Introduce a fast proxy mode to improve HTTP/1.1 performances with backends

Co-authored-by: Romain <rtribotte@users.noreply.github.com>
Co-authored-by: Julien Salleyron <julien.salleyron@gmail.com>

pkg/proxy/fast/connpool.go

@@ -0,0 +1,163 @@
+package fast
+
+import (
+	"fmt"
+	"net"
+	"time"
+
+	"github.com/rs/zerolog/log"
+)
+
+// conn is an enriched net.Conn.
+type conn struct {
+	net.Conn
+
+	idleAt      time.Time // the last time it was marked as idle.
+	idleTimeout time.Duration
+}
+
+func (c *conn) isExpired() bool {
+	expTime := c.idleAt.Add(c.idleTimeout)
+	return c.idleTimeout > 0 && time.Now().After(expTime)
+}
+
+// connPool is a net.Conn pool implementation using channels.
+type connPool struct {
+	dialer          func() (net.Conn, error)
+	idleConns       chan *conn
+	idleConnTimeout time.Duration
+	ticker          *time.Ticker
+	doneCh          chan struct{}
+}
+
+// newConnPool creates a new connPool.
+func newConnPool(maxIdleConn int, idleConnTimeout time.Duration, dialer func() (net.Conn, error)) *connPool {
+	c := &connPool{
+		dialer:          dialer,
+		idleConns:       make(chan *conn, maxIdleConn),
+		idleConnTimeout: idleConnTimeout,
+		doneCh:          make(chan struct{}),
+	}
+
+	if idleConnTimeout > 0 {
+		c.ticker = time.NewTicker(c.idleConnTimeout / 2)
+		go func() {
+			for {
+				select {
+				case <-c.ticker.C:
+					c.cleanIdleConns()
+				case <-c.doneCh:
+					return
+				}
+			}
+		}()
+	}
+
+	return c
+}
+
+// Close closes stop the cleanIdleConn goroutine.
+func (c *connPool) Close() {
+	if c.idleConnTimeout > 0 {
+		close(c.doneCh)
+		c.ticker.Stop()
+	}
+}
+
+// AcquireConn returns an idle net.Conn from the pool.
+func (c *connPool) AcquireConn() (*conn, error) {
+	for {
+		co, err := c.acquireConn()
+		if err != nil {
+			return nil, err
+		}
+
+		if !co.isExpired() {
+			return co, nil
+		}
+
+		// As the acquired conn is expired we can close it
+		// without putting it again into the pool.
+		if err := co.Close(); err != nil {
+			log.Debug().
+				Err(err).
+				Msg("Unexpected error while releasing the connection")
+		}
+	}
+}
+
+// ReleaseConn releases the given net.Conn to the pool.
+func (c *connPool) ReleaseConn(co *conn) {
+	co.idleAt = time.Now()
+	c.releaseConn(co)
+}
+
+// cleanIdleConns is a routine cleaning the expired connections at a regular basis.
+func (c *connPool) cleanIdleConns() {
+	for {
+		select {
+		case co := <-c.idleConns:
+			if !co.isExpired() {
+				c.releaseConn(co)
+				return
+			}
+
+			if err := co.Close(); err != nil {
+				log.Debug().
+					Err(err).
+					Msg("Unexpected error while releasing the connection")
+			}
+
+		default:
+			return
+		}
+	}
+}
+
+func (c *connPool) acquireConn() (*conn, error) {
+	select {
+	case co := <-c.idleConns:
+		return co, nil
+
+	default:
+		errCh := make(chan error, 1)
+		go c.askForNewConn(errCh)
+
+		select {
+		case co := <-c.idleConns:
+			return co, nil
+
+		case err := <-errCh:
+			return nil, err
+		}
+	}
+}
+
+func (c *connPool) releaseConn(co *conn) {
+	select {
+	case c.idleConns <- co:
+
+	// Hitting the default case means that we have reached the maximum number of idle
+	// connections, so we can close it.
+	default:
+		if err := co.Close(); err != nil {
+			log.Debug().
+				Err(err).
+				Msg("Unexpected error while releasing the connection")
+		}
+	}
+}
+
+func (c *connPool) askForNewConn(errCh chan<- error) {
+	co, err := c.dialer()
+	if err != nil {
+		errCh <- fmt.Errorf("create conn: %w", err)
+		return
+	}
+
+	c.releaseConn(&conn{
+		Conn:        co,
+		idleAt:      time.Now(),
+		idleTimeout: c.idleConnTimeout,
+	})
+}