reattempt-promise-function

reattempt-promise-function allows you to easily reattempt async actions.

It does this by re-calling a function that returns a promise when that promise is rejected. You can specify the delay between attempts and the maximum number of attempts.

Perfect for waiting for services to start during Gulp and Grunt build and test tasks or attempting to reconnect to an application backend after becoming disconnected.

Quickstart

Node

npm install reattempt-promise-function

var reattempt = require('reattempt-promise-function');
reattempt(promiseFunction, arguments, delayBetweenAttempts, numberOfAttempts);

Browser

bower install https://github.com/beckyconning/reattempt-promise-function/tarball/master --save

<script src="bower_components/reattempt-promise-function/bundle.js"></script>

reattempt(promiseFunction, arguments, delayBetweenAttempts, numberOfAttempts);

Other options

You can also use bundle.js with Browserify / CommonJS / AMD.

Example

var reattempt = require('reattempt-promise-function');
var requestPromise = require('request-promise');
var uri = 'http://localhost:3000';
var requestOptions = { 'method': 'GET', 'uri': uri };

// Attempt http get request 10 times with a 250ms delay between attmpts
reattempt(requestPromise, [requestOptions], 250, 10)
    .then(function (response) {
        console.log('`' + uri + '` is now available.')
    })
    .catch(function (error) {
        console.log('Couldn\'t connect to `' + uri '`.');
    });

Caveats

If the function you want to reattempt contains references to this make sure you bind the required value of this to it before passing it to reattempt.

var Food = function (name, sodium) {
    this.name = name;
    this.sodium = sodium;
};

Food.prototype.getSummary = function () {
    if (typeof this.name !== 'undefined' && typeof this.sodium !== undefined) {
        var summary = this.name + ' contains ' + this.sodium + 'g of sodium per 100g.'
        return Promise.resolve(summary);
    } else {
        return Promise.reject('Sorry there was nothing to summarise.');
    }
};

var strawberryJam = new Food('Stawberry jam', 0.2);
var getStrawberryJamSummary = strawberryJam.getSummary.bind(strawberryJam);

// The following is attempted 10 times with a 250ms delay between each attempt
// before being rejected.
reattempt(strawberryJam.getSummary, [], 250, 10).then(function (summary) {
    console.log(summary);
}).catch(function (error) {
    console.log(error);
});

// The following resolves immediately.
reattempt(getStrawberryJamSummary, [], 250, 10).then(function (summary) {
    console.log(summary);
}).catch(function (error) {
    console.log(error);
});

For more information about Function.prototype.bind() please see the MDN documentation.

Testing

Use npm test to run the unit tests.

Building

Use npm run build to build the bundle.js.