FRC: JSON-RPC HTTP transport conventions

[LesnyRumcajs]

#1248

Simple Summary

This FRC standardizes how Filecoin JSON-RPC 2.0 endpoints map application-level errors to HTTP status codes. It defines a consistent mapping so that HTTP clients can detect error conditions from the status code alone, without parsing the full JSON response body.

Abstract

The JSON-RPC 2.0 specification defines application-level error codes but is silent on HTTP transport behavior. FRC-0104 specifies the common JSON-RPC API methods but does not address how errors should be represented at the HTTP layer. This gap has led to divergent behavior across Filecoin node implementations: Forest returns HTTP 200 for all JSON-RPC errors, Lotus returns HTTP 500 for some, and third-party RPC providers each follow their own conventions.

This FRC specifies the HTTP transport conventions for Filecoin JSON-RPC endpoints, including HTTP status code mappings for JSON-RPC error codes, Content-Type requirements, HTTP method handling, batch request behavior, and notification responses. The goal is to enable consistent, predictable behavior across all Filecoin node implementations and RPC providers.