Account for prometheus app metrics (#35)

* Account for prometheus app metrics

Mesos tasks may expose metrics via prometheus as an alternative to transmitting metrics via statsd (see
https://jira.mesosphere.com/browse/DCOS_OSS-3717). This commit allows the dcos_metrics output plugin to expose
prometheus task metrics via the /v0/containers/<cid>/app endpoint.

* Fix unittests for new year (influxdata#5213)

* Update comment; combine case statements

plugins/inputs/logparser/grok/grok_test.go

@@ -972,6 +972,7 @@ func TestNewlineInPatterns(t *testing.T) {
 }
 
 func TestSyslogTimestamp(t *testing.T) {
+	currentYear := time.Now().Year()
 	tests := []struct {
 		name     string
 		line     string
@@ -980,17 +981,17 @@ func TestSyslogTimestamp(t *testing.T) {
 		{
 			name:     "two digit day of month",
 			line:     "Sep 25 09:01:55 value=42",
-			expected: time.Date(2018, time.September, 25, 9, 1, 55, 0, time.UTC),
+			expected: time.Date(currentYear, time.September, 25, 9, 1, 55, 0, time.UTC),
 		},
 		{
 			name:     "one digit day of month single space",
 			line:     "Sep 2 09:01:55 value=42",
-			expected: time.Date(2018, time.September, 2, 9, 1, 55, 0, time.UTC),
+			expected: time.Date(currentYear, time.September, 2, 9, 1, 55, 0, time.UTC),
 		},
 		{
 			name:     "one digit day of month double space",
 			line:     "Sep  2 09:01:55 value=42",
-			expected: time.Date(2018, time.September, 2, 9, 1, 55, 0, time.UTC),
+			expected: time.Date(currentYear, time.September, 2, 9, 1, 55, 0, time.UTC),
 		},
 	}
 	for _, tt := range tests {

plugins/outputs/dcos_metrics/translator.go

@@ -39,15 +39,16 @@ func (t *producerTranslator) Translate(metric telegraf.Metric) (msg producers.Me
 	ok = true
 	switch {
 	// Container metrics
-	// We assume any metric with a container_id tag but without a metric_type tag is a container metric from the
-	// dcos_containers input.
-	case hasAllKeys(tags, []string{"container_id"}) && !hasAnyKeys(tags, []string{"metric_type"}):
+	// We assume any metric with a container_id tag but without a metric_type tag or a url tag is a container metric from
+	// the dcos_containers input.
+	case hasAllKeys(tags, []string{"container_id"}) && !hasAnyKeys(tags, []string{"metric_type", "url"}):
 		msg = t.containerMetricsMessage(metric)
 
 	// App metrics
 	// We assume any metric with both a container_id tag and a metric_type tag is an app metric from the dcos_statsd
 	// input.
-	case hasAllKeys(tags, []string{"container_id", "metric_type"}):
+	// We assume any metric with both a container_id tag and a url tag is an app metric from the prometheus input.
+	case hasAllKeys(tags, []string{"container_id"}) && hasAnyKeys(tags, []string{"metric_type", "url"}):
 		msg = t.appMetricsMessage(metric)
 
 	// Node metrics

plugins/outputs/dcos_metrics/translator_test.go

@@ -706,6 +706,52 @@ func TestTranslate(t *testing.T) {
 				},
 			},
 		},
+
+		// Custom metrics from tasks collected by the Prometheus input should appear as app metrics.
+		testCase{
+			name: "prom app metric",
+			input: metricParams{
+				name: "prefix.prom.foo",
+				tags: map[string]string{
+					"container_id": "cid",
+					"service_name": "sname",
+					"task_name":    "tname",
+					"url":          "http://example.com",
+					"label_name":   "label_value",
+				},
+				fields: map[string]interface{}{
+					"metric1": uint64(0),
+					"metric2": uint64(1),
+				},
+				tm: tm,
+				tp: telegraf.Untyped,
+			},
+			output: producers.MetricsMessage{
+				Name: "dcos.metrics.app",
+				Dimensions: producers.Dimensions{
+					MesosID:       translator.MesosID,
+					ClusterID:     translator.DCOSClusterID,
+					Hostname:      translator.DCOSNodePrivateIP,
+					ContainerID:   "cid",
+					FrameworkName: "sname",
+					TaskName:      "tname",
+				},
+				Datapoints: []producers.Datapoint{
+					producers.Datapoint{
+						Name:      "prefix.prom.foo.metric1",
+						Value:     uint64(0),
+						Timestamp: timestamp,
+						Tags:      map[string]string{"label_name": "label_value", "url": "http://example.com"},
+					},
+					producers.Datapoint{
+						Name:      "prefix.prom.foo.metric2",
+						Value:     uint64(1),
+						Timestamp: timestamp,
+						Tags:      map[string]string{"label_name": "label_value", "url": "http://example.com"},
+					},
+				},
+			},
+		},
 	}
 
 	for _, tc := range testCases {