0.2.0 • Public • Published


Node.js library to collect serverless application metrics from OpenWhisk actions.

Serverless functions are wrapped with a proxy to automate recording metrics during invocations.

Metric values for cpu, memory, time, error and cold start collected by default. Supports adding custom metric values.


Wrap action handlers with the metrics library.

const metrics = require('openwhisk-metrics')
const main = params => {
  return { message: "Hello World" }
module.exports.main = metrics(main) 

Metrics values are logged to stdout for each invocation of the serverless function.

METRIC <workspace>.<action_name>.<activation>.memory.rss 53018624 1512489781
METRIC <workspace>.<action_name>.<activation>.memory.heapTotal 34463744 1512489781
METRIC <workspace>.<action_name>.<activation>.memory.heapUsed 16955224 1512489781
METRIC <workspace>.<action_name>.<activation>.memory.external 987361 1512489781
METRIC <workspace>.<action_name>.<activation>.error 0 1512489781
METRIC <workspace>.<action_name>.<activation>.coldstart 0 1512489781
METRIC <workspace>.<action_name>.<activation>.cpu.user 177 1512489781
METRIC <workspace>.<action_name>.<activation>.cpu.system 2 1512489781
METRIC <workspace>.<action_name>.<activation>.time.start 1511605588388 1512489781
METRIC <workspace>.<action_name>.<activation>.time.end 1511605588468 1512489781
METRIC <workspace>.<action_name>.<activation>.time.duration 80 1512489781

See "Forwarding Metrics" for options on sending metric values to external monitoring services.


$ npm install openwhisk-metrics



The library will execute the metric collection handlers registered in metrics.collect.

The default metric handlers configured to run are cpu, memory, time, error and cold start.


Returns the values of process.cpuUsage() for the function execution duration. This can be used to calculate cpu usage during function execution based upon duration. See Node.js documentation for meaning of these values.

  "user": <microseconds>,
  "system": <microseconds>


Returns the values for process.memoryUsage when the wrapped function finishes. See Node.js documentation for meaning of these values.

  "rss": <bytes>,
  "heapTotal": <bytes>,
  "heapUsed": <bytes>,
  "external": <bytes>


Returns start, end and duration times for function execution. start and end are in milliseconds since epoch. Duration is the difference between end and start in milliseconds.

  "start": <millseconds_since_epoch>,
  "end": <millseconds_since_epoch>,
  "duration": <milliseconds_since_start>


Returns whether wrapped function returns an error. Handles errors returned directly or using rejected Promises. If error was returned, metric value is 0. If error was not returned, metric value is 1.

  "error": 0 or 1

cold start

Returns whether a new runtime environment is used for execution. This is used to record cold and warm invocations.

The first time a new runtime environment is used, coldstart will be 1. All further invocations using an existing environment return 0.

  "coldstart": 0 or 1

disable default metrics

Metrics can be disabled by removing the metric handler from metrics.collect.

// disable cpu metric
metrics.collect.cpu = null

disable activationId in metrics

Openwhisk activationId can be disable by setting metrics.config.ignore_activation_ids to true

// disable activationid in metrics
metrics.config.ignore_activation_ids = true

add custom metrics

Set additional properties on the metrics.collect object to collect custom metrics.

metrics.collect.custom = action_response => {
  return 12345

Property names on the metrics.collect object are used as metric labels, e.g. custom. Return values from the functions are used as metric values.

Metric values must be a number. Strings, booleans and other types are not supported.

Metric functions can either return a raw metric value or multiple sub-properties.

// single value....
metrics.collect.custom = action_response => {
  return 12345
// multiple values
metrics.collect.custom = action_response => {
  return {inner: 12345, ...}

Metric functions are called once the wrapped function has returned, with the return value of that invocation.

If you need to capture execution context prior to the invocation, set a metric handler using an object with start and end methods.

// let's record start time for invocations...
let start
metrics.collect.start_times = {
  start: evt_params => {
    start = (new Date()).getTime()
  end: fn_return_val => start

start will be executed with invocation parameters prior to the wrapped handler being called. end will be executed with return value from wrapped function after invocation.

forwarding metrics

background action

Metric values collected during execution are logged to stdout in the following format.

METRIC <> <value> <timestamp> 

Using the alarm trigger feed, an action can run on a periodic schedule to retrieve metrics from actions logs. This action can forward metric values to external monitoring services.

custom agent

Custom agents can be provided to handle forwarding metrics live during invocations.

Overwrite the service property on the metrics class to use a custom forwarding agent.

Agents must be an object with a save method. This method is called with an array of metric values for each invocation.

metrics.service = {
  save: metrics => {
    // do some async save
    return asyncServiceCall(metrics)

Metric service agents can return a Promise for asynchronous operations.

issues / bugs / features?

Something gone wrong? OH NOES 😱!

Open an issue in the repository and I'll have a look… 💯


npm i openwhisk-metrics

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  • jthomas