Docker Reclaim Disk Space on a Host

arazzo: 1.0.1
info:
  title: Docker Reclaim Disk Space on a Host
  summary: Measure disk usage, prune stopped containers, dangling images, unused volumes and networks, and the build cache, then measure again.
  description: >-
    The housekeeping flow that keeps CI hosts from filling their disks. It measures
    usage first, prunes in dependency order — containers before images, because an
    image referenced by a stopped container cannot be removed — and measures again
    so the caller can report the bytes actually reclaimed. Every prune is filtered
    by age and label rather than run bare, since an unfiltered volume prune is one
    of the fastest ways to destroy data on a shared host. Every step spells out its
    request inline so the flow can be read and executed without opening the
    underlying OpenAPI description.
  version: 1.0.0
sourceDescriptions:
- name: dockerEngineApi
  url: ../openapi/docker-openapi.yml
  type: openapi
workflows:
- workflowId: reclaim-disk-space
  summary: Measure, prune in dependency order, and re-measure host disk usage.
  description: >-
    Takes a before reading of image, container, volume, and build-cache usage,
    prunes stopped containers, then dangling images, then unused volumes and
    networks, then the build cache, and takes an after reading to quantify what
    was reclaimed.
  inputs:
    type: object
    properties:
      until:
        type: string
        description: 'Age filter applied to container, image, and network prunes, e.g. "24h" or "168h".'
      pruneVolumes:
        type: boolean
        description: Whether to prune unused volumes. Off by default because volume prunes destroy data.
      volumeFilters:
        type: string
        description: 'JSON-encoded volume prune filters, e.g. {"label":["ci-scratch"]}. Scope this narrowly.'
      buildCacheReservedSpace:
        type: integer
        description: Bytes of build cache to keep when pruning the builder cache.
  steps:
  - stepId: measureBefore
    description: >-
      Take a before reading across all four object types so the reclaim can be
      quantified rather than guessed at.
    operationId: SystemDataUsage
    parameters:
    - name: type
      in: query
      value:
      - container
      - image
      - volume
      - build-cache
    - name: verbose
      in: query
      value: false
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      imageUsageBefore: $response.body#/ImageUsage
      containerUsageBefore: $response.body#/ContainerUsage
      volumeUsageBefore: $response.body#/VolumeUsage
      buildCacheUsageBefore: $response.body#/BuildCacheUsage
  - stepId: pruneContainers
    description: >-
      Prune stopped containers older than the age filter first. This must precede
      the image prune, because an image still referenced by a stopped container
      cannot be removed.
    operationId: ContainerPrune
    parameters:
    - name: filters
      in: query
      value: '{"until": ["$inputs.until"]}'
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      containersDeleted: $response.body#/ContainersDeleted
      containerSpaceReclaimed: $response.body#/SpaceReclaimed
  - stepId: pruneImages
    description: >-
      Prune only dangling — unused and untagged — images. Setting dangling to false
      would remove every unused image, including tagged ones a pipeline expects to
      still be cached.
    operationId: ImagePrune
    parameters:
    - name: filters
      in: query
      value: '{"dangling": ["true"], "until": ["$inputs.until"]}'
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      imagesDeleted: $response.body#/ImagesDeleted
      imageSpaceReclaimed: $response.body#/SpaceReclaimed
  - stepId: pruneVolumes
    description: >-
      Prune unused volumes, scoped by the supplied label filter. This is the
      destructive step in the flow — a volume prune without a filter will take any
      unused named volume with it, data and all.
    operationId: VolumePrune
    parameters:
    - name: filters
      in: query
      value: $inputs.volumeFilters
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      volumesDeleted: $response.body#/VolumesDeleted
      volumeSpaceReclaimed: $response.body#/SpaceReclaimed
  - stepId: pruneNetworks
    description: >-
      Prune user-defined networks with no attached containers, older than the age
      filter. Pre-defined networks are never touched by this call.
    operationId: NetworkPrune
    parameters:
    - name: filters
      in: query
      value: '{"until": ["$inputs.until"]}'
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      networksDeleted: $response.body#/NetworksDeleted
  - stepId: pruneBuildCache
    description: >-
      Trim the BuildKit cache down to a reserved size rather than clearing it
      outright, so subsequent builds keep most of their cache hits.
    operationId: BuildPrune
    parameters:
    - name: reserved-space
      in: query
      value: $inputs.buildCacheReservedSpace
    - name: all
      in: query
      value: false
    - name: filters
      in: query
      value: '{"until": ["$inputs.until"]}'
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      cachesDeleted: $response.body#/CachesDeleted
      buildCacheSpaceReclaimed: $response.body#/SpaceReclaimed
  - stepId: measureAfter
    description: >-
      Take the after reading across the same four object types so the caller can
      diff it against the before reading and report what was actually reclaimed.
    operationId: SystemDataUsage
    parameters:
    - name: type
      in: query
      value:
      - container
      - image
      - volume
      - build-cache
    - name: verbose
      in: query
      value: false
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      imageUsageAfter: $response.body#/ImageUsage
      containerUsageAfter: $response.body#/ContainerUsage
      volumeUsageAfter: $response.body#/VolumeUsage
      buildCacheUsageAfter: $response.body#/BuildCacheUsage
  outputs:
    containerSpaceReclaimed: $steps.pruneContainers.outputs.containerSpaceReclaimed
    imageSpaceReclaimed: $steps.pruneImages.outputs.imageSpaceReclaimed
    volumeSpaceReclaimed: $steps.pruneVolumes.outputs.volumeSpaceReclaimed
    buildCacheSpaceReclaimed: $steps.pruneBuildCache.outputs.buildCacheSpaceReclaimed
    imageUsageBefore: $steps.measureBefore.outputs.imageUsageBefore
    imageUsageAfter: $steps.measureAfter.outputs.imageUsageAfter