Issue #238: Make route update logging format configurable

This patch makes the log format of routing table changes configurable.
The "delta" option logs the additions and deletions and is the new
default. The "full" option restores the previous behavior of logging the
full routing table.

config/config.go

@@ -56,6 +56,7 @@ type Proxy struct {
 	TLSHeader             string
 	TLSHeaderValue        string
 	GZIPContentTypes      *regexp.Regexp
+	LogRoutes             string
 }
 
 type Runtime struct {

config/default.go

@@ -25,6 +25,7 @@ var defaultConfig = &Config{
 		DialTimeout:   30 * time.Second,
 		FlushInterval: time.Second,
 		LocalIP:       LocalIPString(),
+		LogRoutes:     "delta",
 	},
 	Registry: Registry{
 		Backend: "consul",

config/load.go

@@ -131,6 +131,7 @@ func load(cmdline, environ, envprefix []string, props *properties.Properties) (c
 	f.DurationVar(&readTimeout, "proxy.readtimeout", defaultValues.ReadTimeout, "read timeout for incoming requests")
 	f.DurationVar(&writeTimeout, "proxy.writetimeout", defaultValues.WriteTimeout, "write timeout for outgoing responses")
 	f.DurationVar(&cfg.Proxy.FlushInterval, "proxy.flushinterval", defaultConfig.Proxy.FlushInterval, "flush interval for streaming responses")
+	f.StringVar(&cfg.Proxy.LogRoutes, "proxy.log.routes", defaultConfig.Proxy.LogRoutes, "log format of routing table updates")
 	f.StringVar(&cfg.Metrics.Target, "metrics.target", defaultConfig.Metrics.Target, "metrics backend")
 	f.StringVar(&cfg.Metrics.Prefix, "metrics.prefix", defaultConfig.Metrics.Prefix, "prefix for reported metrics")
 	f.StringVar(&cfg.Metrics.Names, "metrics.names", defaultConfig.Metrics.Names, "route metric name template")

config/load_test.go

@@ -288,6 +288,13 @@ func TestLoad(t *testing.T) {
 				return cfg
 			},
 		},
+		{
+			args: []string{"-proxy.log.routes", "foobar"},
+			cfg: func(cfg *Config) *Config {
+				cfg.Proxy.LogRoutes = "foobar"
+				return cfg
+			},
+		},
 		{
 			args: []string{"-registry.backend", "value"},
 			cfg: func(cfg *Config) *Config {

fabio.properties

@@ -371,6 +371,19 @@
 # proxy.gzip.contenttype =
 
 
+# proxy.log.routes configures the log output format of routing table updates.
+#
+# Changes to the routing table are written to the standard log. This option
+# configures the output format:
+#
+# delta:    additions and deletions
+# all:      complete routing table
+#
+# The default is
+#
+# proxy.log.routes = delta
+
+
 # registry.backend configures which backend is used.
 # Supported backends are: consul, static, file
 #

main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
 	"log"
@@ -9,6 +10,7 @@ import (
 	"os"
 	"runtime"
 	"runtime/debug"
+	"strings"
 
 	"github.com/eBay/fabio/admin"
 	"github.com/eBay/fabio/config"
@@ -20,6 +22,7 @@ import (
 	"github.com/eBay/fabio/registry/file"
 	"github.com/eBay/fabio/registry/static"
 	"github.com/eBay/fabio/route"
+	dmp "github.com/sergi/go-diff/diffmatchpatch"
 )
 
 // version contains the version number
@@ -59,7 +62,7 @@ func main() {
 
 	initRuntime(cfg)
 	initBackend(cfg)
-	go watchBackend()
+	go watchBackend(cfg)
 	startAdmin(cfg)
 
 	// create proxies after metrics since they use the metrics registry.
@@ -161,7 +164,7 @@ func initBackend(cfg *config.Config) {
 	}
 }
 
-func watchBackend() {
+func watchBackend(cfg *config.Config) {
 	var (
 		last   string
 		svccfg string
@@ -190,12 +193,47 @@ func watchBackend() {
 			continue
 		}
 		route.SetTable(t)
-		log.Printf("[INFO] Updated config to\n%s", t)
-
+		logRoutes(last, next, cfg.Proxy.LogRoutes)
 		last = next
 	}
 }
 
+func logRoutes(last, next, format string) {
+	fmtDiff := func(diffs []dmp.Diff) string {
+		var b bytes.Buffer
+		for _, d := range diffs {
+			t := strings.TrimSpace(d.Text)
+			if t == "" {
+				continue
+			}
+			switch d.Type {
+			case dmp.DiffDelete:
+				b.WriteString("- ")
+				b.WriteString(strings.Replace(t, "\n", "\n- ", -1))
+			case dmp.DiffInsert:
+				b.WriteString("+ ")
+				b.WriteString(strings.Replace(t, "\n", "\n+ ", -1))
+			}
+		}
+		return b.String()
+	}
+
+	const defFormat = "delta"
+	switch format {
+	case "delta":
+		if delta := fmtDiff(dmp.New().DiffMain(last, next, true)); delta != "" {
+			log.Printf("[INFO] Config updates\n%s", delta)
+		}
+
+	case "all":
+		log.Printf("[INFO] Updated config to\n%s", next)
+
+	default:
+		log.Printf("[WARN] Invalid route format %q. Defaulting to %q", format, defFormat)
+		logRoutes(last, next, defFormat)
+	}
+}
+
 func toJSON(v interface{}) string {
 	data, err := json.MarshalIndent(v, "", "    ")
 	if err != nil {