Observability

Every request goes through, from the outermost:

1. the registered middlewares,
2. the otelhttp instrumentation,
3. the request log,
4. the base transport.

The instrumentation uses the tracer provider, meter provider and propagator of the application, never the OpenTelemetry globals.

Traces

Each request gets a client span:

• named after the method, GET, or HTTP for a non-standard method, following the HTTP semantic conventions,
• with the http.request.method, url.full, server.address, server.port and http.response.status_code attributes; url.full keeps the query, without the user info and the values of known signature parameters,
• with an error status for transport errors and 5xx responses.

The span is a child of the span of the request context: build the requests with http.NewRequestWithContext. The span ends when the response body is closed or fully read.

Propagation

The trace context is injected in the request headers with the application propagator, traceparent and tracestate by default. A server instrumented with OpenTelemetry, like the httpserver module, continues the trace: its server span is a child of the client span.

Metrics

Metric	Description
http.client.request.duration	Duration of the requests, with the http.request.method, server.address, server.port and http.response.status_code attributes
http.client.request.body.size	Size of the request bodies, with the same attributes

Logs

Each request is logged as http client request, at error level for transport errors and 5xx responses, and info level otherwise, with:

Attribute	Example
method	GET
url	https://weather.example.com/cities/paris, without the user info, query and fragment
status	200, unless the request failed
error	dial tcp: connection refused, if the request failed
duration	1.2ms, until the response headers are received

The query is left out of the log as it often holds secrets, like API keys: avoid secrets in URLs, the span url.full attribute keeps it. The log is correlated with the client span. Disable request logs with httpclient.log.enabled: false.

Exclude URLs

To exclude requests from spans, metrics and logs, list URL regular expressions:

httpclient:
  observability:
    exclude:
      - "^https://status\\.example\\.com/"

See Configuration.