RollingFileAppender overwrites an old log even if AppendToFile is true when RollingStyle is Composite and there are some logs on that day.

[WorldRobertProject]

When RollingStyle is Composite, it seems RollingFileAppender ignores AppendToFile flag except for the first log on that day.

The following code makes log files as 2024-08-02.0.log, 2024-08-02.1.log, ...

log4net.config.xml

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <log4net>
    <appender name="LogFileAppender" type="log4net.Appender.RollingFileAppender">
      <param name="File" value=".\Log\" />
      <param name="AppendToFile" value="true" />
      <param name="RollingStyle" value="Composite" />
      <param name="DatePattern" value='yyyy-MM-dd".log"' />
      <param name="MaximumFileSize" value="5MB" />
      <param name="MaxSizeRollBackups" value="10" />
      <param name="StaticLogFileName" value="false" />
      <param name="CountDirection" value="1" />
      <param name="PreserveLogFileNameExtension" value="true"/>
      <lockingModel type="log4net.Appender.FileAppender+MinimalLock" />
      <layout type="log4net.Layout.PatternLayout">
        <param name="ConversionPattern" value="%d{yyyy/MM/dd HH:mm:ss.fff} [%-5p] %m (%M)%n"/>
      </layout>
    </appender>

    <logger name="log">
      <level value="debug" />
      <appender-ref ref="LogFileAppender" />
    </logger>
  </log4net>
</configuration>

Program.cs

using log4net;
using log4net.Config;
using System.Reflection;

var pathConfig = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "log4net.config.xml");
XmlConfigurator.Configure(new FileInfo(pathConfig));

var assembly = Assembly.GetEntryAssembly();
var logger = LogManager.GetLogger(assembly, "log");

logger.Info("Hello, log4net!");

When only 2024-08-02.0.log exists, it appends a new log to 2024-08-02.0.log as expected.
When both 2024-08-02.0.log and 2024-08-02.1.log exist and 2024-08-02.0.log is greater than 5MB, this code overwrites 2024-08-02.1.log and outputs the following error message:

log4net:ERROR RollingFileAppender: INTERNAL ERROR. Append is False but OutputFile [...\Log\2024-08-02.1.log] already exists.

It seems AppendToFile flag is ignored.

All log4net versions from 2.0.10 to 2.0.17 reproduce this issue.

[WorldRobertProject]

I confirmed that 3.0.0-preview.2 also reproduces this issue.

[FreeAndNil]

Hi @WorldRobertProject,

thanks for reporting.
I can reproduce your problem, but I haven't found the time to fix it yet.