summaryrefslogtreecommitdiff
path: root/modules/caddyhttp/encode/encode.go
blob: e20667ff33f530cedf79a0d3ba1bbb4ae345ac67 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
// Package encode implements an encoder middleware for Caddy. The initial
// enhancements related to Accept-Encoding, minimum content length, and
// buffer/writer pools were adapted from https://github.com/xi2/httpgzip
// then modified heavily to accommodate modular encoders. Code borrowed
// from that repository is Copyright (c) 2015 The Httpgzip Authors.
package encode

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"sort"
	"strconv"
	"strings"
	"sync"

	"github.com/caddyserver/caddy"
	"github.com/caddyserver/caddy/modules/caddyhttp"
)

func init() {
	caddy.RegisterModule(caddy.Module{
		Name: "http.middleware.encode",
		New:  func() interface{} { return new(Encode) },
	})
}

// Encode is a middleware which can encode responses.
type Encode struct {
	EncodingsRaw map[string]json.RawMessage `json:"encodings,omitempty"`
	Prefer       []string                   `json:"prefer,omitempty"`
	MinLength    int                        `json:"minimum_length,omitempty"`

	Encodings map[string]Encoding `json:"-"`

	writerPools map[string]*sync.Pool // TODO: these pools do not get reused through config reloads...
}

// Provision provisions enc.
func (enc *Encode) Provision(ctx caddy.Context) error {
	enc.Encodings = make(map[string]Encoding)
	enc.writerPools = make(map[string]*sync.Pool)

	for modName, rawMsg := range enc.EncodingsRaw {
		val, err := ctx.LoadModule("http.encoders."+modName, rawMsg)
		if err != nil {
			return fmt.Errorf("loading encoder module '%s': %v", modName, err)
		}
		encoder := val.(Encoding)
		enc.Encodings[modName] = encoder

		enc.writerPools[modName] = &sync.Pool{
			New: func() interface{} {
				return encoder.NewEncoder()
			},
		}
	}
	enc.EncodingsRaw = nil // allow GC to deallocate - TODO: Does this help?

	if enc.MinLength == 0 {
		enc.MinLength = defaultMinLength
	}

	return nil
}

func (enc *Encode) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
	for _, encName := range acceptedEncodings(r) {
		if _, ok := enc.writerPools[encName]; !ok {
			continue // encoding not offered
		}
		w = enc.openResponseWriter(encName, w)
		defer w.(*responseWriter).Close()
		break
	}

	return next.ServeHTTP(w, r)
}

// openResponseWriter creates a new response writer that may (or may not)
// encode the response with encodingName. The returned response writer MUST
// be closed after the handler completes.
func (enc *Encode) openResponseWriter(encodingName string, w http.ResponseWriter) *responseWriter {
	buf := bufPool.Get().(*bytes.Buffer)
	buf.Reset()
	return &responseWriter{
		ResponseWriterWrapper: &caddyhttp.ResponseWriterWrapper{ResponseWriter: w},
		encodingName:          encodingName,
		buf:                   buf,
		config:                enc,
	}
}

// responseWriter writes to an underlying response writer
// using the encoding represented by encodingName and
// configured by config.
type responseWriter struct {
	*caddyhttp.ResponseWriterWrapper
	encodingName string
	w            Encoder
	buf          *bytes.Buffer
	config       *Encode
	statusCode   int
}

// WriteHeader stores the status to write when the time comes
// to actually write the header.
func (rw *responseWriter) WriteHeader(status int) {
	rw.statusCode = status
}

// Write writes to the response. If the response qualifies,
// it is encoded using the encoder, which is initialized
// if not done so already.
func (rw *responseWriter) Write(p []byte) (int, error) {
	var n, written int
	var err error

	if rw.buf != nil && rw.config.MinLength > 0 {
		written = rw.buf.Len()
		_, err := rw.buf.Write(p)
		if err != nil {
			return 0, err
		}
		if rw.buf.Len() < rw.config.MinLength {
			return len(p), nil
		}
		rw.init()
		p = rw.buf.Bytes()
		defer func() {
			bufPool.Put(rw.buf)
			rw.buf = nil
		}()
	}

	switch {
	case rw.w != nil:
		n, err = rw.w.Write(p)
	default:
		n, err = rw.ResponseWriter.Write(p)
	}
	n -= written
	if n < 0 {
		n = 0
	}
	return n, err
}

// init should be called before we write a response, if rw.buf is not nil.
func (rw *responseWriter) init() {
	if rw.Header().Get("Content-Encoding") == "" && rw.buf.Len() >= rw.config.MinLength {
		rw.w = rw.config.writerPools[rw.encodingName].Get().(Encoder)
		rw.w.Reset(rw.ResponseWriter)
		rw.Header().Del("Content-Length") // https://github.com/golang/go/issues/14975
		rw.Header().Set("Content-Encoding", rw.encodingName)
	}
	rw.Header().Del("Accept-Ranges") // we don't know ranges for dynamically-encoded content
	rw.ResponseWriter.WriteHeader(rw.statusCode)
}

// Close writes any remaining buffered response and
// deallocates any active resources.
func (rw *responseWriter) Close() error {
	var err error
	// only attempt to write the remaining buffered response
	// if there are any bytes left to write; otherwise, if
	// the handler above us returned an error without writing
	// anything, we'd write to the response when we instead
	// should simply let the error propagate back down; this
	// is why the check for rw.buf.Len() > 0 is crucial
	if rw.buf != nil && rw.buf.Len() > 0 {
		rw.init()
		p := rw.buf.Bytes()
		defer func() {
			bufPool.Put(rw.buf)
			rw.buf = nil
		}()
		switch {
		case rw.w != nil:
			_, err = rw.w.Write(p)
		default:
			_, err = rw.ResponseWriter.Write(p)
		}
	}
	if rw.w != nil {
		err2 := rw.w.Close()
		if err2 != nil && err == nil {
			err = err2
		}
		rw.config.writerPools[rw.encodingName].Put(rw.w)
		rw.w = nil
	}
	return err
}

// acceptedEncodings returns the list of encodings that the
// client supports, in descending order of preference. If
// the Sec-WebSocket-Key header is present then non-identity
// encodings are not considered. See
// http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html.
func acceptedEncodings(r *http.Request) []string {
	acceptEncHeader := r.Header.Get("Accept-Encoding")
	websocketKey := r.Header.Get("Sec-WebSocket-Key")
	if acceptEncHeader == "" {
		return []string{}
	}

	var prefs []encodingPreference

	for _, accepted := range strings.Split(acceptEncHeader, ",") {
		parts := strings.Split(accepted, ";")
		encName := strings.ToLower(strings.TrimSpace(parts[0]))

		// determine q-factor
		qFactor := 1.0
		if len(parts) > 1 {
			qFactorStr := strings.ToLower(strings.TrimSpace(parts[1]))
			if strings.HasPrefix(qFactorStr, "q=") {
				if qFactorFloat, err := strconv.ParseFloat(qFactorStr[2:], 32); err == nil {
					if qFactorFloat >= 0 && qFactorFloat <= 1 {
						qFactor = qFactorFloat
					}
				}
			}
		}

		// encodings with q-factor of 0 are not accepted;
		// use a small theshold to account for float precision
		if qFactor < 0.00001 {
			continue
		}

		// don't encode WebSocket handshakes
		if websocketKey != "" && encName != "identity" {
			continue
		}

		prefs = append(prefs, encodingPreference{
			encoding: encName,
			q:        qFactor,
		})
	}

	// sort preferences by descending q-factor
	sort.Slice(prefs, func(i, j int) bool { return prefs[i].q > prefs[j].q })

	// TODO: If no preference, or same pref for all encodings,
	// and not websocket, use default encoding ordering (enc.Prefer)
	// for those which are accepted by the client

	prefEncNames := make([]string, len(prefs))
	for i := range prefs {
		prefEncNames[i] = prefs[i].encoding
	}

	return prefEncNames
}

// encodingPreference pairs an encoding with its q-factor.
type encodingPreference struct {
	encoding string
	q        float64
}

// Encoder is a type which can encode a stream of data.
type Encoder interface {
	io.WriteCloser
	Reset(io.Writer)
}

// Encoding is a type which can create encoders of its kind.
type Encoding interface {
	NewEncoder() Encoder
}

var bufPool = sync.Pool{
	New: func() interface{} {
		return new(bytes.Buffer)
	},
}

// defaultMinLength is the minimum length at which to compress content.
const defaultMinLength = 512

// Interface guards
var (
	_ caddy.Provisioner           = (*Encode)(nil)
	_ caddyhttp.MiddlewareHandler = (*Encode)(nil)
	_ caddyhttp.HTTPInterfaces    = (*responseWriter)(nil)
)