amqprhea-promise
A Promisified layer over rhea AMQP client.
Pre-requisite
- Node.js version: 6.x or higher.
- We would still encourage you to install the latest available LTS version at any given time from https://nodejs.org. It is a good practice to always install the latest available LTS version of node.js.
- Installing node.js on Windows or macOS is very simple with available installers on the node.js website. If you are using a linux based OS, then you can find easy to follow, one step installation instructions over here.
Installation
npm install rhea-promise
Debug logs
You can set the following environment variable to get the debug logs.
- Getting debug logs from this library
export DEBUG=rhea-promise* - Getting debug logs from this and the rhea library
export DEBUG=rhea* - If you are not interested in viewing the message transformation (which consumes lot of console/disk space) then you can set the
DEBUGenvironment variable as follows:export DEBUG=rhea*,-rhea:raw,-rhea:message,-rhea-promise:eventhandler,-rhea-promise:translate
Logging to a file
- Set the
DEBUGenvironment variable as shown above and then run your test script as follows:- Logging statements from you test script go to
out.logand logging statement from the sdk go todebug.log.node your-test-script.js > out.log 2>debug.log - Logging statements from your test script and the sdk go to the same file
out.logby redirecting stderr to stdout (&1), and then redirect stdout to a file:node your-test-script.js >out.log 2>&1 - Logging statements from your test script and the sdk go to the same file
out.log.node your-test-script.js &> out.log
- Logging statements from you test script go to
Notable differences between rhea and rhea-promise
Error propagation to the parent entity
- In
AMQP, for two peers to communicate successfully, different entities (Container, Connection, Session, Link) need to be created. There is a relationship between those entities.- 1 Container can have 1..* Connections.
- 1 Connection can have 1..* Sessions.
- 1 Session can have 1..* Links.
- A Link can have the role of Receiver or Sender.
- Each entity (connection, session, link) maintains its own state to let other entities know about what it is doing. Thus,
- if the connection goes down then, everything on the connection - sessions, links are down.
- if a session goes down then, all the the links on that session are down.
- When an entity goes down rhea emits *_error and *_close events, where * can be "sender", "receiver", "session", "connection". If event listeners for the aforementioned events are not added at the appropriate level, then
rheapropagates those events to its parent entity. If they are not handled at theContainerlevel (uber parent), then they are transformed into anerrorevent. This would cause your application to crash if there is no listener added for theerrorevent. - In
rhea-promise, the library creates, equivalent objectsConnection, Session, Sender, Receiverand wraps objects fromrheawithin them. It adds event listeners to all the possible events that can occur at any level and re-emits those events with the same arguments as one would expect from rhea. This makes it easy for consumers ofrhea-promiseto use the EventEmitter pattern. Users can efficiently use different event emitter methods like.once(),.on(),.prependListeners(), etc. Sincerhea-promiseadd those event listeners onrheaobjects, the errors will never be propagated to the parent entity. This can be good as well as bad depending on what you do.- Good -
*_errorevents and*_closeevents emitted on an entity will not be propagated to it's parent. Thus ensuring that errors are handled at the right level. - Bad - If you do not add listeners for
*_errorand*_closeevents at the right level, then you will never know why an entity shutdown.
- Good -
We believe our design enforces good practices to be followed while using the event emitter pattern.
Examples
Please take a look at the sample.env file for examples on how to provide the values for different parameters like host, username, password, port, senderAddress, receiverAddress, etc.
Sending a message via Sender.
- Running the example from terminal:
> ts-node ./examples/send.ts.
NOTE: If you are running the sample with .env config file, then please run the sample from the directory that contains .env config file.
import {
Connection, Sender, EventContext, Message, ConnectionOptions, Delivery, SenderOptions
} from "rhea-promise";
import * as dotenv from "dotenv"; // Optional for loading environment configuration from a .env (config) file
dotenv.config();
const host = process.env.AMQP_HOST || "host";
const username = process.env.AMQP_USERNAME || "sharedAccessKeyName";
const password = process.env.AMQP_PASSWORD || "sharedAccessKeyValue";
const port = parseInt(process.env.AMQP_PORT || "5671");
const senderAddress = process.env.SENDER_ADDRESS || "address";
async function main(): Promise<void> {
const connectionOptions: ConnectionOptions = {
transport: "tls",
host: host,
hostname: host,
username: username,
password: password,
port: port,
reconnect: false
};
const connection: Connection = new Connection(connectionOptions);
const senderName = "sender-1";
const senderOptions: SenderOptions = {
name: senderName,
target: {
address: senderAddress
},
onError: (context: EventContext) => {
const senderError = context.sender && context.sender.error;
if (senderError) {
console.log(">>>>> [%s] An error occurred for sender '%s': %O.",
connection.id, senderName, senderError);
}
},
onSessionError: (context: EventContext) => {
const sessionError = context.session && context.session.error;
if (sessionError) {
console.log(">>>>> [%s] An error occurred for session of sender '%s': %O.",
connection.id, senderName, sessionError);
}
}
};
await connection.open();
const sender: Sender = await connection.createSender(senderOptions);
const message: Message = {
body: "Hello World!!",
message_id: "12343434343434"
};
// Please, note that we are not awaiting on sender.send()
// You will notice that `delivery.settled` will be `false`.
const delivery: Delivery = sender.send(message);
console.log(">>>>>[%s] Delivery id: %d, settled: %s",
connection.id,
delivery.id,
delivery.settled);
await sender.close();
await connection.close();
}
main().catch((err) => console.log(err));
Sending a message via AwaitableSender
- Running the example from terminal:
> ts-node ./examples/awaitableSend.ts.
import {
Connection, Message, ConnectionOptions, Delivery, AwaitableSenderOptions, AwaitableSender
} from "rhea-promise";
import * as dotenv from "dotenv"; // Optional for loading environment configuration from a .env (config) file
dotenv.config();
const host = process.env.AMQP_HOST || "host";
const username = process.env.AMQP_USERNAME || "sharedAccessKeyName";
const password = process.env.AMQP_PASSWORD || "sharedAccessKeyValue";
const port = parseInt(process.env.AMQP_PORT || "5671");
const senderAddress = process.env.SENDER_ADDRESS || "address";
async function main(): Promise<void> {
const connectionOptions: ConnectionOptions = {
transport: "tls",
host: host,
hostname: host,
username: username,
password: password,
port: port,
reconnect: false
};
const connection: Connection = new Connection(connectionOptions);
const senderName = "sender-1";
const awaitableSenderOptions: AwaitableSenderOptions = {
name: senderName,
target: {
address: senderAddress
},
};
await connection.open();
// Notice that we are awaiting on the message being sent.
const sender: AwaitableSender = await connection.createAwaitableSender(
awaitableSenderOptions
);
for (let i = 0; i < 10; i++) {
const message: Message = {
body: `Hello World - ${i}`,
message_id: i
};
// Note: Here we are awaiting for the send to complete.
// You will notice that `delivery.settled` will be `true`, irrespective of whether the promise resolves or rejects.
const delivery: Delivery = await sender.send(message, {
timeoutInSeconds: 10
});
console.log(
"[%s] await sendMessage -> Delivery id: %d, settled: %s",
connection.id,
delivery.id,
delivery.settled
);
}
await sender.close();
await connection.close();
}
main().catch((err) => console.log(err));
Receiving a message
- Running the example from terminal:
> ts-node ./examples/receive.ts.
NOTE: If you are running the sample with .env config file, then please run the sample from the directory that contains .env config file.
import {
Connection, Receiver, EventContext, ConnectionOptions, ReceiverOptions, delay, ReceiverEvents
} from "rhea-promise";
import * as dotenv from "dotenv"; // Optional for loading environment configuration from a .env (config) file
dotenv.config();
const host = process.env.AMQP_HOST || "host";
const username = process.env.AMQP_USERNAME || "sharedAccessKeyName";
const password = process.env.AMQP_PASSWORD || "sharedAccessKeyValue";
const port = parseInt(process.env.AMQP_PORT || "5671");
const receiverAddress = process.env.RECEIVER_ADDRESS || "address";
async function main(): Promise<void> {
const connectionOptions: ConnectionOptions = {
transport: "tls",
host: host,
hostname: host,
username: username,
password: password,
port: port,
reconnect: false
};
const connection: Connection = new Connection(connectionOptions);
const receiverName = "receiver-1";
const receiverOptions: ReceiverOptions = {
name: receiverName,
source: {
address: receiverAddress
},
onSessionError: (context: EventContext) => {
const sessionError = context.session && context.session.error;
if (sessionError) {
console.log(">>>>> [%s] An error occurred for session of receiver '%s': %O.",
connection.id, receiverName, sessionError);
}
}
};
await connection.open();
const receiver: Receiver = await connection.createReceiver(receiverOptions);
receiver.on(ReceiverEvents.message, (context: EventContext) => {
console.log("Received message: %O", context.message);
});
receiver.on(ReceiverEvents.receiverError, (context: EventContext) => {
const receiverError = context.receiver && context.receiver.error;
if (receiverError) {
console.log(">>>>> [%s] An error occurred for receiver '%s': %O.",
connection.id, receiverName, receiverError);
}
});
// sleeping for 2 mins to let the receiver receive messages and then closing it.
await delay(120000);
await receiver.close();
await connection.close();
}
main().catch((err) => console.log(err));
Building the library
- Clone the repo
git clone https://github.com/amqp/rhea-promise.git - Install typescript, ts-node globally
npm i -g typescript npm i -g ts-node - NPM install from the root of the package
npm i - Build the project
npm run build
AMQP Protocol specification
Amqp protocol specification can be found here.