Add the name of the message queue as a label.

Instead of providing stats for all messages collectively, it would make
more sense to group them by queue. That way it's possible to alert on
the number of active, deferred, etc. messages.

For Postfix 2.x there isn't a lot we can do, as there only is a single
ASCII character distinguishing between two queues specifically.

postfix_exporter.go

@@ -62,30 +62,40 @@ func CollectTextualShowqFromReader(file io.Reader, ch chan<- prometheus.Metric)
 
 	// Regular expression for matching postqueue's output. Example:
 	// "A07A81514      5156 Tue Feb 14 13:13:54  MAILER-DAEMON"
-	messageLine := regexp.MustCompile("^[0-9A-F]+ +(\\d+) (\\w{3} \\w{3} +\\d+ +\\d+:\\d{2}:\\d{2}) +")
+	messageLine := regexp.MustCompile("^[0-9A-F]+([\\*!]?) +(\\d+) (\\w{3} \\w{3} +\\d+ +\\d+:\\d{2}:\\d{2}) +")
 
 	// Histograms tracking the messages by size and age.
-	sizeHistogram := prometheus.NewHistogram(
+	sizeHistogram := prometheus.NewHistogramVec(
 		prometheus.HistogramOpts{
 			Namespace: "postfix",
 			Name:      "queue_message_size_bytes",
 			Help:      "Size of messages in Postfix's message queue, in bytes",
 			Buckets:   []float64{1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9},
-		})
-	ageHistogram := prometheus.NewHistogram(
+		},
+		[]string{"queue"})
+	ageHistogram := prometheus.NewHistogramVec(
 		prometheus.HistogramOpts{
 			Namespace: "postfix",
 			Name:      "queue_message_age_seconds",
 			Help:      "Age of messages in Postfix's message queue, in seconds",
 			Buckets:   []float64{1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8},
-		})
+		},
+		[]string{"queue"})
 
 	now := time.Now()
 	for scanner.Scan() {
 		matches := messageLine.FindStringSubmatch(scanner.Text())
 		if matches != nil {
+			// Derive the name of the message queue.
+			queue := "other"
+			if matches[1] == "*" {
+				queue = "active"
+			} else if matches[1] == "!" {
+				queue = "hold"
+			}
+
 			// Parse the message size.
-			size, err := strconv.ParseFloat(matches[1], 64)
+			size, err := strconv.ParseFloat(matches[2], 64)
 			if err != nil {
 				return err
 			}
@@ -94,7 +104,7 @@ func CollectTextualShowqFromReader(file io.Reader, ch chan<- prometheus.Metric)
 			// output contains no year number. Assume it
 			// applies to the last year for which the
 			// message date doesn't exceed time.Now().
-			date, err := time.Parse("Mon Jan 2 15:04:05", matches[2])
+			date, err := time.Parse("Mon Jan 2 15:04:05", matches[3])
 			if err != nil {
 				return err
 			}
@@ -103,13 +113,13 @@ func CollectTextualShowqFromReader(file io.Reader, ch chan<- prometheus.Metric)
 				date = date.AddDate(-1, 0, 0)
 			}
 
-			sizeHistogram.Observe(size)
-			ageHistogram.Observe(now.Sub(date).Seconds())
+			sizeHistogram.WithLabelValues(queue).Observe(size)
+			ageHistogram.WithLabelValues(queue).Observe(now.Sub(date).Seconds())
 		}
 	}
 
-	ch <- sizeHistogram
-	ch <- ageHistogram
+	sizeHistogram.Collect(ch)
+	ageHistogram.Collect(ch)
 	return scanner.Err()
 }
 
@@ -133,27 +143,31 @@ func CollectBinaryShowqFromReader(file io.Reader, ch chan<- prometheus.Metric) e
 	scanner.Split(ScanNullTerminatedEntries)
 
 	// Histograms tracking the messages by size and age.
-	sizeHistogram := prometheus.NewHistogram(
+	sizeHistogram := prometheus.NewHistogramVec(
 		prometheus.HistogramOpts{
 			Namespace: "postfix",
 			Name:      "queue_message_size_bytes",
 			Help:      "Size of messages in Postfix's message queue, in bytes",
 			Buckets:   []float64{1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9},
-		})
-	ageHistogram := prometheus.NewHistogram(
+		},
+		[]string{"queue"})
+	ageHistogram := prometheus.NewHistogramVec(
 		prometheus.HistogramOpts{
 			Namespace: "postfix",
 			Name:      "queue_message_age_seconds",
 			Help:      "Age of messages in Postfix's message queue, in seconds",
 			Buckets:   []float64{1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8},
-		})
+		},
+		[]string{"queue"})
 
 	now := float64(time.Now().UnixNano()) / 1e9
+	queue := "unknown"
 	for scanner.Scan() {
 		// Parse a key/value entry.
 		key := scanner.Text()
 		if len(key) == 0 {
-			// Empty key means a record separator. We don't care.
+			// Empty key means a record separator.
+			queue := "unknown"
 			continue
 		}
 		if !scanner.Scan() {
@@ -161,25 +175,28 @@ func CollectBinaryShowqFromReader(file io.Reader, ch chan<- prometheus.Metric) e
 		}
 		value := scanner.Text()
 
-		if key == "size" {
+		if key == "queue_name" {
+			// The name of the message queue.
+			queue = value
+		} else if key == "size" {
 			// Message size in bytes.
 			size, err := strconv.ParseFloat(value, 64)
 			if err != nil {
 				return err
 			}
-			sizeHistogram.Observe(size)
+			sizeHistogram.WithLabelValues(queue).Observe(size)
 		} else if key == "time" {
 			// Message time as a UNIX timestamp.
 			time, err := strconv.ParseFloat(value, 64)
 			if err != nil {
 				return err
 			}
-			ageHistogram.Observe(now - time)
+			ageHistogram.WithLabelValues(queue).Observe(now - time)
 		}
 	}
 
-	ch <- sizeHistogram
-	ch <- ageHistogram
+	sizeHistogram.Collect(ch)
+	ageHistogram.Collect(ch)
 	return scanner.Err()
 }