[Feature] enable/disable debugging dynamically

Often when one is investigating a ‘live’ issue, one would rather not restart node to enable debugging: this might make the problem disappear until it is triggered again later. Instead debug configuration should be alterable dynamically through some kind of listener (e.g. file watch, socket –the implementation of the listener is not the purpose of this issue, though that would make a nice addition!).

Support for such dynamic changes would be easy to add in debug.js, here the output of diff -n for the current codebase:

a21 1
exports._debuggers = Object.create(null);
a126 1
  exports._debuggers[namespace] = debug;
a155 10
  for (const namespace in exports._debuggers) {
      exports._debuggers[namespace].enabled = false;
      exports.names.some( (pattern) => {
          const match = pattern.test(namespace);
          if (match) {
              exports._debuggers[namespace].enabled = true;
          }
          return match;
      });
  }

With above one can change the debug settings from any place in the code using the same values as passed through the DEBUG environment variable at initialization time:

const debugCore = require('debug');
debugCore.enable('mymod*');

See also issue #419 (and possibly #416 and #425).

[geonanorch]

Thanks, will do! Initial feedback in the meantime:

• unless I missed it in README.md, the feature is not documented
• the feature is not listed under the release notes for 3.0.0

All the same, thank you for considering and implementing my request 😃

[Qix-]

@tasoss No, as that is a limitation of the operating system. You cannot change an environment variable from outside a process.