`docker://`¶

Docker Engine API integration via raw HTTP over a Unix socket or TCP. The component speaks the Docker Engine REST API directly with stdlib net/http, no external Docker SDK. Useful for orchestrating containers from a workflow — pulling images, starting / stopping containers, tailing logs, running one-shot exec commands.

Producer-only — CreateConsumer returns an error.

URI shape¶

docker://<operation>?host=unix:///var/run/docker.sock
docker://<operation>?host=tcp://docker-host:2375

Operation	Endpoint
`containers/list`	`GET /containers/json`
`containers/create`	`POST /containers/create`
`containers/start`	`POST /containers/{id}/start`
`containers/stop`	`POST /containers/{id}/stop`
`containers/logs`	`GET /containers/{id}/logs?stdout=true&stderr=true`
`containers/inspect`	`GET /containers/{id}/json`
`images/list`	`GET /images/json`
`images/pull`	`POST /images/create?fromImage=...&tag=...`
`exec`	`POST /containers/{id}/exec` + `POST /exec/{execId}/start`

Parameters¶

Param	Type	Default	Producer/Consumer/Both	Description
(path) `operation`	string	required	Producer	One of the operations above.
`host`	string	`unix:///var/run/docker.sock`	Producer	Docker host. `unix://<path>` dials a Unix socket; `tcp://<host:port>` or `http(s)://<host:port>` uses TCP.

Headers¶

Read by the producer¶

Header	Operation	Description
`docker.containerId`	start, stop, logs, inspect, exec	Container ID to act on.
`docker.containerName`	create	Optional `?name=` query param.
`docker.image`	images/pull	Image name (or use body).
`docker.tag`	images/pull	Tag — default `latest`.
`docker.all`	containers/list	When `"true"`, lists all containers (including stopped).
`docker.tail`	containers/logs	`?tail=N` parameter.
`docker.since`	containers/logs	`?since=...` parameter (RFC3339 / Unix).

Written by the producer¶

Header	Operation	Description
`docker.containerId`	create	The newly-created container's ID (extracted from the JSON response).
`docker.execId`	exec	The exec instance ID.

The body becomes either the request JSON (create, exec config) or — for images/pull and exec — a fallback shell command read directly from BodyAsString().

Examples¶

Pull an image and run a one-shot container:

workflows:
  - id: scrape
    trigger: { uri: direct://scrape }
    steps:
      - set-header:
          name: docker.image
          constant: "alpine"
      - target: docker://images/pull
      - set-body:
          starlang: '{ "Image": "alpine", "Cmd": ["echo", "hello"], "AttachStdout": true }'
      - target: docker://containers/create
      - target: docker://containers/start

Tail container logs:

- set-header:
    name: docker.containerId
    constant: my-app
- set-header:
    name: docker.tail
    constant: "100"
- target: docker://containers/logs

Run a shell command via exec:

- set-header:
    name: docker.containerId
    constant: my-app
- set-body:
    constant: "ls -la /app"
- target: docker://exec

Talk to a remote Docker host:

- target: docker://containers/list?host=tcp://docker-host.internal:2375

Behavior notes¶

No TLS auth helpers — host=tcp://... opens a plain TCP socket. For TLS-protected Docker daemons, front them with host=https://... and rely on system root CAs (no client-cert support in this component today).
120 s timeout — both the socket and TCP transports use a 120 s timeout. Image pulls of large images can hit this; consider running the pull out-of-band if needed.
exec is two calls — create returns an exec ID; start actually runs the command. The body of the response is what the executed command wrote to its attached streams (text, with no chunk framing).
304 Not Modified is treated as success for start / stop — the container was already in that state.

Source¶

pkg/component/docker/docker.go

docker://¶