node.js - Nodejs中用于组合多个可读流的策略

Question

我正在尝试解决 Nodejs 流挑战。我已多次阅读有关流的节点文档，并实施了不同的尝试来解决挑战。尝试双工、转换、可读和可写:)

我有多个 HTTP 可读流，目标是将数据发送到单个管道，并具有背压工作。我认为这张照片有助于解释挑战：

更新（2017 年 9 月 13 日）。再次阅读文档后，我正在实现一个自定义的书面双工流。

Answer 1

This represents a great usecase for a duplex stream, combined with manuel flow control of the HTTP stream.

I have written a custom duplex stream, where the readable and writable part, is structured like this:

If you are interested in the specific code for the duplex stream, please send me a PM.

The code could look something like this (but it's pretty old, and could probably be simplified even more):

import 'rxjs/add/operator/skip';
import 'rxjs/add/operator/take';
import { BehaviorSubject } from 'rxjs/BehaviorSubject';
import * as stream from 'stream';
import { logger, streamInspector } from '../shared';

export class DuplexStreamLinker extends stream.Duplex {
    public readCount: number = 0;
    public acceptDataCount: number = 0;
    public acceptData$: BehaviorSubject<boolean>;
    public streamName: string;

    constructor(options) {
        super(options);
        this.streamName = this.constructor.name;
        this.acceptData$ = new BehaviorSubject(false);
        streamInspector(this, this.constructor.name);
    }

    public _read(size) {
        this.readCount++;
        this.acceptData$.next(true);
    }

    public _write(chunk, encoding, cb) {
        const acceptData = this.acceptData$.getValue();
        if (acceptData) {
            cb(this.pushData(chunk));
        } else {
            this.acceptData$.skip(1).take(1).subscribe(() => {
                logger.silly('I dont fire...');
                this.acceptDataCount++;
                cb(this.pushData(chunk));
            });
        }
    }

    public endReadableStream() {
        logger.debug('DuplexStreamLinker@endReadableStream was called!');
        this.end();
        this.push(null);
    }

    public _final(cb) {
        logger.debug('DuplexStreamLinker@_final was called!');
        cb(null);
    }

    private pushData(chunk): null | Error {
        const ok = this.push(chunk);
        if (ok === false) { this.acceptData$.next(false); }
        return null;
    }

}