Truncating/Deleting log files while logging application is running

[damien-sorin]

Hi,

within our windows application there is a debug logging mode which generates quite a lot of log output.

If this mode is active it would be nice to occasionally truncate or delete the log file(s) without stopping and restarting application.

This would be very helpful when "debugging" the application on systems of the application user (without development environment).

Would it be possible to implement a configuration key like "non-exclusive" for the file logger, as the FileShareMode is currently hard coded as FileShare.Read without sharing write and delete operations.

For compatibility reason this option could be defaulting to the current behavior, of course.

[VitaliyMF]

If this mode is active it would be nice to occasionally truncate or delete the log file(s) without stopping and restarting application.

For this purpose you can use rolling file feature, it has several modes so you can choose which one is more suitable exactly for your app.

Would it be possible to implement a configuration key like "non-exclusive" for the file logger, as the FileShareMode is currently hard coded as FileShare.Read without sharing write and delete operations.

FileShare.Read allows other processes to open active log file for 'read'; it is a bit unclear how log file can work in FileShare.ReadWrite mode, most likely you'll not able to achieve what you want by opening active log file for 'write' (and do what?..).

[damien-sorin]

Hi, thanks for your quick answer!

For this purpose you can use rolling file feature, it has several modes so you can choose which one is more suitable exactly for your app.

We know about the rolling feature - sorry for this misunderstanding.

The use case is not to roll the log based on time or file size, but to truncate it to size 0 on an event manually observed while using the application and running into an error on a live system.

for example with this command line

copy /Y nul: logfile.log

or by some code in our application of course.

FileShare.Read allows other processes to open active log file for 'read'; it is a bit unclear how log file can work in FileShare.ReadWrite mode, most likely you'll not able to achieve what you want by opening active log file for 'write' (and do what?..).

Yeah, I know what you mean. But if you know what you are doing an opt-in configuration would enable it if you need it. To be honest, I have seen many loggers not restricting concurrent write or delete operations (or probably just don't keep the file open while not writing into it) without any problems.

It would help devops to do service for their customers ;-)

[VitaliyMF]

But if you know what you are doing an opt-in configuration would enable it if you need it. To be honest, I have seen many loggers not restricting concurrent write or delete operations without any problems.

If you need an option that changes FileShare for opened log file it can be added, no problems with that.

However, I want to ensure that this option really is needed and you can achieve what you need - could you confirm that? You can simply change it here https://github.com/nreco/logging/blob/master/src/NReco.Logging.File/FileLoggerProvider.cs#L220 and try your build to check that.

[damien-sorin]

good idea, we will check that and give you some feedback