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index.spec.ts

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  • prometheus-metrics.js 2.69 KiB
    import decamelize from 'decamelize'
    import prometheus from 'prom-client'
    
    export default class PrometheusMetrics {
      constructor({ register } = {}) {
        this.register = register || new prometheus.Registry()
        this.counters = {
          numRequests: new prometheus.Counter({
            name: 'service_requests_total',
            help: 'Total service requests',
            labelNames: ['category', 'family', 'service'],
            registers: [this.register],
          }),
          responseTime: new prometheus.Histogram({
            name: 'service_response_millis',
            help: 'Service response time in milliseconds',
            // 250 ms increments up to 2 seconds, then 500 ms increments up to 8
            // seconds, then 1 second increments up to 15 seconds.
            buckets: [
              250, 500, 750, 1000, 1250, 1500, 1750, 2000, 2250, 2500, 2750, 3000,
              3250, 3500, 3750, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500,
              8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000,
            ],
            registers: [this.register],
          }),
          serviceResponseSize: new prometheus.Histogram({
            name: 'service_response_bytes',
            help: 'Service response size in bytes',
            labelNames: ['category', 'family', 'service'],
            // buckets: 64KiB, 128KiB, 256KiB, 512KiB, 1MiB, 2MiB, 4MiB, 8MiB
            buckets: prometheus.exponentialBuckets(64 * 1024, 2, 8),
            registers: [this.register],
          }),
        }
        this.interval = prometheus.collectDefaultMetrics({
          register: this.register,
        })
      }
    
      async registerMetricsEndpoint(server) {
        const { register } = this
    
        server.route(/^\/metrics$/, async (data, match, end, ask) => {
          ask.res.setHeader('Content-Type', register.contentType)
          ask.res.end(await register.metrics())
        })
      }
    
      stop() {
        this.register.clear()
        if (this.interval) {
          clearInterval(this.interval)
          this.interval = undefined
        }
      }
    
      async metrics() {
        return await this.register.getMetricsAsJSON()
      }
    
      /**
       * @param {object} attrs Refer to individual attrs
       * @param {string} attrs.category e.g: 'build'
       * @param {string} attrs.serviceFamily e.g: 'npm'
       * @param {string} attrs.name e.g: 'NpmVersion'
       * @returns {object} `{ inc() {} }`.
       */
      createNumRequestCounter({ category, serviceFamily, name }) {
        const service = decamelize(name)
        return this.counters.numRequests.labels(category, serviceFamily, service)