Subscriber.js: Listener not removed on multiple topics
aldotms70 opened this issue · comments
aldotms70 commented
When using SubscriptionContext with array of topic, the listeners are not removed on close function.
Only the listener on the last topic is removed on close.
These issue is a leak of socket, specially if you are using redis.
subscribe (topic, queue) {
return new Promise((resolve, reject) => {
function listener (value, cb) {
queue.push(value.payload)
cb()
}
const close = () => {
this.emitter.removeListener(topic, listener)
}
this.emitter.on(topic, listener, (err) => {
if (err) {
return reject(err)
}
resolve()
})
queue.close = close // <---- The local close function is overrided
})
}
The solution is an array of close functions:
'use strict'
const { Readable } = require('readable-stream')
class PubSub {
constructor (emitter) {
this.emitter = emitter
}
subscribe (topic, queue) {
return new Promise((resolve, reject) => {
function listener (value, cb) {
queue.push(value.payload)
cb()
}
const close = () => {
this.emitter.removeListener(topic, listener)
}
this.emitter.on(topic, listener, (err) => {
if (err) {
return reject(err)
}
resolve()
})
if (!queue.close) queue.close = []
queue.close.push(close)
})
}
publish (event, callback) {
this.emitter.emit(event, callback)
}
}
// One context - and queue for each subscription
class SubscriptionContext {
constructor ({ pubsub, fastify }) {
this.fastify = fastify
this.pubsub = pubsub
this.queue = new Readable({
objectMode: true,
read: () => {}
})
}
subscribe (topics) {
if (typeof topics === 'string') {
return this.pubsub.subscribe(topics, this.queue).then(() => this.queue)
}
return Promise.all(topics.map((topic) => this.pubsub.subscribe(topic, this.queue))).then(() => this.queue)
}
publish (event) {
return new Promise((resolve, reject) => {
this.pubsub.publish(event, (err) => {
if (err) {
return reject(err)
}
resolve()
})
}).catch(err => {
this.fastify.log.error(err)
})
}
close () {
// In rare cases when `subscribe()` not called (e.g. some network error)
// `close` will be `undefined`.
if (Array.isArray(this.queue.close)) {
this.queue.close.map((close) => close())
}
this.queue.push(null)
}
}
function withFilter (subscribeFn, filterFn) {
return async function * (root, args, context, info) {
const subscription = await subscribeFn(root, args, context, info)
for await (const payload of subscription) {
try {
if (await filterFn(payload, args, context, info)) {
yield payload
}
} catch (err) {
context.app.log.error(err)
continue
}
}
}
}
module.exports = {
PubSub,
SubscriptionContext,
withFilter
}