[Question] Enable/disable on runtime for Node.js

[moehlone]

Hi,

is there a way to enable or disable debugging for modules on runtime (Node.js)?

Best regards
Philipp

[360disrupt]

I'm not sure if I understood your question. But you could modify the env. variable in the code e.g.
process.env.DEBUG="error*,-fatal"

If you listen for console inputs than you could modify it from your console:

 process.stdin.on "data", (command) ->
        command = command.toString().trim()
        console.log "now displaying:  ",command
        process.env.DEBUG = command

[moehlone]

I think that this wont be enough, because the logging mechanism is initialized on first require with environment variable DEBUG. Lets say I want to modify the namespace on different HTTP-Requests within my routes, when a special header value was set:

Request-Header:
x-some-debug: "express*, error*"

function getSomething(req, res) {
    process.env.DEBUG = req.headers["x-some-debug"];
    // log everything with express* and error*
    // ...
    process.env.DEBUG = "";
    // restore anything to default after request finished..
    res.send("Hello!");
}

Assignment to process.env.DEBUG was only for example.. Is there any way to change or reinitialize these values during runtime?

[DoumanAsh]

The work around you can try is to clean require cache?
Normally it is available through require.cache[moduleName]

P.s. if you take a look at source code https://github.com/visionmedia/debug/blob/master/src/node.js#L241

[moehlone]

@DoumanAsh: might work, but no solution for me.. thank you anyway.

[DoumanAsh]

@moehlone I linked in my PS how debug inits logging on first import.
I think method enable should be exported and you can do it by yourself anytime you want like debug.enable(process.env.DEBUG)

[geonanorch]

@moehlone it sounds like we have similar needs: I want to be able to dynamically (through some kind of listener, e.g. file watching or socket) change the debug settings.
Until now the debug module does not keep track of its offspring, but a small change in src/debug.js fixes that, here a diff -n:

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;
      });
  }

you can then alter dynamically debug settings by passing the same value as in the DEBUG environment variable:

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

For listeners I am thinking to use file watching, found an example with pinojs/pino-arborsculpture

And by the way I recommend pinojs/pino-debug, it is compatible wiith debug (including the change I described above) and reportedly much faster.

I have raised issue #433 in the hope to get the above code change (or similar) integrated.

[moehlone]

@geonanorch thank you - this is what we thought about. I think #433 is enough and we can close this one.

[manjeshpv]

Enable/Disable Dynamically runtime easily using https://gist.github.com/manjeshpv/106dc2e05d4b9f252dc9f3f41afccb59