typescript 45 lines · 8 steps

Manual RabbitMQ acks in a NestJS controller

A NestJS microservice controller that handles RPC messages over RabbitMQ and acknowledges them by hand.

Explained by highlit
NestJS Intermediate microservices message-queue acknowledgement error-handling rpc
1import { Controller } from '@nestjs/common';
2import {
3 MessagePattern,
4 Payload,
5 Ctx,
6 RmqContext,
7 RpcException,
8} from '@nestjs/microservices';
9import { OrdersService } from './orders.service';
10import { CreateOrderDto } from './dto/create-order.dto';
11 
12@Controller()
13export class OrdersController {
14 constructor(private readonly ordersService: OrdersService) {}
15 
16 @MessagePattern({ cmd: 'create_order' })
17 async createOrder(
18 @Payload() dto: CreateOrderDto,
19 @Ctx() context: RmqContext,
20 ) {
21 const channel = context.getChannelRef();
22 const originalMsg = context.getMessage();
23 
24 try {
25 const order = await this.ordersService.create(dto);
26 channel.ack(originalMsg);
27 return { id: order.id, status: order.status, total: order.total };
28 } catch (err) {
29 channel.nack(originalMsg, false, false);
30 throw new RpcException({
31 code: 'ORDER_CREATION_FAILED',
32 message: err instanceof Error ? err.message : 'Unknown error',
33 });
34 }
35 }
36 
37 @MessagePattern({ cmd: 'get_order' })
38 async getOrder(@Payload('id') id: string) {
39 const order = await this.ordersService.findById(id);
40 if (!order) {
41 throw new RpcException({ code: 'NOT_FOUND', message: `Order ${id} not found` });
42 }
43 return order;
44 }
45}
01 / 01
STEP 01

Walkthrough

Space play ←→ step click any line
Three takeaways
  1. 1Manual acknowledgement lets you commit or reject a message only after your business logic succeeds or fails.
  2. 2Nacking with requeue set to false routes poison messages to a dead-letter queue instead of looping forever.
  3. 3RpcException carries structured error data back to the caller across the microservice transport.

Related explainers

rust 
use std::convert::TryFrom;
 
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum HttpStatus {

Converting HTTP codes with TryFrom in Rust

enums error-handling trait-implementation
Intermediate 8 steps
typescript 
type LazyImageOptions = {
  rootMargin?: string;
  loadedClass?: string;
};

Lazy-loading images with IntersectionObserver

intersectionobserver lazy-loading performance
Intermediate 7 steps
typescript 
type DeepPartial<T> = T extends object
  ? { [K in keyof T]?: DeepPartial<T[K]> }
  : T;
 

Type-safe deep merge in TypeScript

recursion conditional-types mapped-types
Advanced 7 steps
typescript 
type CurrencyFormatOptions = {
  locale?: string;
  currency: string;
  showDecimals?: boolean;

Caching Intl.NumberFormat for currency

memoization internationalization caching
Intermediate 9 steps
rust 
use chrono::NaiveDate;
use serde::{Deserialize, Deserializer};
 
#[derive(Debug, Deserialize)]

Custom date parsing with serde in Rust

serde deserialization csv-parsing
Intermediate 7 steps
python 
import uuid
from pathlib import Path
 
from fastapi import APIRouter, File, Form, HTTPException, UploadFile

Handling multipart file uploads in FastAPI

file-upload validation multipart-form
Intermediate 6 steps

Share this explainer

Here's the card — post it anywhere.

Manual RabbitMQ acks in a NestJS controller — share card
Made with highlit — turn any snippet into a walkthrough like this in about a minute.
Explain your code