When an event occurs that triggers a function, nuv creates an activation record, which contains information about the function execution, such as input parameters, output results, and any metadata associated with the activation. It’s something similar to the classic concept of log.

How activations work

When invoking an action with nuv action invoke, you’ll receive only an invocation id as an answer.

This invocation id allows you to read results and outputs produced by the execution of an action.

Let’s demonstrate how it works by modifying the hello.js file to add a command to log some output.

function main(args) {
  return { "body": "Hello" }

Now, let’s deploy and invoke it (with a parameter hello=world) to get the activation id:

$ nuv action update demo/hello hello.js
ok: updated action demo/hello
$ nuv action invoke demo/hello
ok: invoked /_/demo/hello with id 0367e39ba7c74268a7e39ba7c7126846

Associated with every invocation, there is an activation id (in the example, it is 0367e39ba7c74268a7e39ba7c7126846).

We use this id to retrieve the results of the invocation with nuv activation result or its shortcut, just nuv result, and we can retrieve the logs using nuv activation logs or just nuv logs.

$ nuv result 0367e39ba7c74268a7e39ba7c7126846
  "body": "Hello"
$ nuv logs 0367e39ba7c74268a7e39ba7c7126846
2024-02-17T20:01:31.901124753Z stdout: Hello

List of activations

You can list the activations with nuv activation list and limit the number with --limit if you are interested in a subset.

$ nuv activation list --limit 5
Datetime            Activation ID                    Kind      Start Duration   Status  Entity
2024-02-17 20:01:31 0367e39ba7c74268a7e39ba7c7126846 nodejs:18 warm  8ms        success dashboard/hello:0.0.1
2024-02-17 20:00:00 f4f82ee713444028b82ee71344b0287d nodejs:18 warm  5ms        success dashboard/hello:0.0.1
2024-02-17 19:59:54 98d19fe130da4e93919fe130da7e93cb nodejs:18 cold  33ms       success dashboard/hello:0.0.1
2024-02-17 17:40:53 f25e1f8bc24f4f269e1f8bc24f1f2681 python:3  warm  3ms        success dashboard/index:0.0.2
2024-02-17 17:35:12 bed3213547cc4aed93213547cc8aed8e python:3  warm  2ms        success dashboard/index:0.0.2

Note also the --since option, which is useful to show activations from a given timestamp (you can obtain a timestamp with date +%s).

Since it can be quite annoying to keep track of the activation id, there are two useful alternatives.

With nuv result --last and nuv logs --last, you can retrieve just the last result or log.

Polling activations

With nuv activation poll, the CLI starts a loop and displays all the activations as they happen.

$ nuv activation poll

Enter Ctrl-c to exit.
Polling for activation logs


Activations provide a way to monitor and track the execution of functions, enabling understanding of how code behaves in response to different events and allowing for debugging and optimizing serverless applications.