/
flusher.go
71 lines (60 loc) · 1.47 KB
/
flusher.go
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
package server
import (
"net/http"
"sync"
)
// flushAfterNBytes creates a middleware that flushes the response
// after every N bytes.
//
// This is used to support streaming requests over gRPC, which may need
// chunking in order to not exceed the max gRPC message size.
func flushAfterNBytes(n int) func(http.Handler) http.Handler {
return func(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
flusher, ok := w.(http.Flusher)
if !ok {
http.Error(w,
"Streaming unsupported: ResponseWriter does not implement http.Flusher",
http.StatusInternalServerError)
return
}
hijacker, ok := w.(http.Hijacker)
if !ok {
http.Error(w,
"Streaming unsupported: ResponseWriter does not implement http.Hijacker",
http.StatusInternalServerError)
return
}
flushWriter := &flushAfterNBytesWriter{
ResponseWriter: w,
Flusher: flusher,
Hijacker: hijacker,
limit: n,
mu: &sync.Mutex{},
}
next.ServeHTTP(flushWriter, r)
})
}
}
type flushAfterNBytesWriter struct {
http.ResponseWriter
http.Flusher
http.Hijacker
limit int
written int
mu *sync.Mutex
}
func (w *flushAfterNBytesWriter) Write(bytes []byte) (int, error) {
w.mu.Lock()
defer w.mu.Unlock()
n, err := w.ResponseWriter.Write(bytes)
if err != nil {
return n, err
}
w.written += n
if w.written >= w.limit {
w.Flusher.Flush()
w.written = 0
}
return n, nil
}