RollingFileAppender
The RollingFileAppender is an OutputStreamAppender that writes to the File named in the fileName parameter and rolls the file over according the TriggeringPolicy and the RolloverPolicy. The RollingFileAppender uses a RollingFileManager (which extends OutputStreamManager) to actually perform the file I/O and perform the rollover. While RolloverFileAppenders from different Configurations cannot be shared, the RollingFileManagers can be if the Manager is accessible. For example, two web applications in a servlet container can have their own configuration and safely write to the same file if Log4j is in a ClassLoader that is common to both of them.
A RollingFileAppender requires a TriggeringPolicy and a RolloverStrategy. The triggering policy determines if a rollover should be performed while the RolloverStrategy defines how the rollover should be done. If no RolloverStrategy is configured, RollingFileAppender will use theDefaultRolloverStrategy. Since log4j-2.5, a custom delete action can be configured in the DefaultRolloverStrategy to run at rollover.
File locking is not supported by the RollingFileAppender.
| Parameter Name | Type | Description |
|---|---|---|
| append | boolean | When true - the default, records will be appended to the end of the file. When set to false, the file will be cleared before new records are written. |
| bufferedIO | boolean | When true - the default, records will be written to a buffer and the data will be written to disk when the buffer is full or, if immediateFlush is set, when the record is written. File locking cannot be used with bufferedIO. Performance tests have shown that using buffered I/O significantly improves performance, even if immediateFlush is enabled. |
| bufferSize | int | When bufferedIO is true, this is the buffer size, the default is 8192 bytes. |
| filter | Filter | A Filter to determine if the event should be handled by this Appender. More than one Filter may be used by using a CompositeFilter. |
| fileName | String | The name of the file to write to. If the file, or any of its parent directories, do not exist, they will be created. |
| filePattern | String | The pattern of the file name of the archived log file. The format of the pattern should is dependent on the RolloverPolicy that is used. The DefaultRolloverPolicy will accept both a date/time pattern compatible with SimpleDateFormat and/or a %i which represents an integer counter. The pattern also supports interpolation at runtime so any of the Lookups (such as the DateLookup can be included in the pattern. |
| immediateFlush | boolean | When set to true - the default, each write will be followed by a flush. This will guarantee the data is written to disk but could impact performance. Flushing after every write is only useful when using this appender with synchronous loggers. Asynchronous loggers and appenders will automatically flush at the end of a batch of events, even if immediateFlush is set to false. This also guarantees the data is written to disk but is more efficient. |
| layout | Layout | The Layout to use to format the LogEvent |
| name | String | The name of the Appender. |
| policy | TriggeringPolicy | The policy to use to determine if a rollover should occur. |
| strategy | RolloverStrategy | The strategy to use to determine the name and location of the archive file. |
| ignoreExceptions | boolean | The default is true, causing exceptions encountered while appending events to be internally logged and then ignored. When set to false exceptions will be propagated to the caller, instead. You must set this to false when wrapping this Appender in a FailoverAppender. |