ZooKeeperConfig::heartbeat() - Code Metrics - Inspection of "Added heartbeat functionality to configuration and..." - Gendoria/cruftflake - Measure and Improve Code Quality continuously with Scrutinizer

Completed

Push — master ( 956692...a443d7 )

by Tomasz

created 2016-02-05 12:39 UTC

ZooKeeperConfig::heartbeat() A

↳ Parent: ZooKeeperConfig

Complexity

Conditions	1
Paths	1

Size

Total Lines	4
Code Lines	2

Duplication

Lines	0
Ratio	0 %

Importance

Changes	1
Bugs	0	Features	1

Metric	Value
c	1
b	0
f	1
dl	0
loc	4
rs	10
cc	1
eloc	2
nc	1
nop	0

<?php

/**
 * ZooKeeper-based configuration.
 *
 * Couple of points:
 *
 *  1. We coordinate via ZK on launch - hence ZK must be available at launch
 *     time
 *  2. We create permanent nodes (not ephmeral) so that if we get disconnected
 *     ZK still knows about us running
 *  3. There is a danger that point 2 will mean that we run out of machine IDs
 *     if host name change and we don't manually clean up.
 *  4. All of your machines have to have unique host names.
 *
 * @author @davegardnerisme
 */

namespace Gendoria\CruftFlake\Config;

use BadMethodCallException;
use Psr\Log\LoggerAwareInterface;
use Psr\Log\LoggerInterface;
use Psr\Log\NullLogger;
use RuntimeException;

class ZooKeeperConfig implements ConfigInterface, LoggerAwareInterface
{
    /**
     * Parent path.
     *
     * @var string
     */
    private $parentPath;

    /**
     * ZK.
     *
     * @var \Zookeeper
     */
    private $zk;

    /**
     * Process ID for a multi-process-single-machine setup.
     * 
     * @var int
     */
    private $procesId = 1;

    /**
     * Logger.
     * 
     * @var LoggerInterface
     */
    private $logger;

    /**
     * Constructor.
     *
     * @param string          $hostnames A comma separated list of hostnames (including
     *                                   port)
     * @param int             $processId If you want to run multiple server processes on a single machine, 
     *                                   you have to provide each one an unique ID,
     *                                   so the zookeeper knows, which machine ID belongs to which process.
     * @param string          $zkPath    The ZK path we look to find other machines under
     * @param LoggerInterface $logger    Logger class
     */
    public function __construct($hostnames, $processId = 1, $zkPath = '/cruftflake',
        LoggerInterface $logger = null)
    {
        if (!class_exists('\Zookeeper')) {
            $this->logger->critical('Zookeeper not present');
            throw new BadMethodCallException('ZooKeeper extension not installed. Try hitting PECL.');
        }
        $this->procesId = $processId;
        $this->zk = new \Zookeeper($hostnames);
        $this->parentPath = $zkPath;
        if ($logger) {
            $this->logger = $logger;
        } else {
            $this->logger = new NullLogger();
        }
    }

    /**
     * Get machine identifier.
     *
     * @return int Should be a 10-bit int (decimal 0 to 1023)
     *
     * @throws RuntimeException Thrown, when obtaining machine ID has failed.
     */
    public function getMachine()
    {
        $machineId = null;

        $this->createParentIfNeeded($this->parentPath);

        // get info about _this_ machine
        $machineInfo = $this->getMachineInfo();

        // get current machine list
        $children = $this->zk->getChildren($this->parentPath);

        //Find existing machine info
        foreach ($children as $child) {
            $info = $this->zk->get("{$this->parentPath}/$child");
            $info = json_decode($info, true);
            if ($this->compareMachineInfo($info, $machineInfo)) {
                $machineId = (int) $child;
                break; //We don't have to check further
            }
        }

        //Machine info not found, attempt to create one
        if ($machineId === null) {
            $machineId = $this->createMachineInfo($children, $machineInfo);
        }

        $this->logger->debug('Obtained machine ID '.$machineId.' through ZooKeeper configuration');

        return (int) $machineId;
    }

    /**
     * Periodically re-syncs with zookeeper, to obtain new machine ID, if necessary.
     * 
     * {@inheritdoc}
     */
    public function heartbeat()
    {
        return false;
    }

    /**
     * Compare found machine information with expected values.
     * 
     * @param array $found
     * @param array $expected
     *
     * @return bool
     */
    private function compareMachineInfo(array $found, array $expected)
    {
        if (!isset($found['hostname']) || !isset($found['processId'])) {
            return false;
        }

        return $found['hostname'] === $expected['hostname'] && $found['processId'] === $expected['processId'];
    }

    /**
     * Attempt to claim and create new machine ID in Zookeeper.
     * 
     * @param array $children
     * @param array $machineInfo
     *
     * @return int Machine ID.
     *
     * @throws RuntimeException Thrown, when creation of machine ID has failed.
     */
    private function createMachineInfo(array $children, array $machineInfo)
    {
        // find an unused machine number
        for ($i = 0; $i < 1024; ++$i) {
            $machineNode = $this->machineToNode($i);
            if (in_array($machineNode, $children)) {
                continue; // already used
            }

            // attempt to claim
            $created = $this->zk->create(
                "{$this->parentPath}/{$machineNode}", json_encode($machineInfo),
                array(array(// acl
                    'perms' => \Zookeeper::PERM_ALL,
                    'scheme' => 'world',
                    'id' => 'anyone',
                ))
            );
            if ($created !== null) {
                return $i;
            }
        }

        //Creating machine ID failed, throw an error
        $this->logger->critical('Cannot locate and claim a free machine ID via ZK', array($this));
        throw new RuntimeException('Cannot locate and claim a free machine ID via ZK');
    }

    /**
     * Get mac address and hostname.
     *
     * @return array "hostname","processId", "time" keys
     */
    private function getMachineInfo()
    {
        $info = array();
        $info['hostname'] = php_uname('n');

        if (empty($info['hostname'])) {
            $this->logger->critical('Unable to identify machine hostname', array($this));
            throw new RuntimeException('Unable to identify machine hostname');
        }
        $info['processId'] = $this->procesId;
        $info['time'] = (int) floor(microtime(true) * 1000);

        return $info;
    }

    /**
     * Create parent node, if needed.
     *
     * @param string $nodePath
     */
    private function createParentIfNeeded($nodePath)
    {
        if (!$this->zk->exists($nodePath)) {
            $this->zk->create(
                $nodePath, 'Cruftflake machines',
                array(array(// acl
                    'perms' => \Zookeeper::PERM_ALL,
                    'scheme' => 'world',
                    'id' => 'anyone',
                ))
            );
        }
    }

    /**
     * Machine ID to ZK node.
     *
     * @param int $id
     *
     * @return string The node path to use in ZK
     */
    private function machineToNode($id)
    {
        return str_pad($id, 4, '0', STR_PAD_LEFT);
    }

    /**
     * Set logger.
     * 
     * @param LoggerInterface $logger
     */
    public function setLogger(LoggerInterface $logger)
    {
        $this->logger = $logger;
    }
}


1			<?php
2
3			/**
4			* ZooKeeper-based configuration.
5			*
6			* Couple of points:
7			*
8			* 1. We coordinate via ZK on launch - hence ZK must be available at launch
9			* time
10			* 2. We create permanent nodes (not ephmeral) so that if we get disconnected
11			* ZK still knows about us running
12			* 3. There is a danger that point 2 will mean that we run out of machine IDs
13			* if host name change and we don't manually clean up.
14			* 4. All of your machines have to have unique host names.
15			*
16			* @author @davegardnerisme
17			*/
18
19			namespace Gendoria\CruftFlake\Config;
20
21			use BadMethodCallException;
22			use Psr\Log\LoggerAwareInterface;
23			use Psr\Log\LoggerInterface;
24			use Psr\Log\NullLogger;
25			use RuntimeException;
26
27			class ZooKeeperConfig implements ConfigInterface, LoggerAwareInterface
28			{
29			/**
30			* Parent path.
31			*
32			* @var string
33			*/
34			private $parentPath;
35
36			/**
37			* ZK.
38			*
39			* @var \Zookeeper
40			*/
41			private $zk;
42
43			/**
44			* Process ID for a multi-process-single-machine setup.
45			*
46			* @var int
47			*/
48			private $procesId = 1;
49
50			/**
51			* Logger.
52			*
53			* @var LoggerInterface
54			*/
55			private $logger;
56
57			/**
58			* Constructor.
59			*
60			* @param string $hostnames A comma separated list of hostnames (including
61			* port)
62			* @param int $processId If you want to run multiple server processes on a single machine,
63			* you have to provide each one an unique ID,
64			* so the zookeeper knows, which machine ID belongs to which process.
65			* @param string $zkPath The ZK path we look to find other machines under
66			* @param LoggerInterface $logger Logger class
67			*/
68			public function __construct($hostnames, $processId = 1, $zkPath = '/cruftflake',
69			LoggerInterface $logger = null)
70			{
71			if (!class_exists('\Zookeeper')) {
72			$this->logger->critical('Zookeeper not present');
73			throw new BadMethodCallException('ZooKeeper extension not installed. Try hitting PECL.');
74			}
75			$this->procesId = $processId;
76			$this->zk = new \Zookeeper($hostnames);
77			$this->parentPath = $zkPath;
78			if ($logger) {
79			$this->logger = $logger;
80			} else {
81			$this->logger = new NullLogger();
82			}
83			}
84
85			/**
86			* Get machine identifier.
87			*
88			* @return int Should be a 10-bit int (decimal 0 to 1023)
89			*
90			* @throws RuntimeException Thrown, when obtaining machine ID has failed.
91			*/
92			public function getMachine()
93			{
94			$machineId = null;
95
96			$this->createParentIfNeeded($this->parentPath);
97
98			// get info about _this_ machine
99			$machineInfo = $this->getMachineInfo();
100
101			// get current machine list
102			$children = $this->zk->getChildren($this->parentPath);
103
104			//Find existing machine info
105			foreach ($children as $child) {
106			$info = $this->zk->get("{$this->parentPath}/$child");
107			$info = json_decode($info, true);
108			if ($this->compareMachineInfo($info, $machineInfo)) {
109			$machineId = (int) $child;
110			break; //We don't have to check further
111			}
112			}
113
114			//Machine info not found, attempt to create one
115			if ($machineId === null) {
116			$machineId = $this->createMachineInfo($children, $machineInfo);
117			}
118
119			$this->logger->debug('Obtained machine ID '.$machineId.' through ZooKeeper configuration');
120
121			return (int) $machineId;
122			}
123
124			/**
125			* Periodically re-syncs with zookeeper, to obtain new machine ID, if necessary.
126			*
127			* {@inheritdoc}
128			*/
129			public function heartbeat()
130			{
131			return false;
132			}
133
134			/**
135			* Compare found machine information with expected values.
136			*
137			* @param array $found
138			* @param array $expected
139			*
140			* @return bool
141			*/
142			private function compareMachineInfo(array $found, array $expected)
143			{
144			if (!isset($found['hostname']) \|\| !isset($found['processId'])) {
145			return false;
146			}
147
148			return $found['hostname'] === $expected['hostname'] && $found['processId'] === $expected['processId'];
149			}
150
151			/**
152			* Attempt to claim and create new machine ID in Zookeeper.
153			*
154			* @param array $children
155			* @param array $machineInfo
156			*
157			* @return int Machine ID.
158			*
159			* @throws RuntimeException Thrown, when creation of machine ID has failed.
160			*/
161			private function createMachineInfo(array $children, array $machineInfo)
162			{
163			// find an unused machine number
164			for ($i = 0; $i < 1024; ++$i) {
165			$machineNode = $this->machineToNode($i);
166			if (in_array($machineNode, $children)) {
167			continue; // already used
168			}
169
170			// attempt to claim
171			$created = $this->zk->create(
172			"{$this->parentPath}/{$machineNode}", json_encode($machineInfo),
173			array(array(// acl
174			'perms' => \Zookeeper::PERM_ALL,
175			'scheme' => 'world',
176			'id' => 'anyone',
177			))
178			);
179			if ($created !== null) {
180			return $i;
181			}
182			}
183
184			//Creating machine ID failed, throw an error
185			$this->logger->critical('Cannot locate and claim a free machine ID via ZK', array($this));
186			throw new RuntimeException('Cannot locate and claim a free machine ID via ZK');
187			}
188
189			/**
190			* Get mac address and hostname.
191			*
192			* @return array "hostname","processId", "time" keys
193			*/
194			private function getMachineInfo()
195			{
196			$info = array();
197			$info['hostname'] = php_uname('n');
198
199			if (empty($info['hostname'])) {
200			$this->logger->critical('Unable to identify machine hostname', array($this));
201			throw new RuntimeException('Unable to identify machine hostname');
202			}
203			$info['processId'] = $this->procesId;
204			$info['time'] = (int) floor(microtime(true) * 1000);
205
206			return $info;
207			}
208
209			/**
210			* Create parent node, if needed.
211			*
212			* @param string $nodePath
213			*/
214			private function createParentIfNeeded($nodePath)
215			{
216			if (!$this->zk->exists($nodePath)) {
217			$this->zk->create(
218			$nodePath, 'Cruftflake machines',
219			array(array(// acl
220			'perms' => \Zookeeper::PERM_ALL,
221			'scheme' => 'world',
222			'id' => 'anyone',
223			))
224			);
225			}
226			}
227
228			/**
229			* Machine ID to ZK node.
230			*
231			* @param int $id
232			*
233			* @return string The node path to use in ZK
234			*/
235			private function machineToNode($id)
236			{
237			return str_pad($id, 4, '0', STR_PAD_LEFT);
238			}
239
240			/**
241			* Set logger.
242			*
243			* @param LoggerInterface $logger
244			*/
245			public function setLogger(LoggerInterface $logger)
246			{
247			$this->logger = $logger;
248			}
249			}
250

Gendoria / cruftflake

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ZooKeeperConfig::heartbeat() A

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