add tracing and refactor some api pkgs

internal/tracing/http_handler.go

@@ -0,0 +1,30 @@
+package tracing
+
+import (
+	"net/http"
+	"strings"
+
+	"go.opencensus.io/plugin/ochttp"
+	"go.opencensus.io/trace"
+)
+
+func TraceHandler(handler http.Handler, ignoredMethods ...string) http.Handler {
+	healthEndpoints := strings.Join(ignoredMethods, ";;")
+
+	return &ochttp.Handler{
+		Handler: handler,
+		FormatSpanName: func(r *http.Request) string {
+			host := r.URL.Host
+			if host == "" {
+				host = r.Host
+			}
+			return host + r.URL.Path
+		},
+
+		StartOptions: trace.StartOptions{Sampler: Sampler()},
+		IsHealthEndpoint: func(r *http.Request) bool {
+			n := strings.Contains(healthEndpoints, r.URL.RequestURI())
+			return n
+		},
+	}
+}