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req.go
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req.go
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// Copyright 2018 The Mangos Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use 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 req implements the REQ protocol, which is the request side of
// the request/response pattern. (REP is the response.)
package req
import (
"encoding/binary"
"sync"
"time"
"nanomsg.org/go-mangos"
)
// req is an implementation of the req protocol.
type req struct {
sync.Mutex
sock mangos.ProtocolSocket
eps map[uint32]*reqEp
resend chan *mangos.Message
raw bool
retry time.Duration
nextid uint32
waker *time.Timer
w mangos.Waiter
init sync.Once
// fields describing the outstanding request
reqmsg *mangos.Message
reqid uint32
}
type reqEp struct {
ep mangos.Endpoint
cq chan struct{}
}
func (r *req) Init(socket mangos.ProtocolSocket) {
r.sock = socket
r.eps = make(map[uint32]*reqEp)
r.resend = make(chan *mangos.Message)
r.w.Init()
r.nextid = uint32(time.Now().UnixNano()) // quasi-random
r.retry = time.Minute * 1 // retry after a minute
r.waker = time.NewTimer(r.retry)
r.waker.Stop()
r.sock.SetRecvError(mangos.ErrProtoState)
}
func (r *req) Shutdown(expire time.Time) {
r.w.WaitAbsTimeout(expire)
}
// nextID returns the next request ID.
func (r *req) nextID() uint32 {
// The high order bit is "special", and must always be set. (This is
// how the peer will detect the end of the backtrace.)
v := r.nextid | 0x80000000
r.nextid++
return v
}
// resend sends the request message again, after a timer has expired.
func (r *req) resender() {
defer r.w.Done()
cq := r.sock.CloseChannel()
for {
select {
case <-r.waker.C:
case <-cq:
return
}
r.Lock()
m := r.reqmsg
if m == nil {
r.Unlock()
continue
}
m = m.Dup()
r.Unlock()
r.resend <- m
r.Lock()
if r.retry > 0 {
r.waker.Reset(r.retry)
} else {
r.waker.Stop()
}
r.Unlock()
}
}
func (r *req) receiver(ep mangos.Endpoint) {
rq := r.sock.RecvChannel()
cq := r.sock.CloseChannel()
for {
m := ep.RecvMsg()
if m == nil {
break
}
if len(m.Body) < 4 {
m.Free()
continue
}
m.Header = append(m.Header, m.Body[:4]...)
m.Body = m.Body[4:]
select {
case rq <- m:
case <-cq:
m.Free()
break
}
}
}
func (r *req) sender(pe *reqEp) {
// NB: Because this function is only called when an endpoint is
// added, we can reasonably safely cache the channels -- they won't
// be changing after this point.
defer r.w.Done()
sq := r.sock.SendChannel()
cq := r.sock.CloseChannel()
rq := r.resend
for {
var m *mangos.Message
select {
case m = <-rq:
case m = <-sq:
case <-cq:
return
case <-pe.cq:
return
}
if pe.ep.SendMsg(m) != nil {
r.resend <- m
break
}
}
}
func (*req) Number() uint16 {
return mangos.ProtoReq
}
func (*req) PeerNumber() uint16 {
return mangos.ProtoRep
}
func (*req) Name() string {
return "req"
}
func (*req) PeerName() string {
return "rep"
}
func (r *req) AddEndpoint(ep mangos.Endpoint) {
r.init.Do(func() {
r.w.Add()
go r.resender()
})
pe := &reqEp{cq: make(chan struct{}), ep: ep}
r.Lock()
r.eps[ep.GetID()] = pe
r.Unlock()
go r.receiver(ep)
r.w.Add()
go r.sender(pe)
}
func (r *req) RemoveEndpoint(ep mangos.Endpoint) {
id := ep.GetID()
r.Lock()
pe := r.eps[id]
delete(r.eps, id)
r.Unlock()
if pe != nil {
close(pe.cq)
}
}
func (r *req) SendHook(m *mangos.Message) bool {
if r.raw {
// Raw mode has no automatic retry, and must include the
// request id in the header coming down.
return true
}
r.Lock()
defer r.Unlock()
// We need to generate a new request id, and append it to the header.
r.reqid = r.nextID()
v := r.reqid
m.Header = append(m.Header,
byte(v>>24), byte(v>>16), byte(v>>8), byte(v))
r.reqmsg = m.Dup()
// Schedule a retry, in case we don't get a reply.
if r.retry > 0 {
r.waker.Reset(r.retry)
} else {
r.waker.Stop()
}
r.sock.SetRecvError(nil)
return true
}
func (r *req) RecvHook(m *mangos.Message) bool {
if r.raw {
// Raw mode just passes up messages unmolested.
return true
}
r.Lock()
defer r.Unlock()
if len(m.Header) < 4 {
return false
}
if r.reqmsg == nil {
return false
}
if binary.BigEndian.Uint32(m.Header) != r.reqid {
return false
}
r.waker.Stop()
m = r.reqmsg
r.reqmsg = nil
m.Free()
r.sock.SetRecvError(mangos.ErrProtoState)
return true
}
func (r *req) SetOption(option string, value interface{}) error {
var ok bool
switch option {
case mangos.OptionRaw:
if r.raw, ok = value.(bool); !ok {
return mangos.ErrBadValue
}
if r.raw {
r.sock.SetRecvError(nil)
} else {
r.sock.SetRecvError(mangos.ErrProtoState)
}
return nil
case mangos.OptionRetryTime:
r.Lock()
r.retry, ok = value.(time.Duration)
r.Unlock()
if !ok {
return mangos.ErrBadValue
}
return nil
default:
return mangos.ErrBadOption
}
}
func (r *req) GetOption(option string) (interface{}, error) {
switch option {
case mangos.OptionRaw:
return r.raw, nil
case mangos.OptionRetryTime:
r.Lock()
v := r.retry
r.Unlock()
return v, nil
default:
return nil, mangos.ErrBadOption
}
}
// NewSocket allocates a new Socket using the REQ protocol.
func NewSocket() (mangos.Socket, error) {
return mangos.MakeSocket(&req{}), nil
}