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54 lines
1.8 KiB
54 lines
1.8 KiB
/**
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* @license
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* Copyright 2016 Google Inc. All Rights Reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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exports.inject = function(wait) {
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var Task = require('./task');
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return {
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/**
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* Repeatedly calls the 'do' function, until its result passes the 'until'
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* predicate, or timeout. The 'do' function is retried with exponential
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* backoff.
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*
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* @param {function(): Task<T>} options.do Starts the task to try
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* repeatedly.
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* @param {function(T): boolean} options.until A predicate that checks
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* whether the result of options.do was successful.
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* @return {Task<T>}
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* @template T
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*/
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attempt: function(options) {
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var doSomething = options['do'];
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var isSuccessful = options.until;
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var interval = options.interval || 500;
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var increment = options.increment || 1.5;
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var jitter = options.jitter || 0.5;
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return Task.withValue().thenDo(function loop() {
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return doSomething().thenDo(function(result) {
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if (isSuccessful(result)) {
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return Task.withValue(result);
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}
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var delay = interval * (1 + jitter * (2 * Math.random() - 1));
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interval *= increment;
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return wait(delay).thenDo(loop);
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});
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});
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}
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};
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};
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