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    attemptpublic

    Attempt Build Status Code Climate

    Retries functions that throw or call back with an error, in crazily customizable ways.

    Installation

    In your project folder, type:

    npm install attempt
    

    Usage

    Whenever you have code that looks like this:

    function flakyApiCall(function(err, result) {
        if (err)
            console.log('Flaky API died AGAIN!', err);
        else
            doSomething(result);
    });
    

    Just drop that code in an attempt!

    var attempt = require('attempt');
    attempt(
    	function() {
    		flakyApiCall(this);
    	},
    	function(err, result) {
            if (err)
                console.log('Flaky API failed 3 times.', err);
            else
                doSomething(result);
        });
    

    Details

    Attempt will re-run your attempted function if it throws an error or if it calls back with a non-falsey first argument (following the first-arg-is-an-error standard Node.js convention). The function call looks like this:

    attempt([options], tryFunc, [callback])

    tryFunc is called with one argument: attempts. It is the number of times the tryFunc has been run before.

    attempt(function(attempts) {
    	if (attempts)
    		console.log('This is retry #' + attempts);
    	else
    		console.log('This is the first attempt!');
    });
    

    Options

    The following options are set per request:

    retries

    Default: 2. The number of times to retry the tryFunc before giving up and sending the error to the callback.

    attempt(
    	{ retries: 15 },
    	function() {
    		flakyApiCall(this);
    	},
    	function(err, result) {
    		if (err)
    			console.log('Failed first attempt + 15 retries = 16 failures.', err);
    		else
    			doSomething(result);
    	});
    

    interval

    Default: 0. The number of milliseconds to wait between attempts.

    attempt(
    	{ interval: 5000 },
    	function() {
            flakyApiCall(this);
        },
        function(err, result) {
            if (err)
                console.log('3 attempts * 5 seconds = 15 seconds of failure.', err);
            else
                doSomething(result);
        });
    

    factor

    Default: 1. The factor by which the interval should be multiplied per attempt. If set to 2 with an interval of 5000, the first retry will execute after 5 seconds, the second after 10, the third after 20, and so on.

    This allows an exponential back-off scheme. For a smaller gap between retries, floats like 1.2 can be used to grow the interval at a slower rate.

    onError

    Default: null. Function to call when the tryFunc fails with an error. The first argument is the error.

    attempt(
    	{
    		onError: function(err) {
    			console.log(err);
    		}
    	},
    	function() { flakyApiCall(this); },
    	function(err, result) { /* ... */ });
    

    The second argument, if it exists, is a callback function that will need to be called in order for the next attempt to continue. This is useful if you have to do something asynchronous to fix the error.

    attempt(
    	{
    		onError: function(err, done) {
        		log.write(err, done);
        	}
        },
        function() { flakyApiCall(this); },
    	function(err, result) { /* ... */ });
    

    By default, calling done() will ignore the retry interval. If you still want it to be observed, call done(true).

    max

    Default: Infinity. The maximum number of milliseconds to wait before retrying. If the interval or factor causes a wait time larger than 'max', 'max' will be used.

    random

    Default: 0. Increase the wait interval by a random factor. Generally, this should be a number between 0 (no randomness) and 1 (wait time could double). For example, if .5 is used, the interval could be anywhere between 100% and 150% of its original calculated time.

    attempts

    Default: 0. The number of attempts to fake Attempt into believing were already completed. This is mostly used by Attempt internally, but can be useful for hacking interval times.

    License

    Attempt is distributed under the MIT license.

    Credits

    Attempt was created by Tom Frost in 2012. Because webservice APIs be flaky, man.

    Keywords

    none

    install

    npm i attempt

    Downloadsweekly downloads

    1,994

    version

    1.0.1

    license

    none

    repository

    githubgithub

    last publish

    collaborators

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