Tweaked push package

- Moved the Deliverer parameter to the end of the list to mirror
  Collectors in push.Collectors.
- Improved doc comment and added an example for push.Registry.

prometheus/push/examples_test.go

@@ -35,3 +35,22 @@ func ExampleCollectors() {
 		fmt.Println("Could not push completion time to Pushgateway:", err)
 	}
 }
+
+func ExampleRegistry() {
+	registry := prometheus.NewRegistry()
+
+	completionTime := prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: "db_backup_last_completion_time",
+		Help: "The timestamp of the last succesful completion of a DB backup.",
+	})
+	registry.MustRegister(completionTime)
+
+	completionTime.Set(float64(time.Now().Unix()))
+	if err := push.Registry(
+		"db_backup", push.HostnameGroupingKey(),
+		"http://pushgateway:9091",
+		registry,
+	); err != nil {
+		fmt.Println("Could not push completion time to Pushgateway:", err)
+	}
+}

prometheus/push/push.go

@@ -44,13 +44,14 @@ import (
 
 const contentTypeHeader = "Content-Type"
 
-// Registry triggers a metric collection by the provided Deliverer and pushes all
-// delivered metrics to the Pushgateway specified by url, using the provided job
-// name and the (optional) further grouping labels (the grouping map may be
-// nil). See the Pushgateway documentation for detailed implications of the job
-// and other grouping labels. Neither the job name nor any grouping label value
-// may contain a "/". The metrics pushed must not contain a job label of their
-// own nor any of the grouping labels.
+// Registry triggers a metric collection by the provided Deliverer (which is
+// usually implemented by a prometheus.Registry, thus the name of the function)
+// and pushes all delivered metrics to the Pushgateway specified by url, using
+// the provided job name and the (optional) further grouping labels (the
+// grouping map may be nil). See the Pushgateway documentation for detailed
+// implications of the job and other grouping labels. Neither the job name nor
+// any grouping label value may contain a "/". The metrics pushed must not
+// contain a job label of their own nor any of the grouping labels.
 //
 // You can use just host:port or ip:port as url, in which case 'http://' is
 // added automatically. You can also include the schema in the URL. However, do
@@ -59,18 +60,18 @@ const contentTypeHeader = "Content-Type"
 // Note that all previously pushed metrics with the same job and other grouping
 // labels will be replaced with the metrics pushed by this call. (It uses HTTP
 // method 'PUT' to push to the Pushgateway.)
-func Registry(reg prometheus.Deliverer, job string, grouping map[string]string, url string) error {
-	return push(reg, job, grouping, url, "PUT")
+func Registry(job string, grouping map[string]string, url string, reg prometheus.Deliverer) error {
+	return push(job, grouping, url, reg, "PUT")
 }
 
 // RegistryAdd works like Registry, but only previously pushed metrics with the
 // same name (and the same job and other grouping labels) will be replaced. (It
 // uses HTTP method 'POST' to push to the Pushgateway.)
-func RegistryAdd(reg prometheus.Deliverer, job string, grouping map[string]string, url string) error {
-	return push(reg, job, grouping, url, "POST")
+func RegistryAdd(job string, grouping map[string]string, url string, reg prometheus.Deliverer) error {
+	return push(job, grouping, url, reg, "POST")
 }
 
-func push(reg prometheus.Deliverer, job string, grouping map[string]string, pushURL, method string) error {
+func push(job string, grouping map[string]string, pushURL string, reg prometheus.Deliverer, method string) error {
 	if !strings.Contains(pushURL, "://") {
 		pushURL = "http://" + pushURL
 	}
@@ -154,7 +155,7 @@ func pushCollectors(job string, grouping map[string]string, url, method string,
 			return err
 		}
 	}
-	return push(r, job, grouping, url, method)
+	return push(job, grouping, url, r, method)
 }
 
 // HostnameGroupingKey returns a label map with the only entry

prometheus/push/push_test.go

@@ -150,7 +150,7 @@ func TestPush(t *testing.T) {
 	}
 
 	// Push registry, all good.
-	if err := Registry(reg, "testjob", HostnameGroupingKey(), pgwOK.URL); err != nil {
+	if err := Registry("testjob", HostnameGroupingKey(), pgwOK.URL, reg); err != nil {
 		t.Fatal(err)
 	}
 	if lastMethod != "PUT" {
@@ -161,7 +161,7 @@ func TestPush(t *testing.T) {
 	}
 
 	// PushAdd registry, all good.
-	if err := RegistryAdd(reg, "testjob", map[string]string{"a": "x", "b": "y"}, pgwOK.URL); err != nil {
+	if err := RegistryAdd("testjob", map[string]string{"a": "x", "b": "y"}, pgwOK.URL, reg); err != nil {
 		t.Fatal(err)
 	}
 	if lastMethod != "POST" {