Metrics

A small express middleware to get base metrics for any node.js app.

Installation

• npm install --save @plastdev/metrics

Usage

import { Metrics, MetricType } from '@plastdev/metrics'
let metrics = new Metrics(options)

Note: The options Part may be omitted, as all parts are optional.

Before your Routes:
router.use(metrics.collect)

And to enable the _metrics-Endpoint:
router.get('/_metrics', metrics.endpoint)

Custom Metrics

To Add your own custom Metrics: metrics.addCustomMetric({ name: 'test', help: 'Some Test Metric' }, TYPE)

where TYPE is one of:

• MetricType.COUNTER
• MetricType.GAUGE
• MetricType.HISTOGRAM
• MetricType.SUMMARY

All metrics can take a labelNames property in the configuration object. All labelNames that the metric support needs to be declared here. There are 2 ways to add values to the labels

metrics.addCustomMetric({
  name: 'metric_name',
  help: 'metric_help',
  labelNames: ['method', 'statusCode'],
}, MetricType.GAUGE);

metrics.customMetrics["NAME"].set({ method: 'GET', statusCode: '200' }, 100); // 1st version, Set value 100 with method set to GET and statusCode to 200
metrics.customMetrics["NAME"].labels('GET', '200').set(100); // 2nd version, Same as above

It is also possible to use timers with labels, both before and after the timer is created:

const end = metrics.customMetrics["NAME"].startTimer({ method: 'GET' }); // Set method to GET, we don't know statusCode yet
xhrRequest(function (err, res) {
  if (err) {
    end({ statusCode: '500' }); // Sets value to xhrRequest duration in seconds with statusCode 500
  } else {
    end({ statusCode: '200' }); // Sets value to xhrRequest duration in seconds with statusCode 200
  }
});

Counter

Counters go up, and reset when the process restarts.

• metrics.customMetrics["NAME"].inc(); // Inc with 1
• metrics.customMetrics["NAME"].inc(10); // Inc with 10

Gauge

Gauges are similar to Counters but Gauges value can be decreased.

• metrics.customMetrics["NAME"].set(10); // Set to 10
• metrics.customMetrics["NAME"].inc(); // Inc with 1
• metrics.customMetrics["NAME"].inc(10); // Inc with 10
• metrics.customMetrics["NAME"].dec(); // Dec with 1
• metrics.customMetrics["NAME"].dec(10); // Dec with 10

Histograms

Histograms track sizes and frequency of events.

metrics.customMetrics["NAME"].observe(10); // Observe value in histogram

Utility to observe request durations

const end = metrics.customMetrics["NAME"].startTimer();
xhrRequest(function (err, res) {
  const seconds = end(); // Observes and returns the value to xhrRequests duration in seconds
});

Summary

Summaries calculate percentiles of observed values.

metrics.customMetrics["NAME"].observe(10);

Utility to observe request durations

const end = metrics.customMetrics["NAME"].startTimer();
xhrRequest(function (err, res) {
  end(); // Observes the value to xhrRequests duration in seconds
});

Options

The Following Options may be used to configure the behaviour.

• ignore: A String Array with routes to ignore, e.g. ['/foo'] . Default: []. Important: /_metrics and /favicon.ico are always ignored
• disableErrorCounter: Disable the Error Counter. Default: false
• disableRouteCounter: Disable the Route Counter. Default: false
• disableDurationCounter: Disable the Duration Counter. Default: false
• disableDefaultMetrics: Disable the Collection of default metrics. Default: false

Default Metrics

• process_cpu_user_seconds_total Total user CPU time spent in seconds.
• process_cpu_system_seconds_total Total system CPU time spent in seconds.
• process_cpu_seconds_total Total user and system CPU time spent in seconds.
• process_start_time_seconds Start time of the process since unix epoch in seconds.
• process_resident_memory_bytes Resident memory size in bytes.
• nodejs_eventloop_lag_seconds Lag of event loop in seconds.
• nodejs_eventloop_lag_min_seconds The minimum recorded event loop delay.
• nodejs_eventloop_lag_max_seconds The maximum recorded event loop delay.
• nodejs_eventloop_lag_mean_seconds The mean of the recorded event loop delays.
• nodejs_eventloop_lag_stddev_seconds The standard deviation of the recorded event loop delays.
• nodejs_eventloop_lag_p50_seconds The 50th percentile of the recorded event loop delays.
• nodejs_eventloop_lag_p90_seconds The 90th percentile of the recorded event loop delays.
• nodejs_eventloop_lag_p99_seconds The 99th percentile of the recorded event loop delays.
• nodejs_active_handles Number of active libuv handles grouped by handle type. Every handle type is C++ class name.
• nodejs_active_handles_total Total number of active handles.
• nodejs_active_requests Number of active libuv requests grouped by request type. Every request type is C++ class name.
• nodejs_active_requests_total Total number of active requests.
• nodejs_heap_size_total_bytes Process heap size from Node.js in bytes.
• nodejs_heap_size_used_bytes Process heap size used from Node.js in bytes.
• nodejs_external_memory_bytes Node.js external memory size in bytes.
• nodejs_heap_space_size_total_bytes Process heap space size total from Node.js in bytes.
• nodejs_heap_space_size_used_bytes Process heap space size used from Node.js in bytes.
• nodejs_heap_space_size_available_bytes Process heap space size available from Node.js in bytes.
• nodejs_version_info Node.js version info.

Examples

You can find prebuilt examples in the fitting folder.

Just call node examples/dist/server.js 3000 to start a Test-Server on Port 3000.

Then use your Browser to call the Endpoints:

• /foo
• /bar
• /404
• /401

And check the results on the Endpoint /_metrics