Tag: Logging

In a previous blog post – Custom Layout Renderer for NLog using C#, I have mentioned about how to create a class inheriting LayoutRenderer and writing custom Layout Renderer.

This blog post talks about inheriting from WrapperLayoutRendererBase class.

The WrapperLayoutRendererBase class has a method with the signature:

protected override string Transform(string text)

This method needs to be overridden. The nice thing about using this class is other layout renderers can be used in combination.

Here is a GitHub repo implementing hash functions that can be used as LayoutRenderers.

https://github.com/ALightTechnologyAndServicesLimited/ALight.NLog.LayoutRenderer.Hash

The source code has 4 projects:

1. The actual implementation
2. Unit Tests
3. Benchmark Tests
4. Example

The usage is straightforward, use hash or securehash layout renderer.

  <extensions>
    <add assembly="ALight.NLog.LayoutRenderer.Hash" />
  </extensions>




<target xsi:type="File" name="logfile" fileName="c:\temp\console-example.log"
        layout="${longdate}|${level}|${message} |${all-event-properties} ${exception:format=tostring} ${hash:hello} 
        ${securehash:value=${level}} ${event-properties:item=secret} ${hash:${event-properties:item=secret}} ${hash:${level}}" />

The hash implementation is about 10 – 11 times faster but uses Murmur3 non cryptographic hash.

I might consider a nuget package at a later point, but not now, because the code is very minimal and like a small helper class.

–

Mr. Kanti Kalyan Arumilli

B.Tech, M.B.A

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kantikalyan@gmail.com, kantikalyan@outlook.com, admin@alightservices.com, kantikalyan.arumilli@alightservices.com, KArumilli2020@student.hult.edu, KantiKArumilli@outlook.com and 3 more rarely used email addresses – hardly once or twice a year.

*** use WrapperLayoutRendererBase instead of LayoutRenderer, this blog post is about LayoutRenderer ***

NLog has lot of built-in layout renderers. Here is a list of official layout renderers:

https://nlog-project.org/config/?tab=layout-renderers

Creating custom layout renderer is very simple and straight-forward. Here is the official documentation:

https://github.com/NLog/readthedocs/blob/master/docs/How-to-write-a-custom-layout-renderer.md

There are 2 ways:

Lambda:

LayoutRenderer.Register("name", (logEvent, config) => "Message");

In the above scenarion, we can use ${name} when defining a layout, of course instead of returning static string we can do something useful based on the use-case.

Class:

Define a new class inherited from NLog.LayoutRenderers.LayoutRenderer. Use class attribute LayoutRenderer(“name”). LayoutRenderer is an abstract class, implement the class by overriding Append(StringBuilder builder, LogEventInfo logEvent) method i.e Append the value that needs to be added to the log by appending to the StringBuilder parameter.

[LayoutRenderer("Example")]
public class ExampleLayoutRenderer : NLog.LayoutRenderers.LayoutRenderer
{
    public string Value { get; set; }

    protected override void Append(StringBuilder builder, LogEventInfo logEvent)
    {
        builder.Append("Value");
    }
}

Extra parameters can be passed and assigned as properties of the custom class.

[LayoutRenderer("example")]
public class ExampleLayoutRenderer : NLog.LayoutRenderers.LayoutRenderer
{
    public string Value { get; set; }

    protected override void Append(StringBuilder builder, LogEventInfo logEvent)
    {
        // Your custom code
        builder.Append(Value);
    }
}

In the config file the custom layout renderer with params can be used like follows:

{example}

{example:value=abc}

Sometimes, in logs we write some data that might be needed for identifying but not necessarily the real value and for various reasons we might just need a hash. For example: SessionId / Some Cookie Value / IP address etc… Having a custom renderer for hashing such a value could be used.

Very few lines of code, i.e hashing and appending to a stringbuilder would solve the need i.e 2 – 3 lines of code. But, I think the 2 – 3 lines of code could be helpful for other people. I am considering creating an opensource version. I might or might not release nuget package. If I release nuget package, I would definitely make an anouncement. Anyway, not a big open-source project, but just few lines of code.

–

Mr. Kanti Kalyan Arumilli

B.Tech, M.B.A

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Founder & CEO, Lead Full-Stack .Net developer

ALight Technology And Services Limited

ALight Technologies USA Inc

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Phone / SMS / WhatsApp on the following 3 numbers:

+91-789-362-6688, +1-480-347-6849, +44-07718-273-964

+44-33-3303-1284 (Preferred number if calling from U.K, No WhatsApp)

kantikalyan@gmail.com, kantikalyan@outlook.com, admin@alightservices.com, kantikalyan.arumilli@alightservices.com, KArumilli2020@student.hult.edu, KantiKArumilli@outlook.com and 3 more rarely used email addresses – hardly once or twice a year.

In the past I have written few blog posts on NLog and discussed several techniques:

Programatically configuring NLog in C#

NLog in .Net Applications

Some NLog configuration examples for writing into different log management systems

How to log debug level logs only when an exception occurs in ASP.Net using NLog

And I have discussed about a possibility of capturing more information in logs only when needed such as in the case of errors or exceptions in the following blog post:

An abnormal way of logging – open for discussion

My use-case explanation:

I am planning to use Gelf logging for easier compatibility reasons. Gelf logs can be ingested into pretty much every major centralized logging platforms such as: Kibana, GrayLog, Seq, Grafana. Some would require some intermediary software to accept Gelf formatted logs and some can directly ingest Gelf formatted logs. However, for various reasons, sometimes the logging server might not be available, specifically when the log ingestors are not in a cluster. Log files can be easily ingested into the above mentioned centralized logging agents using different sofware.

Based on the above use-case I wanted to use Gelf for directly logging into the centralized logging server and as a failover, I want to write the logs to a file that would get ingested at a later point by some other software.

Now, by combing the previous post example, we can achieve AspNetBuffering and ingest different levels of logs only when errors occur. The code samples should be very easy to understand.

Read the How to log debug level logs only when an exception occurs in ASP.Net using NLog prior to continuing.

<extensions>
    <add assembly="NLog.Web.AspNetCore"/>
    <add assembly="NLog.Targets.Gelf"/>
</extensions>

<targets>
    <target xsi:type="AspNetBufferingWrapper" name="aspnetbuffer" bufferGrowLimit="100000" growBufferAsNeeded="true">
        <target xsi:type="PostFilteringWrapper" defaultFilter="level &gt;= LogLevel.Info">
            <target xsi:type="FallbackGroup" returnToFirstOnSuccess="true">
                <target xsi:type="gelf" endpoint="tcp://logs.local:12201" facility="console-runner" sendLastFormatParameter="true">
                    <parameter name="param1" layout="${longdate}"/>
                    <parameter name="param2" layout="${callsite}"/>
                 </target>
		<target xsi:type="File" fileName="c:\temp\nlog-AspNetCore-all-${shortdate}.log" layout="${longdate}|${event-properties:item=EventId:whenEmpty=0}|${level:uppercase=true}|${logger}|${message} ${exception:format=tostring}" />
              </target>
              <when exists="level &gt;= LogLevel.Warn" filter="level &gt;= LogLevel.Debug"/>
       </target>
    </target>
</targets>

<rules>
    <logger name="*" minlevel="Debug" writeTo="aspnetbuffer" />
</rules>

In the above code we have wrapped Gelf logger, File logger inside a FallBackGroup logger. The FallBackGroup logger is wrapped inside a PostFilteringWrapper. The PostFilteringWrapper is wrapped inside a AspNetBufferingWrapper.

In the above code in the <rules> section we are sending all Debug and above logs to the AspNetBufferingWrapper.

Now AspNetBufferingWrapper buffers the log messages for an entire request, response cycle and sends the log messages to the PostFilteringWrapper.

The PostFilteringWrapper sees if there are any Warnings or above loglevel, if yes sends all the messages that have Debug and above loglevels. Else sends Info and above messages. The target of PostFilteringWrapper is the FallbackGroup logger which receives these messages.

The FallBackGroup logger attempts to use the Gelf logger, if the Gelf logger is unable to process the messages, the logs are sent to the File logger.

–

Mr. Kanti Kalyan Arumilli

B.Tech, M.B.A

Facebook

LinkedIn

Threads

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Founder & CEO, Lead Full-Stack .Net developer

ALight Technology And Services Limited

ALight Technologies USA Inc

Youtube

Facebook

LinkedIn

Phone / SMS / WhatsApp on the following 3 numbers:

+91-789-362-6688, +1-480-347-6849, +44-07718-273-964

+44-33-3303-1284 (Preferred number if calling from U.K, No WhatsApp)

kantikalyan@gmail.com, kantikalyan@outlook.com, admin@alightservices.com, kantikalyan.arumilli@alightservices.com, KArumilli2020@student.hult.edu, KantiKArumilli@outlook.com and 3 more rarely used email addresses – hardly once or twice a year.

In the past I have written few blog posts on NLog and discussed several techniques:

Programatically configuring NLog in C#

NLog in .Net Applications

Some NLog configuration examples for writing into different log management systems

And I have discussed about a possibility of capturing more information in logs only when needed such as in the case of errors or exceptions in the following blog post:

An abnormal way of logging – open for discussion

This blog post is for Asp.Net Core only.

This should be possible by combining AspNetBufferingWrapper and PostFilteringWrapper.

Sample configuration provided below:

AspNetBufferingWrapper:

AspNetBufferingWrapper buffers all the messages in a ASP.Net request and sends all the messages to the wrapped target.

Remember to set this logger properly. This involves:

1. Adding the NLog.Web.AspNetCore nuget package
2. Properly configuring nlog.config file
3. Registering the middleware

dotnet add package NLog.Web.AspNetCore --version 5.2.1

<extensions>
    <add assembly="NLog.Web.AspNetCore"/>
</extensions>

using NLog.Web;

app.UseMiddleware<NLogBufferingTargetWrapperMiddleware>();

PostFilteringWrapper:

This wrapper evaluates a specified condition and filters logs, then sends the logs to the wrapped target:

<target xsi:type="PostFilteringWrapper" defaultFilter="level &gt;= LogLevel.Info">
    <target .... />
    <when exists="level &gt;= LogLevel.Warn" filter="level &gt;= LogLevel.Debug"/>
</target>

The above configuration by default logs Info and above logs, but if there is a Warn or higher, logs debug or higher. For this to work properly obviously this logger has to receive Debug messages otherwise there is no point in using this logger.

Now combing these two loggers, here is an example:

<extensions>
    <add assembly="NLog.Web.AspNetCore"/>
</extensions>

<targets>
    <target xsi:type="AspNetBufferingWrapper" name="aspnetbuffer" bufferGrowLimit="1000" growBufferAsNeeded="true">
        <target xsi:type="PostFilteringWrapper" defaultFilter="level &gt;= LogLevel.Info">
            <target xsi:type="File" fileName="c:\temp\nlog-AspNetCore-all-${shortdate}.log"
 layout="${longdate}|${event-properties:item=EventId:whenEmpty=0}|${level:uppercase=true}|${logger}|${message} ${exception:format=tostring}" />
        <when exists="level &gt;= LogLevel.Warn" filter="level &gt;= LogLevel.Debug"/>
        </target>
    </target>
</targets>

<rules>
    <logger name="*" minlevel="Debug" writeTo="aspnetbuffer" />
</rules>

Hoping this post helps someone!

Happy development.

–

Mr. Kanti Kalyan Arumilli

B.Tech, M.B.A

Facebook

LinkedIn

Threads

Instagram

Youtube

Founder & CEO, Lead Full-Stack .Net developer

ALight Technology And Services Limited

ALight Technologies USA Inc

Youtube

Facebook

LinkedIn

Phone / SMS / WhatsApp on the following 3 numbers:

+91-789-362-6688, +1-480-347-6849, +44-07718-273-964

+44-33-3303-1284 (Preferred number if calling from U.K, No WhatsApp)

kantikalyan@gmail.com, kantikalyan@outlook.com, admin@alightservices.com, kantikalyan.arumilli@alightservices.com, KArumilli2020@student.hult.edu, KantiKArumilli@outlook.com and 3 more rarely used email addresses – hardly once or twice a year.