Sharath Avadoot Gururaj created LOG4J2-3162:
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Summary: Fix misleading documentation for immediateFlush
Key: LOG4J2-3162
URL: https://issues.apache.org/jira/browse/LOG4J2-3162
Project: Log4j 2
Issue Type: Documentation
Components: Appenders
Affects Versions: 2.14.1
Reporter: Sharath Avadoot Gururaj
In the documentation of
[RollingFileAppender|https://logging.apache.org/log4j/2.x/manual/appenders.html#RollingFileAppender]
{code:java}
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.
{code}
This is misleading. The appender does not really {{guarantee that the data is
written to disk}} . All it does is
[call|https://github.com/agsha/logging-log4j2/blob/1d56dac20d0827300a49a8cd9f0324185451757e/log4j-core/src/main/java/org/apache/logging/log4j/core/appender/OutputStreamManager.java#L264]
the underlying
[OutputStream.flush()|https://docs.oracle.com/javase/7/docs/api/java/io/OutputStream.html#flush()]method,
which does not guaratee that data is written to disk. It only guaratees that
the data is handed over to the operating system
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