Proxy performance (#946)

* proxy: add benchmark

Signed-off-by: Tw <tw19881113@gmail.com>

* replacer: prepare lazily

update issue#939

benchmark            old ns/op     new ns/op     delta
BenchmarkProxy-4     83865         72544         -13.50%

Signed-off-by: Tw <tw19881113@gmail.com>

* proxy: use buffer pool to avoid temporary allocation

Signed-off-by: Tw <tw19881113@gmail.com>

caddyhttp/httpserver/replacer.go

@@ -37,8 +37,8 @@ type Replacer interface {
 // they will be used to overwrite other replacements
 // if there is a name conflict.
 type replacer struct {
-	replacements       map[string]string
-	customReplacements map[string]string
+	replacements       map[string]func() string
+	customReplacements map[string]func() string
 	emptyValue         string
 	responseRecorder   *ResponseRecorder
 }
@@ -53,36 +53,36 @@ type replacer struct {
 func NewReplacer(r *http.Request, rr *ResponseRecorder, emptyValue string) Replacer {
 	rep := &replacer{
 		responseRecorder:   rr,
-		customReplacements: make(map[string]string),
-		replacements: map[string]string{
-			"{method}": r.Method,
+		customReplacements: make(map[string]func() string),
+		replacements: map[string]func() string{
+			"{method}": func() string { return r.Method },
 			"{scheme}": func() string {
 				if r.TLS != nil {
 					return "https"
 				}
 				return "http"
-			}(),
+			},
 			"{hostname}": func() string {
 				name, err := os.Hostname()
 				if err != nil {
 					return ""
 				}
 				return name
-			}(),
-			"{host}": r.Host,
+			},
+			"{host}": func() string { return r.Host },
 			"{hostonly}": func() string {
 				host, _, err := net.SplitHostPort(r.Host)
 				if err != nil {
 					return r.Host
 				}
 				return host
-			}(),
-			"{path}":          r.URL.Path,
-			"{path_escaped}":  url.QueryEscape(r.URL.Path),
-			"{query}":         r.URL.RawQuery,
-			"{query_escaped}": url.QueryEscape(r.URL.RawQuery),
-			"{fragment}":      r.URL.Fragment,
-			"{proto}":         r.Proto,
+			},
+			"{path}":          func() string { return r.URL.Path },
+			"{path_escaped}":  func() string { return url.QueryEscape(r.URL.Path) },
+			"{query}":         func() string { return r.URL.RawQuery },
+			"{query_escaped}": func() string { return url.QueryEscape(r.URL.RawQuery) },
+			"{fragment}":      func() string { return r.URL.Fragment },
+			"{proto}":         func() string { return r.Proto },
 			"{remote}": func() string {
 				if fwdFor := r.Header.Get("X-Forwarded-For"); fwdFor != "" {
 					return fwdFor
@@ -92,25 +92,25 @@ func NewReplacer(r *http.Request, rr *ResponseRecorder, emptyValue string) Repla
 					return r.RemoteAddr
 				}
 				return host
-			}(),
+			},
 			"{port}": func() string {
 				_, port, err := net.SplitHostPort(r.RemoteAddr)
 				if err != nil {
 					return ""
 				}
 				return port
-			}(),
-			"{uri}":         r.URL.RequestURI(),
-			"{uri_escaped}": url.QueryEscape(r.URL.RequestURI()),
-			"{when}":        time.Now().Format(timeFormat),
+			},
+			"{uri}":         func() string { return r.URL.RequestURI() },
+			"{uri_escaped}": func() string { return url.QueryEscape(r.URL.RequestURI()) },
+			"{when}":        func() string { return time.Now().Format(timeFormat) },
 			"{file}": func() string {
 				_, file := path.Split(r.URL.Path)
 				return file
-			}(),
+			},
 			"{dir}": func() string {
 				dir, _ := path.Split(r.URL.Path)
 				return dir
-			}(),
+			},
 			"{request}": func() string {
 				dump, err := httputil.DumpRequest(r, false)
 				if err != nil {
@@ -118,14 +118,15 @@ func NewReplacer(r *http.Request, rr *ResponseRecorder, emptyValue string) Repla
 				}
 
 				return requestReplacer.Replace(string(dump))
-			}(),
+			},
 		},
 		emptyValue: emptyValue,
 	}
 
 	// Header placeholders (case-insensitive)
 	for header, values := range r.Header {
-		rep.replacements[headerReplacer+strings.ToLower(header)+"}"] = strings.Join(values, ",")
+		values := values
+		rep.replacements[headerReplacer+strings.ToLower(header)+"}"] = func() string { return strings.Join(values, ",") }
 	}
 
 	return rep
@@ -141,9 +142,9 @@ func (r *replacer) Replace(s string) string {
 
 	// Make response placeholders now
 	if r.responseRecorder != nil {
-		r.replacements["{status}"] = strconv.Itoa(r.responseRecorder.status)
-		r.replacements["{size}"] = strconv.Itoa(r.responseRecorder.size)
-		r.replacements["{latency}"] = time.Since(r.responseRecorder.start).String()
+		r.replacements["{status}"] = func() string { return strconv.Itoa(r.responseRecorder.status) }
+		r.replacements["{size}"] = func() string { return strconv.Itoa(r.responseRecorder.size) }
+		r.replacements["{latency}"] = func() string { return time.Since(r.responseRecorder.start).String() }
 	}
 
 	// Include custom placeholders, overwriting existing ones if necessary
@@ -158,7 +159,10 @@ func (r *replacer) Replace(s string) string {
 		idxEnd := strings.Index(s[endOffset:], "}")
 		if idxEnd > -1 {
 			placeholder := strings.ToLower(s[idxStart : endOffset+idxEnd+1])
-			replacement := r.replacements[placeholder]
+			replacement := ""
+			if getReplacement, ok := r.replacements[placeholder]; ok {
+				replacement = getReplacement()
+			}
 			if replacement == "" {
 				replacement = r.emptyValue
 			}
@@ -169,7 +173,11 @@ func (r *replacer) Replace(s string) string {
 	}
 
 	// Regular replacements - these are easier because they're case-sensitive
-	for placeholder, replacement := range r.replacements {
+	for placeholder, getReplacement := range r.replacements {
+		if !strings.Contains(s, placeholder) {
+			continue
+		}
+		replacement := getReplacement()
 		if replacement == "" {
 			replacement = r.emptyValue
 		}
@@ -181,7 +189,7 @@ func (r *replacer) Replace(s string) string {
 
 // Set sets key to value in the r.customReplacements map.
 func (r *replacer) Set(key, value string) {
-	r.customReplacements["{"+key+"}"] = value
+	r.customReplacements["{"+key+"}"] = func() string { return value }
 }
 
 const (