func ExampleConnection_NotifyBlocked() {
// Simply logs when the server throttles the TCP connection for publishers
// Test this by tuning your server to have a low memory watermark:
// rabbitmqctl set_vm_memory_high_watermark 0.00000001
conn, err := amqp.Dial("amqp://*****:*****@localhost:5672/")
if err != nil {
log.Fatalf("connection.open: %s", err)
}
defer conn.Close()
blockings := conn.NotifyBlocked(make(chan amqp.Blocking))
go func() {
for b := range blockings {
if b.Active {
log.Printf("TCP blocked: %q", b.Reason)
} else {
log.Printf("TCP unblocked")
}
}
}()
// Your application domain channel setup publishings
publishAllTheThings(conn)
}
// AmqpChannel is the same as amqpConnect in boulder, but with even
// more aggressive error dropping
func AmqpChannel(url string) (ch *amqp.Channel) {
conn, err := amqp.Dial(url)
FailOnError(err, "Unable to connect to AMQP server")
ch, err = conn.Channel()
FailOnError(err, "Unable to establish channel to AMQP server")
return
}
// A simplified way to get a channel for a given AMQP server
func amqpConnect(url string) (ch *amqp.Channel, err error) {
conn, err := amqp.Dial(url)
if err != nil {
return
}
ch, err = conn.Channel()
return
}
// Every connection should declare the topology they expect
func setup(url, queue string) (*amqp.Connection, *amqp.Channel, error) {
conn, err := amqp.Dial(url)
if err != nil {
return nil, nil, err
}
ch, err := conn.Channel()
if err != nil {
return nil, nil, err
}
if _, err := ch.QueueDeclare(queue, false, true, false, false, nil); err != nil {
return nil, nil, err
}
return conn, ch, nil
}
func ExampleChannel_Publish() {
// Connects opens an AMQP connection from the credentials in the URL.
conn, err := amqp.Dial("amqp://*****:*****@localhost:5672/")
if err != nil {
log.Fatalf("connection.open: %s", err)
}
// This waits for a server acknowledgment which means the sockets will have
// flushed all outbound publishings prior to returning. It's important to
// block on Close to not lose any publishings.
defer conn.Close()
c, err := conn.Channel()
if err != nil {
log.Fatalf("channel.open: %s", err)
}
// We declare our topology on both the publisher and consumer to ensure they
// are the same. This is part of AMQP being a programmable messaging model.
//
// See the Channel.Consume example for the complimentary declare.
err = c.ExchangeDeclare("logs", "topic", true, false, false, false, nil)
if err != nil {
log.Fatalf("exchange.declare: %v", err)
}
// Prepare this message to be persistent. Your publishing requirements may
// be different.
msg := amqp.Publishing{
DeliveryMode: amqp.Persistent,
Timestamp: time.Now(),
ContentType: "text/plain",
Body: []byte("Go Go AMQP!"),
}
// This is not a mandatory delivery, so it will be dropped if there are no
// queues bound to the logs exchange.
err = c.Publish("logs", "info", false, false, msg)
if err != nil {
// Since publish is asynchronous this can happen if the network connection
// is reset or if the server has run out of resources.
log.Fatalf("basic.publish: %v", err)
}
}
func main() {
server := *server
conn, err := amqp.Dial(server)
cmd.FailOnError(err, "Could not connect to AMQP")
ch, err := conn.Channel()
cmd.FailOnError(err, "Could not connect to AMQP")
err = ch.ExchangeDeclare(
amqpExchange,
amqpExchangeType,
amqpExchangeDurable,
amqpDeleteUnused,
amqpInternal,
amqpNoWait,
nil)
cmd.FailOnError(err, "Declaring exchange")
_, err = ch.QueueDeclare(
monitorQueueName,
amqpQueueDurable,
amqpDeleteUnused,
amqpExclusive,
amqpNoWait,
nil)
if err != nil {
cmd.FailOnError(err, "Could not declare queue")
}
routingKey := "#" //wildcard
err = ch.QueueBind(
monitorQueueName,
routingKey,
amqpExchange,
false,
nil)
if err != nil {
txt := fmt.Sprintf("Could not bind to queue [%s]. NOTE: You may need to delete %s to re-trigger the bind attempt after fixing permissions, or manually bind the queue to %s.", monitorQueueName, monitorQueueName, routingKey)
cmd.FailOnError(err, txt)
}
}
// AmqpChannel sets a AMQP connection up using SSL if configuration is provided
func AmqpChannel(conf cmd.Config) (*amqp.Channel, error) {
var conn *amqp.Connection
var err error
log := blog.GetAuditLogger()
if conf.AMQP.Insecure == true {
// If the Insecure flag is true, then just go ahead and connect
conn, err = amqp.Dial(conf.AMQP.Server)
} else {
// The insecure flag is false or not set, so we need to load up the options
log.Info("AMQPS: Loading TLS Options.")
if strings.HasPrefix(conf.AMQP.Server, "amqps") == false {
err = fmt.Errorf("AMQPS: Not using an AMQPS URL. To use AMQP instead of AMQPS, set insecure=true.")
return nil, err
}
if conf.AMQP.TLS == nil {
err = fmt.Errorf("AMQPS: No TLS configuration provided. To use AMQP instead of AMQPS, set insecure=true.")
return nil, err
}
cfg := new(tls.Config)
// If the configuration specified a certificate (or key), load them
if conf.AMQP.TLS.CertFile != nil || conf.AMQP.TLS.KeyFile != nil {
// But they have to give both.
if conf.AMQP.TLS.CertFile == nil || conf.AMQP.TLS.KeyFile == nil {
err = fmt.Errorf("AMQPS: You must set both of the configuration values AMQP.TLS.KeyFile and AMQP.TLS.CertFile")
return nil, err
}
cert, err := tls.LoadX509KeyPair(*conf.AMQP.TLS.CertFile, *conf.AMQP.TLS.KeyFile)
if err != nil {
err = fmt.Errorf("AMQPS: Could not load Client Certificate or Key: %s", err)
return nil, err
}
log.Info("AMQPS: Configured client certificate for AMQPS.")
cfg.Certificates = append(cfg.Certificates, cert)
}
// If the configuration specified a CA certificate, make it the only
// available root.
if conf.AMQP.TLS.CACertFile != nil {
cfg.RootCAs = x509.NewCertPool()
ca, err := ioutil.ReadFile(*conf.AMQP.TLS.CACertFile)
if err != nil {
err = fmt.Errorf("AMQPS: Could not load CA Certificate: %s", err)
return nil, err
}
cfg.RootCAs.AppendCertsFromPEM(ca)
log.Info("AMQPS: Configured CA certificate for AMQPS.")
}
conn, err = amqp.DialTLS(conf.AMQP.Server, cfg)
}
if err != nil {
return nil, err
}
err = AMQPDeclareExchange(conn)
if err != nil {
return nil, err
}
return conn.Channel()
}
// AmqpChannel sets a AMQP connection up using SSL if configuration is provided
func AmqpChannel(conf cmd.Config) (*amqp.Channel, error) {
var conn *amqp.Connection
var err error
log := blog.GetAuditLogger()
if conf.AMQP.TLS == nil {
// Configuration did not specify TLS options, but Dial will
// use TLS anyway if the URL scheme is "amqps"
conn, err = amqp.Dial(conf.AMQP.Server)
} else {
// They provided TLS options, so let's load them.
log.Info("AMQPS: Loading TLS Options.")
if strings.HasPrefix(conf.AMQP.Server, "amqps") == false {
err = fmt.Errorf("AMQPS: TLS configuration provided, but not using an AMQPS URL")
return nil, err
}
cfg := new(tls.Config)
// If the configuration specified a certificate (or key), load them
if conf.AMQP.TLS.CertFile != nil || conf.AMQP.TLS.KeyFile != nil {
// But they have to give both.
if conf.AMQP.TLS.CertFile == nil || conf.AMQP.TLS.KeyFile == nil {
err = fmt.Errorf("AMQPS: You must set both of the configuration values AMQP.TLS.KeyFile and AMQP.TLS.CertFile")
return nil, err
}
cert, err := tls.LoadX509KeyPair(*conf.AMQP.TLS.CertFile, *conf.AMQP.TLS.KeyFile)
if err != nil {
err = fmt.Errorf("AMQPS: Could not load Client Certificate or Key: %s", err)
return nil, err
}
log.Info("AMQPS: Configured client certificate for AMQPS.")
cfg.Certificates = append(cfg.Certificates, cert)
}
// If the configuration specified a CA certificate, make it the only
// available root.
if conf.AMQP.TLS.CACertFile != nil {
cfg.RootCAs = x509.NewCertPool()
ca, err := ioutil.ReadFile(*conf.AMQP.TLS.CACertFile)
if err != nil {
err = fmt.Errorf("AMQPS: Could not load CA Certificate: %s", err)
return nil, err
}
cfg.RootCAs.AppendCertsFromPEM(ca)
log.Info("AMQPS: Configured CA certificate for AMQPS.")
}
conn, err = amqp.DialTLS(conf.AMQP.Server, cfg)
}
if err != nil {
return nil, err
}
err = AMQPDeclareExchange(conn)
if err != nil {
return nil, err
}
return conn.Channel()
}
func ExampleChannel_Confirm_bridge() {
// This example acts as a bridge, shoveling all messages sent from the source
// exchange "log" to destination exchange "log".
// Confirming publishes can help from overproduction and ensure every message
// is delivered.
// Setup the source of the store and forward
source, err := amqp.Dial("amqp://source/")
if err != nil {
log.Fatalf("connection.open source: %s", err)
}
defer source.Close()
chs, err := source.Channel()
if err != nil {
log.Fatalf("channel.open source: %s", err)
}
if err := chs.ExchangeDeclare("log", "topic", true, false, false, false, nil); err != nil {
log.Fatalf("exchange.declare destination: %s", err)
}
if _, err := chs.QueueDeclare("remote-tee", true, true, false, false, nil); err != nil {
log.Fatalf("queue.declare source: %s", err)
}
if err := chs.QueueBind("remote-tee", "#", "logs", false, nil); err != nil {
log.Fatalf("queue.bind source: %s", err)
}
shovel, err := chs.Consume("remote-tee", "shovel", false, false, false, false, nil)
if err != nil {
log.Fatalf("basic.consume source: %s", err)
}
// Setup the destination of the store and forward
destination, err := amqp.Dial("amqp://destination/")
if err != nil {
log.Fatalf("connection.open destination: %s", err)
}
defer destination.Close()
chd, err := destination.Channel()
if err != nil {
log.Fatalf("channel.open destination: %s", err)
}
if err := chd.ExchangeDeclare("log", "topic", true, false, false, false, nil); err != nil {
log.Fatalf("exchange.declare destination: %s", err)
}
// Buffer of 1 for our single outstanding publishing
pubAcks, pubNacks := chd.NotifyConfirm(make(chan uint64, 1), make(chan uint64, 1))
if err := chd.Confirm(false); err != nil {
log.Fatalf("confirm.select destination: %s", err)
}
// Now pump the messages, one by one, a smarter implementation
// would batch the deliveries and use multiple ack/nacks
for {
msg, ok := <-shovel
if !ok {
log.Fatalf("source channel closed, see the reconnect example for handling this")
}
err = chd.Publish("logs", msg.RoutingKey, false, false, amqp.Publishing{
// Copy all the properties
ContentType: msg.ContentType,
ContentEncoding: msg.ContentEncoding,
DeliveryMode: msg.DeliveryMode,
Priority: msg.Priority,
CorrelationId: msg.CorrelationId,
ReplyTo: msg.ReplyTo,
Expiration: msg.Expiration,
MessageId: msg.MessageId,
Timestamp: msg.Timestamp,
Type: msg.Type,
UserId: msg.UserId,
AppId: msg.AppId,
// Custom headers
Headers: msg.Headers,
// And the body
Body: msg.Body,
})
if err != nil {
msg.Nack(false, false)
log.Fatalf("basic.publish destination: %s", msg)
}
// only ack the source delivery when the destination acks the publishing
// here you could check for delivery order by keeping a local state of
// expected delivery tags
select {
case <-pubAcks:
msg.Ack(false)
case <-pubNacks:
msg.Nack(false, false)
}
}
}
func ExampleChannel_Consume() {
// Connects opens an AMQP connection from the credentials in the URL.
conn, err := amqp.Dial("amqp://*****:*****@localhost:5672/")
if err != nil {
log.Fatalf("connection.open: %s", err)
}
defer conn.Close()
c, err := conn.Channel()
if err != nil {
log.Fatalf("channel.open: %s", err)
}
// We declare our topology on both the publisher and consumer to ensure they
// are the same. This is part of AMQP being a programmable messaging model.
//
// See the Channel.Publish example for the complimentary declare.
err = c.ExchangeDeclare("logs", "topic", true, false, false, false, nil)
if err != nil {
log.Fatalf("exchange.declare: %s", err)
}
// Establish our queue topologies that we are responsible for
type bind struct {
queue string
key string
}
bindings := []bind{
bind{"page", "alert"},
bind{"email", "info"},
bind{"firehose", "#"},
}
for _, b := range bindings {
_, err = c.QueueDeclare(b.queue, true, false, false, false, nil)
if err != nil {
log.Fatalf("queue.declare: %v", err)
}
err = c.QueueBind(b.queue, b.key, "logs", false, nil)
if err != nil {
log.Fatalf("queue.bind: %v", err)
}
}
// Set our quality of service. Since we're sharing 3 consumers on the same
// channel, we want at least 3 messages in flight.
err = c.Qos(3, 0, false)
if err != nil {
log.Fatalf("basic.qos: %v", err)
}
// Establish our consumers that have different responsibilities. Our first
// two queues do not ack the messages on the server, so require to be acked
// on the client.
pages, err := c.Consume("page", "pager", false, false, false, false, nil)
if err != nil {
log.Fatalf("basic.consume: %v", err)
}
go func() {
for log := range pages {
// ... this consumer is responsible for sending pages per log
log.Ack(false)
}
}()
// Notice how the concern for which messages arrive here are in the AMQP
// topology and not in the queue. We let the server pick a consumer tag this
// time.
emails, err := c.Consume("email", "", false, false, false, false, nil)
if err != nil {
log.Fatalf("basic.consume: %v", err)
}
go func() {
for log := range emails {
// ... this consumer is responsible for sending emails per log
log.Ack(false)
}
}()
// This consumer requests that every message is acknowledged as soon as it's
// delivered.
firehose, err := c.Consume("firehose", "", true, false, false, false, nil)
if err != nil {
log.Fatalf("basic.consume: %v", err)
}
// To show how to process the items in parallel, we'll use a work pool.
for i := 0; i < runtime.NumCPU(); i++ {
go func(work <-chan amqp.Delivery) {
for _ = range work {
// ... this consumer pulls from the firehose and doesn't need to acknowledge
}
}(firehose)
}
// Wait until you're ready to finish, could be a signal handler here.
time.Sleep(10 * time.Second)
// Cancelling a consumer by name will finish the range and gracefully end the
// goroutine
err = c.Cancel("pager", false)
if err != nil {
log.Fatalf("basic.cancel: %v", err)
}
// deferred closing the Connection will also finish the consumer's ranges of
// their delivery chans. If you need every delivery to be processed, make
// sure to wait for all consumers goroutines to finish before exiting your
// process.
}