如何使用node js维护http请求的顺序？

Question

I have a bunch of data that I want to send to a server through http. However in the server side I need to process the data in the same order as they were sent(eg if the order of sending is elem1, elem2 and elem3, I would like to process elem1 first, then elem2 and then elem3). Since in http, there is no grantee that the order will be maintained I need some way to maintain the order. Currently I am keeping the data in a queue and I send one element and await for the response. Once the response reaches me I send the next element.

while (!queue.isEmpty()) {
    let data = queue.dequeue();
    await sendDataToServer(data);
    }

I am not very sure if this will actually work in a production environment and what will be the impact on the performance. Any sort of help is much appreciated. Thank you

Answer 1

Sorry, I don't have enough reputation to comment, thus I am posting this as an answer.

Firstly, your code will work as intended.

However, since the server has to receive them in order, the performance won't be good. If you can change the server, I suggest you implement it like this:

• Add an ID to each data item.
• Send all the data items, no need to ensure order.
• Create a buffer on the server, the buffer will be able to contain all the data items.
• The server receives the items and puts them into the buffer in the right position.

Example code:

Client (see Promise.all )

let i = 0;
let promises = [];
await sendDataLengthToServer(queue.length());
while (!queue.isEmpty()) {
    let data = queue.dequeue();
    data.id = i;
    // no need to wait for a request to finish
    promises.push(sendDataToServer(data));
}
await Promise.all(promises);

Server (pseudo-code)

length = receiveDataLengthFromClient()
buffer = new Array(length)

int received = 0
onDataReceivedFromClient(data, {
    received = received + 1
    buffer[data.id] = data
    if (received == length) {
        // the buffer contains the data in the right order
    }
})