我正在我的网站上开发用户之间的在线聊天。聊天功能正常，但如果打开长轮询连接，则任何人都无法进入该网站。

我的代码[更新]:

$time = $_GET['time'];
while (true) {
    $sth = $db->prepare("SELECT * FROM messages LEFT JOIN users ON users.username=messages.chat_msg_user_id WHERE chat_msg_client_id=:chat_msg_client_id AND chat_msg_id>:chat_msg_id AND chat_notification='0' ORDER BY chat_msg_time DESC LIMIT 1");
    $sth->execute([":chat_msg_client_id" => $client_id, ":chat_msg_id" => $last_message_id]);
    $messages = [];
    while ($answer = $sth->fetch()) {
        $msg = ["chat_msg_id" => $answer["chat_msg_id"], "chat_msg_user_id" => $answer["chat_msg_user_id"], "chat_username" => $answer['username'], "chat_user_photo" => $answer['mainphoto'], "chat_user_status" => $answer['status'], "chat_user_name" => $answer["name"], "chat_msg_from" => $answer['chat_msg_from'], "chat_msg_time" => date("H:i", $answer["chat_msg_time"]), "chat_msg_date" => date("m.d.y", $answer["chat_msg_time"]), "chat_msg_text" => mb_str_replace("\n", "<br>", $answer["chat_msg_text"]), "read" => $answer['chat_read'], ];
        $messages[] = $msg;
        $last_message_id = $answer["chat_msg_id"];

        // some variables here for json_encode below //

    }
    if (count($messages) > 0) {
        $sth2 = $db->prepare("SELECT count(chat_read) as unread_messages_count FROM messages WHERE chat_msg_client_id='$client_id' AND chat_read='0'");
        $sth2->execute();
        $answers = $sth2->fetch();
        $unread_messages_count = $answers['unread_messages_count'];
        echo json_encode(["command" => "new_messages", "messages" => $messages, "last_message_id" => $last_message_id, "chat_msg_id" => $chat_msg_id, "chat_user_name" => $chat_user_name, "chat_user_status" => $chat_user_status, "chat_user_photo" => $chat_user_photo, "chat_msg_from" => $chat_msg_from, "chat_msg_time" => $chat_msg_time, "chat_msg_date" => $chat_msg_date, "chat_msg_text" => $chat_msg_text, "unread_messages_count" => $unread_messages_count, ]);
        exit();
    }
    usleep(10000);
    if ((time() - $time) > 60) {
        echo json_encode(["command" => "timeout"]);
        exit();
    }
 }

更新 2: 我的托管服务提供商发送了一些有关它的信息，但我不明白它是什么...:

sendto(3, "\306\0\0\0\3SELECT * FROM messages LEFT JOIN users ON users.username=messages.chat_msg_user_id WHERE chat_msg_client_id='222' AND chat_msg_id>'571' AND chat_notification='0' ORDER BY chat_msg_time DESC LIMIT 1", 202, MSG_DONTWAIT, NULL, 0) = 202

更新 3: 我忘了说 — 每个用户有 2 个长轮询连接。一个用于获取新聊天和新消息(用于通知)，另一个用于在聊天时获取消息。

最佳答案

PHP 通常使用线程池来处理请求。这种方法并不真正支持让执行休眠。您最终很快就会耗尽可用线程，并且新请求不会得到处理，因为所有线程都在休眠。

您要么需要增加线程数量(这不会扩展并且您的托管服务提供商可能不支持)，要么切换到不同的方法(通过使用支持异步请求处理的语言/框架，例如 NodeJS ).

另请参阅 an answer regarding long polling in PHP 中的这段摘录:

Note: With a real site, running this on a regular web-server like Apache will quickly tie up all the "worker threads" and leave it unable to respond to other requests.. There are ways around this, but it is recommended to write a "long-poll server" in something like Python's twisted, which does not rely on one thread per request. cometD is an popular one (which is available in several languages), and Tornado is a new framework made specifically for such tasks (it was built for FriendFeed's long-polling code)... but as a simple example, Apache is more than adequate! This script could easily be written in any language (I chose Apache/PHP as they are very common, and I happened to be running them locally)

更新:

My hosting provider said that Apache has too many connections to database and my server dieing cause of it

如果这是问题所在，则可以通过在进入休眠前关闭数据库连接来解决(直到有关 PHP 线程的其他问题接管)，see this for PDO .

关于php 长轮询 "killing"服务器，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/53140063/