Utility for AMQP Message Routing

Describe AMQP exchange and routing keys in a compact way (and as templates). Purpose is to allow compact (and external, e.g. via configuration strings) declaration of AMQP Exchange and routing keys, and to create routing key based on message data.

Installation

npm install amqp-route

Basic Usage

Create a template with require("amqp-route").template(tplString). Then make a routing key by using fill method with data objects.

var route = require("amqp-route").template("MyExchange/route.key.{str}")
route.exchange;            // "MyExchange"
route.fill({str: "foo"});  // "route.key.foo"
route.fill({});            // "route.key" (strips dots)
route.fill({skip: "here"}, {str: "hereIam"}) // fallback list of data objects
var route2 = require("amqp-route").template("route.key.{str}")
route2.exchange;           // "" (Exchange is optional)

Exchange Options

Generate a subset of available options for node-amqp connection.exchange().

var route = require("amqp-route").template("MyExchange?dc-a/{routingKey}")
route.exchangeOpts; // {durable: true, confirm: true, autoDelete: false}

Options are a single letter (to set to true), prefixed by a - (to set to false).

• a: autoDelete
• c: confirm
• d: durable
• n: noDeclare
• p: passive

Publishing Options

Generate a subset of available options for node-amqp exchange.publish().

var route = require("amqp-route").template("{routingKey}?mip")
route.pubOpts; // {mandatory: true, immediate: true, deliveryMode: 2}

Simlar to Exchange Options (single letter, optional -). The exception is p (for "persistent", which sets deliveryMode.

• m: mandatory
• i: immediate
• p: deliveryMode
  • "p" sets "deliveryMode=2" (persistent)
  • "-p" sets "deliveryMode=1" (non-persistent)

Template

Template object returned from require("amqp-route").template():

• exchange: exchange name
• exchangeOpts: parsed options suitable for node-amqp connection.exchange()
• template: routing key template used in (template.fill())[#template-fill]
• pubOpts: publishing options suitable for node-amqp exchange.publish()

template.fill(object[, object...])

Creates a routing key for some data by replacing all strings in curly braces with value from the first object having that property. Any leading, trailing, or double work separators (dots) are removed.

var route = require("amqp-route").template("{a}.{b}.{c}.{d}")
var rk = route.fill({a: "A"}); // "A"
rk = route.fill({a: "A"}, {a: "X", c: "C"}); // "A.C"
rk = route.fill({a: "A", b: "B", d: "D, c: null}); // "A.B.D"

Publisher

Publisher builds on Template, setting up an Exchange with options and always calling the callback, even when the Exchange is not in confirm mode. It also uses the publishing options from the Template.

var amqpRoute = require("amqp-route");
var amqpConn = require("amqp").createConnection(connectionOpts);
// create a publisher in confirm mode, durable and no autoDelete
amqpRoute.publisher(amqpConn, "My-Exchange?-acd/{routing}.{template}", function(err, pub){
  var routingKeySources = [{routing: "sample"}, {template: "key"}];
  var message = {important: "data"};
  pub.publish(routingKeySources, message, function(err){
    // message published with routing key "sample.key", confirm mode
    // when NOT using confirm mode, this is called via process.nextTick()
  });
});

Additionally, you can include further Exchange options.

var tpl = "My-Exchange?-acd/{routing}.{template}";
amqpRoute.publisher(amqpConn, tpl, {type: "direct"}, function(err, pub){
  // now we are using a Direct exchange instead of topic
});

publisher.publish(routeFillers, message[, pubOpts[, callback]])

Publish a message, additional options are passed to node-amqp exchange.publish() and any passed callback will be called regardless of confirm mode.

routeFillers is an array of sources to create routing key from Template. It corresponds to arguments passed in Template.fill().