NLog File target and keepFileOpen flag

Question

A FileTarget object in NLog has a property (bool) called "keepFileOpen". By default this property is set to false, meaning that each log event will open the file, write in the file and close the file.

The hit in performance is huge, so I specified "keepFileOpen" to true, instead of false, meaning that the file will be opened only once.

Does anybody has an idea (or just know) why this property is by default set to "false", incuring a HUGE performance hit on logging ?

Is there any scenarios where setting this property to true can cause issues (which would therefore make sense to default it to "false").

Thanks !

EDIT

Performance measurements for basic layout, writing 100K events to the logger :

• keepFileOpen = false (default) : ~ 101 sec
• keepFileOpen = true : ~ 1 sec

Answer 1

I would say that closing the file is the expected behaviour. If you will try to access the file from another process or delete it in file system while the NLog-process is alive it would lead to those annoying system-errors saying that some process holds the file etc.

If the time of opening a file is too long for you, try using the AsyncWrapper and you'll get a fire-and-forget-behavior.

Therefore I think that the default value is ok.