Regressed in https://github.com/matrix-org/matrix-public-archive/pull/61 where we tried to serve this under `/css/hydrogen-styles.css` but it doesn't work because all of the image and font references in the CSS file expect it to be at the domain root so just reverted back to serving at the root `/`.
OpenTelemetry tracing so we can see spans where the app is taking time.
For the user, we specifically show the spans for the external API HTTP requests
that are slow (so we know when the Matrix API is being slow).
Enable tracing:
- `npm run start -- --tracing`
- `npm run start-dev -- --tracing`
What does this PR change:
- Adds OpenTelemetry tracing with some of the automatic instrumentation (includes HTTP and express)
- We ignore traces for serving static assets (just noise)
- Adds `X-Trace-Id` to the response headers
- Adds `window.tracingSpansForRequest` which includes the external HTTP API requests made during the request
- Adds a fancy 504 timeout page that includes trace details and lists the slow HTTP requests
- Adds `jaegerTracesEndpoint` configuration to export tracing spans to Jaeger
- Related to, https://github.com/matrix-org/matrix-public-archive/issues/26
Eric Eastwood