Use IOptions<T> for DI options

[AlexeiScherbakov]

For example StackExchangeRedisCallsCollectorOptions can be be injected as

var options=new StackExchangeRedisCallsCollectorOptions();
services.Configure<StackExchangeRedisCallsCollectorOptions>(options);

and StackExchangeRedisCallsCollector must have ctor with IOptions or IOptionsMonitor(for reloading options dynamically) for example:

public StackExchangeRedisCallsCollector(IOptions<StackExchangeRedisCallsCollectorOptions> options, ITracer tracer, ISampler sampler, IExportComponent exportComponent)
        {
...
        }

link: https://docs.microsoft.com/en-US/aspnet/core/fundamentals/configuration/options?view=aspnetcore-2.2

[SergeyKanzhelev]

@pakrym do you have suggestion on how IOptions can be used alongside this style of configuring:

https://github.com/open-telemetry/opentelemetry-dotnet#configuration-with-microsoftextensionsdependencyinjection

Where the constructor of zipkin collector will get the options from?

services.AddOpenTelemetry(b => b
            .UseZipkin(o => o.ServiceName = "my-service")

I'm a bit lost in injections =)

[pakrym]

You can add a T GetOptions<T>() to TracerBuilder (with default implementation being just new T()) and in AddOpenTelemetry extension method create a derived TracerBuilder that would implement GetOptions via IOptions<> resolution.

Then in UseZipkin method would become something like:

return builder.AddProcessorPipeline(b =>
            {
              var options  = b.GetOptions<ZipkinTraceExporterOptions>();

                b.SetExporter(new ZipkinTraceExporter(options  ));
                processorConfigure.Invoke(b);
            });

[SergeyKanzhelev]

I just realized that this will mean that all packages will have a reference to IOptions (Microsoft.Extensions.Options) from everywhere except OpenTelemetry.Api. It may not work for net45. And in general looks excessive. Is it by design or I'm missing something?

[pakrym]

I think you can design it in a way where only OpenTelemetry.Hosting would have a dependency on IOptions