Logger: simple, convinient and thread safe logger for Qt applications

[nomiz]

Hi there,

I'm starting the logger in main(). When I'm including <Logger.h> in some class of my application the compiler states:

error: invalid use of incomplete type ‘struct QDebug’
error: forward declaration of ‘struct QDebug’

and I still need to incude <QDebug> as well. Is that normal behaviour?

Thanks!

[cyberbobs]

Please update to the current version of Logger. As of commit "c7d9a27":https://gitorious.org/cutelogger/cutelogger/commit/c7d9a27110b110298fdf42b417b6e0e246fa96af QDebug header is included into Logger.h.

[nomiz]

Nice, works!

[01amit]

How to I destroy this logger object and reinstantiate it without existing the application. Say I have three push buttons (1, 2, 3). I want to instantiate when button 1 is pressed. and use LOG_INFO macro when button 2 is pressed. Flush the data to the file when button 3 is pressed and destroy the object. Re-instantiate the class when button 1 is pressed again without closing the application.
In my application we never exit the application it contoneously runs. I am looking for a way to instantiate the class, use log_info, detroy the object and then reinstantiate.

[cyberbobs]

Well, I definitely need to ask a question here: why do you need to manually instantiate and destroy Logger?

This library is created as singleton without any visible initialization by design. Its main object is automatically created on the first Logger::* static function or macro call. As you can see in "Logger.cpp":https://gitorious.org/cutelogger/cutelogger/blobs/master/src/Logger.cpp the object is automatically destroyed after the application have been closed (using the qAddPostRoutine function).

So, once again: why do you want to do manually the thing that is done automatically? :)

[01amit]

I want to desroy the object when the button is clicked not when the application have been closed.

[aekam]

in which version of Qt i can find these files, <Logger.h> and <ConsoleAppender.h> ??? :-?

[andre]

[quote author="aekam" date="1334749555"]in which version of Qt i can find these files, <Logger.h> and <ConsoleAppender.h> ??? :-?[/quote]
You can't. It's an external project. See the very first post in this topic.

[maxvanceffer]

How about logging size ? I searched in several Qt based logging libs ( QxtLogger, log4qt ..... ) didn't find any functions in it, related to the size of log functionality. So it will be very usefull to see this functionality !

[andre]

I don't understand the question. What do you mean with 'logging size'? Do you want to set some kind of maximum size for the log file output or something like that?

[maxvanceffer]

Yes, for example : maximum log messages ( last 100 messages ) , or maximum log file size.

[maxvanceffer]

I search frew several projects, and no one provide such functionality. Only log4qt, but it hard to understand, and implement.

[andre]

Personally, I think log rotation is a separate task. It seems quite expensive to do something like limiting to the last 100 messages. It means re-writing the entire logfile for each message, as you cannot remove from the start of a file. Adding is trivial though.

[maxvanceffer]

i already tried my self re-writing file and this real complex task, and heavy in time execution... but log can be very fast happend... but what, if i don't need handle a lot of messages ....

[andre]

I have no idea what you just asked. Sorry.

[cyberbobs]

IMO the most correct way to implement a log rotation is to create separate log files for every week/day/hour (choose yours interval) and to automatically remove older logs becoming obsolete. For example, Apache web server logging is organized in such a way. We've implemented that kind of log rotation for one of our projects using Logger some time ago, but I've never published those classes. The problem is I can't share the source because of some licensing restrictions (it was created by another developer working on a commercial project).

Anyone interested in implementing that kind of functionality (and adding it to logger mainstream code) could easily contact me via email or simply post a merge request on gitorious.

[cyberbobs]

Just merged "one important change":https://gitorious.org/cutelogger/cutelogger/merge_requests/2 (thanks goes to Pritam Ghanghas). Now LOG_DEBUG() and other similiar macros supports all the features of qDebug() and could also support the printf-like syntax so we can simply search-and-replace qDebug() with LOG_DEBUG() and QDebug or QtDebug header with Logger.h

Still waiting for your contributions to make Logger more useful :)

[dvolosnykh]

Just wanted to notify the project's maintainers that cutelogger doesn't compile using Qt 5 Beta2 with deprecated API turned off by default: qInstallMsgHandler() has become deprecated.

[cyberbobs]

Ok, thank you for notification. Currently there is only one project maintainer and I don't have much time for now to implement and support the Qt 5.0.0 compatibility of the project.

Taking a quick look through the Qt 5 beta2 headers I've noticed there is a lot of work to be done refactoring the Logger to take advantage of the extended Qt 5 logging abilities. If anyone is willing to implement Qt 5 compatibility and post it as a merge request on Gitorious the contribution will be kindly accepted :)

[cyberbobs]

Pushed "e3c2745":https://gitorious.org/cutelogger/cutelogger/commit/e3c2745c6c5f38896f87472e01ea2caf2d9e211b. Now Logger successfully builds with Qt 5 and uses some of its advanced logging feature (e.g. file/line/function name gathered in renewed qDebug and the same macros).

Still some work to be done to support "log categories":https://codereview.qt-project.org/#change,13226 and new Qt log formatting feature in a ConsoleAppender.