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producer.go
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producer.go
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package nsq
import (
"fmt"
"log"
"os"
"sync"
"sync/atomic"
"time"
)
// Producer is a high-level type to publish to NSQ.
//
// A Producer instance is 1:1 with a destination `nsqd`
// and will lazily connect to that instance (and re-connect)
// when Publish commands are executed.
type Producer struct {
id int64
addr string
conn *Conn
config Config
logger logger
logLvl LogLevel
responseChan chan []byte
errorChan chan []byte
closeChan chan int
transactionChan chan *ProducerTransaction
transactions []*ProducerTransaction
state int32
concurrentProducers int32
stopFlag int32
exitChan chan int
wg sync.WaitGroup
guard sync.Mutex
}
// ProducerTransaction is returned by the async publish methods
// to retrieve metadata about the command after the
// response is received.
type ProducerTransaction struct {
cmd *Command
doneChan chan *ProducerTransaction
Error error // the error (or nil) of the publish command
Args []interface{} // the slice of variadic arguments passed to PublishAsync or MultiPublishAsync
}
func (t *ProducerTransaction) finish() {
if t.doneChan != nil {
t.doneChan <- t
}
}
// NewProducer returns an instance of Producer for the specified address
//
// The only valid way to create a Config is via NewConfig, using a struct literal will panic.
// After Config is passed into NewProducer the values are no longer mutable (they are copied).
func NewProducer(addr string, config *Config) (*Producer, error) {
config.assertInitialized()
err := config.Validate()
if err != nil {
return nil, err
}
p := &Producer{
id: atomic.AddInt64(&instCount, 1),
addr: addr,
config: *config,
logger: log.New(os.Stderr, "", log.Flags()),
logLvl: LogLevelInfo,
transactionChan: make(chan *ProducerTransaction),
exitChan: make(chan int),
responseChan: make(chan []byte),
errorChan: make(chan []byte),
closeChan: make(chan int),
}
return p, nil
}
// SetLogger assigns the logger to use as well as a level
//
// The logger parameter is an interface that requires the following
// method to be implemented (such as the the stdlib log.Logger):
//
// Output(calldepth int, s string)
//
func (w *Producer) SetLogger(l logger, lvl LogLevel) {
w.logger = l
w.logLvl = lvl
}
// String returns the address of the Producer
func (w *Producer) String() string {
return w.addr
}
// Stop initiates a graceful stop of the Producer (permanent)
//
// NOTE: this blocks until completion
func (w *Producer) Stop() {
w.guard.Lock()
if !atomic.CompareAndSwapInt32(&w.stopFlag, 0, 1) {
w.guard.Unlock()
return
}
w.log(LogLevelInfo, "stopping")
close(w.exitChan)
w.close()
w.guard.Unlock()
w.wg.Wait()
}
// PublishAsync publishes a message body to the specified topic
// but does not wait for the response from `nsqd`.
//
// When the Producer eventually receives the response from `nsqd`,
// the supplied `doneChan` (if specified)
// will receive a `ProducerTransaction` instance with the supplied variadic arguments
// and the response error if present
func (w *Producer) PublishAsync(topic string, body []byte, doneChan chan *ProducerTransaction,
args ...interface{}) error {
return w.sendCommandAsync(Publish(topic, body), doneChan, args)
}
// MultiPublishAsync publishes a slice of message bodies to the specified topic
// but does not wait for the response from `nsqd`.
//
// When the Producer eventually receives the response from `nsqd`,
// the supplied `doneChan` (if specified)
// will receive a `ProducerTransaction` instance with the supplied variadic arguments
// and the response error if present
func (w *Producer) MultiPublishAsync(topic string, body [][]byte, doneChan chan *ProducerTransaction,
args ...interface{}) error {
cmd, err := MultiPublish(topic, body)
if err != nil {
return err
}
return w.sendCommandAsync(cmd, doneChan, args)
}
// Publish synchronously publishes a message body to the specified topic, returning
// the an error if publish failed
func (w *Producer) Publish(topic string, body []byte) error {
return w.sendCommand(Publish(topic, body))
}
// MultiPublish synchronously publishes a slice of message bodies to the specified topic, returning
// the an error if publish failed
func (w *Producer) MultiPublish(topic string, body [][]byte) error {
cmd, err := MultiPublish(topic, body)
if err != nil {
return err
}
return w.sendCommand(cmd)
}
func (w *Producer) sendCommand(cmd *Command) error {
doneChan := make(chan *ProducerTransaction)
err := w.sendCommandAsync(cmd, doneChan, nil)
if err != nil {
close(doneChan)
return err
}
t := <-doneChan
return t.Error
}
func (w *Producer) sendCommandAsync(cmd *Command, doneChan chan *ProducerTransaction,
args []interface{}) error {
// keep track of how many outstanding producers we're dealing with
// in order to later ensure that we clean them all up...
atomic.AddInt32(&w.concurrentProducers, 1)
defer atomic.AddInt32(&w.concurrentProducers, -1)
if atomic.LoadInt32(&w.state) != StateConnected {
err := w.connect()
if err != nil {
return err
}
}
t := &ProducerTransaction{
cmd: cmd,
doneChan: doneChan,
Args: args,
}
select {
case w.transactionChan <- t:
case <-w.exitChan:
return ErrStopped
}
return nil
}
func (w *Producer) connect() error {
w.guard.Lock()
defer w.guard.Unlock()
if atomic.LoadInt32(&w.stopFlag) == 1 {
return ErrStopped
}
if !atomic.CompareAndSwapInt32(&w.state, StateInit, StateConnected) {
return ErrNotConnected
}
w.log(LogLevelInfo, "(%s) connecting to nsqd", w.addr)
w.conn = NewConn(w.addr, &w.config, &producerConnDelegate{w})
w.conn.SetLogger(w.logger, w.logLvl, fmt.Sprintf("%3d (%%s)", w.id))
_, err := w.conn.Connect()
if err != nil {
w.conn.Close()
w.log(LogLevelError, "(%s) error connecting to nsqd - %s", w.addr, err)
atomic.StoreInt32(&w.state, StateInit)
return err
}
w.wg.Add(1)
go w.router()
return nil
}
func (w *Producer) close() {
if !atomic.CompareAndSwapInt32(&w.state, StateConnected, StateDisconnected) {
return
}
w.conn.Close()
go func() {
// we need to handle this in a goroutine so we don't
// block the caller from making progress
w.wg.Wait()
atomic.StoreInt32(&w.state, StateInit)
}()
}
func (w *Producer) router() {
for {
select {
case t := <-w.transactionChan:
w.transactions = append(w.transactions, t)
err := w.conn.WriteCommand(t.cmd)
if err != nil {
w.log(LogLevelError, "(%s) sending command - %s", w.conn.String(), err)
w.close()
}
case data := <-w.responseChan:
w.popTransaction(FrameTypeResponse, data)
case data := <-w.errorChan:
w.popTransaction(FrameTypeError, data)
case <-w.closeChan:
goto exit
case <-w.exitChan:
goto exit
}
}
exit:
w.transactionCleanup()
w.wg.Done()
w.log(LogLevelInfo, "exiting router")
}
func (w *Producer) popTransaction(frameType int32, data []byte) {
t := w.transactions[0]
w.transactions = w.transactions[1:]
if frameType == FrameTypeError {
t.Error = ErrProtocol{string(data)}
}
t.finish()
}
func (w *Producer) transactionCleanup() {
// clean up transactions we can easily account for
for _, t := range w.transactions {
t.Error = ErrNotConnected
t.finish()
}
w.transactions = w.transactions[:0]
// spin and free up any writes that might have raced
// with the cleanup process (blocked on writing
// to transactionChan)
for {
select {
case t := <-w.transactionChan:
t.Error = ErrNotConnected
t.finish()
default:
// keep spinning until there are 0 concurrent producers
if atomic.LoadInt32(&w.concurrentProducers) == 0 {
return
}
// give the runtime a chance to schedule other racing goroutines
time.Sleep(5 * time.Millisecond)
continue
}
}
}
func (w *Producer) log(lvl LogLevel, line string, args ...interface{}) {
if w.logger == nil {
return
}
if w.logLvl > lvl {
return
}
w.logger.Output(2, fmt.Sprintf("%-4s %3d %s", logPrefix(lvl), w.id, fmt.Sprintf(line, args...)))
}
func (w *Producer) onConnResponse(c *Conn, data []byte) { w.responseChan <- data }
func (w *Producer) onConnError(c *Conn, data []byte) { w.errorChan <- data }
func (w *Producer) onConnHeartbeat(c *Conn) {}
func (w *Producer) onConnIOError(c *Conn, err error) { w.close() }
func (w *Producer) onConnClose(c *Conn) { w.closeChan <- 1 }