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external_backend.go
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external_backend.go
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package netceptor
import (
"context"
"fmt"
"net"
"sync"
"time"
"github.com/ansible/receptor/pkg/framer"
"github.com/ansible/receptor/pkg/utils"
"github.com/gorilla/websocket"
)
// ExternalBackend is a backend implementation for the situation when non-Receptor code
// is initiating connections, outside the control of a Receptor-managed accept loop.
type ExternalBackend struct {
ctx context.Context
sessChan chan BackendSession
}
// MessageConn is an abstract connection that sends and receives whole messages (datagrams).
type MessageConn interface {
WriteMessage(ctx context.Context, data []byte) error
ReadMessage(ctx context.Context, timeout time.Duration) ([]byte, error)
SetReadDeadline(t time.Time) error
Close() error
}
// netMessageConn implements MessageConn for Go net.Conn.
type netMessageConn struct {
conn net.Conn
framer framer.Framer
}
// MessageConnFromNetConn returns a MessageConnection that wraps a net.Conn.
func MessageConnFromNetConn(conn net.Conn) MessageConn {
return &netMessageConn{
conn: conn,
framer: framer.New(),
}
}
// WriteMessage writes a message to the connection.
func (mc *netMessageConn) WriteMessage(ctx context.Context, data []byte) error {
if ctx.Err() != nil {
return fmt.Errorf("session closed: %s", ctx.Err())
}
buf := mc.framer.SendData(data)
n, err := mc.conn.Write(buf)
if err != nil {
return err
}
if n != len(buf) {
return fmt.Errorf("partial data sent")
}
return nil
}
// ReadMessage reads a message from the connection.
func (mc *netMessageConn) ReadMessage(ctx context.Context, timeout time.Duration) ([]byte, error) {
buf := make([]byte, utils.NormalBufferSize)
err := mc.conn.SetReadDeadline(time.Now().Add(timeout))
if err != nil {
return nil, err
}
for {
if ctx.Err() != nil {
return nil, fmt.Errorf("session closed: %s", ctx.Err())
}
if mc.framer.MessageReady() {
break
}
n, err := mc.conn.Read(buf)
if n > 0 {
mc.framer.RecvData(buf[:n])
}
if nerr, ok := err.(net.Error); ok && nerr.Timeout() {
return nil, ErrTimeout
}
if err != nil {
return nil, err
}
}
buf, err = mc.framer.GetMessage()
if err != nil {
return nil, err
}
return buf, nil
}
// SetReadDeadline sets the deadline by which a message must be read from the connection.
func (mc *netMessageConn) SetReadDeadline(t time.Time) error {
panic("implement me")
}
// Close closes the connection.
func (mc *netMessageConn) Close() error {
return mc.conn.Close()
}
// websocketMessageConn implements MessageConn for Gorilla websocket.Conn.
type websocketMessageConn struct {
conn *websocket.Conn
}
// MessageConnFromWebsocketConn returns a MessageConnection that wraps a Gorilla websocket.Conn.
func MessageConnFromWebsocketConn(conn *websocket.Conn) MessageConn {
return &websocketMessageConn{
conn: conn,
}
}
// WriteMessage writes a message to the connection.
func (mc *websocketMessageConn) WriteMessage(ctx context.Context, data []byte) error {
if ctx.Err() != nil {
return fmt.Errorf("session closed: %s", ctx.Err())
}
return mc.conn.WriteMessage(websocket.BinaryMessage, data)
}
// ReadMessage reads a message from the connection.
func (mc *websocketMessageConn) ReadMessage(ctx context.Context, timeout time.Duration) ([]byte, error) {
if ctx.Err() != nil {
return nil, fmt.Errorf("session closed: %s", ctx.Err())
}
messageType, data, err := mc.conn.ReadMessage()
if messageType != websocket.BinaryMessage {
return nil, fmt.Errorf("received message of wrong type")
}
return data, err
}
// SetReadDeadline sets the deadline by which a message must be read from the connection.
func (mc *websocketMessageConn) SetReadDeadline(t time.Time) error {
return mc.conn.SetReadDeadline(t)
}
// Close closes the connection.
func (mc *websocketMessageConn) Close() error {
return mc.conn.Close()
}
// NewExternalBackend initializes a new ExternalBackend object.
func NewExternalBackend() (*ExternalBackend, error) {
return &ExternalBackend{}, nil
}
// Start launches the backend from Receptor's point of view, and waits for connections to happen.
func (b *ExternalBackend) Start(ctx context.Context, _ *sync.WaitGroup) (chan BackendSession, error) {
b.ctx = ctx
b.sessChan = make(chan BackendSession)
return b.sessChan, nil
}
// ExternalSession implements BackendSession for external backends.
type ExternalSession struct {
eb *ExternalBackend
conn MessageConn
shouldClose bool
ctx context.Context
cancel context.CancelFunc
}
// NewConnection is called by the external code when a new connection is available. The
// connection will be closed when the session ends if closeConnWithSession is true. The
// returned context will be cancelled after the connection closes.
func (b *ExternalBackend) NewConnection(conn MessageConn, closeConnWithSession bool) context.Context {
ctx, cancel := context.WithCancel(b.ctx)
ebs := &ExternalSession{
eb: b,
conn: conn,
shouldClose: closeConnWithSession,
ctx: ctx,
cancel: cancel,
}
b.sessChan <- ebs
return ctx
}
// Send sends data over the session.
func (es *ExternalSession) Send(data []byte) error {
return es.conn.WriteMessage(es.ctx, data)
}
// Recv receives data via the session.
func (es *ExternalSession) Recv(timeout time.Duration) ([]byte, error) {
return es.conn.ReadMessage(es.ctx, timeout)
}
// Close closes the session.
func (es *ExternalSession) Close() error {
es.cancel()
var err error
if es.shouldClose {
err = es.conn.Close()
}
return err
}