Grafana Agent Flow returns Not Allowed when called with http OPTIONS (Angular + OTLPTraceExporter)

Grafana Grafana Agent
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1

Hi guys,
I am using Grafana Agent Flow installed as a Windows Service on the development mashine. I have configured it with the .river config to send the traces to Grafana Cloud Loki. OpenTelemetry data is sent from an Angular App on the same host via http/protobuf to the agent and the agent should then transfer the Loki events to the cloud…

AngularApp(OpenTelemtrySDK) → Grafana Agent Flow ->Grafana Loki (Cloud)

This is how I configure the exporter:
new OTLPTraceExporter({
url: ‘http://localhost:4318/v1/traces’,
}),

When Angular/OpenTelemtryExporter tries to send traces it makes OPTION call first. The Grafana agent server returns HTTP/1.1 405 Method Not Allowed

If I try making POST via Fiddler I can make a request but I get “partialSuccess”, but I think this has just something to do with the payload im am posting.
Any ideas?
Thanks!

2

It looks like you are mixing traces (storage Tempo) with logs (storage Loki). Make sure you are using right storage for right signals.

BTW: there is Faro, which may be a better choice for frontend observability.

3

UPDATE: I have added the following configuration entries for preflight requests (CORS) into the config.river.

http { 
		cors { 
			allowed_origins = ["http://localhost:xxx"]	
		}
	}

Now I do get 204 No Content in return, and POST is called afterwards. However, the Response is

HTTP/1.1 200 OK
{"partialSuccess":{}}

And I do not see any data colleted in the Grafana Explorer. What does partialSuccess mean? How can I tell if the agent is trying to forward data to Loki endpoint? Can I enable debug mode/logging somehow?

5

Thanks, I will take a look into that.

6

Silly question, but I haven’t found any answer by myself: Does using the Faro with local Grafana Agent still requires an agent to be run in the old “static” mode?