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'use strict';
import series from './series';
import noop from 'lodash/noop';
import constant from 'lodash/constant';
/**
* Attempts to get a successful response from `task` no more than `times` times
* before returning an error. If the task is successful, the `callback` will be
* passed the result of the successful task. If all attempts fail, the callback
* will be passed the error and result (if any) of the final attempt.
*
* @name retry
* @static
* @memberOf async
* @category Control Flow
* @param {Object|number} [opts = {times: 5, interval: 0}| 5] - Can be either an
* object with `times` and `interval` or a number.
* * `times` - The number of attempts to make before giving up. The default
* is `5`.
* * `interval` - The time to wait between retries, in milliseconds. The
* default is `0`. The interval may also be specified as a function of the
* retry count (see example).
* * If `opts` is a number, the number specifies the number of times to retry,
* with the default interval of `0`.
* @param {Function} task - A function which receives two arguments: (1) a
* `callback(err, result)` which must be called when finished, passing `err`
* (which can be `null`) and the `result` of the function's execution, and (2)
* a `results` object, containing the results of the previously executed
* functions (if nested inside another control flow). Invoked with
* (callback, results).
* @param {Function} [callback] - An optional callback which is called when the
* task has succeeded, or after the final failed attempt. It receives the `err`
* and `result` arguments of the last attempt at completing the `task`. Invoked
* with (err, results).
* @example
*
* // The `retry` function can be used as a stand-alone control flow by passing
* // a callback, as shown below:
*
* // try calling apiMethod 3 times
* async.retry(3, apiMethod, function(err, result) {
* // do something with the result
* });
*
* // try calling apiMethod 3 times, waiting 200 ms between each retry
* async.retry({times: 3, interval: 200}, apiMethod, function(err, result) {
* // do something with the result
* });
*
* // try calling apiMethod 10 times with exponential backoff
* // (i.e. intervals of 100, 200, 400, 800, 1600, ... milliseconds)
* async.retry({
* times: 10,
* interval: function(retryCount) {
* return 50 * Math.pow(2, retryCount);
* }
* }, apiMethod, function(err, result) {
* // do something with the result
* });
*
* // try calling apiMethod the default 5 times no delay between each retry
* async.retry(apiMethod, function(err, result) {
* // do something with the result
* });
*
* // It can also be embedded within other control flow functions to retry
* // individual methods that are not as reliable, like this:
* async.auto({
* users: api.getUsers.bind(api),
* payments: async.retry(3, api.getPayments.bind(api))
* }, function(err, results) {
* // do something with the results
* });
*/
export default function retry(times, task, callback) {
var DEFAULT_TIMES = 5;
var DEFAULT_INTERVAL = 0;
var opts = {
times: DEFAULT_TIMES,
intervalFunc: constant(DEFAULT_INTERVAL)
};
function parseTimes(acc, t) {
if (typeof t === 'object') {
acc.times = +t.times || DEFAULT_TIMES;
acc.intervalFunc = typeof t.interval === 'function' ?
t.interval :
constant(+t.interval || DEFAULT_INTERVAL);
} else if (typeof t === 'number' || typeof t === 'string') {
acc.times = +t || DEFAULT_TIMES;
} else {
throw new Error("Invalid arguments for async.retry");
}
}
if (arguments.length < 3 && typeof times === 'function') {
callback = task || noop;
task = times;
} else {
parseTimes(opts, times);
callback = callback || noop;
}
if (typeof task !== 'function') {
throw new Error("Invalid arguments for async.retry");
}
var attempts = [];
for (var i = 1; i < opts.times + 1; i++) {
var isFinalAttempt = (i == opts.times);
attempts.push(retryAttempt(isFinalAttempt));
var interval = opts.intervalFunc(i);
if (!isFinalAttempt && interval > 0) {
attempts.push(retryInterval(interval));
}
}
series(attempts, function(done, data) {
data = data[data.length - 1];
callback(data.err, data.result);
});
function retryAttempt(isFinalAttempt) {
return function(seriesCallback) {
task(function(err, result) {
seriesCallback(!err || isFinalAttempt, {
err: err,
result: result
});
});
};
}
function retryInterval(interval) {
return function(seriesCallback) {
setTimeout(function() {
seriesCallback(null);
}, interval);
};
}
}
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