diff --git a/metric-collector.go b/metric-collector.go
index 8f0e7dc..ea5c675 100644
--- a/metric-collector.go
+++ b/metric-collector.go
@@ -3,16 +3,18 @@ package main
 import (
 	"encoding/json"
 	"fmt"
+	"github.com/ClusterCockpit/cc-metric-collector/collectors"
+	protocol "github.com/influxdata/line-protocol"
 	"log"
 	"os"
 	"os/signal"
+	"strings"
 	"sync"
 	"time"
-
-	"github.com/ClusterCockpit/cc-metric-collector/collectors"
-	protocol "github.com/influxdata/line-protocol"
 )
 
+// List of provided collectors. Which collector should be run can be
+// configured at 'collectors' list  in 'config.json'.
 var Collectors = map[string]collectors.MetricGetter{
 	"likwid":     &collectors.LikwidCollector{},
 	"loadavg":    &collectors.LoadavgCollector{},
@@ -22,8 +24,10 @@ var Collectors = map[string]collectors.MetricGetter{
 	"lustrestat": &collectors.LustreCollector{},
 }
 
+// Pointer to the InfluxDB line protocol encoder
 var serializer *protocol.Encoder
 
+// Structure of the configuration file
 type GlobalConfig struct {
 	Sink struct {
 		User     string `json:"user"`
@@ -36,6 +40,7 @@ type GlobalConfig struct {
 	Collectors []string `json:"collectors"`
 }
 
+// Load JSON configuration file
 func LoadConfiguration(file string, config *GlobalConfig) error {
 	configFile, err := os.Open(file)
 	defer configFile.Close()
@@ -47,6 +52,8 @@ func LoadConfiguration(file string, config *GlobalConfig) error {
 	return err
 }
 
+// Register an interrupt handler for Ctrl+C and similar. At signal,
+// all collectors are closed
 func shutdown(wg *sync.WaitGroup, config *GlobalConfig) {
 	sigs := make(chan os.Signal, 1)
 	signal.Notify(sigs, os.Interrupt)
@@ -64,6 +71,7 @@ func shutdown(wg *sync.WaitGroup, config *GlobalConfig) {
 	}(wg)
 }
 
+// Create a new measurement in InfluxDB line protocol
 func setupProtocol(scope string, tags map[string]string, fields map[string]interface{}, t time.Time) {
 	cur, err := protocol.New(scope, tags, fields, t)
 	if err != nil {
@@ -85,6 +93,7 @@ func main() {
 		return
 	}
 
+	// Load and check configuration
 	LoadConfiguration("config.json", &config)
 	if config.Interval <= 0 || time.Duration(config.Interval)*time.Second <= 0 {
 		log.Print("Configuration value 'interval' must be greater than zero")
@@ -94,30 +103,51 @@ func main() {
 		log.Print("Configuration value 'duration' must be greater than zero")
 		return
 	}
+	if len(config.Collectors) == 0 {
+		var keys []string
+		for k := range Collectors {
+			keys = append(keys, k)
+		}
+		log.Print("Configuration value 'collectors' does not contain any collector. Available: ", strings.Join(keys, ", "))
+		return
+	}
+	for _, name := range config.Collectors {
+		if _, found := Collectors[name]; !found {
+			log.Print("Invalid collector '", name, "' in configuration")
+			return
+		}
+	}
+	// Register interrupt handler
 	shutdown(&wg, &config)
 
+	// Setup InfluxDB line protocol encoder
 	serializer = protocol.NewEncoder(os.Stdout)
 	serializer.SetPrecision(time.Second)
 	serializer.SetMaxLineBytes(1024)
 
+	// Initialize all collectors
 	for _, c := range config.Collectors {
 		col := Collectors[c]
 		col.Init()
 		log.Print("Start ", col.Name())
 	}
 
-	log.Print(config.Interval, time.Duration(config.Interval)*time.Second)
+	// Setup up ticker loop
+	log.Print("Running loop every ", time.Duration(config.Interval)*time.Second)
 	ticker := time.NewTicker(time.Duration(config.Interval) * time.Second)
 	done := make(chan bool)
 
+	// Storage for all node metrics
 	nodeFields := make(map[string]interface{})
 
+	// Storage for all socket metrics
 	slist := collectors.SocketList()
 	socketsFields := make(map[int]map[string]interface{}, len(slist))
 	for _, s := range slist {
 		socketsFields[s] = make(map[string]interface{})
 	}
 
+	// Storage for all CPU metrics
 	clist := collectors.CpuList()
 	cpuFields := make(map[int]map[string]interface{}, len(clist))
 	for _, s := range clist {
@@ -130,9 +160,12 @@ func main() {
 			case <-done:
 				return
 			case t := <-ticker.C:
+				// Count how many socket and cpu metrics are returned
 				scount := 0
 				ccount := 0
 
+				// Read all collectors are sort the results in the right
+				// storage locations
 				for _, c := range config.Collectors {
 					col := Collectors[c]
 					col.Read(time.Duration(config.Duration))
@@ -153,15 +186,17 @@ func main() {
 						}
 					}
 				}
-
+				// Send out node metrics
 				setupProtocol("node", map[string]string{"host": host}, nodeFields, t)
 
+				// Send out socket metrics (if any)
 				if scount > 0 {
 					for sid, socket := range socketsFields {
 						setupProtocol("socket", map[string]string{"socket": fmt.Sprintf("%d", sid), "host": host}, socket, t)
 					}
 				}
 
+				// Send out CPU metrics (if any)
 				if ccount > 0 {
 					for cid, cpu := range cpuFields {
 						setupProtocol("cpu", map[string]string{"cpu": fmt.Sprintf("%d", cid), "host": host}, cpu, t)
@@ -171,5 +206,6 @@ func main() {
 		}
 	}()
 
+	// Wait until receiving an interrupt
 	wg.Wait()
 }