Lunar Flows API

openapi: 3.0.3
info:
  title: Lunar API Consumption Gateway Admin Configuration Flows API
  description: Administrative REST API for the Lunar API Consumption Gateway (lunar-engine). This API is exposed on the ENGINE_ADMIN_PORT and provides endpoints for managing flows, policies, configuration, discovery state, and gateway health. The gateway also acts as a proxy for outbound HTTP/HTTPS API traffic on port 8000, controlled via x-lunar-scheme, x-lunar-host, and x-lunar-consumer-tag headers. This spec covers the management/admin plane.
  version: 1.0.0
  contact:
    name: Lunar Support
    url: https://docs.lunar.dev/
  license:
    name: MIT
    url: https://opensource.org/licenses/MIT
servers:
- url: http://localhost:{adminPort}
  description: Lunar Engine Admin API (local)
  variables:
    adminPort:
      default: '8081'
      description: Admin port set via ENGINE_ADMIN_PORT environment variable
tags:
- name: Flows
  description: Manage Lunar Flows (streams-based traffic shaping rules)
paths:
  /load_flows:
    post:
      operationId: loadFlows
      summary: Reload flows configuration from disk
      description: Triggers an in-process reload of the Flows configuration from the file system. Used after flows YAML files have been updated on disk. Requires the gateway to be running in streams (flows) mode.
      tags:
      - Flows
      responses:
        '200':
          description: Flows loaded successfully
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/SuccessResponse'
              example:
                msg: Successfully loaded flows
        '400':
          description: Failed to reload flows
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '405':
          description: Method not allowed
  /validate_flows:
    post:
      operationId: validateFlows
      summary: Validate flows configuration
      description: Performs a dry-run validation of the current flows YAML configuration without applying changes. Returns validation errors if the configuration is invalid.
      tags:
      - Flows
      responses:
        '200':
          description: Flows validation succeeded
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/SuccessResponse'
              example:
                msg: Validation succeeded
        '422':
          description: Validation failed with details
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '405':
          description: Method not allowed
  /apply_flows:
    put:
      operationId: applyFlows
      summary: Apply flows configuration payload
      description: Applies a new flows configuration payload sent in the request body. The payload is parsed, saved to disk, and the flows engine is reloaded. On failure, the previous configuration is restored. Only one apply operation may run at a time (returns 423 if already processing).
      tags:
      - Flows
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/FlowsConfigurationPayload'
      responses:
        '200':
          description: Flows configuration update initiated
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/SuccessResponse'
              example:
                msg: Lunar Gateway config is being updated...
        '400':
          description: Failed to decode or parse incoming data
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '422':
          description: Failed to apply or reload flows
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '423':
          description: Another apply flows request is already in progress
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '500':
          description: Internal error saving or backing up configuration
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
  /on_haproxy_error:
    put:
      operationId: reportHAProxyError
      summary: Report HAProxy transaction errors
      description: Called by HAProxy to notify the engine of failed transactions. The engine uses this to trigger error-handling logic within the active flows/streams.
      tags:
      - Flows
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/OnErrorPayload'
      responses:
        '200':
          description: Error logged successfully
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/SuccessResponse'
              example:
                msg: Error logged successfully
        '400':
          description: Failed to decode incoming error data
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '405':
          description: Method not allowed
components:
  schemas:
    OnErrorPayload:
      type: object
      description: Payload from HAProxy reporting failed transactions
      properties:
        failedTransactions:
          type: object
          description: Map of failed transaction IDs to error details
          additionalProperties:
            type: object
            additionalProperties: true
      required:
      - failedTransactions
    SuccessResponse:
      type: object
      description: Generic success message response
      properties:
        msg:
          type: string
          description: Human-readable success message
      required:
      - msg
    FlowsConfigurationPayload:
      type: object
      description: Configuration payload for the /apply_flows endpoint. Contains flow definitions to be applied to the gateway. The exact structure is defined by the Lunar Flows YAML schema.
      additionalProperties: true
    ErrorResponse:
      type: object
      description: Error response with message and optional error detail
      properties:
        msg:
          type: string
          description: Human-readable error message
        error:
          type: string
          description: Underlying error string
      required:
      - msg
externalDocs:
  description: Lunar API Gateway Documentation
  url: https://docs.lunar.dev/api-gateway/get-started/welcome-to-lunar/