Log Stackdriver request when it fails.

Failed requests logged at log level 2.
Successful ones logged at log level 10.

Author: x13n

metrics/sinks/stackdriver/stackdriver.go

@@ -15,6 +15,7 @@
 package stackdriver
 
 import (
+	"encoding/json"
 	"fmt"
 	"math/rand"
 	"net/url"
@@ -302,20 +303,39 @@ func (sink *StackdriverSink) requestSender(reqQueue chan *sd_api.CreateTimeSerie
 	}
 }
 
+func marshalRequestAndLog(printer func (string), req *sd_api.CreateTimeSeriesRequest) {
+	reqJson, errJson := json.Marshal(req)
+	if errJson != nil {
+		printer(reqJson)
+	} else {
+		glog.Errorf("Couldn't marshal Stackdriver request %v", errJson)
+	}
+}
+
 func (sink *StackdriverSink) sendOneRequest(req *sd_api.CreateTimeSeriesRequest) {
 	startTime := time.Now()
 	empty, err := sink.stackdriverClient.Projects.TimeSeries.Create(fullProjectName(sink.project), req).Do()
 
 	var responseCode int
 	if err != nil {
 		glog.Warningf("Error while sending request to Stackdriver %v", err)
+		if glog.V(2) {
+			marshalRequestAndLog(func (reqJson string) {
+				glog.Warningf("The request was: %s", reqJson)
+			}, req)
+		}
 		switch reflect.Indirect(reflect.ValueOf(err)).Type() {
 		case reflect.Indirect(reflect.ValueOf(&googleapi.Error{})).Type():
 			responseCode = err.(*googleapi.Error).Code
 		default:
 			responseCode = httpResponseCodeUnknown
 		}
 	} else {
+		if glog.V(10) {
+			marshalRequestAndLog(func (reqJson string) {
+				glog.Infof("Stackdriver request sent: %s", reqJson)
+			}, req)
+		}
 		responseCode = empty.ServerResponse.HTTPStatusCode
 	}