Question

我正在使用SSE从Node后端向Angular应用发送简单消息。到目前为止，它一直在正常工作，但是今天我意识到它不再工作了，我找不到原因。

这是相关代码：

节点

router.get('/stream', function (req, res) {
    [ ... ]

    // Send headers for event-stream connection
    res.writeHead(200, {
        'Content-Type': 'text/event-stream',
        'Cache-Control': 'no-cache',
        'Connection': 'keep-alive'
    });
    res.write('\n');

    [ ... ]
    // NOTE: This line connects to a Redis server
    subscriber.subscribe(channel);

    // In case we encounter an error...print it out to the console
    subscriber.on("error", function (err) {
        logger.debug("Redis Error: " + err);
    });

    // When we receive a message from the Redis connection
    subscriber.on("message", function (channel, message) {
        logger.debug('MESSAGE RECEIVED: ' + message);   // This message is printed in the log file

        [ ... ]
        // Note: 'msgData' is obtained by parsing the received 'message'
        // Send data to the client
        res.write('data: ' + msgData + "\n\n");
    });
}

Angular应用

declare var EventSource : any;

getSSEMessages(): Observable<string> {
    let sseUrl = `${ConfigService.settings.appURL}/stream`;    

    return new Observable<string>(obs => {
        const es = new EventSource(sseUrl, { withCredentials: true });  

        // This prints '1' (CONNECTION OPEN)
        console.log('SSE Connection: ', es.readyState);               

        // Note: I've also tried 'es.onerror'
        es.addEventListener("error", (error) => {
            console.log("Error in SSE connection", error);

            return false;
        });

        // Note: I've also tried 'es.onmessage'
        es.addEventListener("message", (evt : any) => {
            // Never gets in here
            console.log('SSE Message', evt.data);

            obs.next(evt.data);
        });

        return () => es.close();
    });
}

这是我在界面中选择选项后收到消息的方式：

this.getSSEMessages()
  .subscribe(message => {
    // SHOW MESSAGE TO THE USER
});

就像我说的那样，几周来一切正常。今天我看到我没有收到任何消息，并且我一直在试图找出原因而没有运气。

关于什么是错误的任何线索？

Answer 1

最后，我找到了解决方法：

也许是因为更新了某些Node模块或Node本身，所以添加了某种缓冲区来优化连接流量。为了使应用程序再次正常工作，我要做的就是在每条消息后添加一个position:absolute，如下所示：

<div 
    id="test" 
    fxLayout="row" 
    fxLayoutGap="12px" 
    fxLayoutAlign="start center" 
    [class.hasFocus]="numberMatInput.value">
    <mat-form-field appearance="outline">
         <mat-label>KM</mat-label>
         <input matInput #numberMatInput [formControl]="numberInput">
    </mat-form-field>
</div>

干杯

获取SSE消息，Angular前端，Node后端时出错

1 个答案: