Created
January 11, 2019 14:10
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A nice framework for a generic requestor that puts the requests with a correlation id onto an underlying duplex and gets responses off the same stream
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import { Duplex } from 'stream' | |
export class Requestor { | |
private _map = new Map<number, (reply: string) => void>() | |
private _nextCorrelationId = 1 | |
private _stream: Duplex | |
constructor (stream: Duplex) { | |
this._stream = stream | |
this._stream.on('data', (chunk: any) => { | |
const callback = this._map.get(chunk.id) | |
if (callback) { | |
callback(chunk.message) | |
} else { | |
throw new Error(`unsolicited messaged received with id: ${chunk.id}`) | |
} | |
}) | |
} | |
public request (message: string, timeout: number): Promise<string> { | |
const id = this._nextCorrelationId++ | |
return new Promise<string>((resolve, reject) => { | |
const timer = setTimeout(() => { | |
this._map.delete(id) | |
reject(new Error('timed out')) | |
}, timeout) | |
this._map.set(id, (reply: string) => { | |
this._map.delete(id) | |
clearTimeout(timer) | |
resolve(reply) | |
}) | |
this._stream.write({ id, message }) | |
}) | |
} | |
} | |
// For testing | |
export class MirrorStream extends Duplex { | |
constructor () { | |
super({ objectMode: true }) | |
} | |
_write (chunk: any, encoding: string, callback: (error?: Error) => void): void { | |
try { | |
callback() | |
this.push(chunk) | |
} catch (e) { | |
callback(e) | |
} | |
} | |
_read (size: number): void { | |
// NO OP | |
} | |
} |
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