meter/handler: provide default metrics handler

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

meter/handler/handler.go

@@ -0,0 +1,36 @@
+package pb
+
+import (
+	"bytes"
+	"context"
+
+	"github.com/unistack-org/micro/v3/codec"
+	"github.com/unistack-org/micro/v3/meter"
+)
+
+var (
+	// guard to fail early
+	_ MeterServer = &handler{}
+)
+
+type Empty struct{}
+
+type handler struct {
+	meter meter.Meter
+	opts  []meter.Option
+}
+
+func NewHandler(meter meter.Meter, opts ...meter.Option) *handler {
+	return &handler{meter: meter, opts: opts}
+}
+
+func (h *handler) Metrics(ctx context.Context, req *Empty, rsp *codec.Frame) error {
+	buf := bytes.NewBuffer(nil)
+	if err := h.meter.Write(buf, h.opts...); err != nil {
+		return err
+	}
+
+	rsp.Data = buf.Bytes()
+
+	return nil
+}

meter/handler/handler.pb.go

@@ -1,3 +0,0 @@
-package pb
-
-type Empty struct{}