服务器端事件 - 将睡眠添加到脚本导致消息未发送

Question

当用户想要导出 CSV 数据时，我正在构建一个进度条。一切都按预期工作，直到我想在 while 循环中添加睡眠。

我尝试使用睡眠与刷新但没有成功。

为什么睡眠功能导致消息不输出？

sse.php

<?php
header('Content-Type: text/event-stream; charset=utf-8');
header('Cache-Control: no-cache');

// perform queries

$lines = $res->rowCount();
$writtenLines = 0;

while ($row = $res->fetch(PDO::FETCH_NUM)) {
    writeToCsv($row);
    $writtenLines++;
    sendMsg($writtenLines);
    flush();
    sleep(1);
}

function sendMsg($line) {
    $data = [
        "writtenLines" => $line,
        "totalLines" => $lines
    ];
    echo "data: ".json_encode($data)."\n\n";
}

客户

<div class="progress">
    <div class="progress-bar" role="progressbar"></div>
</div>
<br>
<span id="writtenLines">0</span> written lines

<script type="text/javascript">
    var evtSource = new EventSource('sse.php');
    evtSource.onmessage = (e) => {
        const data = JSON.parse(e.data);
        updateProgress(data);
        if (data.writtenLines === data.totalLines)
            evtSource.close();
    }

    function updateProgress(data) {
        var p_bar = jQuery(".progress").find(".progress-bar");
        document.getElementById("writtenLines").innerHTML = data.writtenLines;
        status = parseInt(data.writtenLines/data.totalLines * 100);
        p_bar.css("width", status + "%");
    }
</script>

Answer 1

我也有同样的问题，我需要睡眠以避免服务器超载