> ## Documentation Index
> Fetch the complete documentation index at: https://headgate.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Discover the active backend's supported capabilities.

> Backends declare capabilities and a backend that cannot honor one does not have
it. The UI needs that at runtime or it will render a "enqueue in transaction"
affordance against Redis. apalis ships a `reenqueue_orphaned_after()` knob that
is never called; this endpoint is the antidote to that class of lie.




## OpenAPI

````yaml /api/headgate.openapi.yaml get /meta
openapi: 3.1.0
info:
  title: headgate control API
  version: 0.1.0
  description: >
    The web UI is one client of this control API and gets no

    privileged access — asynqmon reads Redis directly, which is why its
    compatibility

    note is three minor versions stale.


    Both the Go and Rust implementations serve this spec, and the conformance
    suite

    asserts identical responses. Every list endpoint is bounded to prevent
    inspection

    from becoming an unbounded store operation: asynq's

    GetQueueInfo is O(number of groups) and has pinned Redis CPU for seconds in

    production. Monitoring caused the outage.


    DERIVED FROM THE ARCHITECTURE, NOT FROM A PREDECESSOR'S UI. The first draft
    of this

    spec was the asynq Inspector surface -- list by state, act on one job, pause
    a queue

    -- with new nouns bolted on. That inherited three problems: it omitted bulk

    operations, history, and enqueue (which asynq and apalis-board respectively
    DO have),

    and more importantly it had no endpoint for the question this system's own
    design

    creates. When dequeue is an admission decision, the operator's first
    question is not

    "what is in the queue" but "why is THIS job not running" -- see
    /jobs/{id}/admission.

    No predecessor needs that endpoint because no predecessor has a gate.
servers:
  - url: /api/v1
security: []
paths:
  /meta:
    get:
      summary: Discover the active backend's supported capabilities.
      description: >
        Backends declare capabilities and a backend that cannot honor one does
        not have

        it. The UI needs that at runtime or it will render a "enqueue in
        transaction"

        affordance against Redis. apalis ships a `reenqueue_orphaned_after()`
        knob that

        is never called; this endpoint is the antidote to that class of lie.
      responses:
        '200':
          description: Server version, backend, capabilities, and limits.
          content:
            application/json:
              schema:
                type: object
                required:
                  - version
                  - backend
                  - capabilities
                properties:
                  version:
                    type: string
                  backend:
                    type: string
                    enum:
                      - postgres
                      - mysql
                      - redis
                  capabilities:
                    type: array
                    items:
                      type: string
                      enum:
                        - transactional
                        - notifying
                        - inspect
                        - aggregation
                  limits:
                    type: object
                    properties:
                      max_page_size:
                        type: integer
                      approximate_count_threshold:
                        type: integer

````