@Alexy
The answer to your question is neither...
The following property is relative to the configuration of the "fileNamingPattern" property.
<maxHistory>60</maxHistory>
Let's say we have the following fileNamingPattern property:
<fileNamePattern>logs/archived/app.%d{yyyy-MM-dd}.log.gz</fileNamePattern>
This pattern would create one log file per day and then maxHistory would would dictate number of days to retain as 60. In this specific example the number of days retained and number of files and number of days both equal 60.
and another example:
<fileNamePattern>${org.apache.nifi.bootstrap.config.log.dir}/nifi-app_%d{yyyy-MM-dd_HH}.log</fileNamePattern>
Here you will notice the date pattern is based on hourly logs. So the "maxHistory" property in this example would dictate the number of hours worth of logs to retain (not days).
Now lets look at a slightly different example:
<fileNamePattern>logs/archived/app.%d{yyyy-MM-dd}.%i.log.gz</fileNamePattern>
<maxFileSize>10MB</maxFileSize>
In this example you'll notice "%i" has been added to pattern. "%i" works in conjunction with the "maxFileSize" property. throughout a single day any time the log file sizes reaches 10MB, an incremental number log for the same day is created.
app.2024-01-02.1.log.gz
app.2024-01-02.2.log.gz
app.2024-01-02.3.log.gz
...
The MaxHistory does not take into consideration the "%i" incremental logs. It is still based on the %d pattern to retain 60 days of logs. So in this case you would have any number of files potentially created across those 60 days.
The same applies to the hours based example if "%i" is added to the fileNamingPattern.
in order to protect disk usage you will often see the following used:
<rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
<fileNamePattern>${org.apache.nifi.bootstrap.config.log.dir}/nifi-app_%d{yyyy-MM-dd_HH}.%i.log</fileNamePattern>
<maxFileSize>100MB</maxFileSize>
<maxHistory>30</maxHistory>
<totalSizeCap>10GB</totalSizeCap>
</rollingPolicy>
What this does is create hourly logs that will incrementally role during each hour if the log file reaches 100MB in size.
Then to prevent excessive disk usage should logging unexpectedly increase in log generation, the "TotalSizeCap" will start deleting the oldest rolled logs until max usage is below 10GB. This may mean that 30 hours of logs are no longer retained, but you avoid disk usage issues when the unexpected happens.
Hopefully this clears this up for you.
NOTE: Above is based on the "SizeAndTimeBasedRollingPolicy". LogBack as other rolling Policy providers.
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Thank you,
Matt
