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Retain retained messages and send them to new subscriptions #16

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Retain retained messages and send them to new subscriptions #16

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20 changes: 18 additions & 2 deletions src/mqtt-pubsub.ts
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
import { PubSubEngine } from 'graphql-subscriptions/dist/pubsub-engine';
import { connect, Client, ISubscriptionGrant, IClientPublishOptions, IClientSubscribeOptions } from 'mqtt';
import { connect, Client, ISubscriptionGrant, IClientPublishOptions, IClientSubscribeOptions, IPublishPacket } from 'mqtt';
import { PubSubAsyncIterator } from './pubsub-async-iterator';

export interface PubSubMQTTOptions {
Expand All @@ -22,6 +22,7 @@ export class MQTTPubSub implements PubSubEngine {
private mqttConnection: Client;
private subscriptionMap: { [subId: number]: [string, Function] };
private subsRefsMap: { [trigger: string]: Array<number> };
private retainedMessagesMap: { [trigger: string]: any };
private currentSubscriptionId: number;
private parseMessageWithEncoding: string;

Expand Down Expand Up @@ -70,6 +71,7 @@ export class MQTTPubSub implements PubSubEngine {

this.subscriptionMap = {};
this.subsRefsMap = {};
this.retainedMessagesMap = {};
this.currentSubscriptionId = 0;
this.onMQTTSubscribe = options.onMQTTSubscribe || (() => null);
this.publishOptionsResolver = options.publishOptions || (() => Promise.resolve({} as IClientPublishOptions));
Expand All @@ -95,6 +97,13 @@ export class MQTTPubSub implements PubSubEngine {
if (refs && refs.length > 0) {
const newRefs = [...refs, id];
this.subsRefsMap[triggerName] = newRefs;
// If we have a retained message then send it to this new subscription
const retainedMessage = this.retainedMessagesMap[triggerName];
if (retainedMessage) {
setTimeout(() => {
onMessage(retainedMessage);
}, 0);
}
return Promise.resolve(id);

} else {
Expand Down Expand Up @@ -136,6 +145,9 @@ export class MQTTPubSub implements PubSubEngine {
if (refs.length === 1) {
this.mqttConnection.unsubscribe(triggerName);
newRefs = [];
// Delete the retained messages for this subscription
// we will get sent any retained messages when we resubscribe
delete this.retainedMessagesMap[triggerName];

} else {
const index = refs.indexOf(subId);
Expand All @@ -152,7 +164,7 @@ export class MQTTPubSub implements PubSubEngine {
return new PubSubAsyncIterator<T>(this, triggers);
}

private onMessage(topic: string, message: Buffer) {
private onMessage(topic: string, message: Buffer, packet: IPublishPacket) {
const subscribers = [].concat(
...Object.keys(this.subsRefsMap)
.filter((key) => MQTTPubSub.matches(key, topic))
Expand All @@ -175,6 +187,10 @@ export class MQTTPubSub implements PubSubEngine {
const listener = this.subscriptionMap[subId][1];
listener(parsedMessage);
}
if (packet.retain) {
// Retain the message if it is meant to be retained
this.retainedMessagesMap[topic] = parsedMessage
}
}
}

Expand Down