
To define which should be used, the GitLab Runner process reads the configuration in the following order:
DOCKER_AUTH_CONFIG
variable provided as either:- A variable in
.gitlab-ci.yml
. - A project's variables stored on the projects Settings > CI/CD page.
- A variable in
DOCKER_AUTH_CONFIG
variable provided as environment variable inconfig.toml
of the Runner.config.json
file placed in$HOME/.docker
directory of the user running GitLab Runner process. If the--user
flag is provided to run the GitLab Runner child processes as unprivileged user, the home directory of the main GitLab Runner process user will be used.
NOTE: Note:
GitLab Runner reads this configuration only from config.toml
and ignores it if
it's provided as an environment variable. This is because GitLab Runner uses only
config.toml
configuration and doesn't interpolate ANY environment variables at
runtime.
Requirements and limitations
- This feature requires GitLab Runner 1.8 or higher.
- For GitLab Runner versions >= 0.6, <1.8 there was a partial support for using private registries, which required manual configuration of credentials on runner's host. We recommend to upgrade your Runner to at least version 1.8 if you want to use private registries.
- Not available for Kubernetes executor, follow https://gitlab.com/gitlab-org/gitlab-runner/-/issues/2673 for details.
Using statically-defined credentials
There are two approaches that you can take in order to access a
private registry. Both require setting the environment variable
DOCKER_AUTH_CONFIG
with appropriate authentication information.
- Per-job: To configure one job to access a private registry, add
DOCKER_AUTH_CONFIG
as a job variable. - Per-runner: To configure a Runner so all its jobs can access a
private registry, add
DOCKER_AUTH_CONFIG
to the environment in the Runner's configuration.
See below for examples of each.
Determining your DOCKER_AUTH_CONFIG
data
As an example, let's assume that you want to use the registry.example.com:5000/private/image:latest
image which is private and requires you to login into a private container registry.
Let's also assume that these are the login credentials:
Key | Value |
---|---|
registry | registry.example.com:5000 |
username | my_username |
password | my_password |
There are two ways to determine the value of DOCKER_AUTH_CONFIG
:
-
First way - Do a
docker login
on your local machine:docker login registry.example.com:5000 --username my_username --password my_password
Then copy the content of
~/.docker/config.json
.If you don't need access to the registry from your computer, you can do a
docker logout
:docker logout registry.example.com:5000
-
Second way - In some setups, it's possible that Docker client will use the available system key store to store the result of
docker login
. In that case, it's impossible to read~/.docker/config.json
, so you will need to prepare the required base64-encoded version of${username}:${password}
and create the Docker configuration JSON manually. Open a terminal and execute the following command:echo -n "my_username:my_password" | base64 # Example output to copy bXlfdXNlcm5hbWU6bXlfcGFzc3dvcmQ=
Create the Docker JSON configuration content as follows:
{ "auths": { "registry.example.com:5000": { "auth": "(Base64 content from above)" } } }
Configuring a job
To configure a single job with access for registry.example.com:5000
,
follow these steps:
-
Create a variable
DOCKER_AUTH_CONFIG
with the content of the Docker configuration file as the value:{ "auths": { "registry.example.com:5000": { "auth": "bXlfdXNlcm5hbWU6bXlfcGFzc3dvcmQ=" } } }
-
You can now use any private image from
registry.example.com:5000
defined inimage
and/orservices
in your.gitlab-ci.yml
file:image: registry.example.com:5000/namespace/image:tag
In the example above, GitLab Runner will look at
registry.example.com:5000
for the imagenamespace/image:tag
.
You can add configuration for as many registries as you want, adding more
registries to the "auths"
hash as described above.
NOTE: Note:
The full hostname:port
combination is required everywhere
for the Runner to match the DOCKER_AUTH_CONFIG
. For example, if
registry.example.com:5000/namespace/image:tag
is specified in .gitlab-ci.yml
,
then the DOCKER_AUTH_CONFIG
must also specify registry.example.com:5000
.
Specifying only registry.example.com
will not work.
Configuring a Runner
If you have many pipelines that access the same registry, it'll probably be better to setup registry access at the runner level. This allows pipeline authors to have access to a private registry just by running a job on the appropriate runner. It also makes registry changes and credential rotations much simpler.
Of course this means that any job on that runner can access the registry with the same privilege, even across projects. If you need to control access to the registry, you'll need to be sure to control access to the runner.
To add DOCKER_AUTH_CONFIG
to a Runner:
-
Modify the Runner's
config.toml
file as follows:[[runners]] environment = ["DOCKER_AUTH_CONFIG={\"auths\":{\"registry.example.com:5000\":{\"auth\":\"bXlfdXNlcm5hbWU6bXlfcGFzc3dvcmQ=\"}}}"]
-
Restart the Runner service.
NOTE: Note: The double quotes included in the DOCKER_AUTH_CONFIG
data must be escaped with backslashes. This prevents them from being
interpreted as TOML.
NOTE: Note: The environment
option is a list. So your Runner may
have existing entries and you should add this to the list, not replace
it.
Using Credentials Store
Support for using Credentials Store was added in GitLab Runner 9.5.
To configure credentials store, follow these steps:
-
To use a credentials store, you need an external helper program to interact with a specific keychain or external store. Make sure helper program is available in GitLab Runner
$PATH
. -
Make GitLab Runner use it. There are two ways to accomplish this. Either:
-
Create a variable
DOCKER_AUTH_CONFIG
with the content of the Docker configuration file as the value:{ "credsStore": "osxkeychain" }
-
Or, if you are running self-managed Runners, add the above JSON to
${GITLAB_RUNNER_HOME}/.docker/config.json
. GitLab Runner will read this configuration file and will use the needed helper for this specific repository.
-
NOTE: Note: credsStore
is used to access ALL the registries.
If you will want to use both images from private registry and public images from DockerHub,
pulling from DockerHub will fail, because Docker daemon will try to use the same credentials for ALL the registries.
Using Credential Helpers
Support for using Credential Helpers was added in GitLab Runner 12.0
As an example, let's assume that you want to use the aws_account_id.dkr.ecr.region.amazonaws.com/private/image:latest
image which is private and requires you to log in into a private container registry.
To configure access for aws_account_id.dkr.ecr.region.amazonaws.com
, follow these steps:
-
Make sure
docker-credential-ecr-login
is available in GitLab Runner's$PATH
. -
Have any of the following AWS credentials setup. Make sure that GitLab Runner can access the credentials.
-
Make GitLab Runner use it. There are two ways to accomplish this. Either:
-
Create a variable
DOCKER_AUTH_CONFIG
with the content of the Docker configuration file as the value:{ "credHelpers": { "aws_account_id.dkr.ecr.region.amazonaws.com": "ecr-login" } }
This configures Docker to use the credential helper for a specific registry.
or
{ "credsStore": "ecr-login" }
This configures Docker to use the credential helper for all Amazon ECR registries.
-
Or, if you are running self-managed Runners, add the above JSON to
${GITLAB_RUNNER_HOME}/.docker/config.json
. GitLab Runner will read this configuration file and will use the needed helper for this specific repository.
-
-
You can now use any private image from
aws_account_id.dkr.ecr.region.amazonaws.com
defined inimage
and/orservices
in your.gitlab-ci.yml
file:image: aws_account_id.dkr.ecr.region.amazonaws.com/private/image:latest
In the example above, GitLab Runner will look at
aws_account_id.dkr.ecr.region.amazonaws.com
for the imageprivate/image:latest
.
You can add configuration for as many registries as you want, adding more
registries to the "credHelpers"
hash as described above.
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 the created service containers.
For all possible configuration variables check the documentation of each image provided in their corresponding Docker hub page.
NOTE: Note: All variables will be passed to all services containers. It's not designed to distinguish which variable should go where.
PostgreSQL service example
See the specific documentation for using PostgreSQL as a service.
MySQL service example
See the specific documentation for using MySQL as a service.
How Docker integration works
Below is a high level overview of the steps performed by Docker during job time.
- Create any service container:
mysql
,postgresql
,mongodb
,redis
. - Create cache container to store all volumes as defined in
config.toml
andDockerfile
of build image (ruby:2.6
as in above example). - Create build container and link any service container to build container.
- Start build container and send job script to the container.
- Run job script.
- Checkout code in:
/builds/group-name/project-name/
. - Run any step defined in
.gitlab-ci.yml
. - Check exit status of build script.
- Remove build container and all created service containers.
How to debug a job locally
NOTE: 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
:
cat <<EOF > build_script
git clone https://gitlab.com/gitlab-org/gitlab-runner.git /builds/gitlab-org/gitlab-runner
cd /builds/gitlab-org/gitlab-runner
make
EOF
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 --name service-mysql mysql:latest
docker run -d --name service-postgres postgres:latest
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:2.6 /bin/bash < build_script
The above command will create a container named build
that is spawned from
the ruby:2.6
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
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.