mastodon-glitch/streaming/metrics.js

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// @ts-check
import metrics from 'prom-client';
/**
* @typedef StreamingMetrics
* @property {metrics.Registry} register
* @property {metrics.Gauge<"type">} connectedClients
* @property {metrics.Gauge<"type" | "channel">} connectedChannels
* @property {metrics.Gauge} redisSubscriptions
* @property {metrics.Counter} redisMessagesReceived
* @property {metrics.Counter<"type">} messagesSent
*/
/**
*
* @param {string[]} channels
* @param {import('pg').Pool} pgPool
* @returns {StreamingMetrics}
*/
export function setupMetrics(channels, pgPool) {
// Collect metrics from Node.js
metrics.collectDefaultMetrics();
new metrics.Gauge({
name: 'pg_pool_total_connections',
help: 'The total number of clients existing within the pool',
collect() {
this.set(pgPool.totalCount);
},
});
new metrics.Gauge({
name: 'pg_pool_idle_connections',
help: 'The number of clients which are not checked out but are currently idle in the pool',
collect() {
this.set(pgPool.idleCount);
},
});
new metrics.Gauge({
name: 'pg_pool_waiting_queries',
help: 'The number of queued requests waiting on a client when all clients are checked out',
collect() {
this.set(pgPool.waitingCount);
},
});
const connectedClients = new metrics.Gauge({
name: 'connected_clients',
help: 'The number of clients connected to the streaming server',
labelNames: ['type'],
});
const connectedChannels = new metrics.Gauge({
name: 'connected_channels',
help: 'The number of channels the streaming server is streaming to',
labelNames: [ 'type', 'channel' ]
});
const redisSubscriptions = new metrics.Gauge({
name: 'redis_subscriptions',
help: 'The number of Redis channels the streaming server is subscribed to',
});
const redisMessagesReceived = new metrics.Counter({
name: 'redis_messages_received_total',
help: 'The total number of messages the streaming server has received from redis subscriptions'
});
const messagesSent = new metrics.Counter({
name: 'messages_sent_total',
help: 'The total number of messages the streaming server sent to clients per connection type',
labelNames: [ 'type' ]
});
// Prime the gauges so we don't loose metrics between restarts:
redisSubscriptions.set(0);
connectedClients.set({ type: 'websocket' }, 0);
connectedClients.set({ type: 'eventsource' }, 0);
// For each channel, initialize the gauges at zero; There's only a finite set of channels available
channels.forEach(( channel ) => {
connectedChannels.set({ type: 'websocket', channel }, 0);
connectedChannels.set({ type: 'eventsource', channel }, 0);
});
// Prime the counters so that we don't loose metrics between restarts.
// Unfortunately counters don't support the set() API, so instead I'm using
// inc(0) to achieve the same result.
redisMessagesReceived.inc(0);
messagesSent.inc({ type: 'websocket' }, 0);
messagesSent.inc({ type: 'eventsource' }, 0);
return {
register: metrics.register,
connectedClients,
connectedChannels,
redisSubscriptions,
redisMessagesReceived,
messagesSent,
};
}