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session.go
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session.go
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package common
import (
"context"
"errors"
"sync/atomic"
"github.com/chromedp/cdproto"
"github.com/chromedp/cdproto/cdp"
"github.com/chromedp/cdproto/target"
"github.com/mailru/easyjson"
"github.com/grafana/xk6-browser/log"
)
// Ensure Session implements the EventEmitter and Executor interfaces.
var _ EventEmitter = &Session{}
var _ cdp.Executor = &Session{}
// Session represents a CDP session to a target.
type Session struct {
BaseEventEmitter
conn *Connection
id target.SessionID
targetID target.ID
msgID int64
readCh chan *cdproto.Message
done chan struct{}
closed bool
crashed bool
logger *log.Logger
}
// NewSession creates a new session.
func NewSession(
ctx context.Context, conn *Connection, id target.SessionID, tid target.ID, logger *log.Logger,
) *Session {
s := Session{
BaseEventEmitter: NewBaseEventEmitter(ctx),
conn: conn,
id: id,
targetID: tid,
readCh: make(chan *cdproto.Message),
done: make(chan struct{}),
logger: logger,
}
s.logger.Debugf("Session:NewSession", "sid:%v tid:%v", id, tid)
go s.readLoop()
return &s
}
// ID returns session ID.
func (s *Session) ID() target.SessionID {
return s.id
}
// TargetID returns session's target ID.
func (s *Session) TargetID() target.ID {
return s.targetID
}
func (s *Session) close() {
s.logger.Debugf("Session:close", "sid:%v tid:%v", s.id, s.targetID)
if s.closed {
s.logger.Debugf("Session:close", "already closed, sid:%v tid:%v", s.id, s.targetID)
return
}
// Stop the read loop
close(s.done)
s.closed = true
s.emit(EventSessionClosed, nil)
}
func (s *Session) markAsCrashed() {
s.logger.Debugf("Session:markAsCrashed", "sid:%v tid:%v", s.id, s.targetID)
s.crashed = true
}
// Wraps conn.ReadMessage in a channel.
func (s *Session) readLoop() {
for {
select {
case msg := <-s.readCh:
ev, err := cdproto.UnmarshalMessage(msg)
if errors.Is(err, cdp.ErrUnknownCommandOrEvent("")) && msg.Method == "" {
// Results from commands may not always have methods in them.
// This is the reason of this error. So it's harmless.
//
// Also:
// This is most likely an event received from an older
// Chrome which a newer cdproto doesn't have, as it is
// deprecated. Ignore that error, and emit raw cdproto.Message.
s.emit("", msg)
continue
}
if err != nil {
s.logger.Debugf("Session:readLoop:<-s.readCh", "sid:%v tid:%v cannot unmarshal: %v", s.id, s.targetID, err)
continue
}
s.emit(string(msg.Method), ev)
case <-s.done:
s.logger.Debugf("Session:readLoop:<-s.done", "sid:%v tid:%v", s.id, s.targetID)
return
}
}
}
// Execute implements the cdp.Executor interface.
func (s *Session) Execute(ctx context.Context, method string, params easyjson.Marshaler, res easyjson.Unmarshaler) error {
s.logger.Debugf("Session:Execute", "sid:%v tid:%v method:%q", s.id, s.targetID, method)
if s.crashed {
s.logger.Debugf("Session:Execute:return", "sid:%v tid:%v method:%q crashed", s.id, s.targetID, method)
return ErrTargetCrashed
}
id := atomic.AddInt64(&s.msgID, 1)
// Setup event handler used to block for response to message being sent.
ch := make(chan *cdproto.Message, 1)
evCancelCtx, evCancelFn := context.WithCancel(ctx)
chEvHandler := make(chan Event)
go func() {
for {
select {
case <-evCancelCtx.Done():
s.logger.Debugf("Session:Execute:<-evCancelCtx.Done():return", "sid:%v tid:%v method:%q", s.id, s.targetID, method)
return
case ev := <-chEvHandler:
if msg, ok := ev.data.(*cdproto.Message); ok && msg.ID == id {
select {
case <-evCancelCtx.Done():
s.logger.Debugf("Session:Execute:<-evCancelCtx.Done():2:return", "sid:%v tid:%v method:%q", s.id, s.targetID, method)
case ch <- msg:
// We expect only one response with the matching message ID,
// then remove event handler by cancelling context and stopping goroutine.
evCancelFn()
return
}
}
}
}
}()
s.onAll(evCancelCtx, chEvHandler)
defer evCancelFn() // Remove event handler
s.logger.Debugf("Session:Execute:s.conn.send", "sid:%v tid:%v method:%q", s.id, s.targetID, method)
var buf []byte
if params != nil {
var err error
buf, err = easyjson.Marshal(params)
if err != nil {
return err
}
}
msg := &cdproto.Message{
ID: id,
SessionID: s.id,
Method: cdproto.MethodType(method),
Params: buf,
}
return s.conn.send(contextWithDoneChan(ctx, s.done), msg, ch, res)
}
func (s *Session) ExecuteWithoutExpectationOnReply(ctx context.Context, method string, params easyjson.Marshaler, res easyjson.Unmarshaler) error {
s.logger.Debugf("Session:ExecuteWithoutExpectationOnReply", "sid:%v tid:%v method:%q", s.id, s.targetID, method)
if s.crashed {
s.logger.Debugf("Session:ExecuteWithoutExpectationOnReply", "sid:%v tid:%v method:%q, ErrTargetCrashed", s.id, s.targetID, method)
return ErrTargetCrashed
}
s.logger.Debugf("Session:Execute:s.conn.send", "sid:%v tid:%v method:%q", s.id, s.targetID, method)
var buf []byte
if params != nil {
var err error
buf, err = easyjson.Marshal(params)
if err != nil {
s.logger.Debugf("Session:ExecuteWithoutExpectationOnReply:Marshal", "sid:%v tid:%v method:%q err=%v", s.id, s.targetID, method, err)
return err
}
}
msg := &cdproto.Message{
ID: atomic.AddInt64(&s.msgID, 1),
// We use different sessions to send messages to "targets"
// (browser, page, frame etc.) in CDP.
//
// If we don't specify a session (a session ID in the JSON message),
// it will be a message for the browser target.
//
// With a session specified (set using cdp.WithExecutor(ctx, session)),
// it will properly route the CDP message to the correct target
// (page, frame etc.).
//
// The difference between using Connection and Session to send
// and receive CDP messages basically, they both implement
// the cdp.Executor interface but one adds a sessionID to
// the CPD messages:
SessionID: s.id,
Method: cdproto.MethodType(method),
Params: buf,
}
return s.conn.send(contextWithDoneChan(ctx, s.done), msg, nil, res)
}
// Done returns a channel that is closed when this session is closed.
func (s *Session) Done() <-chan struct{} {
return s.done
}
// Closed returns true if this session is closed.
func (s *Session) Closed() bool {
select {
case <-s.done:
return true
default:
return false
}
}