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Middleware Stack

Aside from the actual communication with the upstream STAC API, the majority of the proxy's functionality occurs within a chain of middlewares. Each request passes through this chain, wherein each middleware performs a specific task:

  1. EnforceAuthMiddleware

    • Handles authentication and authorization
    • Configurable public/private endpoints
    • OIDC integration
    • Places auth token payload in request state

  2. Cql2BuildFilterMiddleware

    • Builds CQL2 filters based on request context/state
    • Places CQL2 expression in request state

  3. Cql2ApplyFilterQueryStringMiddleware

    • Retrieves CQL2 expression from request state
    • Augments GET requests with CQL2 filter by appending to querystring

  4. Cql2ApplyFilterBodyMiddleware

    • Retrieves CQL2 expression from request state
    • Augments POST`/`PUT`/`PATCH requests with CQL2 filter by modifying body

  5. Cql2ValidateResponseBodyMiddleware

    • Retrieves CQL2 expression from request state
    • Validates response against CQL2 filter for non-filterable endpoints

  6. OpenApiMiddleware

    • Modifies OpenAPI specification based on endpoint configuration, adding security requirements
    • Only active if openapi_spec_endpoint is configured

  7. AddProcessTimeHeaderMiddleware

    • Adds processing time headers
    • Useful for monitoring/debugging