express-prometheus-metrics

Express middleware for collecting metrics with Prometheus

Install

yarn add express-prometheus-metrics

Usage

const express = require('express')
const metrics = require('express-prometheus-metrics')

const app = express()

app.use(
  metrics({
    // The route to expose the metrics on
    metricsPath: '/metrics',

    // How often prometheus should collect the metrics
    interval: 60 * 1000,

    // Any routes that should be ignored
    excludeRoutes: [],

    // Percentiles for request duration summary
    requestDurationBuckets: [0.5, 0.9, 0.95, 0.99],

    // Time buckets for request duration histogram
    requestDurationHistogramBuckets: [0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10],

    // Size buckets for request
    requestSizeBuckets: [5, 10, 25, 50, 100, 250, 500, 1000, 2500, 5000, 10000],

    // Size buckets for response
    responseSizeBuckets: [5, 10, 25, 50, 100, 250, 500, 1000, 2500, 5000, 10000],
  }),
)

app.listen(process.env.PORT, error => {
  if (error) throw error

  console.log(`Listening on http://localhost:${process.env.PORT}`)
  console.log(
    `Metrics available at http://localhost:${process.env.PORT}/metrics`,
  )
})

Metrics Example

# HELP process_cpu_user_seconds_total Total user CPU time spent in seconds.
# TYPE process_cpu_user_seconds_total counter
process_cpu_user_seconds_total 0.705806 1558806366238

# HELP process_cpu_system_seconds_total Total system CPU time spent in seconds.
# TYPE process_cpu_system_seconds_total counter
process_cpu_system_seconds_total 0.058946 1558806366238

# HELP process_cpu_seconds_total Total user and system CPU time spent in seconds.
# TYPE process_cpu_seconds_total counter
process_cpu_seconds_total 0.764752 1558806366238

# HELP process_start_time_seconds Start time of the process since unix epoch in seconds.
# TYPE process_start_time_seconds gauge
process_start_time_seconds 1558806355

# HELP process_resident_memory_bytes Resident memory size in bytes.
# TYPE process_resident_memory_bytes gauge
process_resident_memory_bytes 58933248 1558806366238

# HELP nodejs_eventloop_lag_seconds Lag of event loop in seconds.
# TYPE nodejs_eventloop_lag_seconds gauge
nodejs_eventloop_lag_seconds 0.000792479 1558806366239

# HELP nodejs_active_handles_total Number of active handles.
# TYPE nodejs_active_handles_total gauge
nodejs_active_handles_total 8 1558806366238

# HELP nodejs_active_requests_total Number of active requests.
# TYPE nodejs_active_requests_total gauge
nodejs_active_requests_total 0 1558806366238

# HELP nodejs_heap_size_total_bytes Process heap size from node.js in bytes.
# TYPE nodejs_heap_size_total_bytes gauge
nodejs_heap_size_total_bytes 40144896 1558806366238

# HELP nodejs_heap_size_used_bytes Process heap size used from node.js in bytes.
# TYPE nodejs_heap_size_used_bytes gauge
nodejs_heap_size_used_bytes 31756904 1558806366238

# HELP nodejs_external_memory_bytes Nodejs external memory size in bytes.
# TYPE nodejs_external_memory_bytes gauge
nodejs_external_memory_bytes 83838 1558806366238

# HELP nodejs_heap_space_size_total_bytes Process heap space size total from node.js in bytes.
# TYPE nodejs_heap_space_size_total_bytes gauge
nodejs_heap_space_size_total_bytes{space="read_only"} 524288 1558806366238
nodejs_heap_space_size_total_bytes{space="new"} 1048576 1558806366238
nodejs_heap_space_size_total_bytes{space="old"} 32215040 1558806366238
nodejs_heap_space_size_total_bytes{space="code"} 1572864 1558806366238
nodejs_heap_space_size_total_bytes{space="map"} 2109440 1558806366238
nodejs_heap_space_size_total_bytes{space="large_object"} 2674688 1558806366238

# HELP nodejs_heap_space_size_used_bytes Process heap space size used from node.js in bytes.
# TYPE nodejs_heap_space_size_used_bytes gauge
nodejs_heap_space_size_used_bytes{space="read_only"} 35200 1558806366238
nodejs_heap_space_size_used_bytes{space="new"} 8792 1558806366238
nodejs_heap_space_size_used_bytes{space="old"} 28045920 1558806366238
nodejs_heap_space_size_used_bytes{space="code"} 1054912 1558806366238
nodejs_heap_space_size_used_bytes{space="map"} 1289464 1558806366238
nodejs_heap_space_size_used_bytes{space="large_object"} 1327648 1558806366238

# HELP nodejs_heap_space_size_available_bytes Process heap space size available from node.js in bytes.
# TYPE nodejs_heap_space_size_available_bytes gauge
nodejs_heap_space_size_available_bytes{space="read_only"} 480384 1558806366238
nodejs_heap_space_size_available_bytes{space="new"} 1022376 1558806366238
nodejs_heap_space_size_available_bytes{space="old"} 3388192 1558806366238
nodejs_heap_space_size_available_bytes{space="code"} 456512 1558806366238
nodejs_heap_space_size_available_bytes{space="map"} 776104 1558806366238
nodejs_heap_space_size_available_bytes{space="large_object"} 1486573056 1558806366238

# HELP nodejs_version_info Node.js version info.
# TYPE nodejs_version_info gauge
nodejs_version_info{version="v10.14.1",major="10",minor="14",patch="1"} 1

# HELP app_version Application version from the package.json file as string
# TYPE app_version gauge
app_version{version="0.2.5"} 1

# HELP http_request_duration_histogram_seconds Duration of HTTP requests in seconds
# TYPE http_request_duration_histogram_seconds histogram
http_request_duration_histogram_seconds_bucket{le="0.005",route="/graphql",method="POST",code="200"} 0
http_request_duration_histogram_seconds_bucket{le="0.01",route="/graphql",method="POST",code="200"} 0
http_request_duration_histogram_seconds_bucket{le="0.025",route="/graphql",method="POST",code="200"} 0
http_request_duration_histogram_seconds_bucket{le="0.05",route="/graphql",method="POST",code="200"} 1
http_request_duration_histogram_seconds_bucket{le="0.1",route="/graphql",method="POST",code="200"} 2
http_request_duration_histogram_seconds_bucket{le="0.25",route="/graphql",method="POST",code="200"} 2
http_request_duration_histogram_seconds_bucket{le="0.5",route="/graphql",method="POST",code="200"} 2
http_request_duration_histogram_seconds_bucket{le="1",route="/graphql",method="POST",code="200"} 2
http_request_duration_histogram_seconds_bucket{le="2.5",route="/graphql",method="POST",code="200"} 2
http_request_duration_histogram_seconds_bucket{le="5",route="/graphql",method="POST",code="200"} 2
http_request_duration_histogram_seconds_bucket{le="10",route="/graphql",method="POST",code="200"} 2
http_request_duration_histogram_seconds_bucket{le="+Inf",route="/graphql",method="POST",code="200"} 2
http_request_duration_histogram_seconds_sum{route="/graphql",method="POST",code="200"} 0.118276569
http_request_duration_histogram_seconds_count{route="/graphql",method="POST",code="200"} 2

# HELP http_request_duration_summary_seconds Summary of request durations in seconds
# TYPE http_request_duration_summary_seconds summary
http_request_duration_summary_seconds{quantile="0.5",route="/graphql",method="POST",code="200"} 0.058377634
http_request_duration_summary_seconds{quantile="0.9",route="/graphql",method="POST",code="200"} 0.0838918
http_request_duration_summary_seconds{quantile="0.95",route="/graphql",method="POST",code="200"} 0.0838918
http_request_duration_summary_seconds{quantile="0.99",route="/graphql",method="POST",code="200"} 0.0838918
http_request_duration_summary_seconds_sum{route="/graphql",method="POST",code="200"} 0.116755268
http_request_duration_summary_seconds_count{route="/graphql",method="POST",code="200"} 2

# HELP http_request_size_bytes Size of HTTP request in bytes
# TYPE http_request_size_bytes histogram
http_request_size_bytes_bucket{le="5",route="/graphql",method="POST",code="200"} 0
http_request_size_bytes_bucket{le="10",route="/graphql",method="POST",code="200"} 0
http_request_size_bytes_bucket{le="25",route="/graphql",method="POST",code="200"} 0
http_request_size_bytes_bucket{le="50",route="/graphql",method="POST",code="200"} 0
http_request_size_bytes_bucket{le="100",route="/graphql",method="POST",code="200"} 0
http_request_size_bytes_bucket{le="250",route="/graphql",method="POST",code="200"} 0
http_request_size_bytes_bucket{le="500",route="/graphql",method="POST",code="200"} 1
http_request_size_bytes_bucket{le="1000",route="/graphql",method="POST",code="200"} 1
http_request_size_bytes_bucket{le="2500",route="/graphql",method="POST",code="200"} 2
http_request_size_bytes_bucket{le="5000",route="/graphql",method="POST",code="200"} 2
http_request_size_bytes_bucket{le="10000",route="/graphql",method="POST",code="200"} 2
http_request_size_bytes_bucket{le="+Inf",route="/graphql",method="POST",code="200"} 2
http_request_size_bytes_sum{route="/graphql",method="POST",code="200"} 2110
http_request_size_bytes_count{route="/graphql",method="POST",code="200"} 2

# HELP http_response_size_bytes Size of HTTP response in bytes
# TYPE http_response_size_bytes histogram
http_response_size_bytes_bucket{le="5",method="POST",route="/graphql",code="200"} 2
http_response_size_bytes_bucket{le="10",method="POST",route="/graphql",code="200"} 2
http_response_size_bytes_bucket{le="25",method="POST",route="/graphql",code="200"} 2
http_response_size_bytes_bucket{le="50",method="POST",route="/graphql",code="200"} 2
http_response_size_bytes_bucket{le="100",method="POST",route="/graphql",code="200"} 2
http_response_size_bytes_bucket{le="250",method="POST",route="/graphql",code="200"} 2
http_response_size_bytes_bucket{le="500",method="POST",route="/graphql",code="200"} 2
http_response_size_bytes_bucket{le="1000",method="POST",route="/graphql",code="200"} 2
http_response_size_bytes_bucket{le="2500",method="POST",route="/graphql",code="200"} 2
http_response_size_bytes_bucket{le="5000",method="POST",route="/graphql",code="200"} 2
http_response_size_bytes_bucket{le="10000",method="POST",route="/graphql",code="200"} 2
http_response_size_bytes_bucket{le="+Inf",method="POST",route="/graphql",code="200"} 2
http_response_size_bytes_sum{method="POST",route="/graphql",code="200"} 0
http_response_size_bytes_count{method="POST",route="/graphql",code="200"} 2

# HELP http_requests_total Counter for total requests received
# TYPE http_requests_total counter
http_requests_total{route="/graphql",method="POST",code="200"} 2

Running Prometheus & Grafana

This step assumes you have docker and docker-compose set up. If not, install docker here and install docker-compose-here

The easiest way to run both Prometheus and Grafana is to create a docker-compose.yaml file and add the following:

version: '3'
services:
  prometheus:
    image: "prom/prometheus"
    ports:
     - "9090:9090"
    volumes:
     - data:/prometheus-data
  grafana:
    image: "grafana/grafana"
    depends_on:
      - prometheus
    ports:
     - "3000:3000"

volumes:
  data:

Now run both images using:

docker-compose up

If you want to run both images as a background process, using the -d flag with docker-compose up.

This will pull the prometheus and grafana images from their respective registries and expose them on port 9090 and 3000 respectively.

Debugging

This package uses debug for debug logs with the express-prometheus-metrics key.

Run your app with the following environment variable to output the debug logs:

DEBUG=express-prometheus-metrics node index.js