[jira] [Created] (LOG4NET-615) Expose members in SystemStringFormat

["Daniel Lidström (JIRA)" <ji...@apache.org>]

Daniel Lidström created LOG4NET-615:
---------------------------------------

             Summary: Expose members in SystemStringFormat
                 Key: LOG4NET-615
                 URL: https://issues.apache.org/jira/browse/LOG4NET-615
             Project: Log4net
          Issue Type: Wish
          Components: Layouts
    Affects Versions: 2.0.8
            Reporter: Daniel Lidström


Hello

 

I'm trying to create a structured logging format and have a conversion pattern with a custom converter like this:

 

      <layout type="log4net.Layout.PatternLayout">

        <conversionPattern value="%date [%2thread] %-5level [%property\{NDC}] %username - type=%message_checksum %message%newline" />

        <converter>

          <name value="message_checksum" />

          <type value="TestBed.MessageChecksumConverter" />

        </converter>

      </layout>

 

The interesting part of course is the message_checksum. For example, I am logging like this:

 

                Log.Debug("some debugging message");

                Log.Info(new \{ Id = 1, Name = "the name" });

                Log.InfoFormat("Logging msg \{0}", 1);

                Log.InfoFormat("Logging msg \{0}", 2);

                Log.InfoFormat("Logging msg \{0}", 3);

 

I would like the output to be something like this

 

2018-10-26 11:06:44,564 [ 1] DEBUG [(null)] XXX - type=f6d5 some debugging message

2018-10-26 11:06:44,638 [ 1] INFO  [(null)] XXX - type=e0e3 \{ Id = 1, Name = the name }

2018-10-26 11:06:44,648 [ 1] INFO  [(null)] XXX - type=32a6 Logging msg 1

2018-10-26 11:06:44,656 [ 1] INFO  [(null)] XXX - type=32a6 Logging msg 2

2018-10-26 11:06:44,663 [ 1] INFO  [(null)] XXX - type=32a6 Logging msg 3

 

As you can see, I am getting the type=32a6 for the last 3 logging messages. This allows me to search for all of those, regardless of the parameters given.

For example, I can now search and group the number of errors by their unique type and know which error is most common in our system.

 

To implement this, I did the following:

{{public class MessageChecksumConverter : PatternLayoutConverter}}
{{ {}}
{{  private static readonly TraceSource Source = new}}

{{    TraceSource(nameof(MessageChecksumConverter));}}
{{  private static readonly MD5 ChecksumGenerator = MD5.Create();}}

{{protected override void Convert(TextWriter writer, LoggingEvent loggingEvent)}}
{{ {}}
{{  var output = TryGetHash(loggingEvent);}}
{{  writer.Write(output);}}
{{ }}}

{{private string TryGetHash(LoggingEvent loggingEvent)}}
{{ {}}
{{ string output = string.Empty;}}
{{ try}}
{{ {}}
{{ byte[] hash;}}
{{ var fmt = loggingEvent.MessageObject as SystemStringFormat;}}
{{ if (fmt != null)}}
{{ {}}
{{ // read fmt.m_format and use that as input for hash}}
{{ var systemStringFormatType = typeof(SystemStringFormat);}}
{{ var fieldInfo =}}
{{ systemStringFormatType.GetField("m_format", BindingFlags.NonPublic | BindingFlags.Instance);}}
{{ var formatString = fieldInfo?.GetValue(fmt) as string;}}
{{ hash = ChecksumGenerator.ComputeHash(Encoding.ASCII.GetBytes(formatString ?? string.Empty));}}
{{ }}}
{{ else}}
{{ {}}
{{ var str = (loggingEvent.ExceptionObject ?? loggingEvent.MessageObject).ToString();}}
{{ hash = ChecksumGenerator.ComputeHash(Encoding.ASCII.GetBytes(str));}}
{{ }}}{{var builder = new StringBuilder();}}
{{ foreach (var b in hash.Take(2))}}
{{ {}}
{{ builder.Append(b.ToString("x2"));}}
{{ }}}{{output = builder.ToString();}}
{{ }}}
{{ catch (Exception ex)}}
{{ {}}
{{ // can be found if log4net debugging is enabled}}
{{ Source.TraceError(ex.ToString());}}
{{ }}}{{return output;}}
{{ }}}
{{ }}}

 

{{Sorry for the bad formatting (blame Atlassian). }}

I am reading SystemStringFormat.m_format by using reflection. That gives me the string template used when logging and it is the one I think is appropriate when outputting the type of the log message.

 

Now to my feature request: please expose the internals of SystemStringFormat so that I can do this in a safe way.

What do you think?

 

Regards,

Daniel Lidström



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