Trace all http requests (#15064)

Add a generic handler that adds a new tracing context to the request if
tracing is enabled. Other handlers are free to modify the tracing
context to update information on the fly, such as, func name, enable
body logging etc..

With this commit, requests like this 

```
curl -H "Host: ::1:3000" http://localhost:9000/
```

will be traced as well.

cmd/handler-utils.go

@@ -357,30 +357,6 @@ func extractPostPolicyFormValues(ctx context.Context, form *multipart.Form) (fil
 	return filePart, fileName, fileSize, formValues, nil
 }
 
-// Log headers and body.
-func httpTraceAll(f http.HandlerFunc) http.HandlerFunc {
-	return func(w http.ResponseWriter, r *http.Request) {
-		if globalTrace.NumSubscribers() == 0 {
-			f.ServeHTTP(w, r)
-			return
-		}
-		trace := Trace(f, true, w, r)
-		globalTrace.Publish(trace)
-	}
-}
-
-// Log only the headers.
-func httpTraceHdrs(f http.HandlerFunc) http.HandlerFunc {
-	return func(w http.ResponseWriter, r *http.Request) {
-		if globalTrace.NumSubscribers() == 0 {
-			f.ServeHTTP(w, r)
-			return
-		}
-		trace := Trace(f, false, w, r)
-		globalTrace.Publish(trace)
-	}
-}
-
 func collectAPIStats(api string, f http.HandlerFunc) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		globalHTTPStats.currentS3Requests.Inc(api)

cmd/http-tracer.go

@@ -19,6 +19,7 @@ package cmd
 
 import (
 	"bytes"
+	"context"
 	"io"
 	"net"
 	"net/http"
@@ -43,8 +44,6 @@ type recordRequest struct {
 	logBody bool
 	// Internal recording buffer
 	buf bytes.Buffer
-	// request headers
-	headers http.Header
 	// total bytes read including header size
 	bytesRead int
 }
@@ -67,12 +66,8 @@ func (r *recordRequest) Read(p []byte) (n int, err error) {
 	return n, err
 }
 
-func (r *recordRequest) Size() int {
-	sz := r.bytesRead
-	for k, v := range r.headers {
-		sz += len(k) + len(v)
-	}
-	return sz
+func (r *recordRequest) BodySize() int {
+	return r.bytesRead
 }
 
 // Return the bytes that were recorded.
@@ -113,11 +108,47 @@ func getOpName(name string) (op string) {
 	return op
 }
 
-// Trace gets trace of http request
-func Trace(f http.HandlerFunc, logBody bool, w http.ResponseWriter, r *http.Request) madmin.TraceInfo {
-	name := getOpName(runtime.FuncForPC(reflect.ValueOf(f).Pointer()).Name())
+type contextTraceReqType string
 
-	// Setup a http request body recorder
+const contextTraceReqKey = contextTraceReqType("request-trace-info")
+
+// Hold related tracing data of a http request, any handler
+// can modify this struct to modify the trace information .
+type traceCtxt struct {
+	requestRecorder  *recordRequest
+	responseRecorder *logger.ResponseWriter
+	funcName         string
+}
+
+// If trace is enabled, execute the request if it is traced by other handlers
+// otherwise, generate a trace event with request information but no response.
+func httpTracer(h http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if globalTrace.NumSubscribers() == 0 {
+			h.ServeHTTP(w, r)
+			return
+		}
+
+		// Create tracing data structure and associate it to the request context
+		tc := traceCtxt{}
+		ctx := context.WithValue(r.Context(), contextTraceReqKey, &tc)
+		r = r.WithContext(ctx)
+
+		// Setup a http request and response body recorder
+		reqRecorder := &recordRequest{Reader: r.Body}
+		respRecorder := logger.NewResponseWriter(w)
+
+		tc.requestRecorder = reqRecorder
+		tc.responseRecorder = respRecorder
+
+		// Execute call.
+		r.Body = reqRecorder
+
+		reqStartTime := time.Now().UTC()
+		h.ServeHTTP(respRecorder, r)
+		reqEndTime := time.Now().UTC()
+
+		// Calculate input body size with headers
 		reqHeaders := r.Header.Clone()
 		reqHeaders.Set("Host", r.Host)
 		if len(r.TransferEncoding) == 0 {
@@ -125,73 +156,95 @@ func Trace(f http.HandlerFunc, logBody bool, w http.ResponseWriter, r *http.Requ
 		} else {
 			reqHeaders.Set("Transfer-Encoding", strings.Join(r.TransferEncoding, ","))
 		}
-
-	reqBodyRecorder := &recordRequest{Reader: r.Body, logBody: logBody, headers: reqHeaders}
-	r.Body = reqBodyRecorder
-
-	now := time.Now().UTC()
-	t := madmin.TraceInfo{TraceType: madmin.TraceHTTP, FuncName: name, Time: now}
-
-	t.NodeName = r.Host
-	if globalIsDistErasure {
-		t.NodeName = globalLocalNodeName
+		inputBytes := reqRecorder.BodySize()
+		for k, v := range reqHeaders {
+			inputBytes += len(k) + len(v)
 		}
 
-	if t.NodeName == "" {
-		t.NodeName = globalLocalNodeName
+		// Calculate node name
+		nodeName := r.Host
+		if nodeName == "" || globalIsDistErasure {
+			nodeName = globalLocalNodeName
 		}
-
-	// strip only standard port from the host address
-	if host, port, err := net.SplitHostPort(t.NodeName); err == nil {
+		if host, port, err := net.SplitHostPort(nodeName); err == nil {
 			if port == "443" || port == "80" {
-			t.NodeName = host
+				nodeName = host
 			}
 		}
 
+		// Calculate reqPath
+		reqPath := r.URL.RawPath
+		if reqPath == "" {
+			reqPath = r.URL.Path
+		}
+
+		// Calculate function name
+		funcName := tc.funcName
+		if funcName == "" {
+			funcName = "<unknown>"
+		}
+
 		rq := madmin.TraceRequestInfo{
-		Time:     now,
+			Time:     reqStartTime,
 			Proto:    r.Proto,
 			Method:   r.Method,
 			RawQuery: redactLDAPPwd(r.URL.RawQuery),
 			Client:   handlers.GetSourceIP(r),
 			Headers:  reqHeaders,
+			Path:     reqPath,
+			Body:     reqRecorder.Data(),
 		}
 
-	path := r.URL.RawPath
-	if path == "" {
-		path = r.URL.Path
-	}
-	rq.Path = path
-
-	rw := logger.NewResponseWriter(w)
-	rw.LogErrBody = true
-	rw.LogAllBody = logBody
-
-	// Execute call.
-	f(rw, r)
-
 		rs := madmin.TraceResponseInfo{
-		Time:       time.Now().UTC(),
-		Headers:    rw.Header().Clone(),
-		StatusCode: rw.StatusCode,
-		Body:       rw.Body(),
+			Time:       reqEndTime,
+			Headers:    respRecorder.Header().Clone(),
+			StatusCode: respRecorder.StatusCode,
+			Body:       respRecorder.Body(),
 		}
 
-	// Transfer request body
-	rq.Body = reqBodyRecorder.Data()
-
-	if rs.StatusCode == 0 {
-		rs.StatusCode = http.StatusOK
+		cs := madmin.TraceCallStats{
+			Latency:         rs.Time.Sub(respRecorder.StartTime),
+			InputBytes:      inputBytes,
+			OutputBytes:     respRecorder.Size(),
+			TimeToFirstByte: respRecorder.TimeToFirstByte,
 		}
 
-	t.ReqInfo = rq
-	t.RespInfo = rs
+		t := madmin.TraceInfo{
+			TraceType: madmin.TraceHTTP,
+			FuncName:  funcName,
+			NodeName:  nodeName,
+			Time:      reqStartTime,
+			ReqInfo:   rq,
+			RespInfo:  rs,
+			CallStats: cs,
+		}
 
-	t.CallStats = madmin.TraceCallStats{
-		Latency:         rs.Time.Sub(rw.StartTime),
-		InputBytes:      reqBodyRecorder.Size(),
-		OutputBytes:     rw.Size(),
-		TimeToFirstByte: rw.TimeToFirstByte,
+		globalTrace.Publish(t)
+	})
 }
-	return t
+
+func httpTrace(f http.HandlerFunc, logBody bool) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		tc, ok := r.Context().Value(contextTraceReqKey).(*traceCtxt)
+		if !ok {
+			// Tracing is not enabled for this request
+			f.ServeHTTP(w, r)
+			return
+		}
+
+		tc.funcName = getOpName(runtime.FuncForPC(reflect.ValueOf(f).Pointer()).Name())
+		tc.requestRecorder.logBody = logBody
+		tc.responseRecorder.LogAllBody = logBody
+		tc.responseRecorder.LogErrBody = true
+
+		f.ServeHTTP(w, r)
+	}
+}
+
+func httpTraceAll(f http.HandlerFunc) http.HandlerFunc {
+	return httpTrace(f, true)
+}
+
+func httpTraceHdrs(f http.HandlerFunc) http.HandlerFunc {
+	return httpTrace(f, false)
 }

cmd/routers.go

@@ -40,6 +40,9 @@ func registerDistErasureRouters(router *mux.Router, endpointServerPools Endpoint
 
 // List of some generic handlers which are applied for all incoming requests.
 var globalHandlers = []mux.MiddlewareFunc{
+	// The generic tracer needs to be the first handler
+	// to catch all requests returned early by any other handler
+	httpTracer,
 	// Auth handler verifies incoming authorization headers and
 	// routes them accordingly. Client receives a HTTP error for
 	// invalid/unsupported signatures.