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nats-pubsub.ts
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nats-pubsub.ts
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import { PubSubEngine } from 'graphql-subscriptions';
import { connect, Client, ClientOpts, SubscribeOptions, NatsError } from 'nats';
import { PubSubAsyncIterator } from './pubsub-async-iterator';
import _ from 'lodash';
import { CdmLogger } from '@cdm-logger/core';
type Logger = CdmLogger.ILogger;
export type Path = Array<string | number>;
export type Trigger = string | Path;
export type TriggerTransform = (trigger: Trigger, channelOptions?: object) => string;
export type SubscribeOptionsResolver = (trigger: Trigger, channelOptions?: object) => Promise<SubscribeOptions>;
export type PublishOptionsResolver = (trigger: Trigger, payload: any) => Promise<any>;
export interface NatsPubSubOptions {
client?: Client;
subscribeOptions?: SubscribeOptionsResolver;
publishOptions?: PublishOptionsResolver;
connectionListener?: (err: Error) => void;
// onNatsSubscribe?: (id: number, granted: ISubscriptionGrant[]) => void;
triggerTransform?: TriggerTransform;
parseMessageWithEncoding?: BufferEncoding;
logger?: Logger;
}
export class NatsPubSub implements PubSubEngine {
private triggerTransform: TriggerTransform;
private publishOptionsResolver: PublishOptionsResolver;
private subscribeOptionsResolver: SubscribeOptionsResolver;
private natsConnection: Client;
// { [subId]: {topic, natsSid, onMessage} } -- NATS Subscriptions
private subscriptionMap: { [subId: number]: [string, Function] };
// { [topic]: [ subId1, subId2, ...]}
private subsRefsMap: { [trigger: string]: Array<number> };
// { [topic]: { natsSid }}
private natsSubMap: { [trigger: string]: number };
private currentSubscriptionId: number;
private logger: Logger;
public constructor(options: NatsPubSubOptions = {}) {
this.triggerTransform = options.triggerTransform || (trigger => trigger as string);
if (options.client) {
this.natsConnection = options.client;
} else {
const brokerUrl = 'nats://127.0.0.1:4222';
this.natsConnection = connect(brokerUrl);
}
this.logger = options.logger.child({ className: 'nats-subscription' });
if (options.connectionListener) {
this.natsConnection.on('connect', options.connectionListener);
this.natsConnection.on('error', options.connectionListener);
this.natsConnection.on('disconnect', options.connectionListener);
this.natsConnection.on('reconnecting', options.connectionListener);
this.natsConnection.on('reconnect', options.connectionListener);
this.natsConnection.on('close', options.connectionListener);
} else {
this.natsConnection.on('error', this.logger && this.logger.error);
}
this.subscriptionMap = {};
this.subsRefsMap = {};
this.natsSubMap = {};
this.currentSubscriptionId = 0;
// this.onNatsSubscribe = options.onNatsSubscribe || (() => null);
this.publishOptionsResolver = options.publishOptions || (() => Promise.resolve({}));
this.subscribeOptionsResolver = options.subscribeOptions || (() => Promise.resolve({}));
}
public async publish(trigger: string, payload: any): Promise<void> {
this.logger.trace("publishing to queue '%s' (%j)",
trigger, payload);
const message = JSON.stringify(payload);
await this.natsConnection.publish(trigger, message);
}
public async subscribe(trigger: string, onMessage: Function, options?: object): Promise<number> {
this.logger.trace("subscribing to queue '%s' with onMessage (%j), and options (%j) ",
trigger, onMessage, options);
const triggerName: string = this.triggerTransform(trigger, options);
const id = this.currentSubscriptionId++;
this.subscriptionMap[id] = [triggerName, onMessage];
let refs = this.subsRefsMap[triggerName];
if (refs && refs.length > 0) {
this.logger.trace('relavent topic (%s) is already subscribed', triggerName);
const newRefs = [...refs, id];
this.subsRefsMap[triggerName] = newRefs;
return await id;
} else {
// return new Promise<number>((resolve, reject) => {
this.logger.trace('topic (%s) is new and yet to be subscribed', triggerName);
// 1. Resolve options object
// this.subscribeOptionsResolver(trigger, options).then(subscriptionOptions => {
this.logger.trace('resolve subscriptionoptions with options (%j)', options);
// 2. Subscribing using NATS
const subId = this.natsConnection.subscribe(triggerName, (msg) => this.onMessage(triggerName, msg));
this.subsRefsMap[triggerName] = [...(this.subsRefsMap[triggerName] || []), id];
this.natsSubMap[triggerName] = subId;
return await id;
// });
// });
}
}
public unsubscribe(subId: number) {
const [triggerName = null] = this.subscriptionMap[subId] || [];
const refs = this.subsRefsMap[triggerName];
const natsSubId = this.natsSubMap[triggerName];
this.logger.trace("unsubscribing to queue '%s' and natsSid: (%s)", subId, natsSubId);
if (!refs) {
this.logger.error('there are no subscriptions for triggerName (%s) and natsSid (%s)', triggerName, natsSubId);
throw new Error(`There is no subscription of id "${subId}"`);
}
if (refs.length === 1) {
this.natsConnection.unsubscribe(natsSubId);
delete this.natsSubMap[triggerName];
delete this.subsRefsMap[triggerName];
this.logger.trace('unsubscribe on nats for subId (%s) is completed and there is no subscriber to topic (%s)',
natsSubId, triggerName);
} else {
const index = refs.indexOf(subId);
const newRefs = index === -1 ? refs : [...refs.slice(0, index), ...refs.slice(index + 1)];
this.subsRefsMap[triggerName] = newRefs;
this.logger.trace('unsubscribe on nats for subId (%s) is completed and there are still (%s) subscribers', newRefs.length);
}
delete this.subscriptionMap[subId];
}
public asyncIterator<T>(triggers: string | string[]): AsyncIterator<T> {
this.logger.trace('asyncIterator called with trigger (%j)', triggers);
return new PubSubAsyncIterator<T>(this, triggers, this.logger);
}
private onMessage(topic: string, message: string) {
this.logger.trace('triggered onMessage with topic (%s), message (%j)', topic, message);
const subscribers = this.subsRefsMap[topic];
// Don't work for nothing..
if (!subscribers || !subscribers.length) {
return;
}
// for example a client could inject a bogus `toString` property
// which could cause your client to crash should you try to
// concatenation with the `+` like this:
// console.log("received", msg + "here");
// `TypeError: Cannot convert object to primitive value`
// Note that simple `console.log(msg)` is fine.
if (message.hasOwnProperty('toString')) {
console.warn('not suppose to have `toString` in payload, which likely trying to crash the server', message.toString);
return;
}
let parsedMessage;
try {
parsedMessage = JSON.parse(message);
} catch (e) {
parsedMessage = message;
}
for (const subId of subscribers) {
const listener = this.subscriptionMap[subId][1];
this.logger.trace('subscription listener to run for subId (%s)', subId);
listener(parsedMessage);
}
}
}