NodeJS流不等待异步
我在测试NodeJS流时遇到了一个问题。在运行stream.pipeline后，我似乎无法让我的项目等待Duplex和Transform流的输出，即使它返回了一个promise。也许我错过了一些东西，但我相信脚本应该在继续之前等待函数返回。我正在努力工作的项目中最重要的部分是：
// Message system is a duplex (read/write) stream
export class MessageSystem extends Duplex {
constructor() {
super({highWaterMark: 100, readableObjectMode: true, writableObjectMode: true});
}
public _read(size: number): void {
var chunk = this.read();
console.log(`Recieved ${chunk}`);
this.push(chunk);
}
public _write(chunk: Message, encoding: string,
callback: (error?: Error | null | undefined, chunk?: Message) => any): void {
if (chunk.data === null) {
callback(new Error("Message.Data is null"));
} else {
callback();
}
}
}
export class SystemStream extends Transform {
public type: MessageType = MessageType.Global;
public data: Array<Message> = new Array<Message>();
constructor() {
super({highWaterMark: 100, readableObjectMode: true, writableObjectMode: true});
}
public _transform(chunk: Message, encoding: string,
callback: TransformCallback): void {
if (chunk.single && (chunk.type === this.type || chunk.type === MessageType.Global)) {
console.log(`Adding ${chunk}`);
this.data.push(chunk);
chunk = new Message(chunk.data, MessageType.Removed, true);
callback(undefined, chunk); // TODO: Is this correct?
} else if (chunk.type === this.type || chunk.type === MessageType.Global) { // Ours and global
this.data.push(chunk);
callback(undefined, chunk);
} else { // Not ours
callback(undefined, chunk);
}
}
}
export class EngineStream extends SystemStream {
public type: MessageType = MessageType.Engine;
}
export class IOStream extends SystemStream {
public type: MessageType = MessageType.IO;
}
let ms = new MessageSystem();
let es = new EngineStream();
let io = new IOStream();
let pipeline = promisify(Stream.pipeline);
async function start() {
console.log("Running Message System");
console.log("Writing new messages");
ms.write(new Message("Hello"));
ms.write(new Message("world!"));
ms.write(new Message("Engine data", MessageType.Engine));
ms.write(new Message("IO data", MessageType.IO));
ms.write(new Message("Order matters in the pipe, even if Global", MessageType.Global, true));
ms.end(new Message("Final message in the stream"));
console.log("Piping data");
await pipeline(
ms,
es,
io
);
}
Promise.all([start()]).then(() => {
console.log(`Engine Messages to parse: ${es.data.toString()}`);
console.log(`IO Messages to parse: ${io.data.toString()}`);
});
输出应该类似于：
Running message system
Writing new messages
Hello
world!
Engine Data
IO Data
Order Matters in the pipe, even if Global
Engine messages to parse: Engine Data
IO messages to parse: IO Data
任何帮助将不胜感激。谢谢！
注意：我在我的其他帐户中发布了这个，而不是我的实际帐户。为复制道歉。
编辑：我最初私有的回购，但已公开，以帮助澄清答案。更多用法可以在feature/inital_system branch上找到。签出时可以使用npm start运行。
编辑：我把我的自定义流放在这里是为了冗长。我认为我的轨道比以前更好，但现在获得一个“空”对象接收到了管道。
回答如下：正如the documentation所述，stream.pipeline以回调为基础并未返回承诺。
它有自定义的promisified版本，可以使用util.promisify访问：
const pipeline = util.promisify(stream.pipeline);
...
await pipeline(...);
NodeJS流不等待异步
我在测试NodeJS流时遇到了一个问题。在运行stream.pipeline后，我似乎无法让我的项目等待Duplex和Transform流的输出，即使它返回了一个promise。也许我错过了一些东西，但我相信脚本应该在继续之前等待函数返回。我正在努力工作的项目中最重要的部分是：
// Message system is a duplex (read/write) stream
export class MessageSystem extends Duplex {
constructor() {
super({highWaterMark: 100, readableObjectMode: true, writableObjectMode: true});
}
public _read(size: number): void {
var chunk = this.read();
console.log(`Recieved ${chunk}`);
this.push(chunk);
}
public _write(chunk: Message, encoding: string,
callback: (error?: Error | null | undefined, chunk?: Message) => any): void {
if (chunk.data === null) {
callback(new Error("Message.Data is null"));
} else {
callback();
}
}
}
export class SystemStream extends Transform {
public type: MessageType = MessageType.Global;
public data: Array<Message> = new Array<Message>();
constructor() {
super({highWaterMark: 100, readableObjectMode: true, writableObjectMode: true});
}
public _transform(chunk: Message, encoding: string,
callback: TransformCallback): void {
if (chunk.single && (chunk.type === this.type || chunk.type === MessageType.Global)) {
console.log(`Adding ${chunk}`);
this.data.push(chunk);
chunk = new Message(chunk.data, MessageType.Removed, true);
callback(undefined, chunk); // TODO: Is this correct?
} else if (chunk.type === this.type || chunk.type === MessageType.Global) { // Ours and global
this.data.push(chunk);
callback(undefined, chunk);
} else { // Not ours
callback(undefined, chunk);
}
}
}
export class EngineStream extends SystemStream {
public type: MessageType = MessageType.Engine;
}
export class IOStream extends SystemStream {
public type: MessageType = MessageType.IO;
}
let ms = new MessageSystem();
let es = new EngineStream();
let io = new IOStream();
let pipeline = promisify(Stream.pipeline);
async function start() {
console.log("Running Message System");
console.log("Writing new messages");
ms.write(new Message("Hello"));
ms.write(new Message("world!"));
ms.write(new Message("Engine data", MessageType.Engine));
ms.write(new Message("IO data", MessageType.IO));
ms.write(new Message("Order matters in the pipe, even if Global", MessageType.Global, true));
ms.end(new Message("Final message in the stream"));
console.log("Piping data");
await pipeline(
ms,
es,
io
);
}
Promise.all([start()]).then(() => {
console.log(`Engine Messages to parse: ${es.data.toString()}`);
console.log(`IO Messages to parse: ${io.data.toString()}`);
});
输出应该类似于：
Running message system
Writing new messages
Hello
world!
Engine Data
IO Data
Order Matters in the pipe, even if Global
Engine messages to parse: Engine Data
IO messages to parse: IO Data
任何帮助将不胜感激。谢谢！
注意：我在我的其他帐户中发布了这个，而不是我的实际帐户。为复制道歉。
编辑：我最初私有的回购，但已公开，以帮助澄清答案。更多用法可以在feature/inital_system branch上找到。签出时可以使用npm start运行。
编辑：我把我的自定义流放在这里是为了冗长。我认为我的轨道比以前更好，但现在获得一个“空”对象接收到了管道。
回答如下：正如the documentation所述，stream.pipeline以回调为基础并未返回承诺。
它有自定义的promisified版本，可以使用util.promisify访问：
const pipeline = util.promisify(stream.pipeline);
...
await pipeline(...);