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Dynamic Headers Forwarding

Forward Headers from DDN Engine

Headers will be forwarded forth and back between the DDN engine and data connectors:

  • Client -> DDN Engine -> Data Connector: is usually used for forwarding Cookie or OAuth2 access tokens from clients.
  • Data Connector -> DDN Engine -> Client: forward headers from the external HTTP execution back to the client.

Forward Request Headers

  • Enable forwardHeaders in the config.yaml file of the connector directory, and define the name of the headers argument field.
# ...
forwardHeaders:
  enabled: true
  argumentField: headers
  • Introspect the connector to update the relevant schema.
ddn connector introspect \<connector-name\>
  • Finally, add the headers argument, which you defined above, to the argumentPresets in DataConnectorLink metadata with allowed HTTP headers. For instance:
kind: DataConnectorLink
version: v1
definition:
  name: my_api
  # ...
  argumentPresets:
    - argument: headers
      value:
        httpHeaders:
          forward:
            - Cookie
          additional: {}

Forward Response Headers

  • Enable forwardHeaders in the config.yaml file of the connector directory, and configure responseHeaders.
    • headersField and resultField field wrappers will be added in the connector schema.
    • forwardHeaders array is allowed headers that will be forwarded back.
# ...
forwardHeaders:
  enabled: true
  responseHeaders: 
    headersField: headers
    resultField: response
    forwardHeaders:
      - X-Test-Header
      - X-Test-ResponseHeader
  • Introspect the connector to update the relevant schema.
ddn connector introspect \<connector-name\>
  • Finally, add the exact responseHeaders object which you defined above to DataConnectorLink metadata. For instance:
kind: DataConnectorLink
version: v1
definition:
  name: my_api
  # ...
  responseHeaders:
    headersField: headers
    resultField: response
    forwardHeaders:
      - X-Test-Header
      - X-Test-ResponseHeader

Forward Headers from Pre-NDC Request Plugin

You can use a Pre-NDC Request Plugin to modify the request, and add dynamic headers in runtime via request_arguments.headers field, which is a string map. Those headers will be merged into the HTTP request headers before being sent to external services.

See the full example at Pre-NDC Request Plugin Request

{
  // ...
  "ndcRequest": {
    // ...
    "request_arguments": {
        "headers": {
            "Authorization": "Bearer <token>",
            "X-Custom-Header": "foo"
        }
    }
  }
}