feature: Add client.connection.dialer timer to measure DialContext()

changelog/@unreleased/pr-747.v2.yml

@@ -0,0 +1,5 @@
+type: feature
+feature:
+  description: Add client.connection.dialer timer to measure DialContext()
+  links:
+  - https://github.com/palantir/conjure-go-runtime/pull/747

conjure-go-client/httpclient/client_builder.go

@@ -108,7 +108,7 @@ func (b *httpClientBuilder) Build(ctx context.Context, params ...HTTPClientParam
 		tlsProvider = refreshableProvider
 	}
 
-	dialer := refreshingclient.NewRefreshableDialer(ctx, b.DialerParams)
+	dialer := newMetricsDialer(refreshingclient.NewRefreshableDialer(ctx, b.DialerParams), b.ServiceName, b.DisableMetrics)
 	transport := refreshingclient.NewRefreshableTransport(ctx, b.TransportParams, tlsProvider, dialer)
 	transport = wrapTransport(transport, newMetricsMiddleware(b.ServiceName, b.MetricsTagProviders, b.DisableMetrics))
 	transport = wrapTransport(transport, newTraceMiddleware(b.ServiceName, b.DisableRequestSpan, b.DisableTraceHeaders))

conjure-go-client/httpclient/metrics.go

@@ -23,13 +23,15 @@ import (
 	"net/http/httptrace"
 	"time"
 
+	"github.com/palantir/conjure-go-runtime/v2/conjure-go-client/httpclient/internal/refreshingclient"
 	"github.com/palantir/pkg/metrics"
 	"github.com/palantir/pkg/refreshable"
 	werror "github.com/palantir/witchcraft-go-error"
 )
 
 const (
 	MetricTagServiceName = "service-name"
+	metricClientDialer   = "client.connection.dialer"
 	metricClientResponse = "client.response"
 	metricTagFamily      = "family"
 	metricTagMethod      = "method"
@@ -78,6 +80,27 @@ func (s StaticTagsProvider) Tags(_ *http.Request, _ *http.Response, _ error) met
 	return metrics.Tags(s)
 }
 
+type metricsDialer struct {
+	Dialer      refreshingclient.ContextDialer
+	ServiceName refreshable.String
+	Disabled    refreshable.Bool
+}
+
+func newMetricsDialer(dialer refreshingclient.ContextDialer, serviceName refreshable.String, disabled refreshable.Bool) refreshingclient.ContextDialer {
+	return &metricsDialer{Dialer: dialer, ServiceName: serviceName, Disabled: disabled}
+}
+
+func (d *metricsDialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
+	if !d.Disabled.CurrentBool() {
+		defer func(startTime time.Time) {
+			serviceNameTag := metrics.NewTagWithFallbackValue(MetricTagServiceName, d.ServiceName.CurrentString(), "unknown")
+			metrics.FromContext(ctx).Timer(metricClientDialer, serviceNameTag).UpdateSince(startTime)
+		}(time.Now())
+	}
+
+	return d.Dialer.DialContext(ctx, network, address)
+}
+
 // MetricsMiddleware updates the "client.response" timer metric on every request.
 // By default, metrics are tagged with 'service-name', 'method', and 'family' (of the
 // status code). This metric name and tag set matches http-remoting's DefaultHostMetrics: