Tracer configuration system (managed code) (DataDog#289)

* add IConfigurationSource and several implementations

* add assembly and nuget references

* initialize a configuration source

* add xml-doc comments, rename ConfigurationSource to StringConfigurationSource

* reorder configuration sources

* move private method further down to make StyleCop happy

* allow initializer syntax by renaming method to `Add()` and implementing `IEnumerable`

* add `YamlConfigurationSource`

* rewrite `CreateConfigurationSource()`

* fix build errors from last merge

* use ConfigurationSource for default service name

* remove yaml configuration (we can provide as separate nuget later if needed)

* add constants for standard configuration keys and a strongly-typed configuration wrapper around IConfigurationSource

* refactor Tracer to use an IConfigurationSource for all its configuration needs, simplfy the Create() overloads and several constructors

* rename AggregateConfigurationSource to CompositeConfigurationSource

* use the new "default" syntax; reformat code

* add comments and a parameterless constructor

* move another constant to ConfigurationKeys

* fix compiler errors in unit tests

* use default configuration in Tracer.Create()

* add additional settings

* rename CreateAgentUri() to GetAgentUri()

* refactor Configuration to read all value in ctor and not keep the IConfigurationSource reference

* rename Configuration to TracerConfiguration

* refactor Tracer ctor to take a Configuration instead of IConfigurationSource

* fix compiler errors in test project

* rename Configuration to TracerConfiguration

* move CreateDefaultConfigurationSource() from Tracer to TracerConfiguration

* use TracerConfiguration.FromDefaultSources() where possible

* add IScopeManager

* split ctor into public and internal to allow injecting dependencies

* rename TracerConfiguration to TracerSettings

* add constants for default values

* fix compiler errors

* remove unused SimpleSampler

* initialize Tracer.Instance with default configuration sources

* revert change so we ensure we return null

* fix unit tests

* fix comment

* fix xml doc comments

* add new DD_TRACE_AGENT_URL setting

* merge AgentHost and AgentPort into AgentUri

Author: lucaspimentel

src/Datadog.Trace.OpenTracing/OpenTracingTracer.cs

@@ -17,7 +17,7 @@ public OpenTracingTracer(IDatadogTracer datadogTracer)
         {
         }
 
-        public OpenTracingTracer(IDatadogTracer datadogTracer, IScopeManager scopeManager)
+        public OpenTracingTracer(IDatadogTracer datadogTracer, global::OpenTracing.IScopeManager scopeManager)
         {
             DatadogTracer = datadogTracer;
             DefaultServiceName = datadogTracer.DefaultServiceName;
@@ -29,7 +29,7 @@ public OpenTracingTracer(IDatadogTracer datadogTracer, IScopeManager scopeManage
 
         public string DefaultServiceName { get; }
 
-        public IScopeManager ScopeManager { get; }
+        public global::OpenTracing.IScopeManager ScopeManager { get; }
 
         public OpenTracingSpan ActiveSpan => (OpenTracingSpan)ScopeManager.Active?.Span;
 

src/Datadog.Trace.OpenTracing/OpenTracingTracerFactory.cs

@@ -1,7 +1,5 @@
 using System;
 using System.Net.Http;
-using Datadog.Trace.Agent;
-using Datadog.Trace.Sampling;
 using OpenTracing;
 
 namespace Datadog.Trace.OpenTracing
@@ -11,8 +9,6 @@ namespace Datadog.Trace.OpenTracing
     /// </summary>
     public static class OpenTracingTracerFactory
     {
-        private static Uri _defaultUri = new Uri("http://localhost:8126");
-
         /// <summary>
         /// Create a new Datadog compatible ITracer implementation with the given parameters
         /// </summary>
@@ -22,18 +18,13 @@ public static class OpenTracingTracerFactory
         /// <returns>A Datadog compatible ITracer implementation</returns>
         public static ITracer CreateTracer(Uri agentEndpoint = null, string defaultServiceName = null, bool isDebugEnabled = false)
         {
-            agentEndpoint = agentEndpoint ?? _defaultUri;
             return CreateTracer(agentEndpoint, defaultServiceName, null, isDebugEnabled);
         }
 
-        internal static OpenTracingTracer CreateTracer(Uri agentEndpoint, string defaultServiceName = null, DelegatingHandler delegatingHandler = null, bool isDebugEnabled = false)
+        internal static OpenTracingTracer CreateTracer(Uri agentEndpoint, string defaultServiceName, DelegatingHandler delegatingHandler, bool isDebugEnabled)
         {
-            var api = new Api(agentEndpoint, delegatingHandler);
-            var agentWriter = new AgentWriter(api);
-            var sampler = new RateByServiceSampler();
-            var ddTracer = new Tracer(agentWriter, sampler, defaultServiceName, isDebugEnabled);
-            var tracer = new OpenTracingTracer(ddTracer);
-            return tracer;
+            var tracer = Tracer.Create(agentEndpoint, defaultServiceName, isDebugEnabled);
+            return new OpenTracingTracer(tracer);
         }
     }
 }

src/Datadog.Trace/AsyncLocalScopeManager.cs

@@ -2,15 +2,15 @@
 
 namespace Datadog.Trace
 {
-    internal class AsyncLocalScopeManager
+    internal class AsyncLocalScopeManager : IScopeManager
     {
         private static readonly ILog Log = LogProvider.For<AsyncLocalScopeManager>();
 
         private readonly AsyncLocalCompat<Scope> _activeScope = new AsyncLocalCompat<Scope>();
 
         public Scope Active => _activeScope.Get();
 
-        public Scope Activate(Span span, bool finishOnClose = true)
+        public Scope Activate(Span span, bool finishOnClose)
         {
             var activeScope = _activeScope.Get();
             var scope = new Scope(activeScope, span, this, finishOnClose);

src/Datadog.Trace/Configuration/CompositeConfigurationSource.cs

@@ -0,0 +1,89 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Datadog.Trace.Configuration
+{
+    /// <summary>
+    /// Represents one or more configuration sources.
+    /// </summary>
+    public class CompositeConfigurationSource : IConfigurationSource, IEnumerable<IConfigurationSource>
+    {
+        private readonly List<IConfigurationSource> _sources = new List<IConfigurationSource>();
+
+        /// <summary>
+        /// Adds a new configuration source to this instance.
+        /// </summary>
+        /// <param name="source">The configuration source to add.</param>
+        public void Add(IConfigurationSource source)
+        {
+            if (source == null) { throw new ArgumentNullException(nameof(source)); }
+
+            _sources.Add(source);
+        }
+
+        /// <summary>
+        /// Inserts an element into the <see cref="CompositeConfigurationSource"/> at the specified index.
+        /// </summary>
+        /// <param name="index">The zero-based index at which <paramref name="item"/> should be inserted.</param>
+        /// <param name="item">The configuration source to insert.</param>
+        public void Insert(int index, IConfigurationSource item)
+        {
+            if (item == null) { throw new ArgumentNullException(nameof(item)); }
+
+            _sources.Insert(index, item);
+        }
+
+        /// <summary>
+        /// Gets the <see cref="string"/> value of the first setting found with
+        /// the specified key from the current list of configuration sources.
+        /// Sources are queried in the order in which they were added.
+        /// </summary>
+        /// <param name="key">The key that identifies the setting.</param>
+        /// <returns>The value of the setting, or null if not found.</returns>
+        public string GetString(string key)
+        {
+            return _sources.Select(source => source.GetString(key))
+                           .FirstOrDefault(value => value != null);
+        }
+
+        /// <summary>
+        /// Gets the <see cref="int"/> value of the first setting found with
+        /// the specified key from the current list of configuration sources.
+        /// Sources are queried in the order in which they were added.
+        /// </summary>
+        /// <param name="key">The key that identifies the setting.</param>
+        /// <returns>The value of the setting, or null if not found.</returns>
+        public int? GetInt32(string key)
+        {
+            return _sources.Select(source => source.GetInt32(key))
+                           .FirstOrDefault(value => value != null);
+        }
+
+        /// <summary>
+        /// Gets the <see cref="bool"/> value of the first setting found with
+        /// the specified key from the current list of configuration sources.
+        /// Sources are queried in the order in which they were added.
+        /// </summary>
+        /// <param name="key">The key that identifies the setting.</param>
+        /// <returns>The value of the setting, or null if not found.</returns>
+        public bool? GetBool(string key)
+        {
+            return _sources.Select(source => source.GetBool(key))
+                           .FirstOrDefault(value => value != null);
+        }
+
+        /// <inheritdoc />
+        IEnumerator<IConfigurationSource> IEnumerable<IConfigurationSource>.GetEnumerator()
+        {
+            return _sources.GetEnumerator();
+        }
+
+        /// <inheritdoc />
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return _sources.GetEnumerator();
+        }
+    }
+}

src/Datadog.Trace/Configuration/ConfigurationKeys.cs

@@ -0,0 +1,63 @@
+namespace Datadog.Trace.Configuration
+{
+    /// <summary>
+    /// String constants for standard Datadog configuration keys.
+    /// </summary>
+    public static class ConfigurationKeys
+    {
+        /// <summary>
+        /// Configuration key for the path to the configuration file.
+        /// Can only be set with an environment variable.
+        /// </summary>
+        public const string ConfigurationFileName = "DD_DOTNET_TRACER_CONFIG_FILE";
+
+        /// <summary>
+        /// Configuration key for the application's environment. Sets the "env" tag on every <see cref="Span"/>.
+        /// </summary>
+        public const string Environment = "DD_ENV";
+
+        /// <summary>
+        /// Configuration key for the application's default service name.
+        /// Used as the service name for top-level spans,
+        /// and used to determine service name of some child spans.
+        /// </summary>
+        public const string ServiceName = "DD_SERVICE_NAME";
+
+        /// <summary>
+        /// Configuration key for enabling or disabling the Tracer.
+        /// Default is enabled.
+        /// </summary>
+        public const string TraceEnabled = "DD_TRACE_ENABLED";
+
+        /// <summary>
+        /// Configuration key for enabling or disabling the Tracer's debug mode.
+        /// Default is disabled.
+        /// </summary>
+        public const string DebugEnabled = "DD_TRACE_DEBUG";
+
+        /// <summary>
+        /// Configuration key for a list of integrations to disable. All other integrations remain enabled.
+        /// Default is empty (all integrations are enabled).
+        /// Supports multiple values separated with semi-colons.
+        /// </summary>
+        public const string DisabledIntegrations = "DD_DISABLED_INTEGRATIONS";
+
+        /// <summary>
+        /// Configuration key for the Agent host where the Tracer can send traces.
+        /// Default is "localhost".
+        /// </summary>
+        public const string AgentHost = "DD_AGENT_HOST";
+
+        /// <summary>
+        /// Configuration key for the Agent port where the Tracer can send traces.
+        /// Default is 8126.
+        /// </summary>
+        public const string AgentPort = "DD_TRACE_AGENT_PORT";
+
+        /// <summary>
+        /// Configuration key for the Agent URL where the Tracer can send traces.
+        /// Default is "http://localhost:8126".
+        /// </summary>
+        public const string AgentUri = "DD_TRACE_AGENT_URL";
+    }
+}

src/Datadog.Trace/Configuration/EnvironmentConfigurationSource.cs

@@ -0,0 +1,17 @@
+using System;
+
+namespace Datadog.Trace.Configuration
+{
+    /// <summary>
+    /// Represents a configuration source that
+    /// retrieves values from environment variables.
+    /// </summary>
+    public class EnvironmentConfigurationSource : StringConfigurationSource
+    {
+        /// <inheritdoc />
+        public override string GetString(string key)
+        {
+            return Environment.GetEnvironmentVariable(key);
+        }
+    }
+}

src/Datadog.Trace/Configuration/IConfigurationSource.cs

@@ -0,0 +1,34 @@
+using System;
+
+namespace Datadog.Trace.Configuration
+{
+    /// <summary>
+    /// A source of configuration settings, identifiable by a string key.
+    /// </summary>
+    public interface IConfigurationSource
+    {
+        /// <summary>
+        /// Gets the <see cref="string"/> value of
+        /// the setting with the specified key.
+        /// </summary>
+        /// <param name="key">The key that identifies the setting.</param>
+        /// <returns>The value of the setting, or null if not found.</returns>
+        string GetString(string key);
+
+        /// <summary>
+        /// Gets the <see cref="int"/> value of
+        /// the setting with the specified key.
+        /// </summary>
+        /// <param name="key">The key that identifies the setting.</param>
+        /// <returns>The value of the setting, or null if not found.</returns>
+        int? GetInt32(string key);
+
+        /// <summary>
+        /// Gets the <see cref="bool"/> value of
+        /// the setting with the specified key.
+        /// </summary>
+        /// <param name="key">The key that identifies the setting.</param>
+        /// <returns>The value of the setting, or null if not found.</returns>
+        bool? GetBool(string key);
+    }
+}

src/Datadog.Trace/Configuration/JsonConfigurationSource.cs

@@ -0,0 +1,79 @@
+using System.IO;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+
+namespace Datadog.Trace.Configuration
+{
+    /// <summary>
+    /// Represents a configuration source that retrieves
+    /// values from the provided JSON string.
+    /// </summary>
+    public class JsonConfigurationSource : IConfigurationSource
+    {
+        private readonly JObject _configuration;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="JsonConfigurationSource"/>
+        /// class with the specified JSON string.
+        /// </summary>
+        /// <param name="json">A JSON string that contains configuration values.</param>
+        public JsonConfigurationSource(string json)
+        {
+            _configuration = (JObject)JsonConvert.DeserializeObject(json);
+        }
+
+        /// <summary>
+        /// Creates a new <see cref="JsonConfigurationSource"/> instance
+        /// by loading the JSON string from the specified file.
+        /// </summary>
+        /// <param name="filename">A JSON file that contains configuration values.</param>
+        /// <returns>The newly created configuration source.</returns>
+        public static JsonConfigurationSource LoadFile(string filename)
+        {
+            string json = File.ReadAllText(filename);
+            return new JsonConfigurationSource(json);
+        }
+
+        /// <summary>
+        /// Gets the <see cref="string"/> value of
+        /// the setting with the specified key.
+        /// Supports JPath.
+        /// </summary>
+        /// <param name="key">The key that identifies the setting.</param>
+        /// <returns>The value of the setting, or null if not found.</returns>
+        string IConfigurationSource.GetString(string key)
+        {
+            return GetValue<string>(key);
+        }
+
+        /// <summary>
+        /// Gets the <see cref="int"/> value of
+        /// the setting with the specified key.
+        /// Supports JPath.
+        /// </summary>
+        /// <param name="key">The key that identifies the setting.</param>
+        /// <returns>The value of the setting, or null if not found.</returns>
+        int? IConfigurationSource.GetInt32(string key)
+        {
+            return GetValue<int?>(key);
+        }
+
+        /// <summary>
+        /// Gets the <see cref="bool"/> value of
+        /// the setting with the specified key.
+        /// Supports JPath.
+        /// </summary>
+        /// <param name="key">The key that identifies the setting.</param>
+        /// <returns>The value of the setting, or null if not found.</returns>
+        bool? IConfigurationSource.GetBool(string key)
+        {
+            return GetValue<bool?>(key);
+        }
+
+        private T GetValue<T>(string key)
+        {
+            JToken token = _configuration.SelectToken(key, errorWhenNoMatch: false);
+            return token == null ? default(T) : token.Value<T>();
+        }
+    }
+}

src/Datadog.Trace/Configuration/NameValueConfigurationSource.cs

@@ -0,0 +1,29 @@
+using System.Collections.Specialized;
+
+namespace Datadog.Trace.Configuration
+{
+    /// <summary>
+    /// Represents a configuration source that retrieves
+    /// values from the provided <see cref="NameValueCollection"/>.
+    /// </summary>
+    public class NameValueConfigurationSource : StringConfigurationSource
+    {
+        private readonly NameValueCollection _nameValueCollection;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="NameValueConfigurationSource"/> class
+        /// that wraps the specified <see cref="NameValueCollection"/>.
+        /// </summary>
+        /// <param name="nameValueCollection">The collection that will be wrapped by this configuration source.</param>
+        public NameValueConfigurationSource(NameValueCollection nameValueCollection)
+        {
+            _nameValueCollection = nameValueCollection;
+        }
+
+        /// <inheritdoc />
+        public override string GetString(string key)
+        {
+            return _nameValueCollection[key];
+        }
+    }
+}