feat: expose DERP server debug metrics

spikecurtis · spikecurtis · commit 64db8c604e6a · 2024-02-14T10:34:02.000+04:00
diff --git a/coderd/coderd.go b/coderd/coderd.go
@@ -5,6 +5,7 @@ import (
 	"crypto/tls"
 	"crypto/x509"
 	"database/sql"
+	"expvar"
 	"flag"
 	"fmt"
 	"io"
@@ -561,6 +562,10 @@ func New(options *Options) *API {
 
 	derpHandler := derphttp.Handler(api.DERPServer)
 	derpHandler, api.derpCloseFunc = tailnet.WithWebsocketSupport(api.DERPServer, derpHandler)
+	// Register DERP on expvar HTTP handler, which we serve below in the router, c.f. expvar.Handler()
+	// These are the metrics the DERP server exposes.
+	// TODO:
+	expvar.Publish("derp", api.DERPServer.ExpVar())
 	cors := httpmw.Cors(options.DeploymentValues.Dangerous.AllowAllCors.Value())
 	prometheusMW := httpmw.Prometheus(options.PrometheusRegistry)
 
@@ -1038,6 +1043,10 @@ func New(options *Options) *API {
 				r.Use(httpmw.ExtractUserParam(options.Database))
 				r.Get("/debug-link", api.userDebugOIDC)
 			})
+			r.Route("/derp", func(r chi.Router) {
+				r.Get("/traffic", options.DERPServer.ServeDebugTraffic)
+			})
+			r.Mount("/expvar", expvar.Handler()) // contains DERP metrics as well as cmdline and memstats
 		})
 	})
 
