late code injection #37440

Is your feature request related to a problem? Please describe.

Currently, a node process cannot receive and execute custom code after it has started. For monitoring tools, a common use case is to be able to attach to an arbitrary process, inject a (tracing) code, instruct the runtime to execute that, and optionally detach from the process.

Describe the solution you'd like

• define a mechanism to interrupt the runtime (signals in platforms where supported)
• specify a Javascript interface for the code injection:
  • the signal is delegated to a Javascript handler function
  • a module with a predefined name (such as agent) is loaded
  • a function with a predefined name (such as execute) is executed
  • a user can define this module and place it in the search path, prior to signalling
  • upon completion, the module is unloaded
• define security restrictions (only requests from matching UID / GID allowed)

Describe alternatives you've considered

• modify the application and integrate with the monitoring tools
• define a specific function in the application that receives code at runtime