Function TestCompressionDictionaryPreserved

compress_test.go:229–311

TestCompressionDictionaryPreserved verifies that context takeover mode preserves the compression dictionary across Conn.Write calls, resulting in better compression for consecutive similar messages.

(t *testing.T)

// preserves the compression dictionary across Conn.Write calls, resulting
// in better compression for consecutive similar messages.
func TestCompressionDictionaryPreserved(t *testing.T) {
	t.Parallel()

	msg := []byte(strings.Repeat(`{"type":"event","data":"value"}`, 50))

	takeoverClient, takeoverServer := net.Pipe()
	defer takeoverClient.Close()
	defer takeoverServer.Close()

	withTakeover := newConn(connConfig{
		rwc:            takeoverClient,
		client:         true,
		copts:          CompressionContextTakeover.opts(),
		flateThreshold: 64,
		br:             bufio.NewReader(takeoverClient),
		bw:             bufio.NewWriterSize(takeoverClient, 4096),
	})

	noTakeoverClient, noTakeoverServer := net.Pipe()
	defer noTakeoverClient.Close()
	defer noTakeoverServer.Close()

	withoutTakeover := newConn(connConfig{
		rwc:            noTakeoverClient,
		client:         true,
		copts:          CompressionNoContextTakeover.opts(),
		flateThreshold: 64,
		br:             bufio.NewReader(noTakeoverClient),
		bw:             bufio.NewWriterSize(noTakeoverClient, 4096),
	})

	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	defer cancel()

	// Capture compressed sizes for both modes
	var withTakeoverSizes, withoutTakeoverSizes []int64

	reader1 := bufio.NewReader(takeoverServer)
	reader2 := bufio.NewReader(noTakeoverServer)
	readBuf := make([]byte, 8)

	// Send 3 identical messages each
	for range 3 {
		// With context takeover
		writeDone1 := make(chan error, 1)
		go func() {
			writeDone1 <- withTakeover.Write(ctx, MessageText, msg)
		}()

		h1, err := readFrameHeader(reader1, readBuf)
		assert.Success(t, err)

		_, err = io.CopyN(io.Discard, reader1, h1.payloadLength)
		assert.Success(t, err)

		withTakeoverSizes = append(withTakeoverSizes, h1.payloadLength)
		assert.Success(t, <-writeDone1)