118 lines
3.6 KiB
JavaScript
118 lines
3.6 KiB
JavaScript
// @ts-check
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import metrics from 'prom-client';
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/**
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* @typedef StreamingMetrics
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* @property {metrics.Gauge<"type">} connectedClients
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* @property {metrics.Gauge<"type" | "channel">} connectedChannels
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* @property {metrics.Gauge} redisSubscriptions
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* @property {metrics.Counter} redisMessagesReceived
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* @property {metrics.Counter<"type">} messagesSent
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* @property {import('express').RequestHandler<{}>} requestHandler
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*/
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/**
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*
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* @param {string[]} channels
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* @param {import('pg').Pool} pgPool
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* @returns {StreamingMetrics}
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*/
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export function setupMetrics(channels, pgPool) {
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// Collect metrics from Node.js
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metrics.collectDefaultMetrics();
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new metrics.Gauge({
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name: 'pg_pool_total_connections',
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help: 'The total number of clients existing within the pool',
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collect() {
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this.set(pgPool.totalCount);
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},
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});
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new metrics.Gauge({
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name: 'pg_pool_idle_connections',
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help: 'The number of clients which are not checked out but are currently idle in the pool',
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collect() {
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this.set(pgPool.idleCount);
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},
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});
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new metrics.Gauge({
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name: 'pg_pool_waiting_queries',
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help: 'The number of queued requests waiting on a client when all clients are checked out',
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collect() {
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this.set(pgPool.waitingCount);
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},
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});
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const connectedClients = new metrics.Gauge({
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name: 'connected_clients',
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help: 'The number of clients connected to the streaming server',
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labelNames: ['type'],
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});
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const connectedChannels = new metrics.Gauge({
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name: 'connected_channels',
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help: 'The number of channels the streaming server is streaming to',
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labelNames: [ 'type', 'channel' ]
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});
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const redisSubscriptions = new metrics.Gauge({
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name: 'redis_subscriptions',
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help: 'The number of Redis channels the streaming server is subscribed to',
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});
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const redisMessagesReceived = new metrics.Counter({
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name: 'redis_messages_received_total',
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help: 'The total number of messages the streaming server has received from redis subscriptions'
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});
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const messagesSent = new metrics.Counter({
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name: 'messages_sent_total',
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help: 'The total number of messages the streaming server sent to clients per connection type',
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labelNames: [ 'type' ]
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});
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// Prime the gauges so we don't loose metrics between restarts:
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redisSubscriptions.set(0);
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connectedClients.set({ type: 'websocket' }, 0);
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connectedClients.set({ type: 'eventsource' }, 0);
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// For each channel, initialize the gauges at zero; There's only a finite set of channels available
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channels.forEach(( channel ) => {
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connectedChannels.set({ type: 'websocket', channel }, 0);
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connectedChannels.set({ type: 'eventsource', channel }, 0);
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});
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// Prime the counters so that we don't loose metrics between restarts.
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// Unfortunately counters don't support the set() API, so instead I'm using
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// inc(0) to achieve the same result.
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redisMessagesReceived.inc(0);
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messagesSent.inc({ type: 'websocket' }, 0);
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messagesSent.inc({ type: 'eventsource' }, 0);
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/**
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* @type {import('express').RequestHandler<{}>}
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*/
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const requestHandler = (req, res) => {
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metrics.register.metrics().then((output) => {
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res.set('Content-Type', metrics.register.contentType);
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res.set('Cache-Control', 'private, no-store');
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res.end(output);
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}).catch((err) => {
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req.log.error(err, "Error collecting metrics");
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res.set('Cache-Control', 'private, no-store');
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res.status(500).end();
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});
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};
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return {
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requestHandler,
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connectedClients,
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connectedChannels,
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redisSubscriptions,
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redisMessagesReceived,
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messagesSent,
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};
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}
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