Issue #147: Support multiple metrics libraries

metrics/gometrics/provider.go

@@ -0,0 +1,91 @@
+// Package gometrics provides an implementation of the
+// metricslib.Provider interface using the github.com/rcrowley/go-metrics
+// library.
+package gometrics
+
+import (
+	"errors"
+	"fmt"
+	"log"
+	"net"
+	"os"
+	"sort"
+	"time"
+
+	"github.com/eBay/fabio/metrics/metricslib"
+
+	graphite "github.com/cyberdelia/go-metrics-graphite"
+	statsd "github.com/pubnub/go-metrics-statsd"
+	gm "github.com/rcrowley/go-metrics"
+)
+
+// StdoutProvider returns a provider that reports to stdout.
+func StdoutProvider(interval time.Duration) (metricslib.Provider, error) {
+	registry := gm.NewRegistry()
+	logger := log.New(os.Stderr, "localhost: ", log.Lmicroseconds)
+	go gm.Log(gm.DefaultRegistry, interval, logger)
+	go gm.Log(registry, interval, logger)
+	return &gmProvider{registry}, nil
+}
+
+// GraphiteProvider returns a provider that reports to a Graphite server.
+func GraphiteProvider(prefix, addr string, interval time.Duration) (metricslib.Provider, error) {
+	if addr == "" {
+		return nil, errors.New("metrics: graphite addr missing")
+	}
+
+	a, err := net.ResolveTCPAddr("tcp", addr)
+	if err != nil {
+		return nil, fmt.Errorf("metrics: cannot connect to Graphite: %s", err)
+	}
+
+	registry := gm.NewRegistry()
+	go graphite.Graphite(gm.DefaultRegistry, interval, prefix, a)
+	go graphite.Graphite(registry, interval, prefix, a)
+	return &gmProvider{registry}, nil
+}
+
+// StatsDProvider returns a provider that reports to a StatsD server.
+func StatsDProvider(prefix, addr string, interval time.Duration) (metricslib.Provider, error) {
+	if addr == "" {
+		return nil, errors.New("metrics: statsd addr missing")
+	}
+
+	a, err := net.ResolveUDPAddr("udp", addr)
+	if err != nil {
+		return nil, fmt.Errorf("metrics: cannot connect to StatsD: %s", err)
+	}
+
+	registry := gm.NewRegistry()
+	go statsd.StatsD(gm.DefaultRegistry, interval, prefix, a)
+	go statsd.StatsD(registry, interval, prefix, a)
+	return &gmProvider{registry}, nil
+}
+
+// gmProvider implements the metricslib.Provider interface
+// using the github.com/rcrowley/go-metrics library.
+type gmProvider struct {
+	// registry keeps track of registered metrics values
+	// to keep them separate from the default metrics.
+	registry gm.Registry
+}
+
+func (p *gmProvider) Names() (names []string) {
+	p.registry.Each(func(name string, _ interface{}) {
+		names = append(names, name)
+	})
+	sort.Strings(names)
+	return names
+}
+
+func (p *gmProvider) Unregister(name string) {
+	p.registry.Unregister(name)
+}
+
+func (p *gmProvider) UnregisterAll() {
+	p.registry.UnregisterAll()
+}
+
+func (p *gmProvider) GetTimer(name string) metricslib.Timer {
+	return gm.GetOrRegisterTimer(name, p.registry)
+}

metrics/metrics.go

@@ -1,63 +1,86 @@
+// Package metrics provides functions for collecting
+// and managing metrics through different metrics libraries.
+//
+// Metrics library implementations must implement the
+// Provider interface in the metricslib package.
+//
+// The current implementation supports only a single
+// metrics provider.
 package metrics
 
 import (
-	"errors"
-	"fmt"
 	"log"
-	"net"
 	"net/url"
 	"os"
 	"path/filepath"
 	"strings"
-	"time"
 
-	"github.com/cyberdelia/go-metrics-graphite"
 	"github.com/eBay/fabio/config"
 	"github.com/eBay/fabio/exit"
-	"github.com/pubnub/go-metrics-statsd"
-	gometrics "github.com/rcrowley/go-metrics"
+	"github.com/eBay/fabio/metrics/gometrics"
+	"github.com/eBay/fabio/metrics/metricslib"
 )
 
-var pfx string
+// Provider stores the metrics library provider.
+var Provider metricslib.Provider = metricslib.NoopProvider{}
 
-// ServiceRegistry contains a separate metrics registry for
-// the timers for all targets to avoid conflicts
-// with globally registered timers.
-var ServiceRegistry = gometrics.NewRegistry()
+// Names returns the list of registered metrics acquired
+// through the GetXXX() functions in alphabetical order.
+func Names() []string { return Provider.Names() }
 
+// Unregister removes the registered metric and stops
+// reporting it to an external backend.
+func Unregister(name string) { Provider.Unregister(name) }
+
+// UnregisterAll removes all registered metrics and stops
+// reporting  them to an external backend.
+func UnregisterAll() { Provider.UnregisterAll() }
+
+// GetTimer returns a timer metric for the given name.
+// If the metric does not exist yet it should be created
+// otherwise the existing metric should be returned.
+func GetTimer(name string) metricslib.Timer { return Provider.GetTimer(name) }
+
+// prefix stores the prefix for all metrics names.
+var prefix string
+
+// Init configures the metrics library provider and starts reporting.
 func Init(cfg config.Metrics) error {
-	pfx = cfg.Prefix
-	if pfx == "default" {
-		pfx = defaultPrefix()
+	prefix = cfg.Prefix
+	if prefix == "default" {
+		prefix = defaultPrefix()
 	}
 
+	var err error
 	switch cfg.Target {
 	case "stdout":
+		if Provider, err = gometrics.StdoutProvider(cfg.Interval); err != nil {
+			return err
+		}
 		log.Printf("[INFO] Sending metrics to stdout")
-		return initStdout(cfg.Interval)
+
 	case "graphite":
-		if cfg.GraphiteAddr == "" {
-			return errors.New("metrics: graphite addr missing")
+		if Provider, err = gometrics.GraphiteProvider(prefix, cfg.GraphiteAddr, cfg.Interval); err != nil {
+			return err
 		}
+		log.Printf("[INFO] Sending metrics to Graphite on %s as %q", cfg.GraphiteAddr, prefix)
 
-		log.Printf("[INFO] Sending metrics to Graphite on %s as %q", cfg.GraphiteAddr, pfx)
-		return initGraphite(cfg.GraphiteAddr, cfg.Interval)
 	case "statsd":
-		if cfg.StatsDAddr == "" {
-			return errors.New("metrics: statsd addr missing")
+		if Provider, err = gometrics.StatsDProvider(prefix, cfg.StatsDAddr, cfg.Interval); err != nil {
+			return err
 		}
-
-		log.Printf("[INFO] Sending metrics to StatsD on %s as %q", cfg.StatsDAddr, pfx)
-		return initStatsD(cfg.StatsDAddr, cfg.Interval)
+		log.Printf("[INFO] Sending metrics to StatsD on %s as %q", cfg.StatsDAddr, prefix)
 
 	case "":
 		log.Printf("[INFO] Metrics disabled")
+
 	default:
 		exit.Fatal("[FATAL] Invalid metrics target ", cfg.Target)
 	}
 	return nil
 }
 
+// TargetName returns the metrics name from the given parameters.
 func TargetName(service, host, path string, targetURL *url.URL) string {
 	return strings.Join([]string{
 		clean(service),
@@ -67,6 +90,9 @@ func TargetName(service, host, path string, targetURL *url.URL) string {
 	}, ".")
 }
 
+// clean creates safe names for graphite reporting by replacing
+// some characters with underscores.
+// TODO(fs): This may need updating for other metrics backends.
 func clean(s string) string {
 	if s == "" {
 		return "_"
@@ -79,6 +105,8 @@ func clean(s string) string {
 // stubbed out for testing
 var hostname = os.Hostname
 
+// defaultPrefix determines the default metrics prefix from
+// the current hostname and the name of the executable.
 func defaultPrefix() string {
 	host, err := hostname()
 	if err != nil {
@@ -87,31 +115,3 @@ func defaultPrefix() string {
 	exe := filepath.Base(os.Args[0])
 	return clean(host) + "." + clean(exe)
 }
-
-func initStdout(interval time.Duration) error {
-	logger := log.New(os.Stderr, "localhost: ", log.Lmicroseconds)
-	go gometrics.Log(gometrics.DefaultRegistry, interval, logger)
-	go gometrics.Log(ServiceRegistry, interval, logger)
-	return nil
-}
-
-func initGraphite(addr string, interval time.Duration) error {
-	a, err := net.ResolveTCPAddr("tcp", addr)
-	if err != nil {
-		return fmt.Errorf("metrics: cannot connect to Graphite: %s", err)
-	}
-
-	go graphite.Graphite(gometrics.DefaultRegistry, interval, pfx, a)
-	go graphite.Graphite(ServiceRegistry, interval, pfx, a)
-	return nil
-}
-
-func initStatsD(addr string, interval time.Duration) error {
-	a, err := net.ResolveUDPAddr("udp", addr)
-	if err != nil {
-		return fmt.Errorf("metrics: cannot connect to StatsD: %s", err)
-	}
-	go statsd.StatsD(gometrics.DefaultRegistry, interval, pfx, a)
-	go statsd.StatsD(ServiceRegistry, interval, pfx, a)
-	return nil
-}

metrics/metricslib/noop.go

@@ -0,0 +1,25 @@
+package metricslib
+
+import "time"
+
+// NoopProvider is a stub implementation of the Provider interface.
+type NoopProvider struct{}
+
+func (p NoopProvider) Names() []string { return nil }
+
+func (p NoopProvider) Unregister(name string) {}
+
+func (p NoopProvider) UnregisterAll() {}
+
+func (p NoopProvider) GetTimer(name string) Timer { return noopTimer }
+
+var noopTimer = NoopTimer{}
+
+// NoopTimer is a stub implementation of the Timer interface.
+type NoopTimer struct{}
+
+func (t NoopTimer) UpdateSince(start time.Time) {}
+
+func (t NoopTimer) Rate1() float64 { return 0 }
+
+func (t NoopTimer) Percentile(nth float64) float64 { return 0 }

metrics/metricslib/provider.go

@@ -0,0 +1,41 @@
+// Package metricslib defines the common interfaces for
+// different metrics libraries.
+package metricslib
+
+import "time"
+
+// Provider defines a common interface for metric libraries.
+// An implementation must be safe to be used by multiple
+// go routines.
+type Provider interface {
+	// Names returns the list of registered metrics acquired
+	// through the GetXXX() functions. It should return them
+	// sorted in alphabetical order.
+	Names() []string
+
+	// Unregister removes the registered metric and stops
+	// reporting it to an external backend.
+	Unregister(name string)
+
+	// UnregisterAll removes all registered metrics and stops
+	// reporting  them to an external backend.
+	UnregisterAll()
+
+	// GetTimer returns a timer metric for the given name.
+	// If the metric does not exist yet it should be created
+	// otherwise the existing metric should be returned.
+	GetTimer(name string) Timer
+}
+
+// Timer defines a metric for counting and timing durations for events.
+type Timer interface {
+	// Percentile returns the nth percentile of the duration.
+	Percentile(nth float64) float64
+
+	// Rate1 returns the 1min rate.
+	Rate1() float64
+
+	// UpdateSince counts an event and records the duration
+	// as the delta between 'start' and the function is called.
+	UpdateSince(start time.Time)
+}

proxy/proxy.go

@@ -5,22 +5,22 @@ import (
 	"time"
 
 	"github.com/eBay/fabio/config"
-
-	gometrics "github.com/rcrowley/go-metrics"
+	"github.com/eBay/fabio/metrics"
+	"github.com/eBay/fabio/metrics/metricslib"
 )
 
 // Proxy is a dynamic reverse proxy.
 type Proxy struct {
 	tr       http.RoundTripper
 	cfg      config.Proxy
-	requests gometrics.Timer
+	requests metricslib.Timer
 }
 
 func New(tr http.RoundTripper, cfg config.Proxy) *Proxy {
 	return &Proxy{
 		tr:       tr,
 		cfg:      cfg,
-		requests: gometrics.GetOrRegisterTimer("requests", gometrics.DefaultRegistry),
+		requests: metrics.GetTimer("requests"),
 	}
 }
 

route/route.go

@@ -7,8 +7,6 @@ import (
 	"strings"
 
 	"github.com/eBay/fabio/metrics"
-
-	gometrics "github.com/rcrowley/go-metrics"
 )
 
 // Route maps a path prefix to one or more target URLs.
@@ -49,7 +47,7 @@ func (r *Route) addTarget(service string, targetURL *url.URL, fixedWeight float6
 	}
 
 	name := metrics.TargetName(service, r.Host, r.Path, targetURL)
-	timer := gometrics.GetOrRegisterTimer(name, metrics.ServiceRegistry)
+	timer := metrics.GetTimer(name)
 
 	t := &Target{Service: service, Tags: tags, URL: targetURL, FixedWeight: fixedWeight, Timer: timer, timerName: name}
 	r.Targets = append(r.Targets, t)

route/table.go

@@ -58,9 +58,9 @@ func syncRegistry(t Table) {
 	timers := map[string]bool{}
 
 	// get all registered timers
-	metrics.ServiceRegistry.Each(func(name string, m interface{}) {
+	for _, name := range metrics.Names() {
 		timers[name] = false
-	})
+	}
 
 	// mark the ones from this table as active.
 	// this can also add new entries but we do not
@@ -77,7 +77,7 @@ func syncRegistry(t Table) {
 	// unregister inactive timers
 	for name, active := range timers {
 		if !active {
-			metrics.ServiceRegistry.Unregister(name)
+			metrics.Unregister(name)
 			log.Printf("[INFO] Unregistered timer %s", name)
 		}
 	}