How Swoole implements load balancing of TCP proxy services

Swoole is a high-performance network communication framework developed based on PHP language extension. It improves the performance and concurrency capabilities of PHP applications through asynchronous, coroutine and other features. In actual projects, we often need to deploy TCP proxy services on multiple servers to achieve load balancing of services. This article will introduce how Swoole implements load balancing of TCP proxy services.

First of all, it is necessary to clarify the architecture of the TCP proxy service. Normally, TCP proxy service consists of two parts: client and server. The client sends a request to the TCP proxy service, and the server forwards the request to the back-end server and returns the response result to the client. When deploying TCP proxy services on multiple servers, we need to implement a load balancing strategy to evenly distribute requests to each server to improve system availability and throughput.

In Swoole, load balancing of TCP proxy services can be achieved in various ways. Here are two common ways.

1. Swoole-based TCP proxy component

Swoole provides a TCP proxy component that can be used as the middleware of the TCP proxy service to achieve traffic forwarding and load balancing. First, start Swoole's TCP proxy service component on the server:

$proxy = new SwooleProxyServer('0.0.0.0', 8080, SWOOLE_PROCESS);
$proxy->set(
    array(
        'timeout' => 3, //超时时间
        'heartbeat_check_interval' => 60, //心跳检测间隔
        'heartbeat_idle_time' => 600, //连接空闲时间
        'load_balance' => SWOOLE_PROXY_ROUNDROBIN, //负载均衡策略
        'server_list' => array(
            array('host' => '192.168.1.1', 'port' => 8080),
            array('host' => '192.168.1.2', 'port' => 8080),
            array('host' => '192.168.1.3', 'port' => 8080),
        ),
    )
);
$proxy->run();

In the above code, we instantiate a TCP proxy service by calling the SwooleProxyServer class, listen to port 8080, and set relevant parameters. Among them, the load_balance parameter specifies the load balancing strategy, which can be selected from polling, random, and weight-based methods. The server_list parameter specifies the address list of the backend service.

Then, in the client, send the request to the TCP proxy service through Swoole's TCP client component:

$client = new SwooleClient(SWOOLE_SOCK_TCP, SWOOLE_SOCK_ASYNC);
$client->set(
    array(
        'open_length_check' => true,
        'package_length_type' => 'N',
        'package_length_offset' => 0,
        'package_body_offset' => 4,
        'package_max_length' => 2000000, //最大数据长度
    )
);
$client->on('connect', function ($cli) {
    $cli->send("hello,world
");
});
$client->on('receive', function ($cli, $data) {
    echo "Receive: $data";
});
$client->on('error', function ($cli) {
    echo "Connect failed
";
});
$client->on('close', function ($cli) {
    echo "Connection close
";
});
$client->connect('127.0.0.1', 8080, 0.5);

Instantiate a TCP client by calling Swoole's TCP client component end, set relevant parameters, and send the request to the TCP proxy service. The TCP proxy service will forward the request to a backend server according to the load balancing policy and return the response result to the client.

2. Swoole-based reverse proxy server

Swoole also provides a reverse proxy server that can be deployed directly on the front-end server to achieve load balancing and reverse proxy . First, in the reverse proxy server, start Swoole's reverse proxy service component:

$proxy = new SwooleServer('0.0.0.0', 80, SWOOLE_PROCESS);
$proxy->set(
    array(
        'worker_num' => 2, //工作进程数
        'daemonize' => true, //守护进程模式
        'max_conn' => 10000, //最大连接数
        'open_http2_protocol' => true, //启用HTTP2协议
        'ssl_cert_file' => '/path/to/server.crt', //SSL证书文件
        'ssl_key_file' => '/path/to/server.key', //SSL证书私钥
        'ssl_verify_peer' => false, //SSL客户端验证
        'ssl_allow_self_signed' => false, //允许使用自签名证书
        'ssl_client_cert_file' => '/path/to/client.crt', //SSL客户端证书文件
    )
);
$proxy->on('request', function ($request, $response) {
    $filePath = '/path/to/static/files' . $request->server['request_uri'];
    $contentType = getMimeType($filePath);
    if (is_file($filePath)) {
        $response->header('Content-Type', $contentType);
        $response->sendFile($filePath);
    } else {
        $proxy = new SwooleHttpClient('www.example.com', 80);
        $proxy->set(
            array(
                'timeout' => 3,
                'keep_alive' => false,
            )
        );
        $proxy->on('error', function ($cli) use ($response) {
            $response->statusCode(503);
            $response->end();
        });
        $proxy->on('close', function ($cli) use ($response) {
            $response->end();
        });
        $proxy->on('receive', function ($cli, $data) use ($response) {
            $response->header('Content-Type', 'text/html');
            $response->end($data);
        });
        $headers = array();
        foreach ($request as $key => $value) {
            if (strpos($key, 'HTTP_') === 0) {
                $headers[strtolower(str_replace('_', '-', substr($key, 5)))] = $value;
            }
        }
        $proxy->setHeaders($headers);
        $proxy->execute($request->server['request_method'], $request->server['request_uri']);
    }
});
$proxy->start();

In the above code, we instantiate a reverse proxy server by calling the SwooleServer class, listen to port 80, and set Related parameters. In the on('request') callback function, it is judged whether the requested file exists. If it exists, the file content is sent directly; if it does not exist, the request is forwarded to the back-end server and the response result is returned. When forwarding a request, we implement it through Swoole's HTTP client component, send the request to the backend server, and return the response result to the client.

Then, deploy reverse proxy servers on multiple servers, and use load balancing software such as Nginx or LVS to achieve balanced distribution of requests. Since Swoole's reverse proxy server supports the HTTP2 protocol, it can effectively improve performance and concurrency capabilities. It also supports SSL encryption and client verification, which improves system security.

In summary, Swoole provides a variety of ways to implement TCP proxy service load balancing, and you can choose the appropriate solution according to actual needs and scenarios. By configuring parameters appropriately and selecting an appropriate load balancing strategy, the availability and throughput of the system can be effectively improved.

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