pino loses log entries on process.exit()

Question

When my program shuts down via process.exit() (maybe also by some signal), pino loses some log entries because it is not properly flushing them.

Triggering a manual flush does not help.

I am using pino 6.2.0.

How can I prevent log entries from getting lost?

const pino = require("pino");

const p = pino();

process.on("exit", () => {
    console.log("FLUSH");
    p.flush();
});

p.info("A"); // logged
p.info("B"); // NOT logged

process.exit(1);

Back story:
I was missing some dependencies in my NestJS module and configured NestJS to use my pino logger wrapper like this:

const app = await NestFactory.create<NestExpressApplication>(AppModule, {
    logger: new PinoLoggerService(),
});

NestJS was just exiting (using process.exit()) without telling me what was wrong. Removing the logger option made NestJS print the offending module in all details.

Answer 1

Searching the net yielded a comment on a GitHub issue Pino 5.8.1 fails to flush log on process exit with a similar problem where GitHub user brandondoran pointed out the solution:

Use pino.destination() which will use synchronous writes unless you disable them, no explicit flushing needed.

Note that this will likely slow down your logging.

const pino = require("pino");

const p = pino({}, pino.destination());

p.info("A"); // logged
p.info("B"); // logged as well

process.exit(1);