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import { Server } from 'net'
import prometheus, {
collectDefaultMetrics,
DefaultMetricsCollectorConfiguration,
Registry,
} from 'prom-client'
import express from 'express'
import { Logger } from './logger'
export interface MetricsOptions {
prefix?: string
labels?: Object
}
export class Metrics {
options: MetricsOptions
client: typeof prometheus
registry: Registry
constructor(options: MetricsOptions) {
this.options = options
const metricsOptions: DefaultMetricsCollectorConfiguration = {
prefix: options.prefix,
labels: options.labels,
}
this.client = prometheus
this.registry = prometheus.register
// Collect default metrics (event loop lag, memory, file descriptors etc.)
collectDefaultMetrics(metricsOptions)
}
}
export interface MetricsServerOptions {
logger: Logger
registry: Registry
port?: number
route?: string
hostname?: string
}
export const createMetricsServer = async (
options: MetricsServerOptions
): Promise<Server> => {
const logger = options.logger.child({ component: 'MetricsServer' })
const app = express()
const route = options.route || '/metrics'
app.get(route, async (_, res) => {
res.status(200).send(await options.registry.metrics())
})
const port = options.port || 7300
const hostname = options.hostname || '0.0.0.0'
const server = app.listen(port, hostname, () => {
logger.info('Metrics server started', {
port,
hostname,
route,
})
})
return server
}