Add prometheus endpoint for getting metrics (#33)

pkg/metrics/metrics.go

@@ -0,0 +1,123 @@
+//  Vikunja is a todo-list application to facilitate your life.
+//  Copyright 2018 Vikunja and contributors. All rights reserved.
+//
+//  This program is free software: you can redistribute it and/or modify
+//  it under the terms of the GNU General Public License as published by
+//  the Free Software Foundation, either version 3 of the License, or
+//  (at your option) any later version.
+//
+//  This program is distributed in the hope that it will be useful,
+//  but WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//  GNU General Public License for more details.
+//
+//  You should have received a copy of the GNU General Public License
+//  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package metrics
+
+import (
+	"code.vikunja.io/api/pkg/log"
+	"code.vikunja.io/api/pkg/red"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"github.com/spf13/viper"
+)
+
+var r = red.GetRedis()
+
+const (
+	// ListCountKey is the name of the key in which we save the list count
+	ListCountKey = `listcount`
+
+	// UserCountKey is the name of the key we use to store total users in redis
+	UserCountKey = `usercount`
+
+	// NamespaceCountKey is the name of the key we use to store the amount of total namespaces in redis
+	NamespaceCountKey = `namespacecount`
+
+	// TaskCountKey is the name of the key we use to store the amount of total tasks in redis
+	TaskCountKey = `taskcount`
+
+	// TeamCountKey is the name of the key we use to store the amount of total teams in redis
+	TeamCountKey = `teamcount`
+)
+
+func init() {
+	// Register total list count metric
+	promauto.NewGaugeFunc(prometheus.GaugeOpts{
+		Name: "vikunja_list_count",
+		Help: "The number of lists on this instance",
+	}, func() float64 {
+		count, _ := GetCount(ListCountKey)
+		return float64(count)
+	})
+
+	// Register total user count metric
+	promauto.NewGaugeFunc(prometheus.GaugeOpts{
+		Name: "vikunja_user_count",
+		Help: "The total number of users on this instance",
+	}, func() float64 {
+		count, _ := GetCount(UserCountKey)
+		return float64(count)
+	})
+
+	// Register total Namespaces count metric
+	promauto.NewGaugeFunc(prometheus.GaugeOpts{
+		Name: "vikunja_namespcae_count",
+		Help: "The total number of namespaces on this instance",
+	}, func() float64 {
+		count, _ := GetCount(NamespaceCountKey)
+		return float64(count)
+	})
+
+	// Register total Tasks count metric
+	promauto.NewGaugeFunc(prometheus.GaugeOpts{
+		Name: "vikunja_task_count",
+		Help: "The total number of tasks on this instance",
+	}, func() float64 {
+		count, _ := GetCount(TaskCountKey)
+		return float64(count)
+	})
+
+	// Register total user count metric
+	promauto.NewGaugeFunc(prometheus.GaugeOpts{
+		Name: "vikunja_team_count",
+		Help: "The total number of teams on this instance",
+	}, func() float64 {
+		count, _ := GetCount(TeamCountKey)
+		return float64(count)
+	})
+}
+
+// GetCount returns the current count from redis
+func GetCount(key string) (count int64, err error) {
+	count, err = r.Get(key).Int64()
+	if err != nil && err.Error() != "redis: nil" {
+		return
+	}
+	err = nil
+
+	return
+}
+
+// SetCount sets the list count to a given value
+func SetCount(count int64, key string) error {
+	return r.Set(key, count, 0).Err()
+}
+
+// UpdateCount updates a count with a given amount
+func UpdateCount(update int64, key string) {
+	if !viper.GetBool("service.enablemetrics") {
+		return
+	}
+	oldtotal, err := GetCount(key)
+	if err != nil {
+		log.Log.Error(err.Error())
+	}
+
+	err = SetCount(oldtotal+update, key)
+	if err != nil {
+		log.Log.Error(err.Error())
+	}
+}