Some code not executed in production build in Next 14

[jira-zz]

Link to the code that reproduces this issue

https://github.com/jira-zz/next-logging-test

To Reproduce

1. Build the app in prod - next build
2. Run the app - node .next/standalone/server.js
3. Access the home page - localhost:3000

Current vs. Expected behavior

tady1
tady2

should be printed to console

only

tady1

is.

But it is not just console.log. For example, writing to a file is also skipped, logging with winston and other.

Provide environment information

Operating System:
  Platform: linux
  Arch: x64
  Version: #1 SMP Thu Jan 11 04:09:03 UTC 2024
  Available memory (MB): 7759
  Available CPU cores: 16
Binaries:
  Node: 22.6.0
  npm: 10.8.2
  Yarn: N/A
  pnpm: N/A
Relevant Packages:
  next: 14.2.11 // Latest available version is detected (14.2.11).
  eslint-config-next: 14.2.9
  react: 18.3.1
  react-dom: 18.3.1
  typescript: 5.6.2
Next.js Config:
  output: standalone

Which area(s) are affected? (Select all that apply)

Pages Router, Runtime

Which stage(s) are affected? (Select all that apply)

next build (local), next start (local), Other (Deployed)

Additional context

Happens with production build on my local machine, also when deployed in docker container.
The issue seems to be in production build.
I have an app that works in dev but fails in production. At first, I tried to debug it by throwing in some log statements, and then I found they are not executed.

Downgrading to next 13 fixes the issue.

The function in question is called from server component.

[samcx]

@jira-zz This actually happens regardless of using output: standalone.

When you build your project, we're collecting Page data and generating static pages.

70150-logging-test [main] p build && p start

> [email protected] build .../Vercel Next.js/70150-logging-test
> next build

  ▲ Next.js 15.0.0-canary.159

   Creating an optimized production build ...
 ✓ Compiled successfully
 ✓ Linting and checking validity of types
   Collecting page data  .tady1
 ✓ Collecting page data
   Generating static pages (0/5)  [=   ]tady1
tady2
 ✓ Generating static pages (5/5)
 ✓ Collecting build traces
 ✓ Finalizing page optimization

Route (app)                              Size     First Load JS
┌ ○ /                                    138 B          97.4 kB
└ ○ /_not-found                          894 B          98.2 kB
+ First Load JS shared by all            97.3 kB
  ├ chunks/70d2848c-d777040b18d752c2.js  52.9 kB
  ├ chunks/8-30040b63e733d969.js         42.6 kB
  └ other shared chunks (total)          1.85 kB


○  (Static)  prerendered as static content


> [email protected] start .../Vercel Next.js/70150-logging-test
> next start

  ▲ Next.js 15.0.0-canary.159
  - Local:        http://localhost:3000

 ✓ Starting...
 ✓ Ready in 152ms
tady1

Since your Index page is rendered statically, the result of getData() is cached, and the inner console.log doesn't get ran again (it only ran once during the build).

In Development, we always render pages on-demand, so users don't have to wait for, e.g., revalidation periods.

[jira-zz]

Thanks for the reply.
In my situation, the function fetches data from db. The result can obviously vary. How do I handle such situation?
Sorry if this is a dumb question.

[samcx]

@jira-zz You can force it to be dynamic → https://nextjs.org/docs/app/api-reference/file-conventions/route-segment-config#dynamic.

export const dynamic = 'force-dynamic'

Or, you can add a revalidate if you don't want it to request new data every time → https://nextjs.org/docs/app/api-reference/file-conventions/route-segment-config#revalidate.

export const revalidate = 10