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.
You will need a Node.js 4.x or newer 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.
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();
});
});
options], [callback])Creates an IBM MQ Light client instance in starting state.
options - (Object) options for the client. Properties include:
function(err, service)). User names and
passwords may be embedded into the URL (for example, amqp://user:pass@host).AUTO_[0-9a-f]{7}) (optional) a String, with a
maximum length of 256 characters, to serve as 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 to 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 (for example, it contains a colon, it is too long,
or it contains some other forbidden character) then the function will throw
an InvalidArgumentErrorInvalidArgumentError 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.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, malformed and message.
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 (or was already in) 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 a stopped state before it attains a started
state, which can happen as a result of calling the client.stop method.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.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 is 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:
RangeErrorRangeError will be thrown when this method is called.
Refer to the server product documentation for the default and maximum
permitted time-to-live values.boolean, number, string or Buffer.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:
null is supplied for this argument.topic argument supplied to the corresponding
send method call.data argument supplied to the corresponding
send method call.options argument supplied to the corresponding
send method call.Returns true if this message is sent, or is the next to be sent.
Returns false if the message is 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 sent.
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. For more information, see
Wildcards.share - (String) (optional) name for creating or joining a shared
destination for which messages are anycast between connected subscribers. If
omitted, this defaults to a private destination (for example, messages can only be received
by a specific instance of the client).options - (Object) (optional) additional options for the subscribe
operation. Supported options are:
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.)Number and must be finite
and greater than, or equal to 0, otherwise a RangeError will be thrown.RangeError will be thrown for other
value.Number, which must be finite and greater than, or equal to 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:
null is supplied for this argument.topicPattern argument supplied to the
corresponding subscribe method call.share argument supplied to the corresponding
subscribe method call (or undefined if this parameter was not specified).Returns the Client object that the subscribe was called on. message events
will be emitted when messages arrive.
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 optional pattern 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 be
unsubscribed from.share - (String) (optional) matched against the share specified on the
mqlight.Client.subscribe call to determine which destination the client will be
unsubscribed from.options - (Object) (optional) properties that determine the behaviour of the
unsubscribe operation:
callback - (Function) (optional) callback to be notified when the
unsubscribe operation completes. The callback function is passed the
following arguments:
null is supplied for this
argument.topicPattern argument supplied to the
corresponding unsubscribe method call.share argument supplied to the corresponding
unsubscribe method call (or undefined if this parameter was not
specified).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.
Returns the URL of the server to which the client is currently connected
to, or undefined if not connected.
Returns the current state of the client, which will be one of the following states: 'starting', 'started', 'stopping', 'stopped', or 'retrying'.
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 sent.
Properties include:
qos: 1 and
autoConfirm: false options.This event is sent when a client attains the started 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.
This event is sent when a client attains the 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.
Sent 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.This event is sent 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.
Sent 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.
This is a subtype of Error defined by the MQ Light client. It is considered
a programming error. The underlying causes 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 (for example, 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 (for example, a message time to live
value which exceeds the maximum value that the server will permit).
This is a subtype of Error defined by the IBM 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.
This is a subtype of Error defined by the IBM MQ Light client. It is considered
an operational error. NotPermittedError is thrown to indicate that a
requested operation has been rejected because the remote end does not permit
it.
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.
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.
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:
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
(for example, send or 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.
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.
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).
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.
Each instance of a client (as returned from mqlight.createClient(...) is
backed by the following state machine:
Each of the states shown in the state machine diagram corresponds to the values
stored in the mqlight.Client.state property, with the exception of retrying1
and retrying2 which are collapsed into a single retrying value. While in the
retrying state, the client will wait for up approximately 60 seconds (based on
an exponential backoff algorithm) before attempting to transition into a new
state.
Each line shown in the state machine diagram represents a possible way in which the client can transition between states. The lines are labelled with information about the transitions, which includes:
start() corresponds to the mqlight.Client.start function.stop() corresponds to the mqlight.Client.stop function.[broken] occurs when an established network connection between the client
and the server is interrupted.[connected] occurs when the client successfully establishes a network
connection to the server.[failed] occurs when the client unsuccessfully attempts to establish a
network connection to the server.<error> indicates that an error event is sent.<restarted> indicates that a restarted event is sent.<started> indicates that a started event is sent.<stopped> indicates that a stopped event is sent.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 format) to
validate the identity of the server. The connection must
be secured with SSL/TLS (e.g. the service URL must start
with '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 format) to
validate the identity of the server. The connection must
be secured with SSL/TLS (e.g. the service URL must start
with '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>
You can help shape the product we release by trying out the beta code and leaving your feedback.
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.
message.delivery.topic returning an absolute address when
using a secure (amqps) connection.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.user:pass@host service URIs.connect -> start,
disconnect -> stop, to make createClient return an already started
client and to have client properties rather than getter and setter methods.FAQs
IBM MQ Light Client Module
The npm package mqlight receives a total of 124 weekly downloads. As such, mqlight popularity was classified as not popular.
We found that mqlight demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 6 open source maintainers collaborating on the project.
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