fastcgi: Optimize FastCGI transport (#4978)

* break up code and use lazy reading and pool bufio.Writer

* close underlying connection when operation failed

* allocate bufWriter and streamWriter only once

* refactor record writing

* rebase from master

* handle err

* Fix type assertion

Also reduce some duplication

* Refactor client and clientCloser for logging

Should reduce allocations

* Minor cosmetic adjustments; apply Apache license

* Appease the linter

Co-authored-by: Matthew Holt <mholt@users.noreply.github.com>

1 files changed, 145 insertions, 0 deletions

diff --git a/modules/caddyhttp/reverseproxy/fastcgi/writer.go b/modules/caddyhttp/reverseproxy/fastcgi/writer.go
new file mode 100644
index 0000000..3af00d9
--- /dev/null
+++ b/modules/caddyhttp/reverseproxy/fastcgi/writer.go
@@ -0,0 +1,145 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package fastcgi
+
+import (
+	"bytes"
+	"encoding/binary"
+)
+
+// streamWriter abstracts out the separation of a stream into discrete records.
+// It only writes maxWrite bytes at a time.
+type streamWriter struct {
+	c       *client
+	h       header
+	buf     *bytes.Buffer
+	recType uint8
+}
+
+func (w *streamWriter) writeRecord(recType uint8, content []byte) (err error) {
+	w.h.init(recType, w.c.reqID, len(content))
+	w.buf.Write(pad[:8])
+	w.writeHeader()
+	w.buf.Write(content)
+	w.buf.Write(pad[:w.h.PaddingLength])
+	_, err = w.buf.WriteTo(w.c.rwc)
+	return err
+}
+
+func (w *streamWriter) writeBeginRequest(role uint16, flags uint8) error {
+	b := [8]byte{byte(role >> 8), byte(role), flags}
+	return w.writeRecord(BeginRequest, b[:])
+}
+
+func (w *streamWriter) Write(p []byte) (int, error) {
+	// init header
+	if w.buf.Len() < 8 {
+		w.buf.Write(pad[:8])
+	}
+
+	nn := 0
+	for len(p) > 0 {
+		n := len(p)
+		nl := maxWrite + 8 - w.buf.Len()
+		if n > nl {
+			n = nl
+			w.buf.Write(p[:n])
+			if err := w.Flush(); err != nil {
+				return nn, err
+			}
+			// reset headers
+			w.buf.Write(pad[:8])
+		} else {
+			w.buf.Write(p[:n])
+		}
+		nn += n
+		p = p[n:]
+	}
+	return nn, nil
+}
+
+func (w *streamWriter) endStream() error {
+	// send empty record to close the stream
+	return w.writeRecord(w.recType, nil)
+}
+
+func (w *streamWriter) writePairs(pairs map[string]string) error {
+	b := make([]byte, 8)
+	nn := 0
+	// init headers
+	w.buf.Write(b)
+	for k, v := range pairs {
+		m := 8 + len(k) + len(v)
+		if m > maxWrite {
+			// param data size exceed 65535 bytes"
+			vl := maxWrite - 8 - len(k)
+			v = v[:vl]
+		}
+		n := encodeSize(b, uint32(len(k)))
+		n += encodeSize(b[n:], uint32(len(v)))
+		m = n + len(k) + len(v)
+		if (nn + m) > maxWrite {
+			if err := w.Flush(); err != nil {
+				return err
+			}
+			// reset headers
+			w.buf.Write(b)
+			nn = 0
+		}
+		nn += m
+		w.buf.Write(b[:n])
+		w.buf.WriteString(k)
+		w.buf.WriteString(v)
+	}
+	return w.FlushStream()
+}
+
+func encodeSize(b []byte, size uint32) int {
+	if size > 127 {
+		size |= 1 << 31
+		binary.BigEndian.PutUint32(b, size)
+		return 4
+	}
+	b[0] = byte(size)
+	return 1
+}
+
+// writeHeader populate header wire data in buf, it abuses buffer.Bytes() modification
+func (w *streamWriter) writeHeader() {
+	h := w.buf.Bytes()[:8]
+	h[0] = w.h.Version
+	h[1] = w.h.Type
+	binary.BigEndian.PutUint16(h[2:4], w.h.ID)
+	binary.BigEndian.PutUint16(h[4:6], w.h.ContentLength)
+	h[6] = w.h.PaddingLength
+	h[7] = w.h.Reserved
+}
+
+// Flush write buffer data to the underlying connection, it assumes header data is the first 8 bytes of buf
+func (w *streamWriter) Flush() error {
+	w.h.init(w.recType, w.c.reqID, w.buf.Len()-8)
+	w.writeHeader()
+	w.buf.Write(pad[:w.h.PaddingLength])
+	_, err := w.buf.WriteTo(w.c.rwc)
+	return err
+}
+
+// FlushStream flush data then end current stream
+func (w *streamWriter) FlushStream() error {
+	if err := w.Flush(); err != nil {
+		return err
+	}
+	return w.endStream()
+}