NestJS Datadog Trace

Install

npm i @nestpro/dd-trace

Setup

1. Create tracing file (tracing.ts):

   import DataDogTrace from 'dd-trace';
      
   const tracer = DataDogTrace.init({
     logInjection: true,
   });
      
   export { tracer };

   Use already initialized DataDog tracer instance

2. Import the tracing file:

   import './tracing';
   import { NestFactory } from '@nestjs/core';
   import { AppModule } from './app.module';
   import { Logger as PinoLogger } from 'nestjs-pino';
   import { Logger } from '@nestjs/common';
   
   async function bootstrap() {
     const app = await NestFactory.create(AppModule, { bufferLogs: true });
     app.useLogger(app.get(PinoLogger));
   
     const logger = new Logger('main');
     const port = process.env.PORT || 3000;
     await app.listen(3000).then(() => {
       logger.log(`Listening on port: ${port}`);
     });
   }
   bootstrap();

   Use APP_ prefix for your application configuration environment variables.

3. Add LoggerModule and DatadogModule to AppModule:

   import { Module } from '@nestjs/common';
   import { LoggerModule } from 'nestjs-pino';
   import { DatadogTraceModule } from 'nestjs-ddtrace';
   
   @Module({
     imports: [
       LoggerModule.forRoot({
         pinoHttp: {
           level: process.env.APP_ENV !== 'prod' ? 'trace' : 'info'
         },
         exclude: [{ method: RequestMethod.ALL, path: 'health' }], // if you have /health path, exclude it from logs
       }), 
       DatadogTraceModule.forRoot({
         controllers: true,
         providers: true
       })
     ],
   })
   export class AppModule {}

Span Decorator

If you need, you can define a custom Tracing Span for a method or class. It works async or sync. Span takes its name from the parameter; but by default, it is the same as the method's name.

import { DatadogTraceModule } from 'nestjs-ddtrace';

@Module({
  imports: [DatadogTraceModule.forRoot()],
})

export class AppModule {}

Tracing Service

In case you need to access native span methods for special logics in the method block:

import { Span, TraceService } from 'nestjs-ddtrace';

@Injectable()
export class BookService {
  constructor(private readonly traceService: TraceService) {}

  @Span()
  async getBooks() {
    const currentSpan = this.traceService.getActiveSpan(); // --> retrives current span, comes from http or @Span
    await this.doSomething();
    currentSpan.addTags({
      'getBooks': 'true'
    });

    const childSpan = this.traceService.getTracer().startSpan('ms', {childOf: currentSpan});
    childSpan.setTag('userId', 1);
    await this.doSomethingElse();
    childSpan.finish(); // new span ends

    try {
      doSomething();
    } catch (e) {
      currentSpan.setTag('error', e);
      throw e;
    }
    return [`Harry Potter and the Philosopher's Stone`];
  }
}

import { Span } from 'nestjs-ddtrace';

@Injectable()
@Span()
export class BookService {
  async getBooks() { /* ... */ }
  async deleteBook(id: string) { /* ... */ }
}

@Controller()
@Span()
export class HelloController {
  @Get('/books')
  getBooks() { /* ... */ }

  @Delete('/books/:id')
  deleteBooks() { /* ... */ }
}

Miscellaneous

Inspired by the nestjs-otel and nestjs-opentelemetry repository.