Instrumentation
If you export a function named register
from a instrumentation.ts
(or .js
) file in the root directory of your project (or inside the src
folder if using one), we will call that function whenever a new Next.js server instance is bootstrapped.
Good to know
- This feature is experimental. To use it, you must explicitly opt in by defining
experimental.instrumentationHook = true;
in yournext.config.js
.- The
instrumentation
file should be in the root of your project and not inside theapp
orpages
directory. If you're using thesrc
folder, then place the file insidesrc
alongsidepages
andapp
.- If you use the
pageExtensions
config option to add a suffix, you will also need to update theinstrumentation
filename to match.- We have created a basic with-opentelemetry example that you can use.
When your register
function is deployed, it will be called on each cold boot (but exactly once in each environment).
Sometimes, it may be useful to import a file in your code because of the side effects it will cause. For example, you might import a file that defines a set of global variables, but never explicitly use the imported file in your code. You would still have access to the global variables the package has declared.
You can import files with side effects in instrumentation.ts
, which you might want to use in your register
function as demonstrated in the following example:
import { init } from 'package-init'
export function register() {
init()
}
However, we recommend importing files with side effects using import
from within your register
function instead. The following example demonstrates a basic usage of import
in a register
function:
export async function register() {
await import('package-with-side-effect')
}
By doing this, you can colocate all of your side effects in one place in your code, and avoid any unintended consequences from importing files.
We call register
in all environments, so it's necessary to conditionally import any code that doesn't support both edge
and nodejs
. You can use the environment variable NEXT_RUNTIME
to get the current environment. Importing an environment-specific code would look like this:
export async function register() {
if (process.env.NEXT_RUNTIME === 'nodejs') {
await import('./instrumentation-node')
}
if (process.env.NEXT_RUNTIME === 'edge') {
await import('./instrumentation-edge')
}
}
Was this helpful?