# HTTP API Mode

Watchtower provides an HTTP API mode that enables an HTTP endpoint that can be requested to trigger container updating. The current available endpoint list is:

- `/v1/update` - triggers an update for all of the containers monitored by this Watchtower instance.

To enable this mode, use the flag `--http-api-update`. For example, in a Docker Compose config file:

    version: '3'

    services:
      app-monitored-by-watchtower:
        image: myapps/monitored-by-watchtower
        labels:
          - "com.centurylinklabs.watchtower.enable=true"

      watchtower:
        image: containrrr/watchtower
        volumes:
          - /var/run/docker.sock:/var/run/docker.sock
        command: --debug --http-api-update
        environment:
          - WATCHTOWER_HTTP_API_TOKEN=mytoken
        labels:
          - "com.centurylinklabs.watchtower.enable=false"
        ports:
          - 8080:8080

By default, enabling this mode prevents periodic polls (i.e. what is specified using `--interval` or `--schedule`). To run periodic updates regardless, pass `--http-api-periodic-polls`.

Notice that there is an environment variable named WATCHTOWER_HTTP_API_TOKEN. To prevent external services from accidentally triggering image updates, all of the requests have to contain a "Token" field, valued as the token defined in WATCHTOWER_HTTP_API_TOKEN, in their headers. In this case, there is a port bind to the host machine, allowing to request localhost:8080 to reach Watchtower. The following `curl` command would trigger an image update:

    curl -H "Authorization: Bearer mytoken" localhost:8080/v1/update