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Telemetry

Each HTTP request is one trace. The server span is the root, unless the request carries W3C trace context. Pipeline spans are its children, following parentExecutionId. A stage span starts at the started event's timestamp and ends at the executed event's timestamp. The error span starts at startedAt and ends at timestamp.

Spans​

HTTP {method} is the server span. It starts with http.request.started and ends with http.response.sent. Span kind is server. Express 5, Fastify, Hono, and uWebSockets emit it.

Attributes follow the OpenTelemetry HTTP semantic conventions:

  • http.request.method
  • url.path and url.query
  • http.response.status_code
  • redacted request headers and redacted response headers
  • error.type set to abort when the response was aborted

Request and response headers are copied to http.request.header.* and http.response.header.*. authorization, cookie, proxy-authorization, set-cookie, x-api-key, and x-auth-token are replaced with [redacted]. The sink also extracts W3C trace context from the request headers, so the server span continues an incoming trace.

The span status is error when the status code is 500 or above, or the response was aborted.

{middleware name} is an Express 5 native middleware span. A middleware that calls next() stays open until the response finishes, so the controller is its child. Fastify hooks, Hono app.use functions, and uWebSockets handlers do not emit this span.

{MiddlewareClass} is an Inversify middleware span. inversify.http.middleware.phase is preHandler or postHandler. The span covers execute().

{GuardClass} is a guard span. inversify.http.guard.allowed is the decision. The span closes before next(), so the controller is not inside it. A denial is a successful span. A thrown activate() is an error span.

{InterceptorClass} is an interceptor span. intercept() includes the downstream call, so the controller and pipes are children when the interceptor awaits next().

{PipeClass} is a pipe span. Attributes are inversify.http.pipe.method and inversify.http.pipe.parameter_index. Pipes on different parameters are siblings. An empty pipe name is (anonymous).

{Controller}.{method} is the controller span. Attributes are inversify.http.controller and inversify.http.controller.method. Its parent is the span that is still open: an interceptor, an Express native middleware, or the server span.

{ErrorFilter} is the error-handling span. http.error is a single event, and the span is opened and closed from it. The name is the filter class, or http.error when no filter matched. The exception is recorded on this span and on the stage span whose executed event carries error.

A child span's status is error only when its executed event carries error.

Metrics​

  • http.server.request.duration, a histogram in seconds, with method, status code, and error.type when the response was aborted
  • http.server.active_requests, an up-down counter, incremented when the request starts and decremented when the response is sent

uWebSockets records http.response.sent when a response stream ends, fails, or the client aborts. Hono records status 500 when the middleware chain rejects.