func withClientTrace()

in module/apmhttp/clienttrace.go [53:138]
76 lines of code
11 McCabe index (conditional complexity)

func withClientTrace(ctx context.Context, tx *apm.Transaction, parent *apm.Span) (context.Context, *requestTracer) {
	r := requestTracer{
		Connects: make(map[connectKey]*apm.Span),
	}

	return httptrace.WithClientTrace(ctx, &httptrace.ClientTrace{
		DNSStart: func(i httptrace.DNSStartInfo) {
			r.mu.Lock()
			defer r.mu.Unlock()
			if !r.ended {
				r.DNS = tx.StartSpan(fmt.Sprintf("DNS %s", i.Host), "external.http.dns", parent)
			}
		},

		DNSDone: func(i httptrace.DNSDoneInfo) {
			r.mu.Lock()
			defer r.mu.Unlock()
			if r.DNS != nil {
				r.DNS.End()
				r.DNS = nil
			}
		},

		ConnectStart: func(network, addr string) {
			r.mu.Lock()
			defer r.mu.Unlock()
			if !r.ended {
				key := connectKey{network: network, addr: addr}
				span := tx.StartSpan(fmt.Sprintf("Connect %s", addr), "external.http.connect", parent)
				r.Connects[key] = span
			}
		},

		ConnectDone: func(network, addr string, err error) {
			r.mu.Lock()
			defer r.mu.Unlock()
			key := connectKey{network: network, addr: addr}
			if span, ok := r.Connects[key]; ok {
				delete(r.Connects, key)
				if err != nil {
					span.Outcome = "failure"
				}
				span.End()
			}
		},

		GotConn: func(info httptrace.GotConnInfo) {
			r.mu.Lock()
			defer r.mu.Unlock()
			if !r.ended {
				r.Request = tx.StartSpan("Request", "external.http.request", parent)
			}
		},

		TLSHandshakeStart: func() {
			r.mu.Lock()
			defer r.mu.Unlock()
			if !r.ended {
				r.TLS = tx.StartSpan("TLS", "external.http.tls", parent)
			}
		},

		TLSHandshakeDone: func(_ tls.ConnectionState, _ error) {
			// It is possible for TLSHandshakeDone to be called even if
			// TLSHandshakeStart has not, in case a timeout occurs first.
			r.mu.Lock()
			defer r.mu.Unlock()
			if r.TLS != nil {
				r.TLS.End()
				r.TLS = nil
			}
		},

		GotFirstResponseByte: func() {
			r.mu.Lock()
			defer r.mu.Unlock()
			if r.Request != nil {
				r.Request.End()
				r.Request = nil
			}
			if !r.ended {
				r.Response = tx.StartSpan("Response", "external.http.response", parent)
			}
		},
	}), &r
}