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fan_in.go
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fan_in.go
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// Copyright (c) 2014 Ashley Jeffs
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package broker
import (
"time"
"github.com/Jeffail/benthos/lib/types"
"github.com/Jeffail/benthos/lib/util/service/metrics"
)
//------------------------------------------------------------------------------
// wrappedMsg used to forward an inputs message and res channel to the FanIn
// broker.
type wrappedMsg struct {
msg types.Message
resChan chan<- types.Response
}
//------------------------------------------------------------------------------
// FanIn is a broker that implements types.Producer, takes an array of inputs
// and routes them through a single message channel.
type FanIn struct {
stats metrics.Type
messageChan chan types.Message
responseChan <-chan types.Response
closables []types.Closable
wrappedMsgsChan chan wrappedMsg
inputClosedChan chan int
inputMap map[int]struct{}
closedChan chan struct{}
}
// NewFanIn creates a new FanIn type by providing inputs.
func NewFanIn(inputs []types.Producer, stats metrics.Type) (*FanIn, error) {
i := &FanIn{
stats: stats,
messageChan: make(chan types.Message),
responseChan: nil,
wrappedMsgsChan: make(chan wrappedMsg),
inputClosedChan: make(chan int),
inputMap: make(map[int]struct{}),
closables: []types.Closable{},
closedChan: make(chan struct{}),
}
for n, input := range inputs {
if closable, ok := input.(types.Closable); ok {
i.closables = append(i.closables, closable)
}
// Keep track of # open inputs
i.inputMap[n] = struct{}{}
// Create unique response channel for each input
resChan := make(chan types.Response)
if err := inputs[n].StartListening(resChan); err != nil {
return nil, err
}
// Launch goroutine that async writes input into single channel
go func(index int) {
defer func() {
// If the input closes we need to signal to the broker
i.inputClosedChan <- index
}()
for {
in, open := <-inputs[index].MessageChan()
if !open {
return
}
i.wrappedMsgsChan <- wrappedMsg{
msg: in,
resChan: resChan,
}
}
}(n)
}
return i, nil
}
//------------------------------------------------------------------------------
// StartListening assigns a new responses channel for the broker to read.
func (i *FanIn) StartListening(responseChan <-chan types.Response) error {
if i.responseChan != nil {
return types.ErrAlreadyStarted
}
i.responseChan = responseChan
go i.loop()
return nil
}
// MessageChan returns the channel used for consuming messages from this broker.
func (i *FanIn) MessageChan() <-chan types.Message {
return i.messageChan
}
//------------------------------------------------------------------------------
// loop is an internal loop that brokers incoming messages to many outputs.
func (i *FanIn) loop() {
defer func() {
close(i.wrappedMsgsChan)
close(i.inputClosedChan)
close(i.messageChan)
close(i.closedChan)
}()
for len(i.inputMap) > 0 {
select {
case wrap := <-i.wrappedMsgsChan:
i.stats.Incr("broker.fan_in.messages.received", 1)
i.messageChan <- wrap.msg
// TODO: If our output closes it won't be propagated.
wrap.resChan <- <-i.responseChan
case index := <-i.inputClosedChan:
delete(i.inputMap, index)
}
}
}
// CloseAsync shuts down the FanIn broker and stops processing requests.
func (i *FanIn) CloseAsync() {
for _, closable := range i.closables {
closable.CloseAsync()
}
}
// WaitForClose blocks until the FanIn broker has closed down.
func (i *FanIn) WaitForClose(timeout time.Duration) error {
select {
case <-i.closedChan:
case <-time.After(timeout):
return types.ErrTimeout
}
return nil
}
//------------------------------------------------------------------------------