@nestjs/microservices/helpers/json-socket.js

Nest - modern, fast, powerful node.js web framework (@microservices)

import { Buffer } from 'buffer';
import { StringDecoder } from 'string_decoder';
import { CorruptedPacketLengthException } from '../errors/corrupted-packet-length.exception.js';
import { IncompleteMessageTimeoutException } from '../errors/incomplete-message-timeout.exception.js';
import { MaxPacketLengthExceededException } from '../errors/max-packet-length-exceeded.exception.js';
import { MaxSendBufferSizeExceededException } from '../errors/max-send-buffer-size-exceeded.exception.js';
import { TcpSocket } from './tcp-socket.js';
const DEFAULT_MAX_BUFFER_SIZE = (512 * 1024 * 1024) / 4; // 512 MBs in characters with 4 bytes per character (32-bit)
const DEFAULT_INCOMPLETE_MESSAGE_TIMEOUT = 30_000;
const DEFAULT_MAX_SEND_BUFFER_SIZE = 128 * 1024 * 1024; // 128 MBs in bytes
export class JsonSocket extends TcpSocket {
    contentLength = null;
    buffer = '';
    stringDecoder = new StringDecoder();
    delimiter = '#';
    maxBufferSize;
    incompleteMessageTimeout;
    maxSendBufferSize;
    incompleteMessageTimer = null;
    isBackpressured = false;
    constructor(socket, options) {
        super(socket);
        this.maxBufferSize = options?.maxBufferSize ?? DEFAULT_MAX_BUFFER_SIZE;
        this.incompleteMessageTimeout =
            options?.incompleteMessageTimeout ?? DEFAULT_INCOMPLETE_MESSAGE_TIMEOUT;
        this.maxSendBufferSize =
            options?.maxSendBufferSize ?? DEFAULT_MAX_SEND_BUFFER_SIZE;
        this.socket.on("close" /* TcpEventsMap.CLOSE */, () => this.clearIncompleteMessageTimer());
    }
    handleSend(message, callback) {
        const flushed = this.socket.write(this.formatMessageData(message), 'utf-8', callback);
        // "write" returns false once the outgoing buffer is above the socket's
        // high-water mark. Without honouring it, a peer that issues requests but
        // never reads the responses makes the process buffer every response in
        // memory. Reading is suspended until the peer catches up, which also stops
        // further requests from that peer being turned into more queued responses.
        if (flushed === false) {
            this.applyBackpressure();
        }
        this.assertSendBufferWithinLimit();
    }
    /**
     * Suspending reads bounds a peer that keeps asking for more, but responses
     * to requests already in flight still queue up behind a peer that reads
     * nothing at all. This caps how much may be held for one connection, which
     * mirrors "maxBufferSize" on the receiving side.
     */
    assertSendBufferWithinLimit() {
        const bufferedBytes = this.socket.writableLength;
        if (!this.maxSendBufferSize || !(bufferedBytes > this.maxSendBufferSize)) {
            return;
        }
        this.handleDataError(new MaxSendBufferSizeExceededException(bufferedBytes, this.maxSendBufferSize), { destroy: true });
    }
    handleData(dataRaw) {
        const data = Buffer.isBuffer(dataRaw)
            ? this.stringDecoder.write(dataRaw)
            : dataRaw;
        this.buffer += data;
        try {
            this.processBuffer();
        }
        finally {
            this.refreshIncompleteMessageTimer();
        }
    }
    processBuffer() {
        // Iterative loop replaces recursion to prevent stack overflow on pipelined
        // TCP messages (e.g. many small frames arriving in one read event).
        while (true) {
            // Stop turning buffered frames into responses while the outgoing buffer
            // is backed up. Whatever is left stays in the buffer and is picked up
            // again once the socket drains.
            if (this.isBackpressured) {
                break;
            }
            if (this.buffer.length > this.maxBufferSize) {
                const bufferLength = this.buffer.length;
                this.buffer = '';
                throw new MaxPacketLengthExceededException(bufferLength);
            }
            if (this.contentLength === null) {
                const i = this.buffer.indexOf(this.delimiter);
                /**
                 * Check if the buffer has the delimiter (#),
                 * if not, the end of the buffer string might be in the middle of a content length string
                 */
                if (i === -1) {
                    break;
                }
                const rawContentLength = this.buffer.substring(0, i);
                this.contentLength = parseInt(rawContentLength, 10);
                if (isNaN(this.contentLength)) {
                    this.contentLength = null;
                    this.buffer = '';
                    throw new CorruptedPacketLengthException(rawContentLength);
                }
                this.buffer = this.buffer.substring(i + 1);
            }
            if (this.contentLength !== null) {
                const length = this.buffer.length;
                if (length === this.contentLength) {
                    this.handleMessage(this.buffer);
                    // handleMessage resets contentLength and buffer; next iteration will break
                }
                else if (length > this.contentLength) {
                    const message = this.buffer.substring(0, this.contentLength);
                    const rest = this.buffer.substring(this.contentLength);
                    this.handleMessage(message); // resets this.buffer to ''
                    this.buffer = rest; // restore remaining data for next iteration
                    continue;
                }
                else {
                    // Incomplete message — wait for more data
                    break;
                }
            }
            else {
                break;
            }
        }
    }
    applyBackpressure() {
        if (this.isBackpressured) {
            return;
        }
        this.isBackpressured = true;
        // Reads are paused by us, so the peer cannot make progress on an inbound
        // packet. Resume its idle timeout only after outgoing data has drained.
        this.clearIncompleteMessageTimer();
        this.socket.pause();
        this.socket.once("drain" /* TcpEventsMap.DRAIN */, () => this.releaseBackpressure());
    }
    releaseBackpressure() {
        this.isBackpressured = false;
        this.socket.resume();
        // Frames that arrived before the socket was paused may still be buffered.
        try {
            this.processBuffer();
        }
        catch (e) {
            this.handleDataError(e);
        }
        finally {
            this.refreshIncompleteMessageTimer();
        }
    }
    /**
     * Arms an idle timer whenever a packet is only partially received, and
     * disarms it as soon as the buffer is drained. The timer is refreshed on
     * every read, so it only fires when the peer stops sending mid-packet -
     * a slow but progressing transfer is never interrupted.
     */
    refreshIncompleteMessageTimer() {
        this.clearIncompleteMessageTimer();
        const hasIncompleteMessage = this.buffer.length > 0 || this.contentLength !== null;
        if (this.isBackpressured ||
            !this.incompleteMessageTimeout ||
            !hasIncompleteMessage) {
            return;
        }
        this.incompleteMessageTimer = setTimeout(() => this.handleIncompleteMessageTimeout(), this.incompleteMessageTimeout);
        this.incompleteMessageTimer.unref?.();
    }
    clearIncompleteMessageTimer() {
        if (!this.incompleteMessageTimer) {
            return;
        }
        clearTimeout(this.incompleteMessageTimer);
        this.incompleteMessageTimer = null;
    }
    handleIncompleteMessageTimeout() {
        const bufferedLength = this.buffer.length;
        this.buffer = '';
        this.contentLength = null;
        this.incompleteMessageTimer = null;
        // The peer already stopped talking mid-packet, so do not wait on a FIN.
        this.handleDataError(new IncompleteMessageTimeoutException(bufferedLength, this.incompleteMessageTimeout), { destroy: true });
    }
    handleMessage(message) {
        this.contentLength = null;
        this.buffer = '';
        this.emitMessage(message);
    }
    formatMessageData(message) {
        const messageData = JSON.stringify(message);
        const length = messageData.length;
        const data = length + this.delimiter + messageData;
        return data;
    }
}