Fix #4405

freqtrade/rpc/api_server/webserver.py

@@ -2,6 +2,7 @@ import logging
 from ipaddress import IPv4Address
 from typing import Any, Dict
 
+import rapidjson
 import uvicorn
 from fastapi import Depends, FastAPI
 from fastapi.middleware.cors import CORSMiddleware
@@ -14,6 +15,17 @@ from freqtrade.rpc.rpc import RPC, RPCException, RPCHandler
 logger = logging.getLogger(__name__)
 
 
+class FTJSONResponse(JSONResponse):
+    media_type = "application/json"
+
+    def render(self, content: Any) -> bytes:
+        """
+        Use rapidjson for responses
+        Handles NaN and Inf / -Inf in a javascript way by default.
+        """
+        return rapidjson.dumps(content).encode("utf-8")
+
+
 class ApiServer(RPCHandler):
 
     _rpc: RPC
@@ -32,6 +44,7 @@ class ApiServer(RPCHandler):
         self.app = FastAPI(title="Freqtrade API",
                            docs_url='/docs' if api_config.get('enable_openapi', False) else None,
                            redoc_url=None,
+                           default_response_class=FTJSONResponse,
                            )
         self.configure_app(self.app, self._config)