Pino logger does not output JSON within NextJS middleware function

[pawelgalazka]

I was planning to use Pino logger within NextJS middleware function:

pages/_middleware.ts

import { NextFetchEvent, NextRequest, NextResponse } from "next/server"
import pino from "pino"

const logger = pino()

export function middleware(req: NextRequest, ev: NextFetchEvent) {
  logger.info("Pino log from middleware")
  return NextResponse.next()
}

Then when I run next dev and request the page, log in no JSON format is printed out:

Pino log from middleware

Weirdly when I use the same logging within any page component:

const logger = pino()

const Home: NextPage = () => {
  logger.info("Pino log from page component")
  return (<div>Test</div>)
})

export default Home

Pino logs in JSON format:

{"level":30,"time":1643780601305,"pid":26203,"hostname":"xxxx.local","msg":"Pino log from page component"}

Not sure what's going. Does NextJS somehow reformat output coming out from middleware functions? 🤔 The same happens for production build with NODE_ENV=production.

[heschong]

I have a similar issue, but ours is pretty-printing JSON and it's driving me crazy:

logger.info({ foo: 'bar', dogs: 'cats' })

comes out as

{
  foo: 'bar',
  dogs: 'cats'
}

(which is not even technically JSON, it's just a pretty-printed js object) and it's kind of driving me crazy. Anyone know how to turn this off?

[icyJoseph]

Having the same issue, in our case Data Dog consumes each line as new log message.

[icyJoseph]

We've landed on something that looks like this:

const logger = pino({
  browser: {
    write(obj) {
      try {
        console.log(JSON.stringify(obj));
      } catch (err) {
        if (err instanceof Error) {
          // Without a `replacer` argument, stringify on Error results in `{}`
          console.log(JSON.stringify(err, ["name", "message", "stack"]));
        } else {
          console.log(JSON.stringify({ message: "Unknown error type" }));
        }
      }
    }
  }
});

Using this while we wait on an alternative.

The problem is that the browser version of pino is being packaged into the _middleware, so we need to tell this version that we want to serialize the output, however, for some reason serialize: true is not working for us, so we use the write option. Since JSON.stringify, is rather resilient (throws only for cycles and BigInt), this patch works swell for now.

[andrewfritz86]

Thanks. This is driving me insane as I am simply trying to log some basic request info to DD in Middleware, and it's taking every newline separated value as a distinct logging message.

[AkshayKumar007]

Having the same issue while using pino logger in middleware, but I'm trying to output the log in server.

[dejanvasic85]

Thanks @icyJoseph that worked...

[AkshayKumar007]

Having the same issue while using pino logger in middleware, but I'm trying to output the log in server.

[ttristan]

Same issue here. I ended up writing a small wrapper to JSON stringify the error and add a level and time to the Log output.
Moreover though, I can not get the Elastic Search Logger to work because I get this error during build:

Dynamic Code Evaluation (e. g. 'eval', 'new Function', 'WebAssembly.compile') not allowed in Middleware src/middleware

[trentonsnyder]

I think this is because the elastic transport uses fast-json-stringify
https://github.com/fastify/fast-json-stringify/blob/master/index.js#L166

[raman-zherdzeu]

Any updates on this issue? I am having the same problem: none of the logs created in my NextJS middlleware are formatted as JSON. Pino-pretty is not working as well. 😢

[icyJoseph]

You can try to import pino from pino/browser, though TS might get angry, though I find it suspicious that the call to require works, but I guess, you are not allowed to call it within the middleware top level.

import { NextResponse } from "next/server";
import pino from "pino/browser";

const logger = pino({ browser: { asObject: true } });

export default async function middleware(req) {
  const { pathname } = req.nextUrl;

  logger.info({ pathname }, "hello from middleware");

  return NextResponse.next();
}

[groves]

I wasn't able to get this to work with import pino from "pino/browser";, but I was still able to configure pino's browser mode to log objects using import pino from "pino";:

import { NextResponse } from "next/server";
import type { NextRequest } from "next/server";
import pino from "pino";

const log = pino({ browser: { asObject: true } });

export function middleware(request: NextRequest) {
  log.info({ pathname: request.nextUrl.pathname }, "hey");
  return NextResponse.next();
}

[jackliu5]

How is everyone using pino from the middleware at all? I get the You're using a Node.js module (vm) which is not supported in the Edge Runtime. because pino is using fast-redact for redaction which uses the vm module.

[tlenex]

    if (isServer && nextRuntime === 'edge') {
      // pino's dependencies use native node apis,
      // which are not available in the edge runtime,
      // so we're using the browser version of pino here
      // see https://nextjs.org/docs/app/api-reference/edge#unsupported-apis
      config.resolve.alias['pino'] = 'pino/browser.js'
    }

well this kinda does the trick

[myriky]

how about this one?

pino({
  browser: {
    write: (o) => console.log(JSON.stringify(o)),
  },
}).info('Pino info log from middleware');

pino({
  browser: {
    write: (o) => console.log(JSON.stringify(o)),
  },
}).error('Pino error log from middleware');

pino({
  browser: {
    write: (o) => console.log(JSON.stringify(o)),
  },
}).fatal('Pino fatal log from middleware');

const logger = pino({
  browser: {
    write: (o) => console.log(JSON.stringify(o)),
  },
});

logger.child({ '1': '2', '3': '4' }).info('Pino info log from middleware');

[theDanielJLewis]

How are you implementing that code in your middleware? Do you include the full pino code block for your needs, or did you put this in your logger function file?

[sdelano]

To add some context here, the NextJS middleware runs in the edge runtime, which effects more than just pino: #54549

[theDanielJLewis]

Has anyone tested this in Next.js 14?

[Bernix01]

Yes, with next-auth and prisma log keeps behaving weird using this works. As described by @myriky previously

how about this one?

pino({
  browser: {
    write: (o) => console.log(JSON.stringify(o)),
  },
}).info('Pino info log from middleware');

pino({
  browser: {
    write: (o) => console.log(JSON.stringify(o)),
  },
}).error('Pino error log from middleware');

pino({
  browser: {
    write: (o) => console.log(JSON.stringify(o)),
  },
}).fatal('Pino fatal log from middleware');

const logger = pino({
  browser: {
    write: (o) => console.log(JSON.stringify(o)),
  },
});

logger.child({ '1': '2', '3': '4' }).info('Pino info log from middleware');