updraftplus / includes / Google / Task / Runner.php

Runner.php in UpdraftPlus: WP Backup & Migration Plugin 1.16.5, at includes/Google/Task/Runner.php

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1	<?php
2	/*
3	* Copyright 2014 Google Inc.
4	*
5	* Licensed under the Apache License, Version 2.0 (the "License");
6	* you may not use this file except in compliance with the License.
7	* You may obtain a copy of the License at
8	*
9	* http://www.apache.org/licenses/LICENSE-2.0
10	*
11	* Unless required by applicable law or agreed to in writing, software
12	* distributed under the License is distributed on an "AS IS" BASIS,
13	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14	* See the License for the specific language governing permissions and
15	* limitations under the License.
16	*/
17
18	if (!class_exists('Google_Client')) {
19	require_once dirname(__FILE__) . '/../autoload.php';
20	}
21
22	/**
23	* A task runner with exponential backoff support.
24	*
25	* @see https://developers.google.com/drive/web/handle-errors#implementing_exponential_backoff
26	*/
27	class Google_Task_Runner
28	{
29	/**
30	* @var integer $maxDelay The max time (in seconds) to wait before a retry.
31	*/
32	private $maxDelay = 60;
33	/**
34	* @var integer $delay The previous delay from which the next is calculated.
35	*/
36	private $delay = 1;
37
38	/**
39	* @var integer $factor The base number for the exponential back off.
40	*/
41	private $factor = 2;
42	/**
43	* @var float $jitter A random number between -$jitter and $jitter will be
44	* added to $factor on each iteration to allow for a better distribution of
45	* retries.
46	*/
47	private $jitter = 0.5;
48
49	/**
50	* @var integer $attempts The number of attempts that have been tried so far.
51	*/
52	private $attempts = 0;
53	/**
54	* @var integer $maxAttempts The max number of attempts allowed.
55	*/
56	private $maxAttempts = 1;
57
58	/**
59	* @var Google_Client $client The current API client.
60	*/
61	private $client;
62
63	/**
64	* @var string $name The name of the current task (used for logging).
65	*/
66	private $name;
67	/**
68	* @var callable $action The task to run and possibly retry.
69	*/
70	private $action;
71	/**
72	* @var array $arguments The task arguments.
73	*/
74	private $arguments;
75
76	/**
77	* Creates a new task runner with exponential backoff support.
78	*
79	* @param Google_Client $client The current API client
80	* @param string $name The name of the current task (used for logging)
81	* @param callable $action The task to run and possibly retry
82	* @param array $arguments The task arguments
83	* @throws Google_Task_Exception when misconfigured
84	*/
85	public function __construct(
86	Google_Client $client,
87	$name,
88	$action,
89	array $arguments = array()
90	) {
91	$config = (array) $client->getClassConfig('Google_Task_Runner');
92
93	if (isset($config['initial_delay'])) {
94	if ($config['initial_delay'] < 0) {
95	throw new Google_Task_Exception(
96	'Task configuration `initial_delay` must not be negative.'
97	);
98	}
99
100	$this->delay = $config['initial_delay'];
101	}
102
103	if (isset($config['max_delay'])) {
104	if ($config['max_delay'] <= 0) {
105	throw new Google_Task_Exception(
106	'Task configuration `max_delay` must be greater than 0.'
107	);
108	}
109
110	$this->maxDelay = $config['max_delay'];
111	}
112
113	if (isset($config['factor'])) {
114	if ($config['factor'] <= 0) {
115	throw new Google_Task_Exception(
116	'Task configuration `factor` must be greater than 0.'
117	);
118	}
119
120	$this->factor = $config['factor'];
121	}
122
123	if (isset($config['jitter'])) {
124	if ($config['jitter'] <= 0) {
125	throw new Google_Task_Exception(
126	'Task configuration `jitter` must be greater than 0.'
127	);
128	}
129
130	$this->jitter = $config['jitter'];
131	}
132
133	if (isset($config['retries'])) {
134	if ($config['retries'] < 0) {
135	throw new Google_Task_Exception(
136	'Task configuration `retries` must not be negative.'
137	);
138	}
139	$this->maxAttempts += $config['retries'];
140	}
141
142	if (!is_callable($action)) {
143	throw new Google_Task_Exception(
144	'Task argument `$action` must be a valid callable.'
145	);
146	}
147
148	$this->name = $name;
149	$this->client = $client;
150	$this->action = $action;
151	$this->arguments = $arguments;
152	}
153
154	/**
155	* Checks if a retry can be attempted.
156	*
157	* @return boolean
158	*/
159	public function canAttmpt()
160	{
161	return $this->attempts < $this->maxAttempts;
162	}
163
164	/**
165	* Runs the task and (if applicable) automatically retries when errors occur.
166	*
167	* @return mixed
168	* @throws Google_Task_Retryable on failure when no retries are available.
169	*/
170	public function run()
171	{
172	while ($this->attempt()) {
173	try {
174	return call_user_func_array($this->action, $this->arguments);
175	} catch (Google_Task_Retryable $exception) {
176	$allowedRetries = $exception->allowedRetries();
177
178	if (!$this->canAttmpt() \|\| !$allowedRetries) {
179	throw $exception;
180	}
181
182	if ($allowedRetries > 0) {
183	$this->maxAttempts = min(
184	$this->maxAttempts,
185	$this->attempts + $allowedRetries
186	);
187	}
188	}
189	}
190	}
191
192	/**
193	* Runs a task once, if possible. This is useful for bypassing the `run()`
194	* loop.
195	*
196	* NOTE: If this is not the first attempt, this function will sleep in
197	* accordance to the backoff configurations before running the task.
198	*
199	* @return boolean
200	*/
201	public function attempt()
202	{
203	if (!$this->canAttmpt()) {
204	return false;
205	}
206
207	if ($this->attempts > 0) {
208	$this->backOff();
209	}
210
211	$this->attempts++;
212	return true;
213	}
214
215	/**
216	* Sleeps in accordance to the backoff configurations.
217	*/
218	private function backOff()
219	{
220	$delay = $this->getDelay();
221
222	$this->client->getLogger()->debug(
223	'Retrying task with backoff',
224	array(
225	'request' => $this->name,
226	'retry' => $this->attempts,
227	'backoff_seconds' => $delay
228	)
229	);
230
231	usleep($delay * 1000000);
232	}
233
234	/**
235	* Gets the delay (in seconds) for the current backoff period.
236	*
237	* @return float
238	*/
239	private function getDelay()
240	{
241	$jitter = $this->getJitter();
242	$factor = $this->attempts > 1 ? $this->factor + $jitter : 1 + abs($jitter);
243
244	return $this->delay = min($this->maxDelay, $this->delay * $factor);
245	}
246
247	/**
248	* Gets the current jitter (random number between -$this->jitter and
249	* $this->jitter).
250	*
251	* @return float
252	*/
253	private function getJitter()
254	{
255	return $this->jitter * 2 * mt_rand() / mt_getrandmax() - $this->jitter;
256	}
257	}
258