Serilog logger configuration by SourceContext

Question

I am trying to implement serilog in a little sample-project. I´ve did the following so far:

Create new ASP.NET Core Web Application (MVC)
Install-Package Serilog.AspNetCore
Install-Package Serilog.Sinks.File
Install-Package Serilog.Formatting.Compact
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My question:

Is there a possibility to configure two different loggers, based on CategoryName (in my case "MyLogger")? I want this logger to use a different file, than my default-logger. In my happy-world-fantasy it would look like:

        Log.Logger = new LoggerConfiguration()
            .MinimumLevel.Debug()
            .MinimumLevel.Override("Microsoft", LogEventLevel.Warning)
            .Enrich.FromLogContext()
            .WriteTo.File(new CompactJsonFormatter(), @"C:\temp\standardLog.txt")
            .WriteTo.File(new CompactJsonFormatter(), @"C:\temp\specialLog.txt").Filter.ByIncludingOnly(x => x.SourceContext("MySpecialLogger")
            .CreateLogger();

And if I create a new Logger var logger = _loggerFactory.CreateLogger("MySpecialLogger"); the logs will be safed in my specialLog.txt-file.

Any ideas?

Nicholas Blumhardt · Accepted Answer · 2017-11-10 04:36:14Z

1

You need Serilog.Sinks.Map for this.

dotnet add <PROJECT> package Serilog.Sinks.Map -v 1.0.0-dev-00012

Then:

    Log.Logger = new LoggerConfiguration()
        .MinimumLevel.Debug()
        .MinimumLevel.Override("Microsoft", LogEventLevel.Warning)
        .Enrich.FromLogContext()
        .WriteTo.Map("SourceContext", null, (sc, wt) =>
            wt.File(new CompactJsonFormatter(), sc == "MySpecialLogger" ?
                @"C:\temp\specialLog.txt" :
                @"C:\temp\standardLog.txt"))
        .CreateLogger();

edited Nov 10, 2017 at 4:36

answered Nov 8, 2017 at 23:22

Nicholas Blumhardt

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3 Comments

Joshit Over a year ago

First of all: Thanks for having time for my question!! Regarding your answer: The conditional operator fails (compiler-error only assignment, call (...) can be used as a statement).. This param is not valid: Action<string, LoggerSinkConfiguration> configure = (x, wt) => x == "" ? wt.File("") : wt.File("") ; - but I really like the Map-approach.. Any other idea?

Joshit Over a year ago

Great! If I use RollingFile-Sink I have everything I wanted :) Thanks a lot!!! But there is still some unexpected behaviour: MySpecialLogger works as expected. But if I use the File-Sink, my StandardLogger only outputs "Starting Web Host". If I use RollingFile, i get 2 log files (standard-{date}.txt and standard-{date}_001.txt) where the 001-log contains my messages and the other only contains the startup-message. If I remove the Log.Information("Starting web host") -Call, everything works as expected...

Nicholas Blumhardt Over a year ago

Ah! Sorry, the answer's not 100% correct, I'll update it.

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