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Exponential backoff strategy for a generic asynchronous function call
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <meta charset="utf-8"> | |
| <title>Retry with Backoff</title> | |
| </head> | |
| <body> | |
| <pre id="result"></pre> | |
| </body> | |
| </html> |
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| // JSFiddle - https://jsfiddle.net/mdzj/dwwx0889 | |
| // Inspired by https://jsfiddle.net/pajtai/pLka0ow9 | |
| // HTML: <pre id="result"></pre> | |
| // main | |
| retryWithBackoff(sometimesFailsAsync, 10, 1000, 30000, function (error, result) { | |
| console.log('final result is', error ? error : result); | |
| }); | |
| var percentFail = 0.8; | |
| // Replace default | |
| console.log = consoleLog; | |
| function consoleLog() { | |
| var args = [].slice.apply(arguments); | |
| args.unshift((new Date()).toISOString()); // prepend date | |
| document.querySelector('#result').innerHTML += '\n' + args.join(' - '); | |
| } | |
| function sometimesFailsAsync (callback) { | |
| var asyncDelay = Math.floor(Math.random() * 5000); | |
| console.log('async delay', asyncDelay); | |
| setTimeout(function () { | |
| var value = Math.random(); | |
| if (value >= percentFail) { | |
| error = null; | |
| result = 'success = ' + value; | |
| } else { | |
| error = new Error('failed = ' + value); | |
| result = null; | |
| } | |
| return callback(error, result); | |
| }, asyncDelay); | |
| } | |
| function retryWithBackoff (func, attempts, minWait, maxWait, callback) { | |
| var wait = +minWait || 100; // first wait will be 100ms if not specified | |
| var retry = function (fn, cb) { | |
| console.log('retries left', attempts, 'next try in', wait); | |
| setTimeout(function () { return fn(cb); }, wait); // retry after wait time elapsed | |
| wait = wait < maxWait / 2 ? wait * 2 : maxWait; // increase wait time for next attempt | |
| } | |
| var repeater = function (error, result) { | |
| if (!error) { | |
| return callback(null, result); | |
| } else { | |
| if (attempts-- > 0) { | |
| return retry(func, repeater); | |
| } else { | |
| return callback(error); // 0 attempts left, give up | |
| } | |
| } | |
| } | |
| console.log('starting...'); | |
| return func(repeater); | |
| } |
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JSFiddle — https://jsfiddle.net/mdzj/dwwx0889