[#60] Implement periodic white space XML writer

Periodic white space XML writer sends XML header
and white spaces to the io.Writer.

Signed-off-by: Alex Vanin <a.vanin@yadro.com>
This commit is contained in:
Alexey Vanin 2023-03-20 11:13:56 +03:00
parent 5c62010331
commit cf18158da4
2 changed files with 99 additions and 0 deletions

View file

@ -2,6 +2,7 @@ package handler
import ( import (
"encoding/xml" "encoding/xml"
"io"
"net/http" "net/http"
"net/url" "net/url"
"strconv" "strconv"
@ -681,3 +682,53 @@ func encodeListPartsToResponse(info *layer.ListPartsInfo, params *layer.ListPart
Parts: info.Parts, Parts: info.Parts,
} }
} }
// periodicXMLWriter creates go routine to write xml header and whitespaces
// over time to avoid connection drop from the client. To work properly,
// pass `http.ResponseWriter` with implemented `http.Flusher` interface.
// Returns stop function which returns boolean if writer has been used
// during goroutine execution. To disable writer, pass 0 duration value.
func periodicXMLWriter(w io.Writer, dur time.Duration) (stop func() bool) {
if dur == 0 { // 0 duration disables periodic writer
return func() bool { return false }
}
whitespaceChar := []byte(" ")
closer := make(chan struct{})
done := make(chan struct{})
headerWritten := false
go func() {
defer close(done)
tick := time.NewTicker(dur)
defer tick.Stop()
for {
select {
case <-tick.C:
if !headerWritten {
_, err := w.Write([]byte(xml.Header))
headerWritten = err == nil
}
_, err := w.Write(whitespaceChar)
if err != nil {
return // is there anything we can do better than ignore error?
}
if buffered, ok := w.(http.Flusher); ok {
buffered.Flush()
}
case <-closer:
return
}
}
}()
stop = func() bool {
close(closer)
<-done // wait for goroutine to stop
return headerWritten
}
return stop
}

View file

@ -0,0 +1,48 @@
package handler
import (
"bytes"
"encoding/xml"
"testing"
"time"
"github.com/stretchr/testify/require"
)
func TestPeriodicWriter(t *testing.T) {
const dur = 100 * time.Millisecond
const whitespaces = 8
expected := []byte(xml.Header)
for i := 0; i < whitespaces; i++ {
expected = append(expected, []byte(" ")...)
}
t.Run("writes data", func(t *testing.T) {
buf := bytes.NewBuffer(nil)
stop := periodicXMLWriter(buf, dur)
// N number of whitespaces + half durations to guarantee at least N writes in buffer
time.Sleep(whitespaces*dur + dur/2)
require.True(t, stop())
require.Equal(t, expected, buf.Bytes())
t.Run("no additional data after stop", func(t *testing.T) {
time.Sleep(2 * dur)
require.Equal(t, expected, buf.Bytes())
})
})
t.Run("does not write data", func(t *testing.T) {
buf := bytes.NewBuffer(nil)
stop := periodicXMLWriter(buf, dur)
time.Sleep(dur / 2)
require.False(t, stop())
require.Empty(t, buf.Bytes())
t.Run("disabled", func(t *testing.T) {
stop = periodicXMLWriter(buf, 0)
require.False(t, stop())
require.Empty(t, buf.Bytes())
})
})
}