Implement rate limiting on log messages (#356)

Implement rate limiting on log messages

Addresses issue #317, where logs can get spammed with the same message
nonstop. Created a rate limiting closure on logging functions, which
limits the number of messages being logged per second based on format
string. To keep memory usage as constant as possible, the previous cache
purging at periodic time intervals has been replaced by an LRU that
discards the oldest string when the capacity of the cache is reached.


Signed-off-by: Wendi Yu <wendi.yu@yahoo.ca>

cmd/tailscaled/tailscaled.go

@@ -21,6 +21,7 @@ import (
 	"tailscale.com/ipn/ipnserver"
 	"tailscale.com/logpolicy"
 	"tailscale.com/paths"
+	"tailscale.com/types/logger"
 	"tailscale.com/wgengine"
 	"tailscale.com/wgengine/magicsock"
 )
@@ -51,6 +52,7 @@ func main() {
 	socketpath := getopt.StringLong("socket", 's', paths.DefaultTailscaledSocket(), "Path of the service unix socket")
 
 	logf := wgengine.RusagePrefixLog(log.Printf)
+	logf = logger.RateLimitedFn(logf, 1, 1, 100)
 
 	err := fixconsole.FixConsoleIfNeeded()
 	if err != nil {

ipn/e2e_test.go

@@ -23,6 +23,7 @@ import (
 	"tailscale.com/control/controlclient"
 	"tailscale.com/tailcfg"
 	"tailscale.com/tstest"
+	"tailscale.com/types/logger"
 	"tailscale.com/wgengine"
 	"tailscale.com/wgengine/magicsock"
 	"tailscale.com/wgengine/router"
@@ -191,12 +192,10 @@ type testNode struct {
 // Create a new IPN node.
 func newNode(t *testing.T, prefix string, https *httptest.Server, weirdPrefs bool) testNode {
 	t.Helper()
-	logfe := func(fmt string, args ...interface{}) {
-		t.Logf(prefix+".e: "+fmt, args...)
-	}
-	logf := func(fmt string, args ...interface{}) {
-		t.Logf(prefix+": "+fmt, args...)
-	}
+
+	logfe := logger.WithPrefix(t.Logf, prefix+"e: ")
+
+	logf := logger.WithPrefix(t.Logf, prefix+": ")
 
 	var err error
 	httpc := https.Client()

ipn/ipnserver/server_test.go

@@ -13,6 +13,8 @@ import (
 	"strings"
 	"testing"
 
+	"tailscale.com/types/logger"
+
 	"tailscale.com/ipn"
 	"tailscale.com/ipn/ipnserver"
 	"tailscale.com/safesocket"
@@ -32,12 +34,14 @@ func TestRunMultipleAccepts(t *testing.T) {
 	defer os.RemoveAll(td)
 	socketPath := filepath.Join(td, "tailscale.sock")
 
-	logf := func(format string, args ...interface{}) {
+	ulogf := func(format string, args ...interface{}) {
 		format = strings.TrimRight(format, "\n")
 		println(fmt.Sprintf(format, args...))
 		t.Logf(format, args...)
 	}
 
+	logf := logger.RateLimitedFn(ulogf, 1, 1, 100)
+
 	connect := func() {
 		for i := 1; i <= 2; i++ {
 			logf("connect %d ...", i)

types/logger/logger.go

@@ -8,12 +8,18 @@
 package logger
 
 import (
+	"container/list"
+	"fmt"
 	"io"
 	"log"
+	"sync"
+
+	"golang.org/x/time/rate"
 )
 
 // Logf is the basic Tailscale logger type: a printf-like func.
 // Like log.Printf, the format need not end in a newline.
+// Logf functions should be safe for concurrent use.
 type Logf func(format string, args ...interface{})
 
 // WithPrefix wraps f, prefixing each format with the provided prefix.
@@ -42,3 +48,56 @@ func (w funcWriter) Write(p []byte) (int, error) {
 
 // Discard is a Logf that throws away the logs given to it.
 func Discard(string, ...interface{}) {}
+
+// limitData is used to keep track of each format string's associated
+// rate-limiting data.
+type limitData struct {
+	lim        *rate.Limiter // the token bucket associated with this string
+	msgBlocked bool          // whether a "duplicate error" message has already been logged
+	ele        *list.Element // list element used to access this string in the cache
+}
+
+// RateLimitedFn implements rate limiting by fstring on a given Logf.
+// Messages are allowed through at a maximum of f messages/second, in
+// bursts of up to b messages at a time. Up to m strings will be held at a time.
+func RateLimitedFn(logf Logf, f float64, b int, m int) Logf {
+	r := rate.Limit(f)
+	msgLim := make(map[string]*limitData)
+	msgCache := list.New() // a rudimentary LRU that limits the size of the map
+	mu := &sync.Mutex{}
+
+	return func(format string, args ...interface{}) {
+		mu.Lock()
+		rl, ok := msgLim[format]
+		if ok {
+			msgCache.MoveToFront(rl.ele)
+			if rl.lim.Allow() {
+				mu.Lock()
+				rl.msgBlocked = false
+				mu.Unlock()
+				logf(format, args...)
+			} else {
+				if !rl.msgBlocked {
+					rl.msgBlocked = true
+					mu.Unlock()
+					logf("Repeated messages were suppressed by rate limiting. Original message: %s",
+						fmt.Sprintf(format, args...))
+				} else {
+					mu.Unlock()
+				}
+			}
+		} else {
+			msgLim[format] = &limitData{rate.NewLimiter(r, b), false, msgCache.PushFront(format)}
+			msgLim[format].lim.Allow()
+			mu.Unlock()
+			logf(format, args...)
+		}
+
+		mu.Lock()
+		if msgCache.Len() > m {
+			delete(msgLim, msgCache.Back().Value.(string))
+			msgCache.Remove(msgCache.Back())
+		}
+		mu.Unlock()
+	}
+}

types/logger/logger_test.go

@@ -5,6 +5,7 @@
 package logger
 
 import (
+	"fmt"
 	"log"
 	"testing"
 )
@@ -19,3 +20,43 @@ func TestStdLogger(t *testing.T) {
 	lg := StdLogger(t.Logf)
 	lg.Printf("plumbed through")
 }
+
+func TestRateLimiter(t *testing.T) {
+
+	// Testing function. args[0] should indicate what should
+	logTester := func(want []string) Logf {
+		i := 0
+		return func(format string, args ...interface{}) {
+			got := fmt.Sprintf(format, args...)
+			if i >= len(want) {
+				t.Fatalf("Logging continued past end of expected input: %s", got)
+			}
+			if got != want[i] {
+				t.Fatalf("wanted: %s \n got: %s", want[i], got)
+			}
+			i++
+		}
+	}
+
+	want := []string{
+		"boring string with constant formatting (constant)",
+		"templated format string no. 0",
+		"Repeated messages were suppressed by rate limiting. Original message: boring string with constant formatting (constant)",
+		"Repeated messages were suppressed by rate limiting. Original message: templated format string no. 1",
+		"Make sure this string makes it through the rest (that are blocked) 4",
+		"4 shouldn't get filtered.",
+	}
+
+	lg := RateLimitedFn(logTester(want), 1, 1, 50)
+	var prefixed Logf
+	for i := 0; i < 10; i++ {
+		lg("boring string with constant formatting %s", "(constant)")
+		lg("templated format string no. %d", i)
+		if i == 4 {
+			lg("Make sure this string makes it through the rest (that are blocked) %d", i)
+			prefixed = WithPrefix(lg, string('0'+i))
+			prefixed(" shouldn't get filtered.")
+		}
+	}
+
+}