How Swoole supports asynchronous SNMP operations

SNMP (Simple Network Management Protocol) is a protocol used to manage and monitor network devices. In modern software systems, SNMP is widely used in scenarios such as network device status monitoring, performance statistics, and troubleshooting. In PHP development, Swoole, as a high-performance asynchronous network framework, also provides support for SNMP asynchronous operations.

This article will introduce how to use Swoole to implement asynchronous SNMP operations, including basic knowledge of SNMP, how to use the asynchronous SNMP client in Swoole, and some practical application scenarios.

SNMP Basics

The SNMP protocol is composed of several commands and several objects. The commands are mainly divided into GET, SET, GET-NEXT and TRAP, etc., and the objects are some data or status information in the network device. Among them, the GET command is used to obtain the value of one or more objects; the SET command is used to set the value of an object; the GET-NEXT command is used to traverse the next object in the object tree; the TRAP command is used to manage the device. The system sends an alarm or notification.

For an SNMP client, its main job is to send commands to the SNMP agent and receive the results returned by the agent. In traditional synchronous network communication, the SNMP client usually sends commands to the SNMP agent through some class libraries or APIs, and waits for the agent to return the results before proceeding to the next step. This synchronization method has some disadvantages. For example, blocking waiting will reduce the performance of the program, and it is not suitable for high-concurrency application scenarios.

Swoole Asynchronous SNMP Client

Swoole, as an asynchronous network framework, provides support for SNMP asynchronous operations. In Swoole, we can create an SNMP client through the swoole_snmp class, send commands and receive results asynchronously. The swoole_snmp class defines the following methods:

1. swoole_snmp::__construct($host, $community, $timeout = 1, $retries = 5)

Construction method, Create an SNMP client. Among them, $host represents the IP address or host name of the SNMP agent; $community represents the SNMP community name; $timeout represents the timeout (unit: seconds), the default is 1 second; $retries represents the number of retries, the default is 5 times.

2. swoole_snmp::set($oid, $value, $type = SNMP::TYPE_NULL)

Set the value of an object, where $oid represents the object ID ; $value represents the value of the object; $type represents the type of the value.

3. swoole_snmp::get($oids, $callback)

Send the GET command to get the value of one or more objects. Among them, $oids represents one or more object IDs, which can be an array or a comma-separated string; $callback represents a callback function, which will be called when the result is obtained.

4. swoole_snmp::getAsync($oids, $callback)

Send an asynchronous GET command, similar to the get method, except that the method of obtaining the results is asynchronous.

5. swoole_snmp::walk($oid, $callback, $max_oids = 10, $non_repeaters = 0, $max_repetitions = 10)

Send GET-NEXT command, Traverse multiple objects in the object tree. Among them, $oid represents the starting object ID; $callback represents the callback function, which will be called when the result is obtained; $max_oids represents the maximum number of objects obtained each time, the default is 10; $non_repeaters represents non in Get-Next -repeaters parameter, the default is 0; $max_repetitions represents the max-repetitions parameter in Get-Next, the default is 10.

6. swoole_snmp::walkAsync($oid, $callback, $max_oids = 10, $non_repeaters = 0, $max_repetitions = 10)

Send asynchronous GET-NEXT Command is similar to the walk method, except that the method of obtaining results is asynchronous.

7. swoole_snmp::setTimeout($timeout)

Set the timeout (unit: seconds).

8. swoole_snmp::setRetries($retries)

Set the number of retries.

Sample Application

Below, we use a simple example to show how to use the Swoole asynchronous SNMP client. Suppose we need to get some CPU and memory usage from an SNMP agent and write the results to a log file.

1. First, add the swoole/snmp dependency in the composer.json file:

{
    "require": {
        "swoole/swoole": "~2.1.3",
        "swoole/snmp": "~1.2"
    }
}

2. Write a script to asynchronously obtain CPU and memory usage:

 SWOOLE_HOOK_ALL]);

$logFile = __DIR__ . '/snmp.log';

$scheduler = new Scheduler();
$scheduler->add(function () use ($logFile) {
    $snmp = new swoole_snmp('127.0.0.1', 'public');

    $cpuOid = '1.3.6.1.2.1.25.3.3.1.2.196608';
    $memOid = '1.3.6.1.4.1.2021.4.6.0';

    $snmp->getAsync([$cpuOid, $memOid], function ($result) use ($logFile) {
        if (is_array($result) && count($result) == 2) {
            $cpuUsage = $result[$cpuOid];
            $memUsage = round($result[$memOid] / 1024, 2); // KB to MB

            $logMsg = date('Y-m-d H:i:s') . " CPU usage: {$cpuUsage}%, Memory usage: {$memUsage}MB" . PHP_EOL;
            System::writeFile($logFile, $logMsg, FILE_APPEND);
        } else {
            echo "Failed to get CPU and memory usage." . PHP_EOL;
        }
    });
});

$scheduler->start();

In the above example, we created a Swoole coroutine scheduler and added a coroutine task to the scheduler. In this task, we created an SNMP client, used the getAsync method to asynchronously obtain the CPU and memory usage, and wrote the results to the log file. When the results are obtained asynchronously, the callback function will be called for processing.

It should be noted that in the above script we use Swoole's coroutine API, so we need to enable coroutine support. We set the hook_flags parameter to SWOOLE_HOOK_ALL by calling the co::set method, which means that coroutine support for PHP functions is enabled.

3. Run the script and view the log file results:

$ php snmp.php
$ tail -f snmp.log # 或者用其他文本编辑器打开

Summary

This article introduces how to use Swoole to implement asynchronous SNMP operations and provides a sample application. Compared with the traditional synchronous network communication method, using the Swoole asynchronous SNMP client can greatly improve the performance and response speed of the program, and is also more suitable for high-concurrency network application scenarios. In practical applications, we can choose different SNMP commands and parameters according to the needs of business scenarios to meet our monitoring and management needs for network device status.

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