Allow debug logging that can be enabled / disabled

[max-nextcloud]

Use case

In the text app we sometimes need very detailed logging. Think several lines of debug logging per keystroke.

Currently we have some logging statements commented out that we enable then.
But if they were always enabled that would spam the logs too much.

Would be nice to have this build into the logger.

Possible interface

// ExampleService.ts in the text app
const logger = getLoggerBuilder().setApp('text')... .build()
const debug = logger.createOptionalDebugLogger('ExampleService')
...
service.on('update', (update) => debug('received update', { update }))

Usage in the Browser console:

OCA.Logger.debug.text.ExampleService = true

Populating OCA.Logger.debug when the optional debug logger is created would enable auto completion on the browser command line.

[susnux]

What is the problem with using logger.debug? That log level is only emitted to the console if debug => true is set in the Nextcloud config.php

[ShGKme]

I think the problem is having extremely debug logging. That floods the log so much that makes the long almost unusable for other apps.

In this case having a runtime flag allows enabling it only in specific cases when really needed.

[ShGKme]

Alternative proposal: make optional logger still a complete logger with the same interface.

const logger = getLoggerBuilder().setApp('text').build() // instanceof Logger
const exampleServiceLogger = logger.createOptionalLogger('ExampleService') // instanceof Logger

// ...
service.on('update', (update) => exampleServiceLogger.debug('received update', { update }))

[susnux]

I think the problem is having extremely debug logging. That floods the log so much that makes the long almost unusable for other apps.

Sure but normally you only debug in one app, no?

---

Maybe we should then have a new level TRACE which will only be enabled if set on runtime?

[max-nextcloud]

Sure but normally you only debug in one app, no?

So how would you enable debug logging for that one app?

In my dev environment ( based on https://github.com/juliusknorr/nextcloud-docker-dev ) debug logging is always enabled. I think it's because window._oc_debug is true. So I get to see all the debug logging for all the apps.

I was also pondering setting the loggers default log level to something like

OCA.Text.enableDebugLogs ? LogLevel.Debug : window._oc_config?.loglevel ?? LogLevel.Warn

But even there I think it would be nice if we'd have a shared solution so this is possible for all apps.

The more I think about this the more I feel like being able to enable / disable debug logging per app would work for what I am trying to do. That seems simpler than both having a different logger or a TRACE level.

[susnux]

@max-nextcloud so that I understand the requirements correctly:

• You only want to enable debug per app
• Setting should be independent from the frontend log level configured in Nextcloud ( see https://docs.nextcloud.com/server/latest/admin_manual/configuration_server/config_sample_php_parameters.html#loglevel-frontend )

Because currently the logger takes the frontend loglevel and if not set it takes the normal Nextcloud log level. Which can be overridden by setting debug => true in config.php so that window._oc_debug is true and the logger uses debug output.

[max-nextcloud]

Here's the changes I think I would like:

1. The logger uses the specified log levels as you described without debug logging on window._oc_debug.
2. It's possible to enable debug logging per app ideally from the browser console when needed.

About 1. - I am checking with Julius, why debug is set to true in the dev environment by default. I think there may be a number of reasons. Right now it's not possible to have that setting without turning the frontend log level to debug. If we did not take into account window._oc_debug one could choose the server debug setting and the frontend log level independently.

About 2. - we sometimes run into issues even in production where it would be nice to have ad hoc debug logging. Without firing up a dev instance and without recompiling.

[max-nextcloud]

Checked with @juliusknorr why debug is true in the dev environment.

It's sometimes helpful for example because you can navigate dav endpoints in the browser.

So it's quite unrelated to the log level.

Is there any reason to force the log level to debug if debug is true in config.php?

[ShGKme]

Sure but normally you only debug in one app, no?

It doesn't matter, because I see a log for all the apps. And if a single app is flooding the log, I cannot debug another app without additional filtering.

And it can also be not "one app", but "a feature in the app". The ExampleService is not an app, but a service in the Text app in the example above.

I can imagine having many low-level debugs, like:

• Networking with something real-time (Text CRDT, Talk signalling, Talk chat history, Talk chat scrolling)
• Complex UI from app specific like Talk chat scrolling to a UI component
• Performance benchmarking

[ShGKme]

And yes, having the flags on the client helps, because you sometimes need to debug a single client, but it doesn't mean you want to flood every user's log.

[ShGKme]

We already had something similar in Talk, when we enable/disable features/logging via runtime feature flags.

[ShGKme]

Also a good example, but in a different way (via ENV as it is for node.js)
https://www.npmjs.com/package/debug

[max-nextcloud]

The logger uses the specified log levels as you described without debug logging on window._oc_debug.

I opened #906 which would address this. So if this needs further discussion it can happen on the PR.