在启动期间注册OpenTelemetry，并在运行时动态添加更多功能

Question

在ConfigureServices类中的Startup方法中，我注册OpenTelemetry如下：

services.AddOpenTelemetryTracing((builder) =>
                    builder
                    .SetResourceBuilder(ResourceBuilder.CreateDefault().AddService("MyService"))
                        .AddAspNetCoreInstrumentation()
                        .AddHttpClientInstrumentation()
                        .AddOtlpExporter(otlpOptions =>
                        {
                            otlpOptions.Endpoint = new Uri("http://localhost:4317");
                        }));

我也想添加Redis工具，但只有在为请求提供服务时，我才能访问Redis连接字符串，在请求中提取ClientId并从相应的客户端配置中提取该客户端的Redis连接字符串。再次在Startup中，在读取ClientInfo时，我添加了用于检测Redis调用的OpenTelemetry跟踪。

services.AddScoped<ClientInfo>(sp =>
            {
                var context = sp.GetService<IHttpContextAccessor>().HttpContext;
                var clientId = context.Request.Headers["ClientId"].ToString();
                var clientInfo = await GetClientInfo(clientId).Result;
                // ClientInfo will contain Redis connection string. I cache this to avoid fetching repeatedly for same client


                // I cache this ClientId in a dictionary and make sure the below registration happens
                // only once per client Id.
                // RedisConnection is of type IConnectionMultiplexer
                var redisConnection = RedisHelper.GetConnection(clientInfo.RedisConnectionString);
                services.AddOpenTelemetryTracing((builder) =>
                    builder
                    .SetResourceBuilder(ResourceBuilder.CreateDefault().AddService("MyService"))
                    .AddRedisInstrumentation(redisConnection)
                        .AddOtlpExporter(otlpOptions =>
                        {
                            otlpOptions.Endpoint = new Uri("http://localhost:4317");
                        }));

                return clientInfo;
            });

当我执行代码时，它只为传入的HTTP请求和传出的HTTP请求创建范围。但并不是在利用Redis的电话。但是，如果我在注册AddAspNetCoreInstrumentation的第一个调用中添加了Redis工具，那么它可以正常工作。

是否有一种方法可以在启动期间添加一些工具，并在运行时通过添加更多的工具来构建这些工具？

Answer 1

据我所知，目前还没有这样的解决方案，在github上有一个开放的问题。但是，如果使用反射，则可以添加这样的功能。

public interface IRedisRuntimeInstrumentation
{
    void AddInstrumentation(IConnectionMultiplexer multiplexer);
}

internal class RedisRuntimeInstrumentation : IRedisRuntimeInstrumentation
{
    private static readonly BindingFlags BindingFlags = BindingFlags.Instance | BindingFlags.NonPublic;

    private readonly PropertyInfo _instrumentationsProperty;
    private readonly FieldInfo _disposedField;
    private readonly TracerProvider _tracerProvider;
    private readonly IOptions<StackExchangeRedisCallsInstrumentationOptions> _options;

    public RedisRuntimeInstrumentation(TracerProvider tracerProvider,
        IOptions<StackExchangeRedisCallsInstrumentationOptions> options)
    {
        var tracerProviderType = tracerProvider?.GetType() ?? throw new ArgumentNullException(nameof(tracerProvider));

        _instrumentationsProperty = tracerProviderType.GetProperty("Instrumentations", BindingFlags)
            ?? throw new InvalidOperationException($"Failed to get property 'Instrumentations' from type - {tracerProviderType.FullName}");

        _disposedField = tracerProviderType.GetField("disposed", BindingFlags)
            ?? throw new InvalidOperationException($"Failed to get field 'disposed' from type - {tracerProviderType.FullName}");

        _tracerProvider = tracerProvider;
        _options = options;
    }

    public void AddInstrumentation(IConnectionMultiplexer multiplexer)
    {
        if (multiplexer == null)
            throw new ArgumentNullException(nameof(multiplexer));

        if (_disposedField.GetValue(_tracerProvider) is bool disposed && disposed)
            throw new InvalidOperationException("Unable to add instrumentation to disposed trace provider");

        var instrumentationsPropertyValue = _instrumentationsProperty.GetValue(_tracerProvider);
        if (instrumentationsPropertyValue is List<object> instrumentations)
            instrumentations.Add(StackExchangeRedisCallsInstrumentationHelper.CreateInstance(multiplexer, _options.Value));
        else
            throw new InvalidOperationException("Failed to add instrumentation");
    }
}

internal static class StackExchangeRedisCallsInstrumentationHelper
{
    internal const string TypeFullName = "OpenTelemetry.Instrumentation.StackExchangeRedis.StackExchangeRedisCallsInstrumentation";

    internal static readonly Type Type = typeof(StackExchangeRedisCallsInstrumentationOptions).Assembly.GetType(TypeFullName)
        ?? throw new InvalidOperationException($"Failed to get type - {TypeFullName}");

    private static readonly ConstructorInfo TypeConstructor = Type
        .GetConstructor(new[] { typeof(IConnectionMultiplexer), typeof(StackExchangeRedisCallsInstrumentationOptions) })
            ?? throw new InvalidOperationException($"Failed to get constructor from type - {TypeFullName}");

    internal static object CreateInstance(IConnectionMultiplexer multiplexer,
        StackExchangeRedisCallsInstrumentationOptions options) =>
            TypeConstructor.Invoke(new object[] { multiplexer, options });
}

public static class OpenTelemetryExtensions
{
    public static IServiceCollection AddRedisRuntimeInstrumentation(this IServiceCollection services)
    {
        services.AddSingleton<IRedisRuntimeInstrumentation, RedisRuntimeInstrumentation>();

        return services;
    }

    public static TracerProviderBuilder AddRedisRuntimeInstrumentationSource(this TracerProviderBuilder builder)
    {
        var activitySourceNameField = StackExchangeRedisCallsInstrumentationHelper.Type
            .GetField("ActivitySourceName", BindingFlags.Static | BindingFlags.NonPublic);

        if (activitySourceNameField == null)
        {
            throw new InvalidOperationException(
                $"Failed to get field 'ActivitySourceName' from type - {StackExchangeRedisCallsInstrumentationHelper.TypeFullName}");
        }

        builder.AddSource((string)activitySourceNameField.GetValue(null));

        return builder;
    }
}

然后在Startup.cs中，通过DI调用AddRedisRuntimeInstrumentation()和AddRedisRuntimeInstrumentationSource()来使用IRedisRuntimeInstrumentation，并在需要的地方调用AddInstrumentation。