log4j2 RollingFileAppender old file gets removed after 7 rollovers - log4j

Question

I use following log4j RollingFile appender in my webapp.
<Appenders>
<RollingFile name="logFile"
fileName="${env:SYSTEM_LOGS}/${env:LOG_FILE_NAME}.log" immediateFlush="true"
filePattern="${env:SYSTEM_LOGS}/${env:LOG_FILE_NAME}.log.%d{yyyy_MM_dd.HH_mm_ss}.%i">
<PatternLayout pattern="%d{yyyyMMdd-HHmmss.SSS}|%X{username}|%-5p|%t| %-100m (%c{1})%n"/>
<Policies>
<OnStartupTriggeringPolicy/>
</Policies>
</RollingFile>
</Appenders>
With filePattern="${env:SYSTEM_LOGS}/${env:LOG_FILE_NAME}.log.%d{yyyy_MM_dd.HH_mm_ss}.%i", when log is rolled over, old file gets renamed to a filename with an index number (specified with %i), so all old files should get renamed and should be preserved.
I rollover the log programmatically with following code.
org.apache.logging.log4j.Logger logManagerLogger = LogManager.getLogger();
Map<String, org.apache.logging.log4j.core.Appender> appenders = ((org.apache.logging.log4j.core.Logger) logManagerLogger).getAppenders();
appenders.forEach((appenderName, appender) -> {
if (appender instanceof RollingFileAppender) {
LOGGER.info("Switching log for appender " + appenderName);
((RollingFileAppender) appender).getManager().rollover();
}
});
But, after 7 rollovers, the existing file gets removed (not renamed according to the specified filePattern) and log is continued in a new file.
What could be the issue here?

Answer 1

set DefaultRolloverStrategy(default is 7), In your config will be:
<Appenders>
<RollingFile name="logFile"
fileName="${env:SYSTEM_LOGS}/${env:LOG_FILE_NAME}.log" immediateFlush="true"
filePattern="${env:SYSTEM_LOGS}/${env:LOG_FILE_NAME}.log.%d{yyyy_MM_dd.HH_mm_ss}.%i">
<PatternLayout pattern="%d{yyyyMMdd-HHmmss.SSS}|%X{username}|%-5p|%t| %-100m (%c{1})%n"/>
<Policies>
<OnStartupTriggeringPolicy/>
</Policies>
<DefaultRolloverStrategy max="100"/>
</RollingFile>
</Appenders>
now, it will have 100 log file to rollover.

Answer 2

If you want unlimited rollingfile,
According to Log4j2 documentation, from release 2.8, it can be done by setting fileIndex attribute to nomax. For example:
<DefaultRolloverStrategy fileIndex="nomax" />