I am using NLog for DB logging. If the DB is down then I only need it to log to a file. Is there a way to do this?
I don't want to record log entries log in both a file and the DB. If the DB target fails to log (if DB is down) only then do I have to log to the file. Is there any fail over or fallback feature with Nlog?
Yes, there is a way. It's called a FallbackGroup.
Documentation can be found here: https://github.com/nlog/NLog/wiki/FallbackGroup-target
Here is an example taken blatantly and ashamedly from the documentation:
<target xsi:type="FallbackGroup"
name="mail"
returnToFirstOnSuccess="true">
<target xsi:type="Mail"
name="mailserver1"
subject="Layout"
to="Layout"
from="Layout"
smtpServer="mx1.example.com"
smtpPort="Integer"
layout="Layout" />
<target xsi:type="Mail"
name="mailserver2"
subject="Layout"
to="Layout"
from="Layout"
smtpServer="mx2.example.com"
smtpPort="Integer"
layout="Layout" />
</target>
<rules>
<logger name="*" minlevel="Trace" writeTo="mail" />
</rules>
It'll try another mail server if the first fails. It'll also return to the first target if it's successful.
I never used it in production, maybe the other options in the documentation can help you fine tune it to your problem.
Related
I have a single-threaded .NET Winforms application. I am using a static NLog logger to log errors using this syntax:
MyLogger.Log.Error("Error occurred...");
In accordance with my one NLog.config-defined target and one NLog.config-defined rule, that log-error output always is written to a file called "errors.txt". Sometimes I want an error to be written to "errors2.txt" instead. How would I do that without creating another static logger instance?
You could use filters in the config or pass the filename to the logger call.
Note: These examples are using .WithProperty (on the NLog Logger), introduced in NLog 4.6.3
Filters
Use filters in the logger rules, we use the LogFinal so we need only the rules once (not needed for the 2nd logger rule)
See Filtering log messages on the NLog wiki
<rules>
<logger name="*" writeTo="file-error1">
<filters defaultAction='LogFinal'>
<when condition="${event-properties:target} == 'error2'" action="Ignore" />
</filters>
</logger>
<logger name="*" writeTo="file-error2">
</logger>
</rules>
Logger call:
MyLogger.Log.Error("Error occurred..."); // writes to file-error1 target
MyLogger.Log.WithProperty("target", "error2").Error("Error occurred..."); // writes to file-error2 target
Pass file name
Pass the file name in as property. Maybe you could set a default property in the static Log method.
See also Event properties documentation
<targets>
<target name="file" xsi:type="File"
....
fileName="${basedir}/logs/{event-properties:filename}"
... />
</targets>
Logger call:
MyLogger.Log.WithProperty("filename", "error1.txt").Error("Error occurred...");
MyLogger.Log.WithProperty("filename", "error2.txt").Error("Error occurred...");
Just started working with NLog and have it running with the following configuration:
<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
throwConfigExceptions="true">
<targets async="true">
<target name="logfile"
xsi:type="File"
layout="${longdate} [${level:uppercase=true}] (${threadid}) ${logger}: ${message} ${onexception:${newline}Exception\: ${exception:format=type,message,method,stacktrace:maxInnerExceptionLevel=5:innerFormat=shortType,message,method}}"
fileName="logs/current.log"
archiveFileName="logs/Archive/${ticks}.log"
archiveEvery="Minute"
archiveOldFileOnStartup="true"
keepFileOpen="false"
/>
</targets>
<rules>
<logger name="*" minlevel="Debug" writeTo="logfile" />
</rules>
</nlog>
Everything is working as expected. However, I need to have the rotated file be in the format of ${archive_start_ticks}_${arhive_end_ticks}.log rather than the current format which is ${archive_end_ticks}.log.
I was initially hoping I could name the active log file as ${ticks} and then, on archive, use the active log file's name as a parameter into the archive file to compose some like:
fileName="logs/${ticks}"
archiveFileName="logs/Archive/${fileName}_${ticks}.log"
Of course, there's two issues here:
Using ${ticks} for the active file creates a new file for each log line.
I can't seem to reference the original fileName as an input variable into archiveFileName.
That said, what is the best way to achieve this goal? Is this something NLog can handle natively or with minor extensions?
Updating in case anyone ever cares:
I bailed on using the FileTarget with configurations and wrote my own Target wrapped in a BufferedWrapper. On each flush, I use the first and last LogEvents to determine the timespan which gives me what I need to for the required file format with little custom code to support.
I have a service running hourly that uses NLog to send mail when exception occurs. So how do I configure it to not log at Saturday and Sunday? Can I even do that?
Here's my target:
<target name="m"
xsi:type="Mail"
html="true"
smtpServer="*******"
smtpPort="*******"
smtpAuthentication="*******"
smtpUserName="*******"
smtpPassword="*******"
enableSsl="true"
subject="Exception"
from="*******"
to="*******"
layout ="${longdate} ${uppercase:${level}}${newline} ${callsite:className=true:includeSourcePath=true:methodName=true}${newline} ${message}${newline}"
useSystemNetMailSettings="false" />
And rule:
<logger name="*" minlevel="Fatal" writeTo="m" />
Maybe use the PostFilteringWrapper, and use a filter condition like:
not equals('${date:format=ddd}', 'Sat')
not equals('${date:format=ddd}', 'Sun')
https://github.com/NLog/NLog/wiki/PostFilteringWrapper-target
https://github.com/NLog/NLog/wiki/When-filter
https://learn.microsoft.com/en-us/dotnet/standard/base-types/how-to-extract-the-day-of-the-week-from-a-specific-date
I am using NLog with two targets:
<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<targets async="true">
<target name="logfile" xsi:type="File" fileName="my.log"/>
<target name="console" xsi:type="Console"/>
</targets>
<rules>
<logger name="*" minlevel="Trace" writeTo="logfile"/>
<logger name="*" minlevel="Info" writeTo="console"/>
</rules>
</nlog>
Is it possible to log a message only to the "logfile" target, without having the message written to the "console" target as well?
EDIT
To clarify: I want to direct messages from the same class to different loggers at run time (w/o having to change the XML). Something like:
class Program
{
static Logger _logger = LogManager.GetCurrentClassLogger();
static void Main(string[] args)
{
// Note - _logger.InfoToTarget() does not really exist
_logger.InfoToTarget("logfile", "This is my very detailed message, possibly with object dumps");
_logger.InfoToTarget("console", "Short message");
}
}
I'm aware that this couples my code with the NLlog.config file.
One way to accomplish the functionality you are looking for is to name your logger
_logger = LogManager.GetLogger("MyConsoleLogger")
_logger.Info("This will log to the console...");
_logger = LogManager.GetLogger("MyFileLogger")
_logger.Trace("This will log to a file...");
rather than using
LogManager.GetCurrentClassLogger().
In your config file you could then list in the rules
<rules>
<logger name="MyFileLogger" minlevel="Trace" writeTo="logfile"/>
<logger name="MyConsoleLogger" minlevel="Info" writeTo="console"/>
</rules>
This is by far not the most pretty solution to look at, but it does give you the functionality that you are looking for.
There are a few ways to do this, and the correct method depends on your situation.
Keep in mind that you typically want to avoid having your app know too much about the inner-workings of logging. If possible, it's best to configure nlog to decide where things should get logged.
Is there a specific namespace that should not be logged to console? That's easy to configure. Also, you can use the "When" filter (https://github.com/nlog/nlog/wiki/When-filter) or conditions (https://github.com/nlog/nlog/wiki/Conditions)
It may also be best to have multiple logger instances, so you can call the one that is appropriate for each situation (logger per class) (Why do loggers recommend using a logger per class?).
Absolutely, however I am assuming you mean at release you no longer wish to log to the console. You can do this very easily by removing or commenting out the listener that writes to the console target. Now it will only write to the logfile target.
<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<targets async="true">
<target name="logfile" xsi:type="File" fileName="my.log"/>
<target name="console" xsi:type="Console"/>
</targets>
<rules>
<logger name="*" minlevel="Trace" writeTo="logfile"/>
<!--<logger name="*" minlevel="Info" writeTo="console"/>-->
</rules>
</nlog>
The rule that writes to the console is now deactivated, but the log file is active. If this is during release you probably want to change your rule to not process your trace logging as the min level for the log file since it will slow down your app with excessive IO. I have asked this question in the past and it appears that best practice is to do this via the XML configuration files. (Logging in Release Build of Application (C#))
I have following Nlog config section in my web.config (modified to show only relevant info)
<nlog>
<targets async="true">
<target name="mail" type="Mail"
body="${date:format=yyyy-MM-dd HH\:mm\:ss} - ${level} [${logger}] - ${message} ${newline}${newline}${event-context:item=OtherInfo}${newline}${newline}${exception:maxInnerExceptionLevel=2:format=ToString}${newline}${newline}"
subject="[${machinename}] ${logger}"
to="mail#domain.com" encoding="UTF-8" from="anotheremail#domain.com" smtpServer="" enableSsl="true" smtpAuthentication="Basic"
/>
</targets>
<targets>
<target name="mailsync" type="Mail" body="${date:format=yyyy-MM-dd HH\:mm\:ss} - ${level} [${logger}] - ${message} ${newline}${newline}${event-context:item=OtherInfo}${newline}${newline}${exception:maxInnerExceptionLevel=2:format=ToString}${newline}${newline}" subject="[${machinename}] ${logger}"
to="mail#domain.com" encoding="UTF-8" from="anotheremail#domain.com" smtpServer="" enableSsl="true" smtpAuthentication="Basic"
/>
</targets>
<rules>
<logger name="*" level="Error" writeTo="mail" />
</rules>
</nlog>
I am updating the configuration via code in Application_Start,
var config = LogManager.Configuration;
const string targetName = "mail";
var wrapper = (AsyncTargetWrapper) config.FindTargetByName(targetName);
wrapper.WrappedTarget.SmtpServer = "hostname";
wrapper.WrappedTarget.SmtpUserName = "username";
wrapper.WrappedTarget.SmtpPassword = "password";
config.RemoveTarget(targetName);
config.AddTarget(targetName, wrapper);
LogManager.Configuration = config;
However, when I log any errors, the emails are not being sent. I have an additional file target (not shown in the code snippet), that contains the error message. That tells me the errors are getting logged, but somehow not sent via email.
If instead of updating the config via code, if I hard code the values in the web.config, then the emails get sent. I have verified that the smtp values that I am using via code are valid.
I did search through many similar questions on SO, but I haven't yet found one that mentions a solution that works for me.
EDIT:
Based on Xharze's answer, I enabled exceptions, internal logging and I also outputted the values of the target after I had made my changes. The internal log showed an exception about a MailAdrress being the incorrect format. So I checked all target values that accept an email address and I found the issue. The from property of the target accepts an email address whereas I was providing it a display name!
Could you try enabling throw exceptions and the interalnal log, and post it? It may provide more information. See github.com/NLog/NLog/wiki/Logging-troubleshooting.