feat(coderd): add DERP healthcheck (#6936)

coderd/debug.go

@@ -1,6 +1,14 @@
 package coderd
 
-import "net/http"
+import (
+	"context"
+	"net/http"
+	"time"
+
+	"github.com/coder/coder/coderd/healthcheck"
+	"github.com/coder/coder/coderd/httpapi"
+	"github.com/coder/coder/codersdk"
+)
 
 // @Summary Debug Info Wireguard Coordinator
 // @ID debug-info-wireguard-coordinator
@@ -12,3 +20,36 @@ import "net/http"
 func (api *API) debugCoordinator(rw http.ResponseWriter, r *http.Request) {
 	(*api.TailnetCoordinator.Load()).ServeHTTPDebug(rw, r)
 }
+
+// @Summary Debug Info Deployment Health
+// @ID debug-info-deployment-health
+// @Security CoderSessionToken
+// @Produce json
+// @Tags Debug
+// @Success 200 {object} healthcheck.Report
+// @Router /debug/health [get]
+func (api *API) debugDeploymentHealth(rw http.ResponseWriter, r *http.Request) {
+	ctx, cancel := context.WithTimeout(r.Context(), api.HealthcheckTimeout)
+	defer cancel()
+
+	resChan := api.healthCheckGroup.DoChan("", func() (*healthcheck.Report, error) {
+		return api.HealthcheckFunc(ctx)
+	})
+
+	select {
+	case <-ctx.Done():
+		httpapi.Write(ctx, rw, http.StatusNotFound, codersdk.Response{
+			Message: "Healthcheck is in progress and did not complete in time. Try again in a few seconds.",
+		})
+		return
+	case res := <-resChan:
+		if time.Since(res.Val.Time) > api.HealthcheckRefresh {
+			api.healthCheckGroup.Forget("")
+			api.debugDeploymentHealth(rw, r)
+			return
+		}
+
+		httpapi.Write(ctx, rw, http.StatusOK, res.Val)
+		return
+	}
+}