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new 3b36b346 Improve the 'Logging With Multiple Processes' web-site
information (#523)
3b36b346 is described below
commit 3b36b34615d75d548b323238d9e8c0bd0c5ba94a
Author: Stephen Webb <[email protected]>
AuthorDate: Thu Aug 21 09:33:51 2025 +1000
Improve the 'Logging With Multiple Processes' web-site information (#523)
---
src/site/markdown/multiprocess.md | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)
diff --git a/src/site/markdown/multiprocess.md
b/src/site/markdown/multiprocess.md
index 3bad3c87..ac0b2740 100644
--- a/src/site/markdown/multiprocess.md
+++ b/src/site/markdown/multiprocess.md
@@ -21,11 +21,22 @@ Logging With Multiple Processes {#multiprocess-logging}
limitations under the License.
-->
-If you have multiple applications that all log to the same file, it is often
-desirable that the file that these applications write to will roll over when
-required. In order for that to happen, Log4cxx provides the
-log4cxx::rolling::MultiprocessRollingFileAppender that will check the size of
the file when
-writing to the file and roll it over appropriately.
+Log4cxx supports multiple processes logging to the same file,
+providing you do <b>not</b> set the "Append" option
+to "false" (see log4cxx::FileAppender::setOption).
+
+When the "Append" option is "true",
+each logging event (or buffered set of logging events)
+will be separate and contiguous in the log file.
+This is achieved by using "apr_file_write" which
+implements an OS dependent lock/write/unlock sequence
+during which the file pointer is moved the end of the file.
+
+To coordinate rollover across multiple applications
+Log4cxx provides the log4cxx::rolling::MultiprocessRollingFileAppender.
+This appender ensures that only one of the Log4cxx-using processes
+performs the rollover process when the log file
+reaches its size limit.
Coordinating with other processes adds significant overhead compared to
log4cxx::rolling::RollingFileAppender.
Benchmark measurements show the overhead of this appender is more than 3 and
10 times
