// A simplified way to declare and subscribe to an AMQP queue
func amqpSubscribe(ch *amqp.Channel, name string, log *blog.AuditLogger) (msgs <-chan amqp.Delivery, err error) {
err = ch.ExchangeDeclare(
AmqpExchange,
AmqpExchangeType,
AmqpDurable,
AmqpDeleteUnused,
AmqpInternal,
AmqpNoWait,
nil)
if err != nil {
log.Crit(fmt.Sprintf("Could not declare exchange: %s", err))
return
}
q, err := ch.QueueDeclare(
name,
AmqpDurable,
AmqpDeleteUnused,
AmqpExclusive,
AmqpNoWait,
nil)
if err != nil {
log.Crit(fmt.Sprintf("Could not declare queue: %s", err))
return
}
err = ch.QueueBind(
name,
name,
AmqpExchange,
false,
nil)
if err != nil {
log.Crit(fmt.Sprintf("Could not bind queue: %s", err))
return
}
msgs, err = ch.Consume(
q.Name,
"",
AmqpAutoAck,
AmqpExclusive,
AmqpNoLocal,
AmqpNoWait,
nil)
if err != nil {
log.Crit(fmt.Sprintf("Could not subscribe to queue: %s", err))
return
}
return
}
// AMQPDeclareExchange attempts to declare the configured AMQP exchange,
// returning silently if already declared, erroring if nonexistant and
// unable to create.
func amqpDeclareExchange(conn *amqp.Connection) error {
var err error
var ch *amqp.Channel
log := blog.GetAuditLogger()
ch, err = conn.Channel()
if err != nil {
log.Crit(fmt.Sprintf("Could not connect Channel: %s", err))
return err
}
err = ch.ExchangeDeclarePassive(
AmqpExchange,
AmqpExchangeType,
AmqpDurable,
AmqpDeleteUnused,
AmqpInternal,
AmqpNoWait,
nil)
if err != nil {
log.Info(fmt.Sprintf("Exchange %s does not exist on AMQP server, creating.", AmqpExchange))
// Channel is invalid at this point, so recreate
ch.Close()
ch, err = conn.Channel()
if err != nil {
log.Crit(fmt.Sprintf("Could not connect Channel: %s", err))
return err
}
err = ch.ExchangeDeclare(
AmqpExchange,
AmqpExchangeType,
AmqpDurable,
AmqpDeleteUnused,
AmqpInternal,
AmqpNoWait,
nil)
if err != nil {
log.Crit(fmt.Sprintf("Could not declare exchange: %s", err))
ch.Close()
return err
}
log.Info(fmt.Sprintf("Created exchange %s.", AmqpExchange))
}
ch.Close()
return err
}
func startMonitor(rpcCh *amqp.Channel, logger *blog.AuditLogger, stats statsd.Statter) {
ae := analysisengine.NewLoggingAnalysisEngine()
// For convenience at the broker, identifiy ourselves by hostname
consumerTag, err := os.Hostname()
if err != nil {
cmd.FailOnError(err, "Could not determine hostname")
}
err = rpcCh.ExchangeDeclare(
AmqpExchange,
AmqpExchangeType,
AmqpDurable,
AmqpDeleteUnused,
AmqpInternal,
AmqpNoWait,
nil)
if err != nil {
cmd.FailOnError(err, "Could not declare exchange")
}
_, err = rpcCh.QueueDeclare(
QueueName,
AmqpDurable,
AmqpDeleteUnused,
AmqpExclusive,
AmqpNoWait,
nil)
if err != nil {
cmd.FailOnError(err, "Could not declare queue")
}
err = rpcCh.QueueBind(
QueueName,
"#", //wildcard
AmqpExchange,
false,
nil)
if err != nil {
cmd.FailOnError(err, "Could not bind queue")
}
deliveries, err := rpcCh.Consume(
QueueName,
consumerTag,
AmqpAutoAck,
AmqpExclusive,
AmqpNoLocal,
AmqpNoWait,
nil)
if err != nil {
cmd.FailOnError(err, "Could not subscribe to queue")
}
deliveryTimings := make(map[string]time.Time)
// Run forever.
for d := range deliveries {
go timeDelivery(d, stats, deliveryTimings)
// Pass each message to the Analysis Engine
err = ae.ProcessMessage(d)
if err != nil {
logger.Alert(fmt.Sprintf("Could not process message: %s", err))
} else {
// Only ack the delivery we actually handled (ackMultiple=false)
const ackMultiple = false
d.Ack(ackMultiple)
}
}
}