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Isomorphic client library for supporting long-running operations in node.js and browser.

Version published

Package description

What is @azure/core-lro?

The @azure/core-lro package provides a framework for building and working with long-running operations (LROs) in Azure services. It offers a standardized way to poll for the status of these operations and retrieve the final results, abstracting the complexity involved in handling LROs.

What are @azure/core-lro's main functionalities?

Creating and managing long-running operations

This feature allows developers to implement custom pollers for managing long-running operations. The code sample demonstrates how to extend the Poller class to create a custom LRO poller.

const { Poller } = require('@azure/core-lro');

class MyLroPoller extends Poller {
  async cancelOperation() {
    // Cancel the operation if supported

  async delay() {
    // Implement delay between polls

const myPoller = new MyLroPoller();
await myPoller.pollUntilDone();

Polling for operation status

This feature enables polling for the status of a long-running operation until it is completed. The code sample shows how to use the Poller class to poll an operation until it's done.

const { Poller } = require('@azure/core-lro');

async function pollOperation(operation) {
  const poller = new Poller({

  return await poller.pollUntilDone();

Other packages similar to @azure/core-lro



Azure Core LRO client library for JavaScript

This is the default implementation of long running operations in Azure SDK JavaScript client libraries which work in both the browser and NodeJS. This library is primarily intended to be used in code generated by AutoRest and autorest.typescript.

@azure/core-lro follows The Azure SDK Design Guidelines for Long Running Operations

Key links:

Getting started

Currently supported environments


This package is primarily used in generated code and not meant to be consumed directly by end users.

Key concepts


A poller is an object that can poll the long running operation on the server for its state until it reaches a terminal state. It provides the following methods:

  • getOperationState: returns the state of the operation, typed as a type that extends OperationState
  • getResult: returns the result of the operation when it completes and undefined otherwise
  • isDone: returns whether the operation is in a terminal state
  • isStopped: returns whether the polling stopped
  • onProgress: registers callback functions to be called every time a polling response is received
  • poll: sends a single polling request
  • pollUntilDone: returns a promise that will resolve with the result of the operation
  • stopPolling: stops polling;
  • toString: serializes the state of the poller


A type for the operation state. It contains a status field with the following possible values: notStarted, running, succeeded, failed, and canceled. It can be accessed as follows:

switch(poller.getOperationState().status) {
  case "succeeded":  // return poller.getResult();
  case "failed":     // throw poller.getOperationState().error;
  case "canceled":   // throw new Error("Operation was canceled");
  case "running":    // ...
  case "notStarted": // ...


A function that returns an object of type SimplePollerLike. This poller behaves as follows in the presence of errors:

  • calls to poll and pollUntilDone will throw an error in case the operation has failed or canceled unless the resolveOnUnsuccessful option was set to true.
  • poller.getOperationState().status will be set to true when either the operation fails or it returns an error response.


Examples can be found in the samples folder.



Logs can be added at the discretion of the library implementing the Long Running Operation poller. Packages inside of azure-sdk-for-js use @azure/logger.

Next steps

Please take a look at the samples directory for detailed examples on how to use this library.


If you'd like to contribute to this library, please read the contributing guide to learn more about how to build and test the code.


To run our tests, first install the dependencies (with npm install or rush install), then run the unit tests with: npm run unit-test.

Code of Conduct

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact with any additional questions or comments.




Package last updated on 27 Jun 2024

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