OpenTracing doesn't send logs with Serilog

Question

I'm trying to use OpenTracing.Contrib.NetCore with Serilog. I need to send to Jaeger my custom logs. Now, it works only when I use default logger factory Microsoft.Extensions.Logging.ILoggerFactory

My Startup:

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);

    services.AddSingleton<ITracer>(sp =>
    {
        var loggerFactory = sp.GetRequiredService<ILoggerFactory>();
        string serviceName = sp.GetRequiredService<IHostingEnvironment>().ApplicationName;

        var samplerConfiguration = new Configuration.SamplerConfiguration(loggerFactory)
            .WithType(ConstSampler.Type)
            .WithParam(1);

        var senderConfiguration = new Configuration.SenderConfiguration(loggerFactory)
            .WithAgentHost("localhost")
            .WithAgentPort(6831);

        var reporterConfiguration = new Configuration.ReporterConfiguration(loggerFactory)
            .WithLogSpans(true)
            .WithSender(senderConfiguration);

        var tracer = (Tracer)new Configuration(serviceName, loggerFactory)
            .WithSampler(samplerConfiguration)
            .WithReporter(reporterConfiguration)
            .GetTracer();

        //GlobalTracer.Register(tracer);
        return tracer;
    });
    services.AddOpenTracing();
}

and somewhere in controller:

[Route("api/[controller]")]
public class ValuesController : ControllerBase
{
    private readonly ILogger<ValuesController> _logger;

    public ValuesController(ILogger<ValuesController> logger)
    {
        _logger = logger;
    }

    [HttpGet("{id}")]
    public ActionResult<string> Get(int id)
    {
        _logger.LogWarning("Get values by id: {valueId}", id);
        return "value";
    }
}

in a result I will able to see that log in Jaeger UI

But when I use Serilog, there are no any custom logs. I've added UseSerilog() to WebHostBuilder, and all custom logs I can see in console but not in Jaeger. There is open issue in github. Could you please suggest how I can use Serilog with OpenTracing?

Answer 1

You have to tell Serilog to pass the log entry to ILoggerProvider using writeToProviders: true

.UseSerilog(
    (hostingContext, services, loggerConfiguration) => /* snip! */,
    writeToProviders: true)

This only forwards things written using the ILogger. Things written to SeriLog Log methods don't seem to make it.

Answer 2

This is a limitation in the Serilog logger factory implementation; in particular, Serilog currently ignores added providers and assumes that Serilog Sinks will replace them instead.

So, the solutions is implementaion a simple WriteTo.OpenTracing() method to connect Serilog directly to OpenTracing

public class OpenTracingSink : ILogEventSink
{
    private readonly ITracer _tracer;
    private readonly IFormatProvider _formatProvider;

    public OpenTracingSink(ITracer tracer, IFormatProvider formatProvider)
    {
        _tracer = tracer;
        _formatProvider = formatProvider;
    }

    public void Emit(LogEvent logEvent)
    {
        ISpan span = _tracer.ActiveSpan;

        if (span == null)
        {
            // Creating a new span for a log message seems brutal so we ignore messages if we can't attach it to an active span.
            return;
        }

        var fields = new Dictionary<string, object>
        {
            { "component", logEvent.Properties["SourceContext"] },
            { "level", logEvent.Level.ToString() }
        };

        fields[LogFields.Event] = "log";

        try
        {
            fields[LogFields.Message] = logEvent.RenderMessage(_formatProvider);
            fields["message.template"] = logEvent.MessageTemplate.Text;

            if (logEvent.Exception != null)
            {
                fields[LogFields.ErrorKind] = logEvent.Exception.GetType().FullName;
                fields[LogFields.ErrorObject] = logEvent.Exception;
            }

            if (logEvent.Properties != null)
            {
                foreach (var property in logEvent.Properties)
                {
                    fields[property.Key] = property.Value;
                }
            }
        }
        catch (Exception logException)
        {
            fields["mbv.common.logging.error"] = logException.ToString();
        }

        span.Log(fields);
    }
}

public static class OpenTracingSinkExtensions
{
    public static LoggerConfiguration OpenTracing(
              this LoggerSinkConfiguration loggerConfiguration,
              IFormatProvider formatProvider = null)
    {
        return loggerConfiguration.Sink(new OpenTracingSink(GlobalTracer.Instance, formatProvider));
    }
}