MultipleStoreLocker::lockAndCheckQuorumAndTtlOnAllStores() - Code Metrics - Inspection of "Changes in naming and refactoring" - remi-san/lock - Measure and Improve Code Quality continuously with Scrutinizer

Completed

Push — master ( 056009...46877f )

by Rémi

created 2016-09-01 08:41 UTC

lockAndCheckQuorumAndTtlOnAllStores() A

↳ Parent: MultipleStoreLocker

Complexity

Conditions	2
Paths	2

Size

Total Lines	15
Code Lines	9

Duplication

Lines	0
Ratio	0 %

Importance

Changes	1
Bugs	0	Features	0

Metric	Value
c	1
b	0
f	0
dl	0
loc	15
rs	9.4285
cc	2
eloc	9
nc	2
nop	2

<?php

namespace RemiSan\Lock\Locker;

use RemiSan\Lock\LockStore;
use RemiSan\Lock\Exceptions\LockingException;
use RemiSan\Lock\Exceptions\UnlockingException;
use RemiSan\Lock\Lock;
use RemiSan\Lock\Locker;
use RemiSan\Lock\Quorum;
use RemiSan\Lock\TokenGenerator;
use Symfony\Component\Stopwatch\Stopwatch;

final class MultipleStoreLocker implements Locker
{
    /** @var LockStore[] */
    private $stores = [];

    /** @var TokenGenerator */
    private $tokenGenerator;

    /** @var Quorum */
    private $quorum;

    /** @var Stopwatch */
    private $stopwatch;

    /**
     * RedLock constructor.
     *
     * @param LockStore[]    $stores         Array of persistence system connections
     * @param TokenGenerator $tokenGenerator The token generator
     * @param Quorum         $quorum         The quorum implementation to use
     * @param Stopwatch      $stopwatch      A way to measure time passed
     */
    public function __construct(
        array $stores,
        TokenGenerator $tokenGenerator,
        Quorum $quorum,
        Stopwatch $stopwatch
    ) {
        $this->setStores($stores);
        $this->setQuorum($quorum);

        $this->tokenGenerator = $tokenGenerator;
        $this->stopwatch = $stopwatch;
    }

    /**
     * {@inheritdoc}
     */
    public function lock($resource, $ttl = null, $retryDelay = 0, $retryCount = 0)
    {
        $lock = new Lock((string) $resource, $this->tokenGenerator->generateToken());

        $tried = 0;
        while (true) {
            try {
                return $this->lockAndCheckQuorumAndTtlOnAllStores($lock, $ttl);
            } catch (LockingException $e) {
                $this->resetLock($lock);
            }

            if ($tried++ === $retryCount) {
                break;
            }

            $this->waitBeforeRetrying($retryDelay);
        }

        throw new LockingException('Failed locking the resource.');
    }

    /**
     * {@inheritdoc}
     */
    public function isLocked($resource)
    {
        foreach ($this->stores as $store) {
            if ($store->exists((string) $resource)) {
                return true;
            }
        }

        return false;
    }

    /**
     * {@inheritdoc}
     */
    public function unlock(Lock $lock)
    {
        foreach ($this->stores as $store) {
            if (!$store->delete($lock)) {
                if ($store->exists($lock->getResource())) {
                    // Only throw an exception if the lock is still present
                    throw new UnlockingException('Failed releasing the lock.');
                }
            }
        }
    }

    /**
     * Try locking resource on all stores.
     *
     * Measure the time to do it and reject if not enough stores have successfully
     * locked the resource or if time to lock on all stores have exceeded the ttl.
     *
     * @param Lock $lock The lock instance
     * @param int  $ttl  Time to live in milliseconds
     *
     * @throws LockingException
     *
     * @return Lock
     */
    private function lockAndCheckQuorumAndTtlOnAllStores(Lock $lock, $ttl)
    {
        $timeMeasure = $this->stopwatch->start($lock->getToken());
        $storesLocked = $this->lockOnAllStores($lock, $ttl);
        $timeMeasure->stop();

        $this->checkQuorum($storesLocked);

        if ($ttl) {
            $this->checkTtl($timeMeasure->getDuration(), $ttl);
            $lock->setValidityEndTime($timeMeasure->getOrigin() + $ttl);
        }

        return $lock;
    }

    /**
     * Lock resource on all stores and count how many stores did it with success.
     *
     * @param Lock $lock The lock instance
     * @param int  $ttl  Time to live in milliseconds
     *
     * @return int The number of stores on which the resource has been locked
     */
    private function lockOnAllStores(Lock $lock, $ttl)
    {
        $storesLocked = 0;

        foreach ($this->stores as $store) {
            if ($store->set($lock, $ttl)) {
                ++$storesLocked;
            }
        }

        return $storesLocked;
    }

    /**
     * Unlock the resource on all stores.
     *
     * @param Lock $lock The lock to release
     */
    private function resetLock($lock)
    {
        foreach ($this->stores as $store) {
            $store->delete($lock);
        }
    }

    /**
     * Init all stores passed to the constructor.
     *
     * If no store is given, it will return an InvalidArgumentException.
     *
     * @param LockStore[] $stores The lock stores
     *
     * @throws \InvalidArgumentException
     */
    private function setStores(array $stores)
    {
        if (count($stores) === 0) {
            throw new \InvalidArgumentException('You must provide at least one LockStore.');
        }

        $this->stores = $stores;
    }

    /**
     * Set the quorum based on the number of stores passed to the constructor.
     *
     * @param Quorum $quorum The quorum implementation to use
     */
    private function setQuorum(Quorum $quorum)
    {
        $this->quorum = $quorum;
        $this->quorum->init(count($this->stores));
    }

    /**
     * Check if the number of stores where the resource has been locked meet the quorum.
     *
     * @param int $storesLocked The number of stores on which the resource has been locked
     *
     * @throws LockingException
     */
    private function checkQuorum($storesLocked)
    {
        if (!$this->quorum->isMet($storesLocked)) {
            throw new LockingException('Quorum has not been met.');
        }
    }

    /**
     * Make the script wait before retrying to lock.
     *
     * @param int $retryDelay The retry delay in milliseconds
     */
    private function waitBeforeRetrying($retryDelay)
    {
        usleep($retryDelay * 1000);
    }

    /**
     * Checks if the elapsed time is inferior to the ttl.
     *
     * To the elapsed time is added a drift time to have a margin of error.
     * If this adjusted time is greater than the ttl, it will throw a LockingException.
     *
     * @param int $elapsedTime The time elapsed in milliseconds
     * @param int $ttl         The time to live in milliseconds
     *
     * @throws LockingException
     */
    private function checkTtl($elapsedTime, $ttl)
    {
        $adjustedElapsedTime = ($elapsedTime + $this->getDrift($ttl));

        if ($adjustedElapsedTime >= $ttl) {
            throw new LockingException('Time to lock the resource has exceeded the ttl.');
        }
    }

    /**
     * Get the drift time based on ttl in ms.
     *
     * Return the max drift time of all stores
     *
     * @param int $ttl The time to live in milliseconds
     *
     * @return float
     */
    private function getDrift($ttl)
    {
        return max(array_map(function (LockStore $store) use ($ttl) {
            return $store->getDrift($ttl);
        }, $this->stores));
    }
}


1			<?php
2
3			namespace RemiSan\Lock\Locker;
4
5			use RemiSan\Lock\LockStore;
6			use RemiSan\Lock\Exceptions\LockingException;
7			use RemiSan\Lock\Exceptions\UnlockingException;
8			use RemiSan\Lock\Lock;
9			use RemiSan\Lock\Locker;
10			use RemiSan\Lock\Quorum;
11			use RemiSan\Lock\TokenGenerator;
12			use Symfony\Component\Stopwatch\Stopwatch;
13
14			final class MultipleStoreLocker implements Locker
15			{
16			/** @var LockStore[] */
17			private $stores = [];
18
19			/** @var TokenGenerator */
20			private $tokenGenerator;
21
22			/** @var Quorum */
23			private $quorum;
24
25			/** @var Stopwatch */
26			private $stopwatch;
27
28			/**
29			* RedLock constructor.
30			*
31			* @param LockStore[] $stores Array of persistence system connections
32			* @param TokenGenerator $tokenGenerator The token generator
33			* @param Quorum $quorum The quorum implementation to use
34			* @param Stopwatch $stopwatch A way to measure time passed
35			*/
36			public function __construct(
37			array $stores,
38			TokenGenerator $tokenGenerator,
39			Quorum $quorum,
40			Stopwatch $stopwatch
41			) {
42			$this->setStores($stores);
43			$this->setQuorum($quorum);
44
45			$this->tokenGenerator = $tokenGenerator;
46			$this->stopwatch = $stopwatch;
47			}
48
49			/**
50			* {@inheritdoc}
51			*/
52			public function lock($resource, $ttl = null, $retryDelay = 0, $retryCount = 0)
53			{
54			$lock = new Lock((string) $resource, $this->tokenGenerator->generateToken());
55
56			$tried = 0;
57			while (true) {
58			try {
59			return $this->lockAndCheckQuorumAndTtlOnAllStores($lock, $ttl);
60			} catch (LockingException $e) {
61			$this->resetLock($lock);
62			}
63
64			if ($tried++ === $retryCount) {
65			break;
66			}
67
68			$this->waitBeforeRetrying($retryDelay);
69			}
70
71			throw new LockingException('Failed locking the resource.');
72			}
73
74			/**
75			* {@inheritdoc}
76			*/
77			public function isLocked($resource)
78			{
79			foreach ($this->stores as $store) {
80			if ($store->exists((string) $resource)) {
81			return true;
82			}
83			}
84
85			return false;
86			}
87
88			/**
89			* {@inheritdoc}
90			*/
91			public function unlock(Lock $lock)
92			{
93			foreach ($this->stores as $store) {
94			if (!$store->delete($lock)) {
95			if ($store->exists($lock->getResource())) {
96			// Only throw an exception if the lock is still present
97			throw new UnlockingException('Failed releasing the lock.');
98			}
99			}
100			}
101			}
102
103			/**
104			* Try locking resource on all stores.
105			*
106			* Measure the time to do it and reject if not enough stores have successfully
107			* locked the resource or if time to lock on all stores have exceeded the ttl.
108			*
109			* @param Lock $lock The lock instance
110			* @param int $ttl Time to live in milliseconds
111			*
112			* @throws LockingException
113			*
114			* @return Lock
115			*/
116			private function lockAndCheckQuorumAndTtlOnAllStores(Lock $lock, $ttl)
117			{
118			$timeMeasure = $this->stopwatch->start($lock->getToken());
119			$storesLocked = $this->lockOnAllStores($lock, $ttl);
120			$timeMeasure->stop();
121
122			$this->checkQuorum($storesLocked);
123
124			if ($ttl) {
125			$this->checkTtl($timeMeasure->getDuration(), $ttl);
126			$lock->setValidityEndTime($timeMeasure->getOrigin() + $ttl);
127			}
128
129			return $lock;
130			}
131
132			/**
133			* Lock resource on all stores and count how many stores did it with success.
134			*
135			* @param Lock $lock The lock instance
136			* @param int $ttl Time to live in milliseconds
137			*
138			* @return int The number of stores on which the resource has been locked
139			*/
140			private function lockOnAllStores(Lock $lock, $ttl)
141			{
142			$storesLocked = 0;
143
144			foreach ($this->stores as $store) {
145			if ($store->set($lock, $ttl)) {
146			++$storesLocked;
147			}
148			}
149
150			return $storesLocked;
151			}
152
153			/**
154			* Unlock the resource on all stores.
155			*
156			* @param Lock $lock The lock to release
157			*/
158			private function resetLock($lock)
159			{
160			foreach ($this->stores as $store) {
161			$store->delete($lock);
162			}
163			}
164
165			/**
166			* Init all stores passed to the constructor.
167			*
168			* If no store is given, it will return an InvalidArgumentException.
169			*
170			* @param LockStore[] $stores The lock stores
171			*
172			* @throws \InvalidArgumentException
173			*/
174			private function setStores(array $stores)
175			{
176			if (count($stores) === 0) {
177			throw new \InvalidArgumentException('You must provide at least one LockStore.');
178			}
179
180			$this->stores = $stores;
181			}
182
183			/**
184			* Set the quorum based on the number of stores passed to the constructor.
185			*
186			* @param Quorum $quorum The quorum implementation to use
187			*/
188			private function setQuorum(Quorum $quorum)
189			{
190			$this->quorum = $quorum;
191			$this->quorum->init(count($this->stores));
192			}
193
194			/**
195			* Check if the number of stores where the resource has been locked meet the quorum.
196			*
197			* @param int $storesLocked The number of stores on which the resource has been locked
198			*
199			* @throws LockingException
200			*/
201			private function checkQuorum($storesLocked)
202			{
203			if (!$this->quorum->isMet($storesLocked)) {
204			throw new LockingException('Quorum has not been met.');
205			}
206			}
207
208			/**
209			* Make the script wait before retrying to lock.
210			*
211			* @param int $retryDelay The retry delay in milliseconds
212			*/
213			private function waitBeforeRetrying($retryDelay)
214			{
215			usleep($retryDelay * 1000);
216			}
217
218			/**
219			* Checks if the elapsed time is inferior to the ttl.
220			*
221			* To the elapsed time is added a drift time to have a margin of error.
222			* If this adjusted time is greater than the ttl, it will throw a LockingException.
223			*
224			* @param int $elapsedTime The time elapsed in milliseconds
225			* @param int $ttl The time to live in milliseconds
226			*
227			* @throws LockingException
228			*/
229			private function checkTtl($elapsedTime, $ttl)
230			{
231			$adjustedElapsedTime = ($elapsedTime + $this->getDrift($ttl));
232
233			if ($adjustedElapsedTime >= $ttl) {
234			throw new LockingException('Time to lock the resource has exceeded the ttl.');
235			}
236			}
237
238			/**
239			* Get the drift time based on ttl in ms.
240			*
241			* Return the max drift time of all stores
242			*
243			* @param int $ttl The time to live in milliseconds
244			*
245			* @return float
246			*/
247			private function getDrift($ttl)
248			{
249			return max(array_map(function (LockStore $store) use ($ttl) {
250			return $store->getDrift($ttl);
251			}, $this->stores));
252			}
253			}
254

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lockAndCheckQuorumAndTtlOnAllStores() A

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