What is the InvokeHTTP processor and what are key configuration considerations?

InvokeHTTP is NiFi's most flexible HTTP client processor. It sends HTTP requests to configurable URLs using any HTTP method (GET, POST, PUT, PATCH, DELETE) and routes the response to different relationships based on the HTTP response code. It is the Swiss-army knife for REST API integration in NiFi flows.

Key configuration properties:

HTTP Method: The method to use — can be static or an EL expression like ${http.method} to pick dynamically from an attribute.

Remote URL: The target endpoint URL, EL-supported: https://api.example.com/users/${user.id}.

SSL Context Service: A StandardSSLContextService reference for HTTPS endpoints requiring client certificates or custom CA trust.

Send Message Body: Whether to include the FlowFile content as the HTTP request body. Set to false for GET/DELETE requests.

Request Content-Type: Typically application/json or dynamically from ${mime.type}.

Relationships: Response (2xx responses — the response body becomes a new FlowFile), Original (the original request FlowFile), Retry (5xx responses), No Retry (4xx client errors), Failure (network failures, connection timeouts).