mqlight

IBM MQ Light Client Module

node-mqlight

MQ Light is designed to allow applications to exchange discrete pieces of information in the form of messages. This might sound a lot like TCP/IP networking, and MQ Light does use TCP/IP under the covers, but MQ Light takes away much of the complexity and provides a higher level set of abstractions to build your applications with.

This Node.js module provides the high-level API by which you can interact with the MQ Light runtime.

See https://developer.ibm.com/messaging/mq-light/ for more details.

Getting Started

Prerequisites

You will need a Node.js 0.10 runtime environment to use the MQ Light API module. This can be installed from http://nodejs.org/download/, or by using your operating system's package manager.

The following are the currently supported platform architectures:

  • 64-bit or 32-bit runtime on Windows (x64 or x86)
  • 64-bit runtime on Linux (x64)
  • 64-bit runtime on Mac OS X (x64)

You will receive an error if you attempt to use any other combination.

Before using MQ Light on Linux, you will also need to make sure you have the libuuid package installed. For example:

  • To check whether you have the package on Ubuntu, run: dpkg -l libuuid1
  • To check whether you have the package on RedHat, run: rpm -qa | grep libuuid

Usage

Install using npm:

npm install mqlight
var mqlight = require('mqlight');

Then create some instances of the client object to send and receive messages:

var recvClient = mqlight.createClient({service: 'amqp://localhost'});
 
var topicPattern = 'public';
recvClient.on('started', function() {
  recvClient.subscribe(topicPattern);
  recvClient.on('message', function(data, delivery) {
    console.log('Recv: %s', data);
  });
});
 
var sendClient = mqlight.createClient({service: 'amqp://localhost'});
 
var topic = 'public';
sendClient.on('started', function() {
  sendClient.send(topic, 'Hello World!', function (err, data) {
    console.log('Sent: %s', data);
    sendClient.stop();
  });
});

API

mqlight.createClient([options], [callback])

Creates an MQ Light client instance in starting state

  • options - (Object) options for the client. Properties include:
    • service, (String | Array | Function) (required), a String containing the URL for the service to connect to, or alternatively an Array containing a list of URLs to attempt to connect to in turn, or alternatively an async function which will be expected to supply the service URL(s) to a callback function that will be passed to it whenever it is called (in the form function(err, service)). User names and passwords may be embedded into the URL (e.g. amqp://user:pass@host).
    • id, (String, default: AUTO_[0-9a-f]{7}) (optional), a unique identifier for this client. A maximum of one instance of the client (as identified by the value of this property) can be connected the an MQ Light server at a given point in time. If another instance of the same client connects, then the previously connected instance will be disconnected. This is reported, to the first client, as a ReplacedError being emitted as an error event and the client transitioning into stopped state. If the id property is not a valid client identifier (e.g. it contains a colon, it is too long, or it contains some other forbidden character) then the function will throw an InvalidArgumentError
    • user, (String) (optional), user name for authentication. Alternatively, the user name may be embedded in the URL passed via the service property. If you choose to specify a user name via this property and also embed a user name in the URL passed via the surface argument then all the user names must match otherwise an InvalidArgumentError will be thrown. User names and passwords must be specified together (or not at all). If you specify just the user property but no password property an InvalidArgumentError will be thrown.
    • password, (String) (optional), password for authentication. Alternatively, user name may be embedded in the URL passed via the service property.
    • sslTrustCertificate, (String) (optional), SSL trust certificate to use when authentication is required for the MQ Light server. Only used when service specifies the amqps scheme.
    • sslVerifyName, (Boolean, default: true) (optional), whether or not to additionally check the MQ Light server's common name in the certificate matches the actual server's DNS name. Only used when the sslTrustCertificate option is specified.
  • callback - (Function) (optional) callback that is invoked (indicating success) if the client attains started state, or invoked (indicating failure) if the client enters stopped state before attaining started state. The callback function is supplied two arguments, the first being an Error object that is set to null to indicate success. The second is the instance of client, returned by mqlight.createClient, that the callback relates to.

Returns a Client object representing the client instance. The client is an event emitter and listeners can be registered for the following events: started, stopped, restarted, error, drain, and message.

mqlight.Client.start([callback])

Prepares the client to send and/or receive messages from the server. As clients are created in starting state, this method need only be called if an instance of the client has been stopped using the mqlight.Client.stop method.

  • callback - (Function) (optional) callback to be notified when the client has either: transitioned into started state; or has entered stopped state before it can transition into started state. The callback function will be invoked with a StoppedError as its argument if the client transitions into stopped state before it attains started state - which can happen as a result of calling the client.stop method.

mqlight.Client.stop([callback])

Stops the client from sending and/or receiving messages from the server. The client will automatically unsubscribe from all of the destinations that it is subscribed to. Any system resources used by the client will be freed.

  • callback - (Function) (optional) callback to be notified when the client has transitioned into stopped state.

mqlight.Client.send(topic, data, [options], [callback])

Sends the value, specified via the data argument to the specified topic. String and Buffer values will be sent and received as-is. Other types will be converted to JSON before sending and automatically parsed back from JSON when received.

  • topic - (String) the topic to which the message will be sent. A topic can contain any character in the Unicode character set.
  • data - (String | Buffer | Object) the message body to be sent
  • options - (Object) (optional) additional options for the send operation. Supported options are:
    • qos, (Number) (optional) The quality of service to use when sending the message. 0 is used to denote at most once (the default) and 1 is used for at least once. If a value which is not 0 and not 1 is specified then this method will throw a RangeError
    • ttl, (Number) (optional) A time to live value for the message in milliseconds. MQ Light will endeavour to discard, without delivering, any copy of the message that has not been delivered within its time to live period. The default time to live is 604800000 milliseconds (7 days). The value supplied for this argument must be greater than zero and finite, otherwise a RangeError will be thrown when this method is called.
  • callback - (Function) The callback argument is optional if the qos property of the options argument is omitted or set to 0 (at most once). If the qos property is set to 1 (at least once) then the callback argument is required and a InvalidArgumentError is thrown if it is omitted. The callback will be notified when the send operation completes and is passed the following arguments:
    • error, (Error) an error object if the callback is being invoked to indicate that the send call failed. If the send call completes successfully then the value null is supplied for this argument.
    • topic, (String) the topic argument supplied to the corresponding send method call.
    • data, (Object) the data argument supplied to the corresponding send method call.
    • options, (Object) the options argument supplied to the corresponding send method call.

Returns true if this message was sent, or is the next to be sent.

Returns false if the message was queued in user memory, due to either a backlog of messages, or because the client was not in a connected state. When the backlog of messages is cleared, the drain event will be emitted.

mqlight.Client.subscribe(topicPattern, [share], [options], [callback])

Subscribes the client to a destination, based on the supplied topicPattern and share arguments. The client throw a SubscribedError if a call is made to client.subscribe(...) and the client is already associated with the destination (as determined by the pattern and share arguments). It will throw a StoppedError if the client has not been started prior to calling this function.

The topicPattern argument is matched against the topic that messages are sent to, allowing the messaging service to determine whether a particular message will be delivered to a particular destination, and hence the subscribing client.

  • topicPattern - (String) used to match against the topic specified when a message is sent to the messaging service. A pattern can contain any character in the Unicode character set, with # representing a multilevel wildcard and + a single level wildcard as described here.
  • share - (String) (optional) name for creating or joining a shared destination for which messages are anycast between connected subscribers. If omitted defaults to a private destination (e.g. messages can only be received by a specific instance of the client).
  • options - (Object) (optional) additional options for the subscribe operation. Supported options are:
    • autoConfirm, (Boolean) (optional) When set to true (the default) the client will automatically confirm delivery of messages when all of the listeners registered for the client's message event have returned. When set to false, application code is responsible for confirming the delivery of messages using the confirmDelivery method, passed via the delivery argument of the listener registered for message events. autoConfirm is only applicable when the qos property is set to 1. The qos property is described later.
    • credit, (Number) The maximum number of unconfirmed messages a client can have before the server will stop sending new messages to the client and require that it confirms some of the outstanding message deliveries in order to receive more messages. The default for this property is 1024. If specified the value will be coerced to a Number and must be finite and >= 0, otherwise a RangeError will be thrown.
    • qos, (Number) The quality of service to use for delivering messages to the subscription. Valid values are: 0 to denote at most once (the default), and 1 for at least once. A RangeError will be thrown for other value.
    • ttl, (Number) A time-to-live value, in milliseconds, that is applied to the destination that the client is subscribed to. If specified the value will be coerced to a Number, which must be finite and >= 0, otherwise a RangeError will be thrown. This value will replace any previous value, if the destination already exists. Time to live starts counting down when there are no instances of a client subscribed to a destination. It is reset each time a new instance of the client subscribes to the destination. If time to live counts down to zero then MQ Light will delete the destination by discarding any messages held at the destination and not accruing any new messages. The default value for this property is 0 - which means the destination will be deleted as soon as there are no clients subscribed to it.
  • callback - (Function) (optional) callback to be notified when the subscribe operation completes. The callback function is passed the following arguments:
    • error, (Error) an error object if the callback is being invoked to indicate that the subscribe call failed. If the subscribe call completes successfully then the value null is supplied for this argument.
    • topicPattern, (String) the topicPattern argument supplied to the corresponding subscribe method call.
    • share, (String) the share argument supplied to the corresponding subscribe method call (or if this parameter was not specified).

Returns the Client object that the subscribe was called on. message events will be emitted when messages arrive.

mqlight.Client.unsubscribe(topicPattern, [share], [options], [callback])

Stops the flow of messages from a destination to this client. The client's message callback will not longer be driven when messages arrive, that match the pattern associated with the destination. Messages may still be stored at the destination if it has a non-zero time to live value or is shared and is subscribed to by other clients instances. If the client is not subscribed to a subscription, as identified by the pattern (and optional) share arguments then this method will throw a UnsubscribedError. The pattern and share arguments will be coerced to type String. The pattern argument must be present otherwise this method will throw a TypeError.

  • topicPattern - (String) Matched against the topicPattern specified on the mqlight.Client.subscribe call to determine which destination the client will unsubscribed from.
  • share - (String) (optional) Matched against the share specified on the mqlight.Client.subscribe call to determine which destination the client will unsubscribed from.
  • options - (Object) (optional) Properties that determine the behaviour of the unsubscribe operation:
    • ttl, (Number) (optional) Sets the destination's time to live as part of the unsubscribe operation. The default (when this property is not specified) is not to change the destination's time to live. When specified the only valid value for this property is 0.
  • callback - (Function) (optional) callback to be notified when the unsubscribe operation completes. The callback function is passed the following arguments:
    • error, (Error) an error object if the callback is being invoked to indicate that the unsubscribe call failed. If the unsubscribe call completes successfully then the value null is supplied for this argument.
    • topicPattern, (String) the topicPattern argument supplied to the corresponding unsubscribe method call.
    • share, (String) the share argument supplied to the corresponding unsubscribe method call (or if this parameter was not specified).

mqlight.Client.id

Returns the identifier associated with the client. This will either be what was passed in on the Client.createClient call or an auto-generated id.

mqlight.Client.service

Returns the URL of the server to which the client is currently connected to, or undefined if not connected.

mqlight.Client.state

Returns the current state of the client, which will be one of: 'starting', 'started', 'stopping', 'stopped', or 'retrying'.

Event: 'message'

Emitted when a message is delivered from a destination matching one of the client's subscriptions.

  • data - (String | Buffer | Object) the message body.
  • delivery - (Object) additional information about why the event was emitted. Properties include:
    • message, (Object) additional information about the message. Properties include:
    • topic, (Object) the topic that the message was sent to.
    • confirmDelivery, (Function) A method that can be used to confirm (settle) the delivery of a at least once quality of service (qos:1) message. This method does not expect any arguments. This property will only be present if the message was delivered due to a subscribe call that specified both qos: 1 and autoConfirm: false options.
    • ttl, (Number) the remaining time to live period for this message in milliseconds. This is calculated by subtracting the time the message spends at an MQ Light destination from the time to live value specified when the message is sent to MQ Light.
    • destination, (Object) collects together the values that the client specified when it subscribed to the destination from which the message was received.
    • topicPattern, (String) the topic specified when the client subscribed to the destination from which the message was received.
    • share, (String) the share name specified when the client subscribed to the destination from which the message was received. This property will not be present if the client subscribed to a private destination.

Event: 'started'

This event is emitted when a client attains stated state by successfully establishing a connection to the MQ Light server. The client is ready to send messages. The client is also ready to receive messages by subscribing to topic patterns.

Event: 'stopped'

This event is emitted when a client attains stopped state as a result of the mqlight.Client.stop method being invoked. In this state the client will not receive messages, and attempting to send messages or subscribe to topic patterns will result in an error being thrown from the respective method call.

Event: 'error'

Emitted when an error is detected that prevents or interrupts a client's connection to the messaging server. The client will automatically try to reestablish connectivity unless either successful or the client is stopped by a call to the mqlight.Client.stop method. error events will periodically be emitted for each unsuccessful attempt the client makes to reestablish connectivity to the MQ Light server.

  • error (Error) the error.

Event: 'restarted'

This event is emitted when the client has reestablished connectivity to the MQ Light server. The client will automatically re-subscribe to any destinations that it was subscribed to prior to losing connectivity. Any send or subscribe requests made while the client was not connected to the MQ Light server will also be automatically forwarded when connectivity is reestablished.

Event: 'drain'

Emitted to indicate that the client has flushed any buffered messages to the network. This event can be used in conjunction with the value returned by the mqlight.Client.send method to efficiently send messages without buffering a large number of messages in memory allocated by the client.

Errors

Error: InvalidArgumentError

This is a subtype of Error defined by the MQ Light client. It is considered a programming error. The underlying cause for this error are the parameter values passed into a method. Typically InvalidArgumentError is thrown directly from a method where TypeError and RangeError do not adequately describe the problem (e.g., you specified a client id that contains a colon). InvalidArgumentError may also arrive asynchronously if, for example, the server rejects a value supplied by the client (e.g. a message time to live value which exceeds the maximum value that the server will permit).

Error: NetworkError

This is a subtype of Error defined by the MQ Light client. It is considered an operational error. NetworkError is passed to an application if the client cannot establish a network connection to the MQ Light server, or if an established connection is broken.

Error: RangeError

This is a built-in subtype of Error. It is considered a programming error. The MQ Light client throws RangeError from a method when a numeric value falls outside the range accepted by the client.

Error: ReplacedError

This is a subtype of Error defined by the MQ Light client. It is considered an operational error. ReplacedError is thrown to signify that an instance of the client has been replaced by another instance that connected specifying the exact same client id. Applications should react to ReplacedError by ending as any other course of action is likely to cause two (or more) instances of the application to loop replacing each other.

Error: SecurityError

This is a subtype of Error defined by the MQ Light client. It is considered an operational error. SecurityError is thrown when an operation fails due to a security related problem. Examples include:

  • The client specifies an incorrect user/password combination.
  • The client specifies a user / password but the server is not configured to require a user / password.
  • The client is configured to use an SSL / TLS certificate to establish the identity of the server - but cannot.
  • etc.

Error: StoppedError

This is a subtype of Error defined by the MQ Light client. It is considered a programming error - but is unusual in that, in some circumstances, a client may reasonably expect to receive StoppedError as a result of its actions and would typically not be altered to avoid this condition occurring. StoppedError is thrown by methods which require connectivity to the server (e.g. send, subscribe) when they are invoked while the client is in stopping or stopped states. StoppedError is also supplied to the callbacks and supplied to methods which require connectivity to the server, when the client transitions into stopped state before it can perform the action. It is this latter case where applications may reasonably be written to expect StoppedError.

Error: SubscribedError

This is a subtype of Error defined by the MQ Light client. It is considered a programming error. SubscribedError is thrown from the client.subscribe(...) method call when a request is made to subscribe to a destination that the client is already subscribed to.

Error: TypeError

This is a built-in subtype of Error. It is considered a programming error. The MQ Light client throws TypeError if the type of a method argument cannot be coerced to the type expected by the client code. For example specifying a numeric constant instead of a function. TypeError is also used when a required parameter is omitted (the justification being that the argument is assigned a value of undefined - which isn't the type that the client is expecting).

Error: UnsubscribedError

This is a subtype of Error defined by the MQ Light client. It is considered a programming error. UnsubscribedError is thrown from the client.unsubscribe(...) method call when a request is made to unsubscribe from a destination that the client is not subscribed to.

Samples

To run the samples, install the module via npm and navigate to the mqlight/samples/ folder.

Usage:

Receiver Example:

Usage: recv.js [options]
 
Options:
  -h, --help            show this help message and exit
  -s URL, --service=URL service to connect to, for example:
                        amqp://user:password@host:5672 or
                        amqps://host:5671 to use SSL/TLS
                        (default: amqp://localhost)
  -c FILE, --trust-certificate=FILE
                        use the certificate contained in FILE (in
                        PEM or DER format) to validate the
                        identify of the server. The connection must
                        be secured with SSL/TLS (e.g. the service
                        URL must start 'amqps://')
  -t TOPICPATTERN, --topic-pattern=TOPICPATTERN
                        subscribe to receive messages matching TOPICPATTERN
                        (default: public)
  -i ID, --id=ID        the ID to use when connecting to MQ Light
                        (default: recv_[0-9a-f]{7})
  --destination-ttl=NUM set destination time-to-live to NUM seconds
  -n NAME, --share-name NAME
                        optionally, subscribe to a shared destination using
                        NAME as the share name
  -f FILE, --file=FILE  write the payload of the next message received to
                        FILE (overwriting previous file contents) then end.
                        (default is to print messages to stdout)
  -d NUM, --delay=NUM   delay for NUM seconds each time a message is received.
  --verbose             print additional information about each message
                        received

Sender Example:

Usage: send.js [options] <msg_1> ... <msg_n>
 
Options:
  -h, --help            show this help message and exit
  -s URL, --service=URL service to connect to, for example:
                        amqp://user:password@host:5672 or
                        amqps://host:5671 to use SSL/TLS
                        (default: amqp://localhost)
  -c FILE, --trust-certificate=FILE
                        use the certificate contained in FILE (in
                        PEM or DER format) to validate the
                        identify of the server. The connection must
                        be secured with SSL/TLS (e.g. the service
                        URL must start 'amqps://')
  -t TOPIC, --topic=TOPIC
                        send messages to topic TOPIC
                        (default: public)
  -i ID, --id=ID        the ID to use when connecting to MQ Light
                        (default: send_[0-9a-f]{7})
  --message-ttl=NUM     set message time-to-live to NUM seconds
  -d NUM, --delay=NUM   add NUM seconds delay between each request
  -r NUM, --repeat=NUM  send messages NUM times, default is 1, if
                        NUM <= 0 then repeat forever
   --sequence           prefix a sequence number to the message
                        payload (ignored for binary messages)
  -f FILE, --file=FILE  send FILE as binary data. Cannot be
                        specified at the same time as <msg1>

Feedback

You can help shape the product we release by trying out the beta code and leaving your feedback.

Reporting bugs

If you think you've found a bug, please leave us feedback. To help us fix the bug a log might be helpful. You can get a log by setting the environment variable MQLIGHT_NODE_LOG to debug and by collecting the output that goes to stderr when you run your application.

Release notes

1.0.2014091000

  • First official release.
  • Support for supplying time-to-live options when sending a message or creating a destination.
  • Support for unsubscribing from an existing destination.
  • Support flow control for sending applications by having the send method return a boolean value to indicate when data is being buffered and have the client emit a drain event when all buffered data has been written.
  • Support passing authentication details as user:pass@host service URIs.
  • API changes based on user feedback to rename connect -> start, disconnect -> stop, to make createClient return an already started client and to have client properties rather than getter and setter methods.
  • Necessary OpenSSL libraries are now included within the module package to simplify deployment (particularly on Windows).
  • Improve the samples so that they demonstrate more areas of the available API functionality.
  • Numerous other bug fixes and performance improvements.

0.1.2014062301

  • Second beta release.
  • Support for Mac OS X.
  • Support for sending and receiving 'at-least-once' messages either with automatic or manual confirmation by the receiver.
  • Updated samples to use service/topic arguments instead of address.

0.1.2014042204

  • Initial beta release.
  • Support for sending and receiving 'at-most-once' messages.
  • Support for wildcard subscriptions.
  • Support for shared subscriptions.

Maintainers

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Keywords

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Dependencies (5)

node-uuid, nopt, npmlog, moment, hashmap

Dependents

node-red-bluemix-nodes, node-red-node-mqlight.