Question

我们正在使用aws-sdk中的createReadStream()从节点中的S3流式传输内容。我们想添加etag支持。如果我们从客户端添加'If-None-Match'标头，则s3将NotModified抛出为我似乎无法处理的错误。

retrieveFile = function(req, res) {
    var s3 = new AWS.S3(); 
    var params = {
        Bucket: bucket,
        key: key
    };
    if (req.get('If-None-Match')) {
        params.IfNoneMatch = req.get('If-None-Match');
    }
    return s3.getObject(params).on('httpHeaders', function(statusCode, headers) {
        if (headers.etag) {
            res.set('etag', headers.etag);
        }
        if (headers['content-length']) {
            return res.set('content-length', headers['content-length']);
        }
    }).createReadStream().pipe(res);
};

我尝试在流上侦听事件，并在getObject返回的Request上使用回调。我可以通过这种方式获取错误消息，但是aws-sdk中的其他内容似乎正在杀死我的进程。

/Projects/my-app/node_modules/aws-sdk/lib/request.js:31
            throw err;
            ^

NotModified: null
  at Request.extractError (/Projects/my-app/node_modules/aws-sdk/lib/services/s3.js:519:35)
  at Request.callListeners (/Projects/my-app/node_modules/aws-sdk/lib/sequential_executor.js:105:20)
  at Request.emit (/Projects/my-app/node_modules/aws-sdk/lib/sequential_executor.js:77:10)
  at Request.emit (/Projects/my-app/node_modules/aws-sdk/lib/request.js:673:14)
  at Request.transition (/Projects/my-app/node_modules/aws-sdk/lib/request.js:22:10)
  at AcceptorStateMachine.runTo (/Projects/my-app/node_modules/aws-sdk/lib/state_machine.js:14:12)
  at /Projects/my-app/node_modules/aws-sdk/lib/state_machine.js:26:10
  at Request.<anonymous> (/Projects/my-app/node_modules/aws-sdk/lib/request.js:38:9)
  at Request.<anonymous> (/Projects/my-app/node_modules/aws-sdk/lib/request.js:675:12)
  at Request.callListeners (/Projects/my-app/node_modules/aws-sdk/lib/sequential_executor.js:115:18)
  at Request.emit (/Projects/my-app/node_modules/aws-sdk/lib/sequential_executor.js:77:10)
  at Request.emit (/Projects/my-app/node_modules/aws-sdk/lib/request.js:673:14)
  at Request.transition (/Projects/my-app/node_modules/aws-sdk/lib/request.js:22:10)
  at AcceptorStateMachine.runTo (/Projects/my-app/node_modules/aws-sdk/lib/state_machine.js:14:12)
  at /Projects/my-app/node_modules/aws-sdk/lib/state_machine.js:26:10
  at Request.<anonymous> (/Projects/my-app/node_modules/aws-sdk/lib/request.js:38:9)
  at Request.<anonymous> (/Projects/my-app/node_modules/aws-sdk/lib/request.js:675:12)
  at Request.callListeners (/Projects/my-app/node_modules/aws-sdk/lib/sequential_executor.js:115:18)
  at callNextListener (/Projects/my-app/node_modules/aws-sdk/lib/sequential_executor.js:95:12)
  at IncomingMessage.onEnd (/Projects/my-app/node_modules/aws-sdk/lib/event_listeners.js:244:11)
  at emitNone (events.js:91:20)
  at IncomingMessage.emit (events.js:185:7)
  at endReadableNT (_stream_readable.js:974:12)
  at _combinedTickCallback (internal/process/next_tick.js:74:11)
  at process._tickDomainCallback (internal/process/next_tick.js:122:9)

Answer 1

似乎错误是在流上抛出的，如果您正在侦听AWS.Request，您将收到错误，但仍然没有捕获流错误。

考虑一下：

s3.getObject({
    Bucket: 'foo',
    Key: 'bar'
}).on('error', function (err) {
    console.log('Error event!');
}).createReadStream();

这将显示错误事件！＆＃39;但它也会抛出错误并退出进程。这是因为createReadStream创建的流也收到错误。

考虑一下：

s3.getObject({
    Bucket: 'lalaland',
    Key: 'blabaliets'
}).on('error', function (err) {
    console.log('Error event!');
}).createReadStream().on('error', function (err) {
    console.log('Error event on stream!');
});

它会在AWS.Request对象上侦听错误，但也是在流对象上。这将首先打印“错误”事件！＆＃39;然后“正在播放错误事件！＆＃39;并且该过程不会退出。

请注意：

s3.getObject({
    Bucket: 'lalaland',
    Key: 'blabaliets'
}).createReadStream().on('error', function (err) {
    console.log('Error event on stream!');
});

仅打印＆＃39;错误事件在流上！＆＃39;而不是退出。最后一个选项可能是您想要的：只侦听流上的错误而不是请求对象上的错误。

回到原来的意图;此时（在流上的错误中），您要检查它是否确实是NotModified错误并执行res.status(304).end()之类的操作。

s3使用etags（节点）流式传输

1 个答案: