The composition step runs a Docker Composition as a means to execute finite commands in a more complex interaction of services.
Motivation for Compositions
The primary purpose of compositions is to run integration tests or any kind of tests that require multiple services for their execution.
The syntax offered by Codefresh closely follows the syntax for Docker-compose files (version 2), so if already know how Docker compose works, you will be immediately familiar with Codefresh compositions.
The big difference between the two, is that Codefresh is distinguishing between two kinds of services
- Composition Services
- Composition Candidates
Composition services are helper services that are needed for the tests to run. These can be a database, a queue, a cache, or the back-end docker image of your application.
Composition candidates are special services that will execute the tests. Codefresh will monitor their execution and fail the build if they do not succeed. Almost always composition candidates are Docker images that contain unit/integration tests or other kinds of tests (e.g. performance)
You need at least one composition service and one candidate for the composition step.
Composition step syntax
Here is an example of a composition. There is one composition service (PostgreSQL database) and one candidate (tests executed with gulp)
The most important part is the
command line that executes the tests. If it fails, then the whole composition step will fail.
||The free-text display name of the step.||Optional|
||A basic, free-text description of the step.||Optional|
||Parent group of this step. See using stages for more information.||Optional|
||The directory in which to search for the composition file. It can be an explicit path in the container’s file system, or a variable that references another step.
The default is
||The composition you want to run. It can be an inline YAML definition, a path to a composition file on the file system, or the logical name of a composition stored in the Codefresh system. We support most features of Docker compose version 2.0||Required|
||The definition of the service to monitor. Each candidate has a single
||environment that will be accessible to the container||Optional|
||A set of environment variables to substitute in the composition. Notice that these veriables are docker-compose variables and NOT envirvonment variables||Optional|
||If a step fails, and the process is halted. The default value is
||Define a set of conditions which need to be satisfied in order to execute this step.
You can find more information in the Conditional Execution of Steps article.
||Define operations to perform upon step completion using a set of predefined Post-Step Operations.||Optional|
||Define retry behavior as described in Retrying a step.||Optional|
Composition versus Composition Candidates
For Codefresh to determine if the step and operations were successfully executed, you must specify at least one
composition_candidate is a single service component of the normal Docker composition that is monitored for a successful exit code, and determines the outcome of the step. During runtime, the
composition_candidate is merged into the specified
composition, and is monitored for successful execution.
The critical part of each candidate is the
command parameter. This takes a single command that will
be executed inside the Docker container of the candidate and will decide if the whole composition is successful or not. Only one command is allowed (similar to Docker compose). If you wish to test multiple commands you need to connect them with
composition already contains a service with the same name as the
composition_candidate, the two service definitions are combined, with preference given to the
For example, we create a new Codefresh composition named ‘test_composition’:
Now we want to reuse this composition during our build for testing purposes.
We can add the following composition step to our
codefresh.yml file, and define the composition step so that
test_service always uses the latest image that was built.
In the above example, both
composition_candidates define a service named
test_service. After merging these definitions,
test_service will maintain the
command that was defined in the original composition, but will refer to the image built by the step named
Composition variables versus environment variables
Docker compose supports two kinds of variables in its syntax.
- There are environment variables that are used in the docker-compose file itself (
- There are environment variables that are passed in containers (
Codefresh supports both kinds, but notice that variables mentioned in the
composition_variables yaml group refer to the first kind. Any variables defined there are NOT passed automatically to containers (use the
environment yaml group for that purpose).
This can be illustrated with the following example:
If you run the composition you will see that the
printenv command shows the following:
test_service_1 | FIRST_KEY=VALUE
FIRST_KEY variable which is defined explicitly in the
environment yaml part is correctly passed to the alpine container. The
ANOTHER_KEY is not visible in the container at all.
You should use the
composition_variables yaml group for variables that you wish to reuse in other parts of your composition using the