FileTarget Archive Examples

NLog ver. 4.5 improves dynamic archive mode, so it is easy to archive old files.

These examples shows the archive options for the static-archive-mode. One should Not mix dynamic with static-archive-mode.

Size-based file archival

Log files can be automatically archived by moving them to another location after reaching certain size. The following configuration will create logs/logfile.txt which will be archived to archives/log.000000.txt', archives/log.000001.txt', archives/log.000002.txt' and so on once the main log file reaches 10KB.

<?xml version="1.0" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
 
    <targets>
        <target name="file" xsi:type="File"
            layout="${longdate} ${logger} ${message}" 
            fileName="${basedir}/logs/logfile.txt" 
            archiveFileName="${basedir}/archives/log.{#####}.txt"
            archiveAboveSize="10240"
            archiveNumbering="Sequence"
            concurrentWrites="true"
            keepFileOpen="false"
            encoding="iso-8859-2" />
    </targets>
 
    <rules>
        <logger name="*" minlevel="Debug" writeTo="file" />
    </rules>
</nlog>

Time-based file archival

Log files can also be automatically archived based on time. This configuration will archive a file at the beginning of each day and will use rolling file naming, so log file from the previous day can always be found in archives//log.0.txt, log from two days ago is in archives//log.1.txt and so on. This configuration will keep at most 7 archive files, so logs older than one week will be automatically deleted.

<?xml version="1.0" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
 
    <targets>
        <target name="file" xsi:type="File"
            layout="${longdate} ${logger} ${message}" 
            fileName="${basedir}/logs/logfile.txt" 
            archiveFileName="${basedir}/archives/log.{#}.txt"
            archiveEvery="Day"
            archiveNumbering="Rolling"
            maxArchiveFiles="7"
            concurrentWrites="true"
            keepFileOpen="false"
            encoding="iso-8859-2" />
    </targets>
 
    <rules>
        <logger name="*" minlevel="Debug" writeTo="file" />
    </rules>
</nlog>

Archive every Week

You can specify different archival time periods. For example, if you wanted to archive once a week on Tuesdays, you would set archiveEvery="Tuesday". Possible values for archiveEvery can be found above. This will result in the following files being created:

• logfile.txt // the current log being written to
• logfile.20170307.txt
• logfile.20170314.txt
• logfile.20170321.txt
• etc.

<?xml version="1.0" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
 
    <targets>
        <target name="file" xsi:type="File"
            layout="${longdate} ${logger} ${message}" 
            fileName="${basedir}/logs/logfile.txt" 
            archiveFileName="${basedir}/archives/logfile.{#}.txt"
            archiveEvery="Tuesday"
            maxArchiveFiles="7" />
    </targets>
 
    <rules>
        <logger name="*" minlevel="Debug" writeTo="file" />
    </rules>
</nlog>

Archive Numbering Examples

Rolling

        <target name="file" xsi:type="File"
            ...
            fileName="logfile.txt"
            archiveFileName="log.{####}.txt"
            archiveNumbering="Rolling"  />

Example of file names (newest files first):

• logfile.txt
• log.0000.txt
• log.0001.txt
• log.0002.txt

Sequence

        <target name="file" xsi:type="File"
            ...
            fileName="logfile.txt"
            archiveFileName="log.{####}.txt"
            archiveNumbering="Sequence"  />

Example of file names (newest files first):

• logfile.txt
• log.0002.txt
• log.0001.txt
• log.0000.txt

Date

        <target name="file" xsi:type="File"
            ...
            fileName="logfile.txt"
            archiveFileName="log.{#}.txt"
            archiveNumbering="Date"
            archiveEvery="Day"
            archiveDateFormat="yyyyMMdd"
  />

Example of file names (newest files first):

• logfile.txt
• log.20150731.txt
• log.20150730.txt

DateAndSequence

        <target name="file" xsi:type="File"
            ...
            fileName="logfile.txt"
            archiveFileName="log.{#}.txt"
            archiveNumbering="DateAndSequence"
            archiveAboveSize="1000"
            archiveDateFormat="yyyyMMdd"
  />

Example of file names (newest files first):

• logfile.txt
• log.20150730.3.txt
• log.20150730.2.txt
• log.20150730.1.txt

Archive file in new folder

NLog also has support for writing to a static fileName-Layout, and then move the file to archive-location and re-create new fresh file. But it only works when not including dynamic layout (Ex. ${date}) in the fileName-Layout or archiveFileName-Layout. See also Do not mix dynamic-filename with static archive logic

<?xml version="1.0" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
 
    <targets>
        <target name="file" xsi:type="File"
            layout="${longdate} ${logger} ${message}${exception:format=ToString}" 
            fileName="${basedir}/logs/AppLog.txt" 
            archiveFileName="${basedir}/archives/AppLog.{#}.txt"
            archiveEvery="Day"
            maxArchiveFiles="4"
            archiveAboveSize="10240" />
    </targets>
 
    <rules>
        <logger name="*" minlevel="Debug" writeTo="file" />
    </rules>
</nlog>

It will generate the following filenames (newest first):

* AppLog.txt // the current log being written to
* AppLog.20170321.txt
* AppLog.20170314.txt
* AppLog.20170307.txt

One log file per application instance, remove old logs

The following configuration will create a dedicated log file for each start of your application. Multiple instances can run in parallel and write to their respective log file. By adding a timestamp to the filename, each filename is unique (up to the second). Up to ten log files (active + nine archive) are kept. The removal of old logs works, when the archiveFileName contains a placeholder, archiveDateFormat has the same datetime format as in the name property, and archiveNumbering and archiveEvery are enabled. The $(cached:...) directive prevents that a new log file name is generated for every log entry. Log files will be named:

• 2017-11-05 08_00_00.log
• 2017-11-05 08_00_01.log
• 2017-11-05 12_35_04.log
• 2017-11-06 09_54_32.log
• ...

<?xml version="1.0" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

     <targets>
        <target name="file" xsi:type="File"
            layout="${longdate} ${logger} ${message}${exception:format=ToString}" 
            fileName="${basedir}/logs/${cached:${date:format=yyyy-MM-dd HH_mm_ss}}.log"
            archiveFileName="${basedir}/{#}.log"
            archiveDateFormat="yyyy-MM-dd HH_mm_ss"
            archiveNumbering="Date"
            archiveEvery="Year"
            maxArchiveFiles="9" />
    </targets>
 
    <rules>
        <logger name="*" minlevel="Debug" writeTo="file" />
    </rules>
</nlog>