How can I require a custom module in an n8n Docker setup?

Below is an explanation of what’s happening and what you can do:

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What’s Happening

• When your Code node runs, it executes in the context of n8n’s built-in nodes (the working directory is something like
  /usr/local/lib/node_modules/n8n/node_modules/n8n-nodes-base/dist/nodes).
• Although you see that your custom module exists at /home/node/modules/test/TestNode.node.js (and an fs.existsSync check confirms that), the Code node isn’t automatically set up to resolve modules from an arbitrary location on disk.

• Even though you’ve set environment variables to allow external imports (NODE_FUNCTION_ALLOW_EXTERNAL, NODE_FUNCTION_ALLOW_BUILTIN), the module resolution in the Code node still relies on Node’s default lookup paths. In your case, require is not “seeing” the file at /home/node/modules because it’s not in the standard resolution paths.

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Why It Fails

• The __dirname in the Code node points to the internal location of n8n’s base nodes.
• Your call to path.resolve() returns /home/node because that’s the home directory of the node user, but when you try to require an absolute path ("/home/node/modules/test/TestNode.node.js"), Node doesn’t find it in its module resolution cache because the file isn’t installed as a module in a standard location.

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What Can You Do?

1. Install as a Custom n8n Node Module:
   The recommended approach in n8n for using custom code is to package it as an npm module (following the naming convention starting with n8n-nodes-) and install it alongside n8n. This way, n8n will load your node automatically on startup. See the Install private nodes guide for Docker setups.

2. Adjust Your Module Resolution:
   If you must load files via require from a fixed directory:

   • Make sure to use an absolute path. Even though your code shows that the file exists, you might need to verify that the absolute path you are constructing is identical to what Node expects.
   • Instead of relying on __dirname (which points to the n8n base node folder), consider using a different base, for example using process.cwd() (which in your Docker container should be /home/node if you set WORKDIR properly).

   For example:

   JSCopied
   const basePath = process.cwd(); // should be /home/node in your container
   const modulePath = require('path').resolve(basePath, 'modules/test/TestNode.node.js');
   console.log('modulePath:', modulePath);
   const TestNode = require(modulePath);

3. Review Docker Mounts and Working Directory:
   Verify that your Docker volumes and WORKDIR settings ensure that /home/node/modules is available and that process.cwd() or any other path you build correctly points to that location.

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Summary

Because n8n’s Code node runs in a sandboxed context with its own location as __dirname, directly requiring a file from /home/node isn’t in the default module lookup paths. The best practices are either to package your custom code as a dedicated n8n node module (so that it gets loaded during startup) or adjust your code to use the container’s working directory (via process.cwd()) to construct the absolute path for require.

This approach should help avoid the “Cannot find module” error when trying to import your user code.