Interface DockerRequirementProperties

Indicates that a workflow component should be run in a Docker or Docker-compatible (such as Singularity and udocker) container environment and specifies how to fetch or build the image.

If a CommandLineTool lists DockerRequirement under hints (or requirements), it may (or must) be run in the specified Docker container.

The platform must first acquire or install the correct Docker image as specified by dockerPull, dockerImport, dockerLoad or dockerFile.

The platform must execute the tool in the container using docker run with the appropriate Docker image and tool command line.

The workflow platform may provide input files and the designated output directory through the use of volume bind mounts. The platform should rewrite file paths in the input object to correspond to the Docker bind mounted locations. That is, the platform should rewrite values in the parameter context such as runtime.outdir, runtime.tmpdir and others to be valid paths within the container. The platform must ensure that runtime.outdir and runtime.tmpdir are distinct directories.

When running a tool contained in Docker, the workflow platform must not assume anything about the contents of the Docker container, such as the presence or absence of specific software, except to assume that the generated command line represents a valid command within the runtime environment of the container.

A container image may specify an ENTRYPOINT and/or CMD. Command line arguments will be appended after all elements of ENTRYPOINT, and will override all elements specified using CMD (in other words, CMD is only used when the CommandLineTool definition produces an empty command line).

Use of implicit ENTRYPOINT or CMD are discouraged due to reproducibility concerns of the implicit hidden execution point (For further discussion, see https://doi.org/10.12688/f1000research.15140.1). Portable CommandLineTool wrappers in which use of a container is optional must not rely on ENTRYPOINT or CMD. CommandLineTools which do rely on ENTRYPOINT or CMD must list DockerRequirement in the requirements section.

If EnvVarRequirement is specified alongside a DockerRequirement, the environment variables must be provided to Docker using --env or --env-file and interact with the container's preexisting environment as defined by Docker.