wouter-vdb / retrying-promise

Create fault tolerant promises that retry upon failure according to a retry strategy.

retrying-promise

Create fault tolerant promises that retry upon failure according to a retry strategy.

The implementation of the retry strategies reuses code from the node-retry project.

Usage

Install retrying-promise:

npm install retrying-promise

Import retrying-promise:

const retryPromise = require('retrying-promise');

The constant retryPromise is a function that returns a promise. Use this function similar to how you call the new Promise() constructor, but pass it a function that takes four arguments: resolve, retry, reject and attempt.

var promise = retryPromise(function (resolve, retry, reject, attempt) {

			console.log(`current attempt: ${attempt}`);

    resolve(result);  // the promise resolves normally

    retry(error);     // the promise failed and a retry may be attempted

    reject(error);    // the promise failed and no retry should be attempted

});

Call the resolve function when the promise resolves normally.

Call the retry function when the promise failed and a retry may be attempted.

Call the reject function when the promise failed and no retry should be attempted.

Test

Install Mocha.

sudo npm install -g mocha

Run tests:

npm test

API Reference

Author: Wouter Van den Broeck
Copyright: 2016

module.exports([options], executor) ⇒ Promise ⏏

Returns a promise that conditionally tries to resolve multiple times, as specified by the retry policy.

Kind: Exported function

Param	Type	Description
[options]	retryPolicy	Either An object that specifies the retry policy.
executor	retryExecutor	A function that is called for each attempt to resolve the promise.

module.exports~createTimeout(attempt, opts) ⇒ number

Get a timeout value in milliseconds.

Kind: inner method of module.exports
Returns: number - The timeout value in milliseconds.

Param	Type	Description
attempt	number	The attempt count.
opts	Object	The options.

module.exports~retryPolicy : Object

An object that specifies the retry policy.

Kind: inner typedef of module.exports
Properties

Name	Type	Default	Description
retries	number	10	The maximum amount of times to retry the operation.
factor	number	2	The exponential factor to use.
minTimeout	number	1000	The number of milliseconds before starting the first retry.
maxTimeout	number	Infinity	The maximum number of milliseconds between two retries.
randomize	boolean	false	Randomizes the timeouts by multiplying with a factor between 1 to 2.

module.exports~retryExecutor : function

The function that is called for each attempt to resolve the promise.

Kind: inner typedef of module.exports

Param	Type	Description
resolveFn	function	To be called when the promise resolves normally.
retryFn	function	To be called when the promise failed and a retry may be attempted.
[rejectFn]	function	To be called when the promise failed and no retry should be attempted.
attempt	number	The current attempt number.

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© 2016, Wouter Van den Broeck