Serilog : Log to different files

Question

I am logging events of all types to single Json file irrespective of LogLevel. Now I have a requirement to log some custom performance counters to a seperate Json file. How can this be done in Serilog. Should I create different Logger Instance and use that where ever I am going to Log the performance counters? Want to use this with LibLog

Answer 1

You can do this by first making sure the performance counter events are tagged with either a particular property value (OpenMappedContext() in LibLog) or from a particular type/namespace.

var log = LogProvider.For<MyApp.Performance.SomeCounter>()
log.Info(...);

When configuring Serilog, a sub-logger with filter applied can send just the required events to the second file.

Log.Logger = new LoggerConfiguration()
    .WriteTo.Logger(lc => lc
        .Filter.ByExcluding(Matching.FromSource("MyApp.Performance"))
        .WriteTo.File("first.json", new JsonFormatter()))
    .WriteTo.Logger(lc => lc
        .Filter.ByIncludingOnly(Matching.FromSource("MyApp.Performance"))
        .WriteTo.File("second.json", new JsonFormatter()))
    .CreateLogger();