Initial delivery of metrics code (#81)

* Initial delivery of metrics code

* Fix build issues

* Fix build issue with go vet

internal/metrics/update.go

@@ -0,0 +1,119 @@
+/*
+© Copyright IBM Corporation 2018
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package metrics contains code to provide metrics for the queue manager
+package metrics
+
+import (
+	"strings"
+	"time"
+
+	"github.com/ibm-messaging/mq-container/internal/logger"
+	"github.com/ibm-messaging/mq-golang/mqmetric"
+)
+
+const (
+	qmgrLabelValue = mqmetric.QMgrMapKey
+	requestTimeout = 10
+)
+
+var (
+	requestChannel  = make(chan bool)
+	responseChannel = make(chan map[string]*metricData)
+)
+
+type metricData struct {
+	name        string
+	description string
+	objectType  bool
+	values      map[string]float64
+}
+
+// processMetrics processes publications of metric data and handles describe/collect requests
+func processMetrics(log *logger.Logger) {
+
+	// Initialise metrics
+	metrics := initialiseMetrics()
+
+	for {
+		// Process publications of metric data
+		mqmetric.ProcessPublications()
+
+		// Handle describe/collect requests
+		select {
+		case collect := <-requestChannel:
+			if collect {
+				updateMetrics(metrics)
+			}
+			responseChannel <- metrics
+		case <-time.After(requestTimeout * time.Second):
+			log.Debugf("Metrics: No requests received within timeout period (%d seconds)", requestTimeout)
+		}
+	}
+}
+
+// initialiseMetrics sets initial details for all available metrics
+func initialiseMetrics() map[string]*metricData {
+
+	metrics := make(map[string]*metricData)
+
+	for _, metricClass := range mqmetric.Metrics.Classes {
+		for _, metricType := range metricClass.Types {
+			if !strings.Contains(metricType.ObjectTopic, "%s") {
+				for _, metricElement := range metricType.Elements {
+					metric := metricData{
+						name:        metricElement.MetricName,
+						description: metricElement.Description,
+					}
+					key := makeKey(metricElement)
+					metrics[key] = &metric
+				}
+			}
+		}
+	}
+	return metrics
+}
+
+// updateMetrics updates values for all available metrics
+func updateMetrics(metrics map[string]*metricData) {
+
+	for _, metricClass := range mqmetric.Metrics.Classes {
+		for _, metricType := range metricClass.Types {
+			if !strings.Contains(metricType.ObjectTopic, "%s") {
+				for _, metricElement := range metricType.Elements {
+
+					// Clear existing metric values
+					metric := metrics[makeKey(metricElement)]
+					metric.values = make(map[string]float64)
+
+					// Update metric with cached values of publication data
+					for label, value := range metricElement.Values {
+						normalisedValue := mqmetric.Normalise(metricElement, label, value)
+						metric.values[label] = normalisedValue
+					}
+
+					// Reset cached values of publication data for this metric
+					metricElement.Values = make(map[string]int64)
+				}
+			}
+		}
+	}
+}
+
+// makeKey builds a unique key for each metric
+func makeKey(metricElement *mqmetric.MonElement) string {
+	return metricElement.Parent.Parent.Name + "/" + metricElement.Parent.Name + "/" + metricElement.MetricName
+}