Instrumentation¶

OpenTelemetry¶

The app exports logs and traces using OpenTelemetry Protocol only when OTEL_EXPORTER_OTLP_ENDPOINT is set. Without it, the app runs normally and needs no extra setup.

For local testing, use otel-gui. It is a lightweight OpenTelemetry trace viewer that needs no configuration.

If the OTLP backend needs authentication, set OTEL_EXPORTER_OTLP_HEADERS. This is a comma-separated list of name=value pairs. Percent-encode any value that contains special characters. Here is an example with a Logfire write token:

OTEL_EXPORTER_OTLP_ENDPOINT=https://logfire-api.pydantic.dev
OTEL_EXPORTER_OTLP_HEADERS=Authorization=Bearer <logfire-write-token>

To change the service name, set OTEL_SERVICE_NAME (default: remotebrowser).

Client address¶

Behind a reverse proxy, the socket peer is the proxy, not the user. This applies to any proxy that sets X-Forwarded-For, such as nginx, a cloud load balancer, or a platform router. Set TRUSTED_PROXY_HOPS to the number of proxies in front of the app, so that logs and traces record the real client address.

For example, a single proxy in front of the app needs TRUSTED_PROXY_HOPS=1. This is the case on Dokku, which puts nginx in front of each app.

A CDN in front of that proxy adds one more hop, so the value becomes 2. This works only if the inner proxy appends to X-Forwarded-For instead of replacing it.

A client can send any X-Forwarded-For header it wants (IP spoofing via HTTP headers), so the app does not simply take the leftmost entry. Each proxy appends the address it saw. The app walks back from the right through exactly TRUSTED_PROXY_HOPS entries, so any forged entries on the left are ignored. The app also ignores the header when the socket peer is a public address, because then the request did not come through your proxy. Do not set this value higher than the real number of proxies: each extra hop lets a client choose the address that gets logged.