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node-amqp

This is a client for RabbitMQ (and maybe other servers?). It partially
implements the 0.9.1 version of the AMQP protocol.

Table of Contents

• Installation
• Synopsis
• Connection
  • Connection options and URL
  • connection.publish(routingKey, body, options, callback)
  • connection.disconnect()
  • connection.on('tag.change', callback)
• Queue
  • connection.queue(name[, options][, openCallback])
  • queue.subscribe([options,] listener)
  • queue.subscribeRaw([options,] listener)
  • queue.unsubscribe(consumerTag)
  • queue.shift([reject[, requeue]])
  • queue.bind([exchange,] routing)
  • queue.unbind([exchange,] routing)
  • queue.bind_headers([exchange,] routing)
  • queue.destroy(options)
• Exchange
  • exchange.on('open', callback)
  • connection.exchange()
  • connection.exchange(name, options={}, openCallback)
  • exchange.publish(routingKey, message, options, callback)
  • exchange.destroy(ifUnused = true)
  • exchange.bind(srcExchange, routingKey [, callback])
  • exchange.unbind(srcExchange, routingKey [, callback])
  • exchange.bind_headers(exchange, routing [, bindCallback])

Installation

npm install amqp

Synopsis

IMPORTANT: This module only works with node v0.4.0 and later.

An example of connecting to a server and listening on a queue.

var amqp = require('amqp');

var connection = amqp.createConnection({ host: 'dev.rabbitmq.com' });

// add this for better debuging
connection.on('error', function(e) {
  console.log("Error from amqp: ", e);
});

// Wait for connection to become established.
connection.on('ready', function () {
  // Use the default 'amq.topic' exchange
  connection.queue('my-queue', function (q) {
      // Catch all messages
      q.bind('#');
    
      // Receive messages
      q.subscribe(function (message) {
        // Print messages to stdout
        console.log(message);
      });
  });
});

Connection

new amqp.Connection() Instantiates a new connection. Use
connection.connect() to connect to a server.

amqp.createConnection() returns an instance of amqp.Connection, which contains
an instance of net.Socket at its socket property. All events and methods which work on
net.Socket can also be used on an amqp.Connection instance. (e.g., the
events 'connect' and 'close'.)

Connection options and URL

amqp.createConnection([options, [implOptions]]) takes two options
objects as parameters. The first options object has these defaults:

{ host: 'localhost'
, port: 5672
, login: 'guest'
, password: 'guest'
, connectionTimeout: 10000
, authMechanism: 'AMQPLAIN'
, vhost: '/'
, noDelay: true
, ssl: { enabled : false
       }
}

An example options object for creating an SSL connection has these properties:

{ host: 'localhost'
, port: 5671
, login: 'guest'
, password: 'guest'
, authMechanism: 'AMQPLAIN'
, vhost: '/'
, ssl: { enabled : true
       , keyFile : '/path/to/key/file'
       , certFile : '/path/to/cert/file'
       , caFile : '/path/to/cacert/file'
       , rejectUnauthorized : true
       }
}

The key, certificate, and certificate authority files must be in pem format.
Alternatively, pfxFile can be used to read key and certificate from a single
file. If port is not specified, the default AMQPS port 5671 is used.
If rejectUnauthorized is not specified, it defaults to true.

Options can also be passed in a single URL of the form

amqp[s]://[user:password@]hostname[:port][/vhost]

AMQPLAIN is assumed for the auth mechanism.

Note that the vhost must be URL-encoded and appear as the only segment
of the path, i.e., the only unencoded slash is that leading; leaving
the path entirely empty indicates that the vhost /, as
above, should be used (it could also be supplied as the path /%2f).

The heartbeat setting sets the heartbeat interval (in seconds) for
the connection. There is no default for this option meaning no
heartbeating is taking place.

This URL is supplied as the field url in the options; for example

var conn =
  amqp.createConnection({url: "amqp://guest:guest@localhost:5672"});

Options provided as individual fields will override values given in
the URL.

You can also specify additional client properties for your connection
by setting the clientProperties field on the options object.

{ clientProperties: { applicationName: 'myApplication'
                    , capabilities: { consumer_cancel_notify: true
                                    }
                    }
}

If the consumer_cancel_notify capability is set to true (as above), then
RabbitMQ's Consumer Cancel Notification
feature will be enabled.

By default the following client properties are set

{ product: 'node-amqp'
, platform: 'node-' + process.version
, version: nodeAMQPVersion
}

The second options are specific to the node AMQP implementation. It has
the default values:

{ defaultExchangeName: ''
, reconnect: true
, reconnectBackoffStrategy: 'linear'
, reconnectExponentialLimit: 120000
, reconnectBackoffTime: 1000
}

The defaultExchangeName is the default exchange to which
connection.publish will publish. In the past, the default exchange was
amq.topic, which is not ideal. To emulate this behaviour, one can
create a connection like:

var conn =
  amqp.createConnection({url: "amqp://guest:guest@localhost:5672"},
                        {defaultExchangeName: "amq.topic"});

If the reconnect option is true, then the driver will attempt to reconnect using the
configured strategy any time the connection becomes unavailable. If this is not
appropriate for your application, set this option to false.

If you would like this option, you can set parameters controlling how aggressively the
reconnections will be attempted. Valid strategies are "linear" and "exponential".

Backoff times are in milliseconds. Under the "linear" strategy, the driver will pause
reconnectBackoffTime ms before the first attempt, and between each subsequent attempt.
Under the "exponential" strategy, the driver will pause reconnectBackoffTime ms before
the first attempt, and will double the previous pause between each subsequent attempt
until a connection is reestablished.

After a connection is established the 'connect' event is fired as it is
with any net.Connection instance. AMQP requires a 7-way handshake which
must be completed before any communication can begin. net.Connection does
the handshake automatically and emits the 'ready' event when the handshaking
is complete.

For backward compatibility, two additional options are available. Older
versions of this library placed the routingKey and deliveryTag for incoming
messages into the JSON payload received. This module was changed to
leave inbound JSON payloads pristine. Some applications may need the
old behaviour. If the key routingKeyInPayload is set to true in the
connection options, the messages resulting from a subscribe call will
include a 'routingKey' key in the JSON payload. If the key
deliveryTagInPayload is set to true in the connection options, the
deliveryTag of the incoming message will be placed in the JSON payload.

connection.publish(routingKey, body, options, callback)

Publishes a message to the default exchange; if the defaultExchange is
left as '', this effectively publishes the message on the routing key named.

This method proxies to the default exchange's publish method and parameters are passed
through untouched.

connection.disconnect()

Cleanly disconnect from the server, the socket will not be closed until the
server responds to the disconnection request.

connection.on('tag.change', callback)

Fired when an existing consumer tag has changed. Use this event to update your consumer tag references.

When an error or reconnection occurs, any existing consumers will be automatically replaced with new ones.
If your application is holding onto a reference to a consumer tag (e.g. to unsubscribe later) and reconnects,
the held tag will no longer be valid, preventing the application from gracefully unsubscribing.

The callback function takes one parameter, event, which contains two properties: oldConsumerTag and consumerTag.

var connection = amqp.createConnection({ host: 'dev.rabbitmq.com' });

// Local references to the exchange, queue and consumer tag
var _exchange = null;
var _queue = null;
var _consumerTag = null;

// Report errors
connection.on('error', function(err) { 
    console.error('Connection error', err); 
});

// Update our stored tag when it changes
connection.on('tag.change', function(event) {
    if (_consumerTag === event.oldConsumerTag) {
        _consumerTag = event.consumerTag;
        // Consider unsubscribing from the old tag just in case it lingers
        _queue.unsubscribe(event.oldConsumerTag);
    }
});

// Initialize the exchange, queue and subscription
connection.on('ready', function() {
    connection.exchange('exchange-name', function(exchange) {
        _exchange = exchange;
        
        connection.queue('queue-name', function(queue) {
            _queue = queue;
            
            // Bind to the exchange
            queue.bind('exchange-name', 'routing-key');
            
            // Subscribe to the queue
            queue
                .subscribe(function(message) {
                    // Handle message here
                    console.log('Got message', message);
                    queue.shift(false, false);
                })
                .addCallback(function(res) {
                    // Hold on to the consumer tag so we can unsubscribe later
                    _consumerTag = res.consumerTag;
                })
            ;
        });
    });
});

// Some time in the future, you'll want to unsubscribe or shutdown 
setTimeout(function() {
    if (_queue) {
        _queue
            .unsubscribe(_consumerTag)
            .addCallback(function() {
                // unsubscribed
            })
        ;
    } else {
        // unsubscribed
    }
}, 60000);

Queue

Events: A queue will call the callback given to the connection.queue()
method once it is usable. For example:

var q = connection.queue('my-queue', function (queue) {
  console.log('Queue ' + queue.name + ' is open');
});

Declaring a queue with an empty name will make the server generate a
random name.

connection.queue(name[, options][, openCallback])

Returns a reference to a queue. The name parameter is required, unlike pika which defaults the name to ''. The options are

• passive: boolean, default false.
  If set, the server will not create the queue. The client can use
  this to check whether a queue exists without modifying the server
  state.
• durable: boolean, default false.
  Durable queues remain active when a server restarts.
  Non-durable queues (transient queues) are purged if/when a
  server restarts. Note that durable queues do not necessarily
  hold persistent messages, although it does not make sense to
  send persistent messages to a transient queue.
• exclusive: boolean, default false.
  Exclusive queues may only be consumed from by the current connection.
  Setting the 'exclusive' flag always implies 'autoDelete'.
• autoDelete: boolean, default true.
  If set, the queue is deleted when all consumers have finished
  using it. Last consumer can be cancelled either explicitly or because
  its channel is closed. If there was no consumer ever on the queue, it
  won't be deleted.
• noDeclare: boolean, default false.
  If set, the queue will not be declared, this will allow a queue to be
  deleted if you don't know its previous options.
• arguments: a map of additional arguments to pass in when creating a queue.
• closeChannelOnUnsubscribe : a boolean when true the channel will close on
  unsubscribe, default false.

queue.subscribe([options,] listener)

An easy subscription command. It works like this

q.subscribe(function (message, headers, deliveryInfo, messageObject) {
  console.log('Got a message with routing key ' + deliveryInfo.routingKey);
});
    

It will automatically acknowledge receipt of each message.

There are several options available. Setting the options argument to
{ ack: true } (which defaults to false) will make it so that the AMQP
server only delivers a single message at a time. When you want the next
message, call q.shift(). When ack is false then you will receive
messages as fast as they come in.

You can also use the prefetchCount option to increase the window of how
many messages the server will send you before you need to ack (quality of service).
{ ack: true, prefetchCount: 1 } is the default and will only send you one
message before you ack. Setting prefetchCount to 0 will make that window unlimited.
If this option is used q.shift() should not be called. Instead the listener
function should take four parameters (message, headers, deliveryInfo, ack) and
ack.acknowledge() should be called to ack a single message.

The routingKeyInPayload and deliveryKeyInPayload options determine
if the reception process will inject the routingKey and deliveryKey,
respectively, into the JSON payload received. These default to unset
thus adopting the parent connection's values (which default to false).
Setting these to true provide backward compatibility for older
applications.

The exclusive option will subscribe to the queue in exclusive mode. Only one
subscriber is allowed at a time, and subsequent attempts to subscribe to the
same queue will result in an exception. This option differs from the exclusive
option passed when creating in a queue in that the queue itself is not exclusive,
only the consumers. This means that long lived durable queues can be used
as exclusive queues.

The messageObject can be used to acknowledge a given message using:

messageObject.acknowledge(false); // use true if you want to acknowledge all previous messages of the queue

If the consumer_cancel_notify capability was enabled when the connection was
created, the queue will emit basicCancel upon receiving a consumer cancel
notification from the server. The queue's channel will be automatically closed.
In a clustered environment, developers may want to consider automatically
re-subscribing to the queue on this event.

This method will emit 'basicQosOk' when ready.

queue.subscribeRaw([options,] listener)

Subscribes to a queue. The listener argument should be a function which
receives a message. This is a low-level interface - the message that the
listener receives will be a stream of binary data. You probably want to use
subscribe instead. For now this low-level interface is left undocumented.
Look at the source code if you need to do this.

This method will emit 'basicConsumeOk' when ready.

queue.unsubscribe(consumerTag)

Unsubscribe from a queue, given the consumer tag. The consumer tag is
supplied to the promise callback of Queue.subscribeRaw or
Queue.subscribe:

connection.queue('foo', function(queue) {
  var ctag;
  queue.subscribe(function(msg) {...})
    .addCallback(function(ok) { ctag = ok.consumerTag; });
  // ... and in some other callback
  queue.unsubscribe(ctag);
});

Note that Queue.unsubscribe will not requeue messages that have not
been acknowledged. You need to close the queue or connection for that
to happen. You may also receive messages after calling unsubscribe;
you will not receive messages from the queue after the unsubscribe
promise callback has been invoked, however.

queue.shift([reject[, requeue]])

For use with subscribe({ack: true}, fn). Acknowledges the last
message if no arguments are provided or if reject is false. If
reject is true then the message will be rejected and put back onto
the queue if requeue is true, otherwise it will be discarded.

queue.bind([exchange,] routing[, callback])

This method binds a queue to an exchange. Until a queue is
bound it will not receive any messages, unless they are sent through
the unnamed exchange (see defaultExchangeName above).

If the exchange argument is left out 'amq.topic' will be used.

This method will emit 'queueBindOk' when complete.

If callback is provided it will also be triggered when complete,
note that if you perform multiple bindings, only the last callback
will be called.

queue.unbind([exchange,] routing)

This method unbinds a queue from an exchange.

If the exchange argument is left out 'amq.topic' will be used.

This method will emit 'queueUnbindOk' when complete.

queue.bind_headers([exchange,] routing)

This method binds a queue to an exchange. Until a queue is
bound it will not receive any messages.

This method is to be used on an "headers"-type exchange. The routing
argument must contain the routing keys and the x-match value (all or any).

If the exchange argument is left out 'amq.headers' will be used.

queue.unbind_headers([exchange,] routing)

This method unbinds a queue from an exchange. Whilst a queue is
bound it will continue receive messages that have matching headers.

This method is to be used on an "headers"-type exchange. The routing
argument must contain the routing keys and the x-match value (all or any).

If the exchange argument is left out 'amq.headers' will be used.

queue.purge()

This method purges a queue.

This method will emit 'queuePurgeOk' when complete.

queue.destroy(options)

Delete the queue. Without options, the queue will be deleted even if it has
pending messages or attached consumers. If +options.ifUnused+ is true, then
the queue will only be deleted if there are no consumers. If
+options.ifEmpty+ is true, the queue will only be deleted if it has no
messages.

Note: the successful destruction of a queue will cause a consumer cancel
notification to be emitted (for clients who have enabled the
consumer_cancel_notify option when creating the connection).

Exchange

Events: An exchange will call the callback given to the connection.exchange()
method once it is usable. For example:

var exc = connection.exchange('my-exchange', function (exchange) {
  console.log('Exchange ' + exchange.name + ' is open');
});

exchange.on('open', callback)

The open event is emitted when the exchange is declared and ready to
be used. This interface is considered deprecated.

connection.exchange()

connection.exchange(name, options={}, openCallback)

An exchange can be created using connection.exchange(). The method returns
an amqp.Exchange object.

Without any arguments, this method returns the default exchange.
Otherwise a string, name, is given as the first argument and an options
object for the second. The options are

• type: the type of exchange 'direct', 'fanout', or 'topic' (default).
• passive: boolean, default false.
  If set, the server will not create the exchange. The client can use
  this to check whether an exchange exists without modifying the server
  state.
• durable: boolean, default false.
  If set when creating a new exchange, the exchange will be marked as
  durable. Durable exchanges remain active when a server restarts.
  Non-durable exchanges (transient exchanges) are purged if/when a
  server restarts.
• autoDelete: boolean, default true.
  If set, the exchange is deleted when there are no longer queues
  bound to it.
• noDeclare: boolean, default false.
  If set, the exchange will not be declared, this will allow the exchange
  to be deleted if you dont know its previous options.
• confirm: boolean, default false.
  If set, the exchange will be in confirm mode, and you will get a
  'ack', 'error' event emitted on a publish, or the callback on the publish
  will be called.
• arguments: a map of additional arguments to pass in when creating an exchange.

An exchange will emit the 'open' event when it is finally declared.

exchange.publish(routingKey, message, options, callback)

Publishes a message to the exchange. The routingKey argument is a string
which helps routing in topic and direct exchanges. The message can be
either a Buffer or Object. A Buffer is used for sending raw bytes; an Object
is converted to JSON.

options is an object with any of the following

• mandatory: boolean, default false.
  This flag tells the server how to react if the message cannot be
  routed to a queue. If this flag is set, the server will return an
  unroutable message with a Return method. If this flag is false, the
  server silently drops the message.
• immediate: boolean, default false.
  This flag tells the server how to react if the message cannot be
  routed to a queue consumer immediately. If this flag is set, the
  server will return an undeliverable message with a Return method.
  If this flag is false, the server will queue the message, but with
  no guarantee that it will ever be consumed.
• contentType: default 'application/octet-stream'
• contentEncoding: default null.
• headers: default {}. Arbitrary application-specific message headers.
• deliveryMode: Non-persistent (1) or persistent (2)
• priority: The message priority, 0 to 9.
• correlationId: string, default null. Application correlation identifier
• replyTo: Usually used to name a reply queue for a request message.
• expiration: default null. Message expiration specification
• messageId: default null. Application message identifier
• timestamp: default null. Message timestamp
• type: default null. Message type name
• userId: default null. Creating user id
• appId: default null. Creating application id

callback is a function that will get called if the exchange is in confirm mode,
the value sent will be true or false, this is the presense of a error so true, means
an error occured and false, means the publish was successfull

exchange.destroy(ifUnused = true)

Deletes an exchange.
If the optional boolean second argument is set, the server will only
delete the exchange if it has no queue bindings. If the exchange has queue
bindings the server does not delete it but raises a channel exception
instead.

exchange.bind(srcExchange, routingKey [, callback])

Binds the exchange (destination) to the given source exchange (srcExchange).
When one exchange is bound to another, the destination (or receiving) exchange
will receive all messages published to the source exchange that match the
given routingKey.

This method will emit 'exchangeBindOk' when complete.

Please note that Exchange to Exchange Bindings (E2E) are an extension to the
AMQP spec introduced by RabbitMQ, and that by using this feature, you will be
reliant on RabbitMQ's AMQP implementation. For more information on E2E
Bindings with RabbitMQ see:

http://www.rabbitmq.com/e2e.html

exchange.unbind(srcExchange, routingKey [, callback])

Unbinds the exchange (destination) from the given source exchange (srcExchange).
This is the reverse of the exchange.bind method above, and will stop messages
from srcExchange/routingKey from being sent to the destination exchange.

This method will emit 'exchangeUnbindOk' when complete.

exchange.bind_headers(exchange, routing [, bindCallback])

This method is to be used on an "headers"-type exchange. The routing
argument must contain the routing keys and the x-match value (all or any).

Debugging

The NODE_DEBUG_AMQP=1 environment variable enables built-in low-level debugging support.