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client.go
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client.go
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package amqp
import (
"bytes"
"context"
"crypto/tls"
"encoding/base64"
"encoding/binary"
"errors"
"fmt"
"math"
"math/rand"
"net"
"net/url"
"sync"
"sync/atomic"
"time"
)
var (
// ErrSessionClosed is propagated to Sender/Receivers
// when Session.Close() is called.
ErrSessionClosed = errors.New("amqp: session closed")
// ErrLinkClosed returned by send and receive operations when
// Sender.Close() or Receiver.Close() are called.
ErrLinkClosed = errors.New("amqp: link closed")
)
// Client is an AMQP client connection.
type Client struct {
conn *conn
}
// Dial connects to an AMQP server.
//
// If the addr includes a scheme, it must be "amqp" or "amqps".
// If no port is provided, 5672 will be used for "amqp" and 5671 for "amqps".
//
// If username and password information is not empty it's used as SASL PLAIN
// credentials, equal to passing ConnSASLPlain option.
func Dial(addr string, opts ...ConnOption) (*Client, error) {
u, err := url.Parse(addr)
if err != nil {
return nil, err
}
host, port, err := net.SplitHostPort(u.Host)
if err != nil {
host = u.Host
port = "5672" // use default port values if parse fails
if u.Scheme == "amqps" {
port = "5671"
}
}
// prepend SASL credentials when the user/pass segment is not empty
if u.User != nil {
pass, _ := u.User.Password()
opts = append([]ConnOption{
ConnSASLPlain(u.User.Username(), pass),
}, opts...)
}
// append default options so user specified can overwrite
opts = append([]ConnOption{
ConnServerHostname(host),
}, opts...)
c, err := newConn(nil, opts...)
if err != nil {
return nil, err
}
switch u.Scheme {
case "amqp", "":
c.net, err = net.Dial("tcp", host+":"+port)
case "amqps":
c.initTLSConfig()
c.tlsNegotiation = false
c.net, err = tls.Dial("tcp", host+":"+port, c.tlsConfig)
default:
return nil, errorErrorf("unsupported scheme %q", u.Scheme)
}
if err != nil {
return nil, err
}
err = c.start()
return &Client{conn: c}, err
}
// New establishes an AMQP client connection over conn.
func New(conn net.Conn, opts ...ConnOption) (*Client, error) {
c, err := newConn(conn, opts...)
if err != nil {
return nil, err
}
err = c.start()
return &Client{conn: c}, err
}
// Close disconnects the connection.
func (c *Client) Close() error {
return c.conn.Close()
}
// NewSession opens a new AMQP session to the server.
func (c *Client) NewSession(opts ...SessionOption) (*Session, error) {
// get a session allocated by Client.mux
var sResp newSessionResp
select {
case <-c.conn.done:
return nil, c.conn.getErr()
case sResp = <-c.conn.newSession:
}
if sResp.err != nil {
return nil, sResp.err
}
s := sResp.session
for _, opt := range opts {
err := opt(s)
if err != nil {
_ = s.Close(context.Background()) // deallocate session on error
return nil, err
}
}
// send Begin to server
begin := &performBegin{
NextOutgoingID: 0,
IncomingWindow: s.incomingWindow,
OutgoingWindow: s.outgoingWindow,
HandleMax: s.handleMax,
}
debug(1, "TX: %s", begin)
s.txFrame(begin, nil)
// wait for response
var fr frame
select {
case <-c.conn.done:
return nil, c.conn.getErr()
case fr = <-s.rx:
}
debug(1, "RX: %s", fr.body)
begin, ok := fr.body.(*performBegin)
if !ok {
_ = s.Close(context.Background()) // deallocate session on error
return nil, errorErrorf("unexpected begin response: %+v", fr.body)
}
// start Session multiplexor
go s.mux(begin)
return s, nil
}
// Default session options
const (
DefaultMaxLinks = 4294967296
DefaultWindow = 100
)
// SessionOption is an function for configuring an AMQP session.
type SessionOption func(*Session) error
// SessionIncomingWindow sets the maximum number of unacknowledged
// transfer frames the server can send.
func SessionIncomingWindow(window uint32) SessionOption {
return func(s *Session) error {
s.incomingWindow = window
return nil
}
}
// SessionOutgoingWindow sets the maximum number of unacknowledged
// transfer frames the client can send.
func SessionOutgoingWindow(window uint32) SessionOption {
return func(s *Session) error {
s.outgoingWindow = window
return nil
}
}
// SessionMaxLinks sets the maximum number of links (Senders/Receivers)
// allowed on the session.
//
// n must be in the range 1 to 4294967296.
//
// Default: 4294967296.
func SessionMaxLinks(n int) SessionOption {
return func(s *Session) error {
if n < 1 {
return errorNew("max sessions cannot be less than 1")
}
if int64(n) > 4294967296 {
return errorNew("max sessions cannot be greater than 4294967296")
}
s.handleMax = uint32(n - 1)
return nil
}
}
// Session is an AMQP session.
//
// A session multiplexes Receivers.
type Session struct {
channel uint16 // session's local channel
remoteChannel uint16 // session's remote channel, owned by conn.mux
conn *conn // underlying conn
rx chan frame // frames destined for this session are sent on this chan by conn.mux
tx chan frameBody // non-transfer frames to be sent; session must track disposition
txTransfer chan *performTransfer // transfer frames to be sent; session must track disposition
// flow control
incomingWindow uint32
outgoingWindow uint32
handleMax uint32
allocateHandle chan *link // link handles are allocated by sending a link on this channel, nil is sent on link.rx once allocated
deallocateHandle chan *link // link handles are deallocated by sending a link on this channel
nextDeliveryID uint32 // atomically accessed sequence for deliveryIDs
// used for gracefully closing link
close chan struct{}
closeOnce sync.Once
done chan struct{}
err error
}
func newSession(c *conn, channel uint16) *Session {
return &Session{
conn: c,
channel: channel,
rx: make(chan frame),
tx: make(chan frameBody),
txTransfer: make(chan *performTransfer),
incomingWindow: DefaultWindow,
outgoingWindow: DefaultWindow,
handleMax: DefaultMaxLinks - 1,
allocateHandle: make(chan *link),
deallocateHandle: make(chan *link),
close: make(chan struct{}),
done: make(chan struct{}),
}
}
// Close gracefully closes the session.
//
// If ctx expires while waiting for servers response, ctx.Err() will be returned.
// The session will continue to wait for the response until the Client is closed.
func (s *Session) Close(ctx context.Context) error {
s.closeOnce.Do(func() { close(s.close) })
select {
case <-s.done:
case <-ctx.Done():
return ctx.Err()
}
if s.err == ErrSessionClosed {
return nil
}
return s.err
}
// txFrame sends a frame to the connWriter
func (s *Session) txFrame(p frameBody, done chan deliveryState) error {
return s.conn.wantWriteFrame(frame{
type_: frameTypeAMQP,
channel: s.channel,
body: p,
done: done,
})
}
// lockedRand provides a rand source that is safe for concurrent use.
type lockedRand struct {
mu sync.Mutex
src *rand.Rand
}
func (r *lockedRand) Read(p []byte) (int, error) {
r.mu.Lock()
defer r.mu.Unlock()
return r.src.Read(p)
}
// package scoped rand source to avoid any issues with seeding
// of the global source.
var pkgRand = &lockedRand{
src: rand.New(rand.NewSource(time.Now().UnixNano())),
}
// randBytes returns a base64 encoded string of n bytes.
func randString(n int) string {
b := make([]byte, n)
pkgRand.Read(b)
return base64.RawURLEncoding.EncodeToString(b)
}
// NewReceiver opens a new receiver link on the session.
func (s *Session) NewReceiver(opts ...LinkOption) (*Receiver, error) {
r := &Receiver{
batching: DefaultLinkBatching,
batchMaxAge: DefaultLinkBatchMaxAge,
maxCredit: DefaultLinkCredit,
}
l, err := attachLink(s, r, opts)
if err != nil {
return nil, err
}
r.link = l
// batching is just extra overhead when maxCredits == 1
if r.maxCredit == 1 {
r.batching = false
}
// create dispositions channel and start dispositionBatcher if batching enabled
if r.batching {
// buffer dispositions chan to prevent disposition sends from blocking
r.dispositions = make(chan messageDisposition, r.maxCredit)
go r.dispositionBatcher()
}
return r, nil
}
// Sender sends messages on a single AMQP link.
type Sender struct {
link *link
mu sync.Mutex // protects buf and nextDeliveryTag
buf buffer
nextDeliveryTag uint64
}
// Send sends a Message.
//
// Blocks until the message is sent, ctx completes, or an error occurs.
//
// Send is safe for concurrent use. Since only a single message can be
// sent on a link at a time, this is most useful when settlement confirmation
// has been requested (receiver settle mode is "Second"). In this case,
// additional messages can be sent while the current goroutine is waiting
// for the confirmation.
func (s *Sender) Send(ctx context.Context, msg *Message) error {
done, err := s.send(ctx, msg)
if err != nil {
return err
}
// wait for transfer to be confirmed
select {
case state := <-done:
if state, ok := state.(*stateRejected); ok {
return state.Error
}
return nil
case <-s.link.done:
return s.link.err
case <-ctx.Done():
return errorWrapf(ctx.Err(), "awaiting send")
}
}
// send is separated from Send so that the mutex unlock can be deferred without
// locking the transfer confirmation that happens in Send.
func (s *Sender) send(ctx context.Context, msg *Message) (chan deliveryState, error) {
if len(msg.DeliveryTag) > maxDeliveryTagLength {
return nil, errorErrorf("delivery tag is over the allowed %v bytes, len: %v", maxDeliveryTagLength, len(msg.DeliveryTag))
}
s.mu.Lock()
defer s.mu.Unlock()
s.buf.reset()
err := msg.marshal(&s.buf)
if err != nil {
return nil, err
}
if s.link.maxMessageSize != 0 && uint64(s.buf.len()) > s.link.maxMessageSize {
return nil, errorErrorf("encoded message size exceeds max of %d", s.link.maxMessageSize)
}
var (
maxPayloadSize = int64(s.link.session.conn.peerMaxFrameSize) - maxTransferFrameHeader
sndSettleMode = s.link.senderSettleMode
rcvSettleMode = s.link.receiverSettleMode
senderSettled = sndSettleMode != nil && *sndSettleMode == ModeSettled
deliveryID = atomic.AddUint32(&s.link.session.nextDeliveryID, 1)
)
deliveryTag := msg.DeliveryTag
if len(deliveryTag) == 0 {
// use uint64 encoded as []byte as deliveryTag
deliveryTag = make([]byte, 8)
binary.BigEndian.PutUint64(deliveryTag, s.nextDeliveryTag)
s.nextDeliveryTag++
}
fr := performTransfer{
Handle: s.link.handle,
DeliveryID: &deliveryID,
DeliveryTag: deliveryTag,
MessageFormat: &msg.Format,
More: s.buf.len() > 0,
}
for fr.More {
buf, _ := s.buf.next(maxPayloadSize)
fr.Payload = append([]byte(nil), buf...)
fr.More = s.buf.len() > 0
if !fr.More {
// mark final transfer as settled when sender mode is settled
fr.Settled = senderSettled
// set done on last frame to be closed after network transmission
//
// If confirmSettlement is true (ReceiverSettleMode == "second"),
// Session.mux will intercept the done channel and close it when the
// receiver has confirmed settlement instead of on net transmit.
fr.done = make(chan deliveryState, 1)
fr.confirmSettlement = rcvSettleMode != nil && *rcvSettleMode == ModeSecond
}
select {
case s.link.transfers <- fr:
case <-s.link.done:
return nil, s.link.err
case <-ctx.Done():
return nil, errorWrapf(ctx.Err(), "awaiting send")
}
// clear values that are only required on first message
fr.DeliveryID = nil
fr.DeliveryTag = nil
fr.MessageFormat = nil
}
return fr.done, nil
}
// Address returns the link's address.
func (s *Sender) Address() string {
if s.link.target == nil {
return ""
}
return s.link.target.Address
}
// Close closes the Sender and AMQP link.
func (s *Sender) Close(ctx context.Context) error {
return s.link.Close(ctx)
}
// NewSender opens a new sender link on the session.
func (s *Session) NewSender(opts ...LinkOption) (*Sender, error) {
l, err := attachLink(s, nil, opts)
if err != nil {
return nil, err
}
return &Sender{link: l}, nil
}
func (s *Session) mux(remoteBegin *performBegin) {
defer close(s.done)
var (
links = make(map[uint32]*link) // mapping of remote handles to links
linksByName = make(map[string]*link) // maping of names to links
handles = &bitmap{max: s.handleMax} // allocated handles
handlesByDeliveryID = make(map[uint32]uint32) // mapping of deliveryIDs to handles
deliveryIDByHandle = make(map[uint32]uint32) // mapping of handles to latest deliveryID
handlesByRemoteDeliveryID = make(map[uint32]uint32) // mapping of remote deliveryID to handles
settlementByDeliveryID = make(map[uint32]chan deliveryState)
// flow control values
nextOutgoingID uint32
nextIncomingID = remoteBegin.NextOutgoingID
remoteIncomingWindow = remoteBegin.IncomingWindow
remoteOutgoingWindow = remoteBegin.OutgoingWindow
)
for {
txTransfer := s.txTransfer
// disable txTransfer if flow control windows have been exceeded
if remoteIncomingWindow == 0 || s.outgoingWindow == 0 {
txTransfer = nil
}
select {
// conn has completed, exit
case <-s.conn.done:
s.err = s.conn.getErr()
return
// session is being closed by user
case <-s.close:
s.txFrame(&performEnd{}, nil)
// discard frames until End is received or conn closed
EndLoop:
for {
select {
case fr := <-s.rx:
_, ok := fr.body.(*performEnd)
if ok {
break EndLoop
}
case <-s.conn.done:
s.err = s.conn.getErr()
return
}
}
// release session
select {
case s.conn.delSession <- s:
s.err = ErrSessionClosed
case <-s.conn.done:
s.err = s.conn.getErr()
}
return
// handle allocation request
case l := <-s.allocateHandle:
// Check if link name already exists, if so then an error should be returned
if linksByName[l.name] != nil {
l.err = errorErrorf("link with name '%v' already exists", l.name)
l.rx <- nil
continue
}
next, ok := handles.next()
if !ok {
l.err = errorErrorf("reached session handle max (%d)", s.handleMax)
l.rx <- nil
continue
}
l.handle = next // allocate handle to the link
linksByName[l.name] = l // add to mapping
l.rx <- nil // send nil on channel to indicate allocation complete
// handle deallocation request
case l := <-s.deallocateHandle:
delete(links, l.remoteHandle)
delete(deliveryIDByHandle, l.handle)
delete(linksByName, l.name)
handles.remove(l.handle)
close(l.rx) // close channel to indicate deallocation
// incoming frame for link
case fr := <-s.rx:
debug(1, "RX(Session): %s", fr.body)
switch body := fr.body.(type) {
// Disposition frames can reference transfers from more than one
// link. Send this frame to all of them.
case *performDisposition:
start := body.First
end := start
if body.Last != nil {
end = *body.Last
}
for deliveryID := start; deliveryID <= end; deliveryID++ {
handles := handlesByDeliveryID
if body.Role == roleSender {
handles = handlesByRemoteDeliveryID
}
handle, ok := handles[deliveryID]
if !ok {
continue
}
delete(handles, deliveryID)
if body.Settled && body.Role == roleReceiver {
// check if settlement confirmation was requested, if so
// confirm by closing channel
if done, ok := settlementByDeliveryID[deliveryID]; ok {
delete(settlementByDeliveryID, deliveryID)
select {
case done <- body.State:
default:
}
close(done)
}
}
link, ok := links[handle]
if !ok {
continue
}
s.muxFrameToLink(link, fr.body)
}
continue
case *performFlow:
if body.NextIncomingID == nil {
// This is a protocol error:
// "[...] MUST be set if the peer has received
// the begin frame for the session"
s.txFrame(&performEnd{
Error: &Error{
Condition: ErrorNotAllowed,
Description: "next-incoming-id not set after session established",
},
}, nil)
s.err = errors.New("protocol error: received flow without next-incoming-id after session established")
return
}
// "When the endpoint receives a flow frame from its peer,
// it MUST update the next-incoming-id directly from the
// next-outgoing-id of the frame, and it MUST update the
// remote-outgoing-window directly from the outgoing-window
// of the frame."
nextIncomingID = body.NextOutgoingID
remoteOutgoingWindow = body.OutgoingWindow
// "The remote-incoming-window is computed as follows:
//
// next-incoming-id(flow) + incoming-window(flow) - next-outgoing-id(endpoint)
//
// If the next-incoming-id field of the flow frame is not set, then remote-incoming-window is computed as follows:
//
// initial-outgoing-id(endpoint) + incoming-window(flow) - next-outgoing-id(endpoint)"
remoteIncomingWindow = body.IncomingWindow - nextOutgoingID
remoteIncomingWindow += *body.NextIncomingID
// Send to link if handle is set
if body.Handle != nil {
link, ok := links[*body.Handle]
if !ok {
continue
}
s.muxFrameToLink(link, fr.body)
continue
}
if body.Echo {
niID := nextIncomingID
resp := &performFlow{
NextIncomingID: &niID,
IncomingWindow: s.incomingWindow,
NextOutgoingID: nextOutgoingID,
OutgoingWindow: s.outgoingWindow,
}
debug(1, "TX: %s", resp)
s.txFrame(resp, nil)
}
case *performAttach:
// On Attach response link should be looked up by name, then added
// to the links map with the remote's handle contained in this
// attach frame.
link, linkOk := linksByName[body.Name]
if !linkOk {
break
}
link.remoteHandle = body.Handle
links[link.remoteHandle] = link
s.muxFrameToLink(link, fr.body)
case *performTransfer:
// "Upon receiving a transfer, the receiving endpoint will
// increment the next-incoming-id to match the implicit
// transfer-id of the incoming transfer plus one, as well
// as decrementing the remote-outgoing-window, and MAY
// (depending on policy) decrement its incoming-window."
nextIncomingID++
remoteOutgoingWindow--
link, ok := links[body.Handle]
if !ok {
continue
}
select {
case <-s.conn.done:
case link.rx <- fr.body:
}
// if this message is received unsettled and link rcv-settle-mode == second, add to handlesByRemoteDeliveryID
if !body.Settled && body.DeliveryID != nil && link.receiverSettleMode != nil && *link.receiverSettleMode == ModeSecond {
handlesByRemoteDeliveryID[*body.DeliveryID] = body.Handle
}
// Update peer's outgoing window if half has been consumed.
if remoteOutgoingWindow < s.incomingWindow/2 {
nID := nextIncomingID
flow := &performFlow{
NextIncomingID: &nID,
IncomingWindow: s.incomingWindow,
NextOutgoingID: nextOutgoingID,
OutgoingWindow: s.outgoingWindow,
}
debug(1, "TX(Session): %s", flow)
s.txFrame(flow, nil)
remoteOutgoingWindow = s.incomingWindow
}
case *performDetach:
link, ok := links[body.Handle]
if !ok {
continue
}
s.muxFrameToLink(link, fr.body)
case *performEnd:
s.txFrame(&performEnd{}, nil)
s.err = errorErrorf("session ended by server: %s", body.Error)
return
default:
fmt.Printf("Unexpected frame: %s\n", body)
}
case fr := <-txTransfer:
// record current delivery ID
var deliveryID uint32
if fr.DeliveryID != nil {
deliveryID = *fr.DeliveryID
deliveryIDByHandle[fr.Handle] = deliveryID
// add to handleByDeliveryID if not sender-settled
if !fr.Settled {
handlesByDeliveryID[deliveryID] = fr.Handle
}
} else {
// if fr.DeliveryID is nil it must have been added
// to deliveryIDByHandle already
deliveryID = deliveryIDByHandle[fr.Handle]
}
// frame has been sender-settled, remove from map
if fr.Settled {
delete(handlesByDeliveryID, deliveryID)
}
// if confirmSettlement requested, add done chan to map
// and clear from frame so conn doesn't close it.
if fr.confirmSettlement && fr.done != nil {
settlementByDeliveryID[deliveryID] = fr.done
fr.done = nil
}
debug(2, "TX(Session): %s", fr)
s.txFrame(fr, fr.done)
// "Upon sending a transfer, the sending endpoint will increment
// its next-outgoing-id, decrement its remote-incoming-window,
// and MAY (depending on policy) decrement its outgoing-window."
nextOutgoingID++
remoteIncomingWindow--
case fr := <-s.tx:
switch fr := fr.(type) {
case *performFlow:
niID := nextIncomingID
fr.NextIncomingID = &niID
fr.IncomingWindow = s.incomingWindow
fr.NextOutgoingID = nextOutgoingID
fr.OutgoingWindow = s.outgoingWindow
debug(1, "TX(Session): %s", fr)
s.txFrame(fr, nil)
remoteOutgoingWindow = s.incomingWindow
case *performTransfer:
panic("transfer frames must use txTransfer")
default:
debug(1, "TX(Session): %s", fr)
s.txFrame(fr, nil)
}
}
}
}
func (s *Session) muxFrameToLink(l *link, fr frameBody) {
select {
case l.rx <- fr:
case <-l.done:
case <-s.conn.done:
}
}
// DetachError is returned by a link (Receiver/Sender) when a detach frame is received.
//
// RemoteError will be nil if the link was detached gracefully.
type DetachError struct {
RemoteError *Error
}
func (e *DetachError) Error() string {
return fmt.Sprintf("link detached, reason: %+v", e.RemoteError)
}
// Default link options
const (
DefaultLinkCredit = 1
DefaultLinkBatching = false
DefaultLinkBatchMaxAge = 5 * time.Second
)
// link is a unidirectional route.
//
// May be used for sending or receiving.
type link struct {
name string // our name
handle uint32 // our handle
remoteHandle uint32 // remote's handle
dynamicAddr bool // request a dynamic link address from the server
rx chan frameBody // sessions sends frames for this link on this channel
transfers chan performTransfer // sender uses to send transfer frames
closeOnce sync.Once // closeOnce protects close from being closed multiple times
close chan struct{} // close signals the mux to shutdown
done chan struct{} // done is closed by mux/muxDetach when the link is fully detached
detachErrorMu sync.Mutex // protects detachError
detachError *Error // error to send to remote on detach, set by closeWithError
session *Session // parent session
receiver *Receiver // allows link options to modify Receiver
source *source
target *target
properties map[symbol]interface{} // additional properties sent upon link attach
// "The delivery-count is initialized by the sender when a link endpoint is created,
// and is incremented whenever a message is sent. Only the sender MAY independently
// modify this field. The receiver's value is calculated based on the last known
// value from the sender and any subsequent messages received on the link. Note that,
// despite its name, the delivery-count is not a count but a sequence number
// initialized at an arbitrary point by the sender."
deliveryCount uint32
linkCredit uint32 // maximum number of messages allowed between flow updates
senderSettleMode *SenderSettleMode
receiverSettleMode *ReceiverSettleMode
maxMessageSize uint64
detachReceived bool
err error // err returned on Close()
// message receiving
paused uint32 // atomically accessed; indicates that all link credits have been used by sender
receiverReady chan struct{} // receiver sends on this when mux is paused to indicate it can handle more messages
messages chan Message // used to send completed messages to receiver
buf buffer // buffered bytes for current message
more bool // if true, buf contains a partial message
msg Message // current message being decoded
}
// attachLink is used by Receiver and Sender to create new links
func attachLink(s *Session, r *Receiver, opts []LinkOption) (*link, error) {
l, err := newLink(s, r, opts)
if err != nil {
return nil, err
}
isReceiver := r != nil
// buffer rx to linkCredit so that conn.mux won't block
// attempting to send to a slow reader
if isReceiver {
l.rx = make(chan frameBody, l.linkCredit)
} else {
l.rx = make(chan frameBody, 1)
}
// request handle from Session.mux
select {
case <-s.done:
return nil, s.err
case s.allocateHandle <- l:
}
// wait for handle allocation
select {
case <-s.done:
return nil, s.err
case <-l.rx:
}
// check for link request error
if l.err != nil {
return nil, l.err
}
attach := &performAttach{
Name: l.name,
Handle: l.handle,
ReceiverSettleMode: l.receiverSettleMode,
SenderSettleMode: l.senderSettleMode,
MaxMessageSize: l.maxMessageSize,
Source: l.source,
Target: l.target,
Properties: l.properties,
}
if isReceiver {
attach.Role = roleReceiver
if attach.Source == nil {
attach.Source = new(source)
}
attach.Source.Dynamic = l.dynamicAddr
} else {
attach.Role = roleSender
if attach.Target == nil {
attach.Target = new(target)
}
attach.Target.Dynamic = l.dynamicAddr
}
// send Attach frame
debug(1, "TX: %s", attach)
s.txFrame(attach, nil)
// wait for response
var fr frameBody
select {
case <-s.done:
return nil, s.err
case fr = <-l.rx:
}
debug(3, "RX: %s", fr)
resp, ok := fr.(*performAttach)
if !ok {
return nil, errorErrorf("unexpected attach response: %#v", fr)
}
if l.maxMessageSize == 0 || resp.MaxMessageSize < l.maxMessageSize {
l.maxMessageSize = resp.MaxMessageSize
}
if isReceiver {
// if dynamic address requested, copy assigned name to address
if l.dynamicAddr && resp.Source != nil {
l.source.Address = resp.Source.Address
}
// deliveryCount is a sequence number, must initialize to sender's initial sequence number
l.deliveryCount = resp.InitialDeliveryCount
// buffer receiver so that link.mux doesn't block
l.messages = make(chan Message, l.receiver.maxCredit)
if resp.SenderSettleMode != nil {
l.senderSettleMode = resp.SenderSettleMode
}
} else {
// if dynamic address requested, copy assigned name to address
if l.dynamicAddr && resp.Target != nil {
l.target.Address = resp.Target.Address
}
l.transfers = make(chan performTransfer)
if resp.ReceiverSettleMode != nil {
l.receiverSettleMode = resp.ReceiverSettleMode
}
}
go l.mux()
return l, nil
}
func newLink(s *Session, r *Receiver, opts []LinkOption) (*link, error) {
l := &link{
name: randString(40),
session: s,
receiver: r,
close: make(chan struct{}),
done: make(chan struct{}),
receiverReady: make(chan struct{}, 1),
}
// configure options
for _, o := range opts {
err := o(l)
if err != nil {
return nil, err
}
}
return l, nil
}
func (l *link) mux() {
defer l.muxDetach()
var (
isReceiver = l.receiver != nil
isSender = !isReceiver
)
Loop:
for {