PHP implements open source Zookeeper distributed coordination service

With the continuous development of the Internet, distributed systems have become a part of modern software architecture that cannot be ignored. In a distributed system, various services and processes need to be coordinated and synchronized to ensure system stability and consistency. To solve this problem, distributed coordination services were born. One of the well-known distributed coordination services is Zookeeper. This article will introduce how to use PHP to implement an open source Zookeeper distributed coordination service.

1. What is Zookeeper?

Zookeeper is a distributed coordination service, which is mainly used to solve various coordination problems in distributed systems. It provides a distributed, highly available naming service based on a tree structure, and also provides a complete set of APIs to solve distributed coordination, shared configuration, naming services, cluster management, distributed locks, etc. A series of questions.

The core of Zookeeper is a distributed data storage system, which can support the collaborative work of multiple nodes and select leader nodes through an internal election mechanism. Zookeeper also provides a listening mechanism that can automatically send notifications to the client when the node's data changes.

2. How to connect Zookeeper with PHP?

The PHP language itself does not support Zookeeper, but Zookeeper can be easily used in PHP through the third-party plug-in php-zookeeper.

Installing php-zookeeper requires the PHP extension management tool PECL. Before installation, please ensure that PECL has been installed correctly, and the SOCKETS extension and JSON extension have been enabled.

The installation steps are as follows:

1. First you need to install the Zookeeper C language client and execute the following command on the command line:

wget https://archive.apache.org/dist/zookeeper/zookeeper-3.4.6/zookeeper-3.4.6.tar.gz
tar -zxf zookeeper-3.4.6.tar.gz
cd zookeeper-3.4.6/src/c

2. Compile Zookeeper C language client and install it into the system directory:

./configure
make
make install

3. Install the php-zookeeper extension and execute the following command on the command line:

pecl install zookeeper

4. Add the following configuration in php.ini:

extension=zookeeper.so

5. Restart the web server to take effect.

You can now connect and use Zookeeper through PHP code.

Code example:

<?php
$zk = new Zookeeper("localhost:2181");
$zk->create("/test", "Hello Zookeeper!");
$value = $zk->get("/test");
echo "Node value: " . $value['value'] . "
";
$zk->delete("/test");
?>

3. How does PHP use Zookeeper to achieve distributed coordination?

1. Implementing distributed locks

Zookeeper provides the implementation of distributed locks and controls the access sequence of distributed processes by applying for lock nodes.

Code example:

<?php
$zk = new Zookeeper("localhost:2181");
$lock_path = "/test/lock";
$lock = $zk->create($lock_path . "/lock-", null, array(
    array('perms' => Zookeeper::PERM_ALL, 'scheme' => 'world', 'id' => 'anyone')
), Zookeeper::EPHEMERAL | Zookeeper::SEQUENCE);

while (!$zk->exists($lock, null)) {}

$children = $zk->getChildren($lock_path);
sort($children);
$lowest_node = reset($children);

if ($lock == $lock_path . '/' . $lowest_node) {
    echo "I got the lock!
";
    // do something
    $zk->delete($lock);
} else {
    echo "I failed getting the lock!
";
}
?>

2. Implementing distributed node monitoring

Zookeeper provides a node monitoring function, which can obtain node data changes by monitoring nodes. notify.

Code example:

<?php
$zk = new Zookeeper("localhost:2181");

function node_change_callback($event_type, $state, $path) {
    global $zk;
    $value = $zk->get($path, node_change_callback);
    echo "Node value changed to: " . $value['value'] . "
";
}

$zk->create("/test", "Hello, world");

$value = $zk->get("/test", node_change_callback);

sleep(10);

$zk->set("/test", "Hello, Zookeeper!");

sleep(10);

$zk->delete("/test");
?>

4. Summary

Zookeeper is a powerful distributed coordination service that can be used to solve various coordination problems in distributed systems. Through the third-party plug-in php-zookeeper, we can easily use Zookeeper in PHP. This article introduces how to use PHP to implement distributed locks and node monitoring functions. In actual projects, we can combine Zookeeper to achieve a more efficient and reliable distributed system.

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