http請求可以直接用workerman或者webman自定義進程來做，做成非阻塞http服務，包括服務端會繼續(xù)向客戶端A發(fā)送請求獲取金額這個過程做成非阻塞的請求。
如果你不會做，也可以把服務端會繼續(xù)向客戶端A發(fā)送請求獲取金額這個過程設置個超時時間，比如1秒。

準備工作

安裝channel

composer require workerman/channel

代碼

start.php

<?php
use Workerman\Worker;
define('GLOBAL_START', 1);
require_once __DIR__ . '/vendor/autoload.php';

// 加載所有Applications/*/start.php，以便啟動所有服務
foreach(glob(__DIR__.'/Applications/*/start*.php') as $start_file)
{
    require_once $start_file;
}

// channel服務用來多進程或者跨服務器通訊
$channel_server = new Channel\Server('0.0.0.0', 2206);

// 保存設備到connection的映射
global $connection_maps;
$connection_maps = [];
$http_worker = new Worker('http://0.0.0.0:1234');
$http_worker->onWorkerStart = function () {
    // Channel客戶端連接到Channel服務端
    Channel\Client::connect('127.0.0.1', 2206);
    Channel\Client::on('get_amount_result', function($data)  {
        global $connection_maps;
        $device_id = $data['device_id'];
        foreach ($connection_maps[$device_id]??[] as $connection) {
            $connection->close($data['amount']);
        }
    });
};
$http_worker->onMessage = function (\Workerman\Connection\TcpConnection $connection, \Workerman\Protocols\Http\Request $request) {
    global $connection_maps;
    $device_id = $request->get('device_id');
    if (!$device_id) {
        $connection->send('not found');
        return;
    }
    $connection->device_id = $device_id;
    $connection_maps[$device_id][$connection->id] = $connection;
    // 通過channel向gatewayWorker咨詢客戶端金額
    Channel\Client::publish('get_amount', [
        'device_id' => $device_id
    ]);
};
$http_worker->onClose = function (\Workerman\Connection\TcpConnection $connection) {
    if (empty($connection->device_id)) {
        return;
    }
    // 刪除$connection_maps對應的連接，避免內(nèi)存泄漏
    $device_id = $connection->device_id;
    global $connection_maps;
    unset($connection_maps[$device_id][$connection->id]);
    if (empty($connection_maps[$device_id])) {
        unset($connection_maps[$device_id]);
    }
};

// 運行所有服務
Worker::runAll();

Events.php

<?php
use \GatewayWorker\Lib\Gateway;
class Events
{
    public static function onWorkerStart($worker)
    {
        // Channel客戶端連接到Channel服務端
        Channel\Client::connect('127.0.0.1', 2206);
        // 只需要在0號進程上開啟get_amount監(jiān)聽
        if ($worker->id !== 0) {
            Channel\Client::on('get_amount', function($data)  {
                $device_id = $data['device_id'];
                Gateway::sendToUid($device_id, 'get_amount');
            });
        }
    }
   public static function onMessage($client_id, $message)
   {
       // 忽略客戶端心跳
       if ($message === '{"type":"ping"}') {
           return;
       }
       // 假設客戶端發(fā)的第一個消息當作device_id
       if (empty($_SESSION['device_id'])) {
           $device_id = trim($message);
           Gateway::bindUid($client_id, $device_id);
           $_SESSION['device_id'] = $device_id;
           return;
       }
       // 客戶端后續(xù)發(fā)的消息當作金額
       $amount = $message;
       // 通知http進程得到device_id的金額
       Channel\Client::publish('get_amount_result', [
           'device_id' => $_SESSION['device_id'],
           'amount' => $amount
       ]);
   }
}

啟動

php start.php start

測試

瀏覽器打開頁面 http://127.0.0.1:1234/?device_id=d2

開啟一個終端，輸入

telnet 127.0.0.1 8282
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
d2
800

提示
d2代表設備id
800代表金額

瀏覽器顯示 800

原理

啟動一個channel server作為多進程或者跨服務器通訊組件
businessWorker的Events里onWorkerStart連接channelserver并監(jiān)聽http進程發(fā)來的get_amount請求(請求中包含設備id)
啟動一個httpworker作為http接口，onWorkerStart里連接channelserver并監(jiān)聽get_amount_result結(jié)果(結(jié)果中包含設備id)
瀏覽器向httpworker發(fā)起請求，httpworker獲得要查詢的設備id，并將連接保存到connection_maps中，然后通過channel發(fā)布一個get_amount事件給businessWorke的Events.php
設備返回金額后在Events里的onMessage里通過channel發(fā)送get_amount_result事件通知http進程對應的設備返回了金額
httpworker獲得金額后查找本地連接里($connection_maps)是否有查詢對應設備金額的連接，有的話返回金額