Adding support for links and capturing all types of spans (#50)

* Introducing Stackdriver Exporter for Opencensus C# library

- Current implementation can only store string values
- Added the exporter and trace handler only
- The exporter relies on newest Trace API from Stackdriver.

* Updating translation from ISpan to Stackdriver's Span to cover more fields

* Fixing the issue that prevented Stackdriver API call to succeed:
now construction of Span resource is taken care of by SpanName class that
is part of Stackdriver Trace V2 API.

* - Added support for capturing all types of trace spans (long/bool/string)
- Fixed csproj, so it produces both .NET Core and .NET versions. It also means signing the assembly using the same mechanism as other assemblies in the solution

* - Added support for storing links
- Minor fixes to proto<->opencensus translation methods

* Fixing merge issue

Author: Simon Zeltser

src/OpenCensus.Exporter.Stackdriver/Implementation/StackdriverTraceExporter.cs

@@ -20,6 +20,8 @@ static class SpanExtensions
         public static Span ToSpan(this ISpanData spanData, string projectId)
         {
             string spanId = spanData.Context.SpanId.ToLowerBase16();
+
+            // Base span settings
             var span = new Span
             {
                 SpanName = new SpanName(projectId, spanData.Context.TraceId.ToLowerBase16(), spanId),
@@ -29,7 +31,26 @@ public static Span ToSpan(this ISpanData spanData, string projectId)
                 EndTime = spanData.EndTimestamp.ToTimestamp(),
                 ChildSpanCount = spanData.ChildSpanCount,
             };
+            if (spanData.ParentSpanId != null)
+            {
+                string parentSpanId = spanData.ParentSpanId.ToLowerBase16();
+                if (!string.IsNullOrEmpty(parentSpanId))
+                {
+                    span.ParentSpanId = parentSpanId;
+                }
+            }
 
+            // Span Links
+            if (spanData.Links != null)
+            {
+                span.Links = new Span.Types.Links
+                {
+                    DroppedLinksCount = spanData.Links.DroppedLinksCount,
+                    Link = { spanData.Links.Links.Select(l => l.ToLink()) }
+                };
+            }
+
+            // Span Attributes
             if (spanData.Attributes != null)
             {
                 span.Attributes = new Span.Types.Attributes
@@ -42,33 +63,59 @@ public static Span ToSpan(this ISpanData spanData, string projectId)
                 };
             }
 
-            if (spanData.ParentSpanId != null)
+            return span;
+        }
+
+        public static Span.Types.Link ToLink(this ILink link)
+        {
+            var ret = new Span.Types.Link();
+            ret.SpanId = link.SpanId.ToLowerBase16();
+            ret.TraceId = link.TraceId.ToLowerBase16();
+            
+            if (link.Attributes != null)
             {
-                string parentSpanId = spanData.ParentSpanId.ToLowerBase16();
-                if (!string.IsNullOrEmpty(parentSpanId))
+                ret.Attributes = new Span.Types.Attributes
                 {
-                    span.ParentSpanId = parentSpanId;
-                }
+                    
+                    DroppedAttributesCount = OpenCensus.Trace.Config.TraceParams.DEFAULT.MaxNumberOfAttributes - link.Attributes.Count,
+
+                    AttributeMap = { link.Attributes.ToDictionary(
+                         att => att.Key,
+                         att => att.Value.ToAttributeValue()) }
+                };
             }
 
-            return span;
+            return ret;
         }
 
         public static Google.Cloud.Trace.V2.AttributeValue ToAttributeValue(this IAttributeValue av)
         {
-            // TODO Currently we assume we store only strings.
-            return new Google.Cloud.Trace.V2.AttributeValue
+            var ret = new Google.Cloud.Trace.V2.AttributeValue();
+            var attributeType = av.GetType();
+
+            // Handle all primitive types
+            if (attributeType == typeof(AttributeValue<bool>))
             {
-                StringValue = new TruncatableString
+                ret.BoolValue = ((AttributeValue<bool>)av).Value;
+            }
+            else if (attributeType == typeof(AttributeValue<long>))
+            {
+                ret.IntValue = ((AttributeValue<long>)av).Value;
+            }
+            else // String or anything else is written as string
+            {
+                ret.StringValue = new TruncatableString()
                 {
                     Value = av.Match(
-                    s => s,
-                    b => b.ToString(),
-                    l => l.ToString(),
-                    obj => obj.ToString(),
-                    obj => obj.ToString())
-                }
-            };
+                        s => s,
+                        b => b.ToString(),
+                        l => l.ToString(),
+                        d => d.ToString(),
+                        o => o.ToString())
+                };
+            }
+
+            return ret;
         }
     }
 

src/OpenCensus.Exporter.Stackdriver/OpenCensus.Exporter.Stackdriver.csproj

@@ -1,22 +1,23 @@
 <Project Sdk="Microsoft.NET.Sdk">
-  <!--
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildProjectDirectory), 'OpenCensus.sln'))\build\Common.prod.props" />
-  -->
-  <PropertyGroup>
-    <TargetFramework>netstandard2.0</TargetFramework>
-    <IncludeSymbols>True</IncludeSymbols>
-  </PropertyGroup>
-
   <PropertyGroup>
+    <TargetFrameworks>net46;netstandard2.0</TargetFrameworks>
+    <TargetFrameworks Condition="$(OS) != 'Windows_NT'">netstandard2.0</TargetFrameworks>
     <Description>Stackdriver Exporter for OpenCensus.</Description>
+    <IncludeSymbols>True</IncludeSymbols>
     <PackageTags>Tracing;OpenCensus;Management;Monitoring;Stackdriver;Google;GCP;distributed-tracing</PackageTags>
     <PackageIconUrl>https://opencensus.io/images/opencensus-logo.png</PackageIconUrl>
     <PackageProjectUrl>https://opencensus.io</PackageProjectUrl>
     <PackageLicenseUrl>https://www.apache.org/licenses/LICENSE-2.0</PackageLicenseUrl>
     <Authors>OpenCensus authors</Authors>
     <PackageRequireLicenseAcceptance>true</PackageRequireLicenseAcceptance>
   </PropertyGroup>
-
+  
+  <PropertyGroup Condition="'$(Configuration)'=='Debug'">
+    <DebugType>full</DebugType>
+    <DebugSymbols>true</DebugSymbols>
+  </PropertyGroup>
+  
   <ItemGroup>
     <PackageReference Include="Google.Cloud.Trace.V2" Version="1.0.0-beta02" />
   </ItemGroup>

src/OpenCensus.Exporter.Stackdriver/Utils/ProtoExtensions.cs

@@ -4,8 +4,17 @@ namespace OpenCensus.Exporter.Stackdriver.Utils
     using Google.Protobuf.WellKnownTypes;
     using OpenCensus.Common;
 
+    /// <summary>
+    /// Translation methods from Opencensus structures to common
+    /// Protobuf structures
+    /// </summary>
     public static class ProtoExtensions
     {
+        /// <summary>
+        /// Translates Opencensus Timestamp to Protobuf's timestamp
+        /// </summary>
+        /// <param name="timestamp">Opencensus timestamp</param>
+        /// <returns>Protobuf's timestamp</returns>
         public static Timestamp ToTimestamp(this ITimestamp timestamp)
         {
             return new Timestamp { Seconds = timestamp.Seconds, Nanos = timestamp.Nanos };