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ChannelWrapper.js
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ChannelWrapper.js
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import { EventEmitter } from 'events';
import pb from 'promise-breaker';
/**
* Calls to `publish()` or `sendToQueue()` work just like in amqplib, but messages are queued internally and
* are guaranteed to be delivered. If the underlying connection drops, ChannelWrapper will wait for a new
* connection and continue.
*
* Events:
* * `connect` - emitted every time this channel connects or reconnects.
* * `error(err, {name})` - emitted if an error occurs setting up the channel.
* * `drop({message, err})` - called when a JSON message was dropped because it could not be encoded.
* * `close` - emitted when this channel closes via a call to `close()`
*
*/
export default class ChannelWrapper extends EventEmitter {
/**
* Adds a new 'setup handler'.
*
* `setup(channel, [cb])` is a function to call when a new underlying channel is created - handy for asserting
* exchanges and queues exists, and whatnot. The `channel` object here is a ConfigChannel from amqplib.
* The `setup` function should return a Promise (or optionally take a callback) - no messages will be sent until
* this Promise resolves.
*
* If there is a connection, `setup()` will be run immediately, and the addSetup Promise/callback won't resolve
* until `setup` is complete. Note that in this case, if the setup throws an error, no 'error' event will
* be emitted, since you can just handle the error here (although the `setup` will still be added for future
* reconnects, even if it throws an error.)
*
* Setup functions should, ideally, not throw errors, but if they do then the ChannelWrapper will emit an 'error'
* event.
*
* @param {function} setup - setup function.
* @param {function} [done] - callback.
* @returns {void | Promise} - Resolves when complete.
*/
addSetup(setup, done = null) {
return pb.addCallback(
done,
(this._settingUp || Promise.resolve()).then(() => {
this._setups.push(setup);
if (this._channel) {
return pb.call(setup, this, this._channel);
} else {
return undefined;
}
})
);
}
/**
* Remove a setup function added with `addSetup`. If there is currently a
* connection, `teardown(channel, [cb])` will be run immediately, and the
* returned Promise will not resolve until it completes.
*
* @param {function} setup - the setup function to remove.
* @param {function} [teardown] - `function(channel, [cb])` to run to tear
* down the channel.
* @param {function} [done] - Optional callback.
* @returns {void | Promise} - Resolves when complete.
*/
removeSetup(setup, teardown = null, done = null) {
return pb.addCallback(done, () => {
this._setups = this._setups.filter((s) => s !== setup);
return (this._settingUp || Promise.resolve()).then(() =>
this._channel ? pb.call(teardown, this, this._channel) : undefined
);
});
}
/**
* Returns a Promise which resolves when this channel next connects.
* (Mainly here for unit testing...)
*
* @param {function} [done] - Optional callback.
* @returns {void | Promise} - Resolves when connected.
*/
waitForConnect(done = null) {
return pb.addCallback(
done,
this._channel && !this._settingUp
? Promise.resolve()
: new Promise((resolve) => this.once('connect', resolve))
);
}
/*
* Publish a message to the channel.
*
* This works just like amqplib's `publish()`, except if the channel is not
* connected, this will wait until the channel is connected. Returns a
* Promise which will only resolve when the message has been succesfully sent.
* The returned promise will be rejected if `close()` is called on this
* channel before it can be sent, if `options.json` is set and the message
* can't be encoded, or if the broker rejects the message for some reason.
*
*/
publish(exchange, routingKey, content, options, done = null) {
return pb.addCallback(
done,
new Promise((resolve, reject) => {
this._messages.push({
type: 'publish',
exchange,
routingKey,
content,
options,
resolve,
reject,
});
this._startWorker();
})
);
}
/*
* Send a message to a queue.
*
* This works just like amqplib's `sendToQueue`, except if the channel is not connected, this will wait until the
* channel is connected. Returns a Promise which will only resolve when the message has been succesfully sent.
* The returned promise will be rejected only if `close()` is called on this channel before it can be sent.
*
* `message` here should be a JSON-able object.
*/
sendToQueue(queue, content, options, done = null) {
return pb.addCallback(
done,
new Promise((resolve, reject) => {
this._messages.push({
type: 'sendToQueue',
queue,
content,
options,
resolve,
reject,
});
return this._startWorker();
})
);
}
/**
* Create a new ChannelWrapper.
*
* @param {AmqpConnectionManager} connectionManager - connection manager which
* created this channel.
* @param {Object} [options] -
* @param {string} [options.name] - A name for this channel. Handy for debugging.
* @param {function} [options.setup] - A default setup function to call. See
* `addSetup` for details.
* @param {boolean} [options.json] - if true, then ChannelWrapper assumes all
* messages passed to `publish()` and `sendToQueue()` are plain JSON objects.
* These will be encoded automatically before being sent.
*
*/
constructor(connectionManager, options = {}) {
super();
this._onConnect = this._onConnect.bind(this);
this._onDisconnect = this._onDisconnect.bind(this);
this._connectionManager = connectionManager;
this.name = options.name;
this.context = {};
this._json = 'json' in options ? options.json : false;
// Place to store queued messages.
this._messages = [];
// Place to store published, but not yet confirmed messages
this._unconfirmedMessages = [];
// Place to store reason code during publish or sendtoqueue messages.
this._irrecoverableCode = null;
// Irrecoverable error.
this._irrecoverableError = [
403, // AMQP Access Refused Error.
404, // AMQP Not Found Error.
406, // AMQP Precondition Failed Error.
501, // AMQP Frame Error.
502, // AMQP Frame Syntax Error.
503, // AMQP Invalid Command Error.
504, // AMQP Channel Not Open Error.
505, // AMQP Unexpected Frame.
530, // AMQP Not Allowed Error.
540, // AMQP Not Implemented Error.
541, // AMQP Internal Error.
];
// True if the "worker" is busy sending messages. False if we need to
// start the worker to get stuff done.
this._working = false;
// If we're in the process of creating a channel, this is a Promise which
// will resolve when the channel is set up. Otherwise, this is `null`.
this._settingUp = null;
// The currently connected channel. Note that not all setup functions
// have been run on this channel until `@_settingUp` is either null or
// resolved.
this._channel = null;
// We kill off workers when we disconnect. Whenever we start a new
// worker, we bump up the `_workerNumber` - this makes it so if stale
// workers ever do wake up, they'll know to stop working.
this._workerNumber = 0;
// Array of setup functions to call.
this._setups = [];
if (options.setup) {
this._setups.push(options.setup);
}
if (connectionManager.isConnected()) {
this._onConnect({
connection: this._connectionManager._currentConnection,
});
}
connectionManager.on('connect', this._onConnect);
connectionManager.on('disconnect', this._onDisconnect);
}
// Called whenever we connect to the broker.
_onConnect({ connection }) {
this._connection = connection;
this._irrecoverableCode = null;
return connection
.createConfirmChannel()
.then((channel) => {
this._channel = channel;
channel.on('close', () => this._onChannelClose(channel));
this._settingUp = Promise.all(
this._setups.map((setupFn) =>
// TODO: Use a timeout here to guard against setupFns that never resolve?
pb.call(setupFn, this, channel).catch((err) => {
if (err.name === 'IllegalOperationError') {
// Don't emit an error if setups failed because the channel closed.
return;
}
this.emit('error', err, { name: this.name });
})
)
).then(() => {
this._settingUp = null;
return this._channel;
});
return this._settingUp;
})
.then(() => {
if (!this._channel) {
// Can happen if channel closes while we're setting up.
return;
}
if (this._unconfirmedMessages.length > 0) {
// requeu any messages that were left unconfirmed when connection was lost
while (this._unconfirmedMessages.length) {
this._messages.push(this._unconfirmedMessages.shift());
}
}
// Since we just connected, publish any queued messages
this._startWorker();
this.emit('connect');
})
.catch((err) => {
this.emit('error', err, { name: this.name });
this._settingUp = null;
this._channel = null;
});
}
// Called whenever the channel closes.
_onChannelClose(channel) {
if (this._channel === channel) {
this._channel = null;
}
}
// Wait for another reconnect to create a new channel.
// Called whenever we disconnect from the AMQP server.
_onDisconnect(ex) {
this._irrecoverableCode = (ex.err instanceof Error ? ex.err.code : null) || null;
this._channel = null;
this._settingUp = null;
// Kill off the current worker. We never get any kind of error for messages in flight - see
// https://github.com/squaremo/amqp.node/issues/191.
this._working = false;
}
// Returns the number of unsent messages queued on this channel.
queueLength() {
return this._messages.length;
}
// Destroy this channel.
//
// Any unsent messages will have their associated Promises rejected.
//
close() {
return Promise.resolve().then(() => {
this._working = false;
if (this._messages.length !== 0) {
// Reject any unsent messages.
this._messages.forEach((message) => message.reject(new Error('Channel closed')));
}
if (this._unconfirmedMessages.length !== 0) {
// Reject any unconfirmed messages.
this._unconfirmedMessages.forEach((message) =>
message.reject(new Error('Channel closed'))
);
}
this._connectionManager.removeListener('connect', this._onConnect);
this._connectionManager.removeListener('disconnect', this._onDisconnect);
const answer = (this._channel && this._channel.close()) || undefined;
this._channel = null;
this.emit('close');
return answer;
});
}
_shouldPublish() {
return this._messages.length > 0 && !this._settingUp && this._channel;
}
// Start publishing queued messages, if there isn't already a worker doing this.
_startWorker() {
if (!this._working && this._shouldPublish()) {
this._working = true;
this._workerNumber++;
this._publishQueuedMessages(this._workerNumber);
}
}
// Define if a message can cause irrecoverable error
_canWaitReconnection() {
return !this._irrecoverableError.includes(this._irrecoverableCode);
}
_publishQueuedMessages(workerNumber) {
if (!this._shouldPublish() || !this._working || workerNumber !== this._workerNumber) {
// Can't publish anything right now...
this._working = false;
return Promise.resolve();
}
const channel = this._channel;
const message = this._messages.shift();
this._unconfirmedMessages.push(message);
Promise.resolve()
.then(() => {
const encodedMessage = this._json
? new Buffer.from(JSON.stringify(message.content))
: message.content;
let result = true;
const sendPromise = (() => {
switch (message.type) {
case 'publish':
return new Promise(function (resolve, reject) {
result = channel.publish(
message.exchange,
message.routingKey,
encodedMessage,
message.options,
(err) => {
if (err) {
reject(err);
} else {
setImmediate(() => resolve(result));
}
}
);
});
case 'sendToQueue':
return new Promise(function (resolve, reject) {
result = channel.sendToQueue(
message.queue,
encodedMessage,
message.options,
(err) => {
if (err) {
reject(err);
} else {
setImmediate(() => resolve(result));
}
}
);
});
/* istanbul ignore next */
default:
throw new Error(`Unhandled message type ${message.type}`);
}
})();
if (result) {
this._publishQueuedMessages(workerNumber);
} else {
this._channel.once('drain', () => this._publishQueuedMessages(workerNumber));
}
return sendPromise;
})
.then(
(result) => {
removeUnconfirmedMessage(this._unconfirmedMessages, message);
message.resolve(result);
},
(err) => {
if (!this._channel && this._canWaitReconnection()) {
// Tried to write to a closed channel. Leave the message in the queue and we'll try again when
// we reconnect.
removeUnconfirmedMessage(this._unconfirmedMessages, message);
this._messages.push(message);
} else {
// Something went wrong trying to send this message - could be JSON.stringify failed, could be
// the broker rejected the message. Either way, reject it back
removeUnconfirmedMessage(this._unconfirmedMessages, message);
message.reject(err);
}
}
)
.catch(
/* istanbul ignore next */ (err) => {
this.emit('error', err);
this._working = false;
}
);
return null;
}
// Send an `ack` to the underlying channel.
ack() {
return this._channel && this._channel.ack.apply(this._channel, arguments);
}
// Send an `ackAll` to the underlying channel.
ackAll() {
return this._channel && this._channel.ackAll.apply(this._channel, arguments);
}
// Send a `nack` to the underlying channel.
nack() {
return this._channel && this._channel.nack.apply(this._channel, arguments);
}
// Send a `nackAll` to the underlying channel.
nackAll() {
return this._channel && this._channel.nackAll.apply(this._channel, arguments);
}
// Send a `purgeQueue` to the underlying channel.
purgeQueue() {
return this._channel && this._channel.purgeQueue.apply(this._channel, arguments);
}
// Send a `checkQueue` to the underlying channel.
checkQueue() {
return this._channel && this._channel.checkQueue.apply(this._channel, arguments);
}
// Send a `assertQueue` to the underlying channel.
assertQueue() {
return this._channel && this._channel.assertQueue.apply(this._channel, arguments);
}
// Send a `bindQueue` to the underlying channel.
bindQueue() {
return this._channel && this._channel.bindQueue.apply(this._channel, arguments);
}
// Send a `deleteQueue` to the underlying channel.
deleteQueue() {
return this._channel && this._channel.deleteQueue.apply(this._channel, arguments);
}
// Send a `assertExchange` to the underlying channel.
assertExchange() {
return this._channel && this._channel.assertExchange.apply(this._channel, arguments);
}
// Send a `get` to the underlying channel.
get() {
return this._channel && this._channel.get.apply(this._channel, arguments);
}
}
function removeUnconfirmedMessage(arr, message) {
const toRemove = arr.indexOf(message);
if (toRemove === -1) {
throw new Error(`Message is not in _unconfirmedMessages!`);
}
const removed = arr.splice(toRemove, 1);
return removed[0];
}