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// Copyright 2013-2018 The NATS Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this 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 nats
import (
"errors"
"reflect"
)
// This allows the functionality for network channels by binding send and receive Go chans
// to subjects and optionally queue groups.
// Data will be encoded and decoded via the EncodedConn and its associated encoders.
// BindSendChan binds a channel for send operations to NATS.
func (c *EncodedConn) BindSendChan(subject string, channel interface{}) error {
chVal := reflect.ValueOf(channel)
if chVal.Kind() != reflect.Chan {
return ErrChanArg
}
go chPublish(c, chVal, subject)
return nil
}
// Publish all values that arrive on the channel until it is closed or we
// encounter an error.
func chPublish(c *EncodedConn, chVal reflect.Value, subject string) {
for {
val, ok := chVal.Recv()
if !ok {
// Channel has most likely been closed.
return
}
if e := c.Publish(subject, val.Interface()); e != nil {
// Do this under lock.
c.Conn.mu.Lock()
defer c.Conn.mu.Unlock()
if c.Conn.Opts.AsyncErrorCB != nil {
// FIXME(dlc) - Not sure this is the right thing to do.
// FIXME(ivan) - If the connection is not yet closed, try to schedule the callback
if c.Conn.isClosed() {
go c.Conn.Opts.AsyncErrorCB(c.Conn, nil, e)
} else {
c.Conn.ach.push(func() { c.Conn.Opts.AsyncErrorCB(c.Conn, nil, e) })
}
}
return
}
}
}
// BindRecvChan binds a channel for receive operations from NATS.
func (c *EncodedConn) BindRecvChan(subject string, channel interface{}) (*Subscription, error) {
return c.bindRecvChan(subject, _EMPTY_, channel)
}
// BindRecvQueueChan binds a channel for queue-based receive operations from NATS.
func (c *EncodedConn) BindRecvQueueChan(subject, queue string, channel interface{}) (*Subscription, error) {
return c.bindRecvChan(subject, queue, channel)
}
// Internal function to bind receive operations for a channel.
func (c *EncodedConn) bindRecvChan(subject, queue string, channel interface{}) (*Subscription, error) {
chVal := reflect.ValueOf(channel)
if chVal.Kind() != reflect.Chan {
return nil, ErrChanArg
}
argType := chVal.Type().Elem()
cb := func(m *Msg) {
var oPtr reflect.Value
if argType.Kind() != reflect.Ptr {
oPtr = reflect.New(argType)
} else {
oPtr = reflect.New(argType.Elem())
}
if err := c.Enc.Decode(m.Subject, m.Data, oPtr.Interface()); err != nil {
c.Conn.err = errors.New("nats: Got an error trying to unmarshal: " + err.Error())
if c.Conn.Opts.AsyncErrorCB != nil {
c.Conn.ach.push(func() { c.Conn.Opts.AsyncErrorCB(c.Conn, m.Sub, c.Conn.err) })
}
return
}
if argType.Kind() != reflect.Ptr {
oPtr = reflect.Indirect(oPtr)
}
// This is a bit hacky, but in this instance we may be trying to send to a closed channel.
// and the user does not know when it is safe to close the channel.
defer func() {
// If we have panicked, recover and close the subscription.
if r := recover(); r != nil {
m.Sub.Unsubscribe()
}
}()
// Actually do the send to the channel.
chVal.Send(oPtr)
}
return c.Conn.subscribe(subject, queue, cb, nil, false)
}
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