Simplify HTTP trace related code (#7833)

cmd/admin-handlers.go

@@ -43,6 +43,7 @@ import (
 	"github.com/minio/minio/pkg/mem"
 	xnet "github.com/minio/minio/pkg/net"
 	"github.com/minio/minio/pkg/quick"
+	trace "github.com/minio/minio/pkg/trace"
 )
 
 const (
@@ -1483,11 +1484,6 @@ func (a adminAPIHandlers) TraceHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if globalTrace == nil {
-		writeErrorResponseJSON(ctx, w, errorCodes.ToAPIErr(ErrServerNotInitialized), r.URL)
-		return
-	}
-
 	// Avoid reusing tcp connection if read timeout is hit
 	// This is needed to make r.Context().Done() work as
 	// expected in case of read timeout
@@ -1496,14 +1492,33 @@ func (a adminAPIHandlers) TraceHandler(w http.ResponseWriter, r *http.Request) {
 	doneCh := make(chan struct{})
 	defer close(doneCh)
 
-	traceCh := globalTrace.Trace(doneCh, trcAll)
+	// Trace Publisher and peer-trace-client uses nonblocking send and hence does not wait for slow receivers.
+	// Use buffered channel to take care of burst sends or slow w.Write()
+	traceCh := make(chan interface{}, 4000)
+
+	filter := func(entry interface{}) bool {
+		if trcAll {
+			return true
+		}
+		trcInfo := entry.(trace.Info)
+		return !strings.HasPrefix(trcInfo.ReqInfo.Path, minioReservedBucketPath)
+	}
+	remoteHosts := getRemoteHosts(globalEndpoints)
+	peers, err := getRestClients(remoteHosts)
+	if err != nil {
+		return
+	}
+	globalHTTPTrace.Subscribe(traceCh, doneCh, filter)
+
+	for _, peer := range peers {
+		peer.Trace(traceCh, doneCh, trcAll)
+	}
+
+	enc := json.NewEncoder(w)
 	for {
 		select {
 		case entry := <-traceCh:
-			if _, err := w.Write(entry); err != nil {
+			if err := enc.Encode(entry); err != nil {
-				return
-			}
-			if _, err := w.Write([]byte("\n")); err != nil {
 				return
 			}
 			w.(http.Flusher).Flush()

cmd/gateway-main.go

@@ -158,9 +158,6 @@ func StartGateway(ctx *cli.Context, gw Gateway) {
 		registerSTSRouter(router)
 	}
 
-	// initialize globalTrace system
-	globalTrace = NewTraceSys(context.Background(), globalEndpoints)
-
 	enableConfigOps := globalEtcdClient != nil && gatewayName == "nas"
 	enableIAMOps := globalEtcdClient != nil
 

cmd/globals.go

@@ -35,6 +35,7 @@ import (
 	"github.com/minio/minio/pkg/dns"
 	iampolicy "github.com/minio/minio/pkg/iam/policy"
 	"github.com/minio/minio/pkg/iam/validator"
+	"github.com/minio/minio/pkg/pubsub"
 )
 
 // minio configuration related constants.
@@ -161,7 +162,7 @@ var (
 
 	// global Trace system to send HTTP request/response logs to
 	// registered listeners
-	globalTrace *HTTPTraceSys
+	globalHTTPTrace = pubsub.New()
 
 	globalEndpoints EndpointList
 

cmd/handler-utils.go

@@ -326,24 +326,24 @@ func extractPostPolicyFormValues(ctx context.Context, form *multipart.Form) (fil
 // Log headers and body.
 func httpTraceAll(f http.HandlerFunc) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		if !globalTrace.HasTraceListeners() {
+		if !globalHTTPTrace.HasSubscribers() {
 			f.ServeHTTP(w, r)
 			return
 		}
 		trace := Trace(f, true, w, r)
-		globalTrace.Publish(trace)
+		globalHTTPTrace.Publish(trace)
 	}
 }
 
 // Log only the headers.
 func httpTraceHdrs(f http.HandlerFunc) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		if !globalTrace.HasTraceListeners() {
+		if !globalHTTPTrace.HasSubscribers() {
 			f.ServeHTTP(w, r)
 			return
 		}
 		trace := Trace(f, false, w, r)
-		globalTrace.Publish(trace)
+		globalHTTPTrace.Publish(trace)
 	}
 }
 

cmd/httptrace.go

@@ -1,115 +0,0 @@
-/*
- * MinIO Cloud Storage, (C) 2019 MinIO, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package cmd
-
-import (
-	"bytes"
-	"context"
-	"encoding/json"
-	"strings"
-	"sync"
-
-	"github.com/minio/minio/cmd/logger"
-	"github.com/minio/minio/pkg/pubsub"
-	"github.com/minio/minio/pkg/trace"
-)
-
-//HTTPTraceSys holds global trace state
-type HTTPTraceSys struct {
-	peers  []*peerRESTClient
-	pubsub *pubsub.PubSub
-}
-
-// NewTraceSys - creates new HTTPTraceSys with all nodes subscribed to
-// the trace pub sub system
-func NewTraceSys(ctx context.Context, endpoints EndpointList) *HTTPTraceSys {
-	remoteHosts := getRemoteHosts(endpoints)
-	remoteClients, err := getRestClients(remoteHosts)
-	if err != nil {
-		logger.FatalIf(err, "Unable to start httptrace sub system")
-	}
-
-	ps := pubsub.New()
-	return &HTTPTraceSys{
-		remoteClients, ps,
-	}
-}
-
-// HasTraceListeners returns true if trace listeners are registered
-// for this node or peers
-func (sys *HTTPTraceSys) HasTraceListeners() bool {
-	return sys != nil && sys.pubsub.HasSubscribers()
-}
-
-// Publish - publishes trace message to the http trace pubsub system
-func (sys *HTTPTraceSys) Publish(traceMsg trace.Info) {
-	sys.pubsub.Publish(traceMsg)
-}
-
-// Trace writes http trace to writer
-func (sys *HTTPTraceSys) Trace(doneCh chan struct{}, trcAll bool) chan []byte {
-	traceCh := make(chan []byte)
-	go func() {
-		defer close(traceCh)
-
-		var wg = &sync.WaitGroup{}
-		wg.Add(1)
-		go func() {
-			defer wg.Done()
-
-			buf := &bytes.Buffer{}
-			ch := sys.pubsub.Subscribe()
-			defer sys.pubsub.Unsubscribe(ch)
-			for {
-				select {
-				case entry := <-ch:
-					trcInfo := entry.(trace.Info)
-					path := strings.TrimPrefix(trcInfo.ReqInfo.Path, "/")
-					// omit inter-node traffic if trcAll is false
-					if !trcAll && strings.HasPrefix(path, minioReservedBucket) {
-						continue
-					}
-					buf.Reset()
-					enc := json.NewEncoder(buf)
-					enc.SetEscapeHTML(false)
-					if err := enc.Encode(trcInfo); err != nil {
-						continue
-					}
-					traceCh <- buf.Bytes()
-				case <-doneCh:
-					return
-				}
-			}
-		}()
-
-		for _, peer := range sys.peers {
-			wg.Add(1)
-			go func(peer *peerRESTClient) {
-				defer wg.Done()
-				ch, err := peer.Trace(doneCh, trcAll)
-				if err != nil {
-					return
-				}
-				for entry := range ch {
-					traceCh <- entry
-				}
-			}(peer)
-		}
-		wg.Wait()
-	}()
-	return traceCh
-}

cmd/peer-rest-client.go

@@ -17,7 +17,6 @@
 package cmd
 
 import (
-	"bufio"
 	"bytes"
 	"context"
 	"crypto/tls"
@@ -34,6 +33,7 @@ import (
 	"github.com/minio/minio/pkg/madmin"
 	xnet "github.com/minio/minio/pkg/net"
 	"github.com/minio/minio/pkg/policy"
+	trace "github.com/minio/minio/pkg/trace"
 )
 
 // client to talk to peer Nodes.
@@ -435,52 +435,59 @@ func (client *peerRESTClient) BackgroundHealStatus() (madmin.BgHealState, error)
 	return state, err
 }
 
-// Trace - send http trace request to peer nodes
+func (client *peerRESTClient) doTrace(traceCh chan interface{}, doneCh chan struct{}, trcAll bool) {
-func (client *peerRESTClient) Trace(doneCh chan struct{}, trcAll bool) (chan []byte, error) {
-	ch := make(chan []byte)
-	go func() {
-		cleanupFn := func(cancel context.CancelFunc, ch chan []byte, respBody io.ReadCloser) {
-			close(ch)
-			if cancel != nil {
-				cancel()
-			}
-			http.DrainBody(respBody)
-		}
-		for {
 	values := make(url.Values)
 	values.Set(peerRESTTraceAll, strconv.FormatBool(trcAll))
-			// get cancellation context to properly unsubscribe peers
+
+	// To cancel the REST request in case doneCh gets closed.
 	ctx, cancel := context.WithCancel(context.Background())
-			respBody, err := client.callWithContext(ctx, peerRESTMethodTrace, values, nil, -1)
+
-			if err != nil {
+	cancelCh := make(chan struct{})
-				//retry
+	defer close(cancelCh)
-				time.Sleep(5 * time.Second)
+	go func() {
 		select {
 		case <-doneCh:
-					cleanupFn(cancel, ch, respBody)
+		case <-cancelCh:
+			// There was an error in the REST request.
+		}
+		cancel()
+	}()
+
+	respBody, err := client.callWithContext(ctx, peerRESTMethodTrace, values, nil, -1)
+	defer http.DrainBody(respBody)
+
+	if err != nil {
 		return
+	}
+
+	dec := gob.NewDecoder(respBody)
+	for {
+		var info trace.Info
+		if err = dec.Decode(&info); err != nil {
+			return
+		}
+		select {
+		case traceCh <- info:
 		default:
+			// Do not block on slow receivers.
 		}
-				continue
 	}
-			bio := bufio.NewScanner(respBody)
+}
+
+// Trace - send http trace request to peer nodes
+func (client *peerRESTClient) Trace(traceCh chan interface{}, doneCh chan struct{}, trcAll bool) {
 	go func() {
-				<-doneCh
+		for {
-				cancel()
+			client.doTrace(traceCh, doneCh, trcAll)
-			}()
-			// Unmarshal each line, returns marshaled values.
-			for bio.Scan() {
-				ch <- bio.Bytes()
-			}
 			select {
 			case <-doneCh:
-				cleanupFn(cancel, ch, respBody)
 				return
 			default:
+				// There was error in the REST request, retry after sometime as probably the peer is down.
+				time.Sleep(5 * time.Second)
 			}
 		}
 	}()
-	return ch, nil
 }
 
 func getRemoteHosts(endpoints EndpointList) []*xnet.Host {

cmd/peer-rest-server.go

@@ -19,7 +19,6 @@ package cmd
 import (
 	"context"
 	"encoding/gob"
-	"encoding/json"
 	"errors"
 	"fmt"
 	"net/http"
@@ -679,32 +678,33 @@ func (s *peerRESTServer) TraceHandler(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Connection", "close")
 	w.WriteHeader(http.StatusOK)
 	w.(http.Flusher).Flush()
-	ch := globalTrace.pubsub.Subscribe()
-	defer globalTrace.pubsub.Unsubscribe(ch)
 
-	enc := json.NewEncoder(w)
+	filter := func(entry interface{}) bool {
-	enc.SetEscapeHTML(false)
+		if trcAll {
-	for {
+			return true
-		select {
+		}
-		case entry := <-ch:
 		trcInfo := entry.(trace.Info)
-			path := strings.TrimPrefix(trcInfo.ReqInfo.Path, "/")
+		return !strings.HasPrefix(trcInfo.ReqInfo.Path, minioReservedBucketPath)
-			// omit inter-node traffic if trcAll is false
-			if !trcAll && strings.HasPrefix(path, minioReservedBucket) {
-				continue
 	}
 
-			if err := enc.Encode(trcInfo); err != nil {
+	doneCh := make(chan struct{})
-				return
+	defer close(doneCh)
-			}
+
+	// Trace Publisher uses nonblocking publish and hence does not wait for slow subscribers.
+	// Use buffered channel to take care of burst sends or slow w.Write()
+	ch := make(chan interface{}, 2000)
+	globalHTTPTrace.Subscribe(ch, doneCh, filter)
 
-			if _, err := w.Write([]byte("\n")); err != nil {
+	enc := gob.NewEncoder(w)
+	for {
+		select {
+		case entry := <-ch:
+			if err := enc.Encode(entry); err != nil {
 				return
 			}
 			w.(http.Flusher).Flush()
 		case <-r.Context().Done():
 			return
-
 		}
 	}
 }

cmd/server-main.go

@@ -294,9 +294,6 @@ func serverMain(ctx *cli.Context) {
 		globalSweepHealState = initHealState()
 	}
 
-	// initialize globalTrace system
-	globalTrace = NewTraceSys(context.Background(), globalEndpoints)
-
 	// Configure server.
 	var handler http.Handler
 	handler, err = configureServerHandler(globalEndpoints)

pkg/madmin/api-trace.go

@@ -17,9 +17,7 @@
 package madmin
 
 import (
-	"bufio"
 	"encoding/json"
-	"io"
 	"net/http"
 	"net/url"
 	"strconv"
@@ -35,7 +33,7 @@ type TraceInfo struct {
 
 // Trace - listen on http trace notifications.
 func (adm AdminClient) Trace(allTrace bool, doneCh <-chan struct{}) <-chan TraceInfo {
-	traceInfoCh := make(chan TraceInfo, 1)
+	traceInfoCh := make(chan TraceInfo)
 	// Only success, start a routine to start reading line by line.
 	go func(traceInfoCh chan<- TraceInfo) {
 		defer close(traceInfoCh)
@@ -58,30 +56,16 @@ func (adm AdminClient) Trace(allTrace bool, doneCh <-chan struct{}) <-chan Trace
 				return
 			}
 
-			// Initialize a new bufio scanner, to read line by line.
+			dec := json.NewDecoder(resp.Body)
-			bio := bufio.NewScanner(resp.Body)
+			for {
-
+				var info trace.Info
-			// Close the response body.
+				if err = dec.Decode(&info); err != nil {
-			defer resp.Body.Close()
+					break
-
-			// Unmarshal each line, returns marshaled values.
-			for bio.Scan() {
-				var traceRec trace.Info
-				if err = json.Unmarshal(bio.Bytes(), &traceRec); err != nil {
-					continue
 				}
 				select {
 				case <-doneCh:
 					return
-				case traceInfoCh <- TraceInfo{Trace: traceRec}:
+				case traceInfoCh <- TraceInfo{Trace: info}:
-				}
-			}
-			// Look for any underlying errors.
-			if err = bio.Err(); err != nil {
-				// For an unexpected connection drop from server, we close the body
-				// and re-connect.
-				if err == io.ErrUnexpectedEOF {
-					resp.Body.Close()
 				}
 			}
 		}

pkg/pubsub/pubsub.go

@@ -20,64 +20,65 @@ import (
 	"sync"
 )
 
+// Sub - subscriber entity.
+type Sub struct {
+	ch     chan interface{}
+	filter func(entry interface{}) bool
+}
+
 // PubSub holds publishers and subscribers
 type PubSub struct {
-	subs  []chan interface{}
+	subs []*Sub
-	pub   chan interface{}
+	sync.RWMutex
-	mutex sync.Mutex
 }
 
-// process item to subscribers.
+// Publish message to the subscribers.
-func (ps *PubSub) process() {
+// Note that publish is always nob-blocking send so that we don't block on slow receivers.
-	for item := range ps.pub {
+// Hence receivers should use buffered channel so as not to miss the published events.
-		ps.mutex.Lock()
+func (ps *PubSub) Publish(item interface{}) {
+	ps.RLock()
+	defer ps.RUnlock()
+
 	for _, sub := range ps.subs {
-			go func(s chan interface{}) {
+		if sub.filter(item) {
-				s <- item
+			select {
-			}(sub)
+			case sub.ch <- item:
+			default:
+			}
 		}
-		ps.mutex.Unlock()
 	}
-}
-
-// Publish message to pubsub system
-func (ps *PubSub) Publish(item interface{}) {
-	ps.pub <- item
 }
 
 // Subscribe - Adds a subscriber to pubsub system
-func (ps *PubSub) Subscribe() chan interface{} {
+func (ps *PubSub) Subscribe(subCh chan interface{}, doneCh chan struct{}, filter func(entry interface{}) bool) {
-	ps.mutex.Lock()
+	ps.Lock()
-	defer ps.mutex.Unlock()
+	defer ps.Unlock()
-	ch := make(chan interface{})
+
-	ps.subs = append(ps.subs, ch)
+	sub := &Sub{subCh, filter}
-	return ch
+	ps.subs = append(ps.subs, sub)
-}
+
+	go func() {
+		<-doneCh
 
-// Unsubscribe removes current subscriber
+		ps.Lock()
-func (ps *PubSub) Unsubscribe(ch chan interface{}) {
+		defer ps.Unlock()
-	ps.mutex.Lock()
-	defer ps.mutex.Unlock()
 
-	for i, sub := range ps.subs {
+		for i, s := range ps.subs {
-		if sub == ch {
+			if s == sub {
-			close(ch)
 				ps.subs = append(ps.subs[:i], ps.subs[i+1:]...)
 			}
 		}
+	}()
 }
 
 // HasSubscribers returns true if pubsub system has subscribers
 func (ps *PubSub) HasSubscribers() bool {
-	ps.mutex.Lock()
+	ps.RLock()
-	defer ps.mutex.Unlock()
+	defer ps.RUnlock()
 	return len(ps.subs) > 0
 }
 
 // New inits a PubSub system
 func New() *PubSub {
-	ps := &PubSub{}
+	return &PubSub{}
-	ps.pub = make(chan interface{})
-	go ps.process()
-	return ps
 }

pkg/pubsub/pubsub_test.go

@@ -19,12 +19,19 @@ package pubsub
 import (
 	"fmt"
 	"testing"
+	"time"
 )
 
 func TestSubscribe(t *testing.T) {
 	ps := New()
-	ps.Subscribe()
+	ch1 := make(chan interface{}, 1)
-	ps.Subscribe()
+	ch2 := make(chan interface{}, 1)
+	doneCh := make(chan struct{})
+	defer close(doneCh)
+	ps.Subscribe(ch1, doneCh, nil)
+	ps.Subscribe(ch2, doneCh, nil)
+	ps.Lock()
+	defer ps.Unlock()
 	if len(ps.subs) != 2 {
 		t.Errorf("expected 2 subscribers")
 	}
@@ -32,20 +39,33 @@ func TestSubscribe(t *testing.T) {
 
 func TestUnsubscribe(t *testing.T) {
 	ps := New()
-	c1 := ps.Subscribe()
+	ch1 := make(chan interface{}, 1)
-	ps.Subscribe()
+	ch2 := make(chan interface{}, 1)
-	ps.Unsubscribe(c1)
+	doneCh1 := make(chan struct{})
+	doneCh2 := make(chan struct{})
+	ps.Subscribe(ch1, doneCh1, nil)
+	ps.Subscribe(ch2, doneCh2, nil)
+
+	close(doneCh1)
+	// Allow for the above statement to take effect.
+	time.Sleep(100 * time.Millisecond)
+	ps.Lock()
 	if len(ps.subs) != 1 {
 		t.Errorf("expected 1 subscriber")
 	}
+	ps.Unlock()
+	close(doneCh2)
 }
 
 func TestPubSub(t *testing.T) {
 	ps := New()
-	c1 := ps.Subscribe()
+	ch1 := make(chan interface{}, 1)
+	doneCh1 := make(chan struct{})
+	defer close(doneCh1)
+	ps.Subscribe(ch1, doneCh1, func(entry interface{}) bool { return true })
 	val := "hello"
 	ps.Publish(val)
-	msg := <-c1
+	msg := <-ch1
 	if msg != "hello" {
 		t.Errorf(fmt.Sprintf("expected %s , found %s", val, msg))
 	}
@@ -53,13 +73,17 @@ func TestPubSub(t *testing.T) {
 
 func TestMultiPubSub(t *testing.T) {
 	ps := New()
-	c1 := ps.Subscribe()
+	ch1 := make(chan interface{}, 1)
-	c2 := ps.Subscribe()
+	ch2 := make(chan interface{}, 1)
+	doneCh := make(chan struct{})
+	defer close(doneCh)
+	ps.Subscribe(ch1, doneCh, func(entry interface{}) bool { return true })
+	ps.Subscribe(ch2, doneCh, func(entry interface{}) bool { return true })
 	val := "hello"
 	ps.Publish(val)
 
-	msg1 := <-c1
+	msg1 := <-ch1
-	msg2 := <-c2
+	msg2 := <-ch2
 	if msg1 != "hello" && msg2 != "hello" {
 		t.Errorf(fmt.Sprintf("expected both subscribers to have%s , found %s and  %s", val, msg1, msg2))
 	}