MultipleInstanceLocker::checkQuorum() - Code Metrics - Inspection of "Implementation of connection abstraction" - remi-san/lock - Measure and Improve Code Quality continuously with Scrutinizer

Completed

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by Rémi

created 2016-08-31 13:24 UTC

MultipleInstanceLocker::checkQuorum() A

↳ Parent: MultipleInstanceLocker

Complexity

Conditions	2
Paths	2

Size

Total Lines	6
Code Lines	3

Duplication

Lines	0
Ratio	0 %

Code Coverage

Tests	4
CRAP Score	2

Importance

Changes	1
Bugs	0	Features	0

Metric	Value
c	1
b	0
f	0
dl	0
loc	6
ccs	4
cts	4
cp	1
rs	9.4285
cc	2
eloc	3
nc	2
nop	1
crap	2

<?php

namespace RemiSan\Lock\Locker;

use RemiSan\Lock\Connection;
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 MultipleInstanceLocker implements Locker
{
    /** @var Connection[] */
    private $instances = [];

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

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

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

    /**
     * RedLock constructor.
     *
     * @param Connection\[]  $instances      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 $instances,
        TokenGenerator $tokenGenerator,
        Quorum $quorum,
        Stopwatch $stopwatch
    ) {
        $this->setInstances($instances);
        $this->setQuorum($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 $this->monitoredLockingOfAllInstances($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->instances as $instance) {
            if ($instance->exists((string) $resource)) {
                return true;
            }
        }

        return false;
    }

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

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

        $this->checkQuorum($instancesLocked);

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

        return $lock;
    }

    /**
     * Lock resource in connected instances and count how many instance did it with success.
     *
     * @param Lock $lock The lock instance
     * @param int  $ttl  Time to live in milliseconds
     *
     * @return int The number of instances locked
     */
    private function lockInstances(Lock $lock, $ttl)
    {
        $instancesLocked = 0;

        foreach ($this->instances as $instance) {
            if ($instance->set($lock, $ttl)) {
                ++$instancesLocked;
            }
        }

        return $instancesLocked;
    }

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

    /**
     * Init all Redis instances passed to the constructor.
     *
     * If no Redis instance is given, it will return a InvalidArgumentException.
     * If one or more Redis instance is not connected, it will return a InvalidArgumentException.
     *
     * @param \Redis[] $instances The connected Redis instances
     *
     * @throws \InvalidArgumentException
     */
    private function setInstances(array $instances)
    {
        if (count($instances) === 0) {
            throw new \InvalidArgumentException('You must provide at least one Redis instance.');
        }

        $this->instances = $instances;

    }

    /**
     * Set the quorum based on the number of instances 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->instances));
    }

    /**
     * Check if the number of instances that have been locked reach the quorum.
     *
     * @param int $instancesLocked The number of instances that have been locked
     *
     * @throws LockingException
     */
    private function checkQuorum($instancesLocked)
    {
        if (!$this->quorum->isMet($instancesLocked)) {
            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.
     *
     * @param int $ttl The time to live in milliseconds
     *
     * @return float
     */
    private function getDrift($ttl)
    {
        return array_values($this->instances)[0]->getDrift($ttl);
    }
}


1		<?php
2
3		namespace RemiSan\Lock\Locker;
4
5		use RemiSan\Lock\Connection;
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 MultipleInstanceLocker implements Locker
15		{
16		/** @var Connection[] */
17		private $instances = [];
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 Connection\[] $instances 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	36	public function __construct(
37		array $instances,
38		TokenGenerator $tokenGenerator,
39		Quorum $quorum,
40		Stopwatch $stopwatch
41		) {
42	36	$this->setInstances($instances);
43	36	$this->setQuorum($quorum);
44
45	36	$this->tokenGenerator = $tokenGenerator;
46	36	$this->stopwatch = $stopwatch;
47	36	}
48
49		/**
50		* {@inheritdoc}
51		*/
52	12	public function lock($resource, $ttl = null, $retryDelay = 0, $retryCount = 0)
53		{
54	12	$lock = new Lock((string) $resource, $this->tokenGenerator->generateToken());
55
56	12	$tried = 0;
57	12	while (true) {
58		try {
59	12	return $this->monitoredLockingOfAllInstances($lock, $ttl);
60	6	} catch (LockingException $e) {
61	6	$this->resetLock($lock);
62		}
63
64	6	if ($tried++ === $retryCount) {
65	6	break;
66		}
67
68	6	$this->waitBeforeRetrying($retryDelay);
69	4	}
70
71	6	throw new LockingException('Failed locking the resource.');
72		}
73
74		/**
75		* {@inheritdoc}
76		*/
77	9	public function isLocked($resource)
78		{
79	9	foreach ($this->instances as $instance) {
80	9	if ($instance->exists((string) $resource)) {
81	7	return true;
82		}
83	4	}
84
85	3	return false;
86		}
87
88		/**
89		* {@inheritdoc}
90		*/
91	12	public function unlock(Lock $lock)
92		{
93	12	foreach ($this->instances as $instance) {
94	12	if (!$instance->delete($lock)) {
95	9	if ($instance->exists($lock->getResource())) {
96		// Only throw an exception if the lock is still present
97	8	throw new UnlockingException('Failed releasing the lock.');
98		}
99	2	}
100	6	}
101	6	}
102
103		/**
104		* Try locking all connected instances.
105		*
106		* Measure the time to do it and reject if not enough connected instance have successfully
107		* locked the resource or if time to lock all instances 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	12	private function monitoredLockingOfAllInstances(Lock $lock, $ttl)
117		{
118	12	$timeMeasure = $this->stopwatch->start($lock->getToken());
119	12	$instancesLocked = $this->lockInstances($lock, $ttl);
120	12	$timeMeasure->stop();
121
122	12	$this->checkQuorum($instancesLocked);
123
124	9	if ($ttl) {
125	6	$this->checkTtl($timeMeasure->getDuration(), $ttl);
126	3	$lock->setValidityEndTime($timeMeasure->getOrigin() + $ttl);
127	2	}
128
129	6	return $lock;
130		}
131
132		/**
133		* Lock resource in connected instances and count how many instance 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 instances locked
139		*/
140	12	private function lockInstances(Lock $lock, $ttl)
141		{
142	12	$instancesLocked = 0;
143
144	12	foreach ($this->instances as $instance) {
145	12	if ($instance->set($lock, $ttl)) {
146	12	++$instancesLocked;
147	8	}
148	8	}
149
150	12	return $instancesLocked;
151		}
152
153		/**
154		* Unlock the resource on all Redis instances.
155		*
156		* @param Lock $lock The lock to release
157		*/
158	6	private function resetLock($lock)
159		{
160	6	foreach ($this->instances as $instance) {
161	6	$instance->delete($lock);
162	4	}
163	6	}
164
165		/**
166		* Init all Redis instances passed to the constructor.
167		*
168		* If no Redis instance is given, it will return a InvalidArgumentException.
169		* If one or more Redis instance is not connected, it will return a InvalidArgumentException.
170		*
171		* @param \Redis[] $instances The connected Redis instances
172		*
173		* @throws \InvalidArgumentException
174		*/
175	36	private function setInstances(array $instances)
176		{
177	36	if (count($instances) === 0) {
178	3	throw new \InvalidArgumentException('You must provide at least one Redis instance.');
179		}
180
181	36	$this->instances = $instances;
		0 ignored issues – show Documentation Bug introduced 2016-08-31 13:26 UTC by Report Bug Copy Issue Report It seems like `$instances` of type `array<integer,object<Redis>>` is incompatible with the declared type `array<integer,object<RemiSan\Lock\Connection>>` of property `$instances`. Our type inference engine has found an assignment to a property that is incompatible with the declared type of that property. Either this assignment is in error or the assigned type should be added to the documentation/type hint for that property.. Loading history...
182	36	}
183
184		/**
185		* Set the quorum based on the number of instances passed to the constructor.
186		*
187		* @param Quorum $quorum The quorum implementation to use
188		*/
189	36	private function setQuorum(Quorum $quorum)
190		{
191	36	$this->quorum = $quorum;
192	36	$this->quorum->init(count($this->instances));
193	36	}
194
195		/**
196		* Check if the number of instances that have been locked reach the quorum.
197		*
198		* @param int $instancesLocked The number of instances that have been locked
199		*
200		* @throws LockingException
201		*/
202	12	private function checkQuorum($instancesLocked)
203		{
204	12	if (!$this->quorum->isMet($instancesLocked)) {
205	3	throw new LockingException('Quorum has not been met.');
206		}
207	9	}
208
209		/**
210		* Make the script wait before retrying to lock.
211		*
212		* @param int $retryDelay The retry delay in milliseconds
213		*/
214	6	private function waitBeforeRetrying($retryDelay)
215		{
216	6	usleep($retryDelay * 1000);
217	6	}
218
219		/**
220		* Checks if the elapsed time is inferior to the ttl.
221		*
222		* To the elapsed time is added a drift time to have a margin of error.
223		* If this adjusted time is greater than the ttl, it will throw a LockingException.
224		*
225		* @param int $elapsedTime The time elapsed in milliseconds
226		* @param int $ttl The time to live in milliseconds
227		*
228		* @throws LockingException
229		*/
230	6	private function checkTtl($elapsedTime, $ttl)
231		{
232	6	$adjustedElapsedTime = ($elapsedTime + $this->getDrift($ttl));
233
234	6	if ($adjustedElapsedTime >= $ttl) {
235	3	throw new LockingException('Time to lock the resource has exceeded the ttl.');
236		}
237	3	}
238
239		/**
240		* Get the drift time based on ttl in ms.
241		*
242		* @param int $ttl The time to live in milliseconds
243		*
244		* @return float
245		*/
246	6	private function getDrift($ttl)
247		{
248	6	return array_values($this->instances)[0]->getDrift($ttl);
249		}
250		}
251

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MultipleInstanceLocker::checkQuorum() A

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