Added an option to specify metrics log file

Previously the metrics log file was hardcoded and the broker wasn't
behaving properly if it was unable to open the file for logging.

Added a commandline option to specify the logfile that defaults to
Stdout.

Fixed up some documentation and log output formatting

broker/broker.go

@@ -10,6 +10,7 @@ import (
 	"crypto/tls"
 	"flag"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"log"
 	"net"
@@ -37,10 +38,10 @@ type BrokerContext struct {
 	metrics       *Metrics
 }
 
-func NewBrokerContext() *BrokerContext {
+func NewBrokerContext(metricsLogger *log.Logger) *BrokerContext {
 	snowflakes := new(SnowflakeHeap)
 	heap.Init(snowflakes)
-	metrics, err := NewMetrics()
+	metrics, err := NewMetrics(metricsLogger)
 
 	if err != nil {
 		panic(err.Error())
@@ -253,6 +254,7 @@ func main() {
 	var geoip6Database string
 	var disableTLS bool
 	var disableGeoip bool
+	var metricsFilename string
 
 	flag.StringVar(&acmeEmail, "acme-email", "", "optional contact email for Let's Encrypt notifications")
 	flag.StringVar(&acmeHostnamesCommas, "acme-hostnames", "", "comma-separated hostnames for TLS certificate")
@@ -261,11 +263,27 @@ func main() {
 	flag.StringVar(&geoip6Database, "geoip6db", "/usr/share/tor/geoip6", "path to correctly formatted geoip database mapping IPv6 address ranges to country codes")
 	flag.BoolVar(&disableTLS, "disable-tls", false, "don't use HTTPS")
 	flag.BoolVar(&disableGeoip, "disable-geoip", false, "don't use geoip for stats collection")
+	flag.StringVar(&metricsFilename, "metrics-log", "", "path to metrics logging output")
 	flag.Parse()
 
+	var metricsFile io.Writer = os.Stdout
+	var err error
+
 	log.SetFlags(log.LstdFlags | log.LUTC)
 
-	ctx := NewBrokerContext()
+	if metricsFilename != "" {
+		metricsFile, err = os.OpenFile(metricsFilename, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
+
+		if err != nil {
+			log.Fatal(err.Error())
+		}
+	} else {
+		metricsFile = os.Stdout
+	}
+
+	metricsLogger := log.New(metricsFile, "", log.LstdFlags|log.LUTC)
+
+	ctx := NewBrokerContext(metricsLogger)
 
 	if !disableGeoip {
 		err := ctx.metrics.LoadGeoipDatabases(geoipDatabase, geoip6Database)
@@ -283,7 +301,6 @@ func main() {
 	http.Handle("/answer", SnowflakeHandler{ctx, proxyAnswers})
 	http.Handle("/debug", SnowflakeHandler{ctx, debugHandler})
 
-	var err error
 	server := http.Server{
 		Addr: addr,
 	}

broker/geoip.go

@@ -209,7 +209,8 @@ func GeoIPLoadFile(table GeoIPTable, pathname string) error {
 	return nil
 }
 
-//Returns the country location of an IPv4 or IPv6 address.
+//Returns the country location of an IPv4 or IPv6 address, and a boolean value
+//that indicates whether the IP address was present in the geoip database
 func GetCountryByAddr(table GeoIPTable, ip net.IP) (string, bool) {
 
 	table.Lock()

broker/metrics.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"log"
 	"net"
-	"os"
 	"sync"
 	"time"
 )
@@ -28,7 +27,7 @@ type Metrics struct {
 }
 
 func (s CountryStats) Display() string {
-	return fmt.Sprintln(s.counts)
+	return fmt.Sprint(s.counts)
 }
 
 func (m *Metrics) UpdateCountryStats(addr string) {
@@ -56,9 +55,7 @@ func (m *Metrics) UpdateCountryStats(addr string) {
 	}
 
 	//update map of countries and counts
-	if country != "" {
 	m.countryStats.counts[country]++
-	}
 
 	return
 }
@@ -88,17 +85,9 @@ func (m *Metrics) LoadGeoipDatabases(geoipDB string, geoip6DB string) error {
 	return nil
 }
 
-func NewMetrics() (*Metrics, error) {
+func NewMetrics(metricsLogger *log.Logger) (*Metrics, error) {
 	m := new(Metrics)
 
-	f, err := os.OpenFile("metrics.log", os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
-
-	if err != nil {
-		return nil, err
-	}
-
-	metricsLogger := log.New(f, "", log.LstdFlags|log.LUTC)
-
 	m.countryStats = CountryStats{
 		counts: make(map[string]int),
 	}