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maintaining-single-executable-application-support.md

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Maintaining Single Executable Applications support

Support for single executable applications is one of the key technical priorities identified for the success of Node.js.

High level strategy

From the Next-10 discussions there are 2 approaches the project believes are important to support:

Compile with Node.js into executable

This is the approach followed by boxednode.

No additional code within the Node.js project is needed to support the option of compiling a bundled application along with Node.js into a single executable application.

Bundle into existing Node.js executable

This is the approach followed by pkg.

The project does not plan to provide the complete solution but instead the key elements which are required in the Node.js executable in order to enable bundling with the pre-built Node.js binaries. This includes:

  • Looking for a segment within the executable that holds bundled code.
  • Running the bundled code when such a segment is found.

It is left up to external tools/solutions to:

  • Bundle code into a single script.
  • Generate a command line with appropriate options.
  • Add a segment to an existing Node.js executable which contains the command line and appropriate headers.
  • Re-generate or removing signatures on the resulting executable
  • Provide a virtual file system, and hooking it in if needed to support native modules or reading file contents.

However, the project also maintains a separate tool, postject, for injecting arbitrary read-only resources into the binary such as those needed for bundling the application into the runtime.

Planning

Planning for this feature takes place in the single-executable repository.

Upcoming features

Currently, only running a single embedded CommonJS file is supported but support for the following features are in the list of work we'd like to get to:

  • Running an embedded ESM file.
  • Running an archive of multiple files.
  • Embedding Node.js CLI options into the binary.
  • XCOFF executable format.
  • Run tests on Alpine Linux.
  • Run tests on s390x Linux.
  • Run tests on ppc64 Linux.

Disabling single executable application support

To disable single executable application support, build Node.js with the --disable-single-executable-application configuration option.

Implementation

When built with single executable application support, the Node.js process uses postject-api.h to check if the NODE_JS_CODE section exists in the binary. If it is found, it passes the buffer to single_executable_application.js, which executes the contents of the embedded script.