fastapi + newrelic mcve with late license_key plugging bug

app.py

#import os
#os.environ["NEW_RELIC_LICENSE_KEY"] = "some_valid_key"

import sys
import logging
logging.basicConfig(stream=sys.stdout, level=logging.INFO)

import newrelic.agent

newrelic.agent.initialize("newrelic.ini")
newrelic.agent.global_settings().license_key = "some_valid_key"
newrelic.agent.register_application()


import fastapi

app = fastapi.FastAPI()
@app.get("/")
async def health():
    return "hello world!"

newrelic.ini

[newrelic]
app_name = HelloWorld
monitor_mode = true

requirements.txt

fastapi==0.60.2
newrelic==5.22.0.151
uvicorn==0.12.2

Found the solution: If using an EU based license key, you need to set the host together with the license:

newrelic.agent.initialize("newrelic.ini")
newrelic.agent.global_settings().license_key = "some_valid_key"
newrelic.agent.global_settings().host = newrelic.core.config.default_host("some_valid_key")  # EU-only
newrelic.agent.register_application()

Cheers to a-feld for debugging it for me.