nslog is a structured logger for NestJS. In production, you can output logs in JSON format, making it compatible with services like Cloud Logging. In local development, you can output logs in a color-coded format in the terminal for easy viewing.
npm install --save @ubie/nslog
import { NestFactory } from "@nestjs/core";
import { StructuredLogger } from "@ubie/nslog";
async function bootstrap() {
const app = await NestFactory.create(AppModule, { bufferLogs: true });
app.useLogger(new StructuredLogger({ logLevel: "debug", format: "json" }));
await app.listen(3000);
}import { Logger, Injectable } from "@nestjs/common";
@Injectable()
class MyService {
private readonly logger = new Logger(MyService.name);
doSomething() {
this.logger.log("Doing something...");
}
}see also: https://docs.nestjs.com/techniques/logger
If you have common parameters that you want to output in all logs, you can override the printMessage.
import { Injectable } from "@nestjs/common";
import {
PrintMessageArgs,
StructuredLogger,
StructuredLoggerOptions,
} from "./structured-logger";
@Injectable()
class MyLogger extends StructuredLogger {
protected printMessage(args: PrintMessageArgs): void {
args.params.push({ requestId: getRequestId() });
super.printMessage(args);
}
}Passing an Error object to logger.error is handled specially.
const new Error("something went wrong");
logger.error(err);This will be output as follows.
{
"severity": "ERROR",
"message": "something went wrong",
"stack_trace": "Error: something went wrong\n at Object.<anonymous> (/path/to/app.js:1:13)\n at Module._compile (node:internal/modules/cjs/loader:1376:14)\n at Module._extensions..js (node:internal/modules/cjs/loader:1435:10)\n at Module.load (node:internal/modules/cjs/loader:1207:32)\n at Module._load (node:internal/modules/cjs/loader:1023:12)\n at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:135:12)\n at node:internal/main/run_main_module:28:49"
}