Question regarding configuration of FileAppender and Appender in general about log4cplus HOT 2 CLOSED

If you create multiple file appenders targeting the same files, you are going to run into some issues. You have identified one, that is the flushing issue. In case of rolling appenders, there is also an issue with who does the rolling and how to synchronize it. In newer log4cplus, it is possible to specify UseLockFile property and the appender will use file locking to synchronize appending to file and also rolling multiple files in rolling appenders. The flushing is silently enabled, if you use the UseLockFile property. So, it is best to use single appender in a process per file.

The log level threshold filtering is done at two points,

1. at the point of logging, logger is checked for threshold, if one is missing, the threshold is searched for by following path towards root logger
2. in appender

Yes, the scenario that you are describing can happen. You are right that you have to be careful how you set up your logging properties / hierarchy. Log level threshold on the root logger serves as a threshold for all loggers without explicit log level threshold of their own. You are right that you have to add an appender filter on the root logger's appenders, if you want to avoid the scenario that you are describing. You could also turn off additivity for your one logger to avoid events to propagate towards root.

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Ok, great - thanks a lot for your quick and comprehensive answer!

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