Configuring Serilog RollingFile with appsettings.json

Question

I'm trying to configure Serilog for a .NET Core project. Here's what I have in my appsettings.json:

 "Serilog": 
{
    "MinimumLevel": "Verbose",
    "Enrich": ["FromLogContext", "WithMachineName", "WithProcessId", "WithThreadId"],
    "WriteTo": [
      { "Name": "RollingFile",
        "Args": {
          "pathFormat": "C:/Logfiles/testapp/log-{Date}.json",
          "textFormatter": "JsonFormatter",
          "fileSizeLimitBytes": 2147483648,
          "retainedFileCountLimit": 5
        }
      }
    ]
  }

The problem I see is that JsonFormatter is not picked up, and instead I get entries using the default text formatter. I tried using "formatter": "JsonFormatter", but got the same result.

It all works fine if I configure Serilog in code:

var jsonSink = new RollingFileSink(config["Logger:FilePath"], new JsonFormatter(), 2147483648, 5);

var logger = new Serilog.LoggerConfiguration().WriteTo.Sink(jsonSink);

Here is the relevant section of my project.json:

"Serilog": "2.2.1",
"Serilog.Extensions.Logging": "1.1.0",
"Serilog.Sinks.Literate": "2.0.0",
"Serilog.Sinks.Seq": "2.0.0",
"Microsoft.Extensions.Configuration.EnvironmentVariables": "1.0.0",
"Microsoft.Extensions.Configuration.Json": "1.0.0",
"Microsoft.Extensions.Configuration.UserSecrets": "1.0.0",
"Microsoft.Extensions.Logging": "1.0.0",
"Microsoft.Extensions.Logging.Console": "1.0.0",
"Microsoft.Extensions.Logging.Debug": "1.0.0",
"Microsoft.Extensions.Options.ConfigurationExtensions": "1.0.0",
"Serilog.Enrichers.Thread": "2.0.0",
"Serilog.Enrichers.Process": "2.0.0",
"Serilog.Sinks.ColoredConsole": "2.0.0",
"Serilog.Settings.Configuration": "2.2.0"

Answer 1

The formatter argument needs to be a fully-qualified type name. Try:

"formatter": "Serilog.Formatting.Json.JsonFormatter, Serilog"