k8s operator example and dev docs. (#155)

Ensuring our container for our autoinstrumentation distribution loads
correctly
using the OpenTelemetry k8s Operator

Cc @akhileshpok

---------

Co-authored-by: Steve Gordon <sgordon@hotmail.co.uk>

Elastic.OpenTelemetry.sln

@@ -47,6 +47,13 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "AutoInstrumentation.Integra
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Elastic.OpenTelemetry.AutoInstrumentation", "src\Elastic.OpenTelemetry.AutoInstrumentation\Elastic.OpenTelemetry.AutoInstrumentation.csproj", "{B1CA9165-89D9-4D6E-AFEF-5434A8D8A672}"
 EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "k8s", "k8s", "{21E61166-2640-4E38-8108-1BA510C07110}"
+	ProjectSection(SolutionItems) = preProject
+		examples\k8s\elastic-otel-dotnet.yml = examples\k8s\elastic-otel-dotnet.yml
+		examples\k8s\my-dotnet-application.yml = examples\k8s\my-dotnet-application.yml
+		examples\k8s\README.md = examples\k8s\README.md
+	EndProjectSection
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -130,6 +137,7 @@ Global
 		{F3AA76EC-C7D8-42DA-947D-4376B6562772} = {4E95C87B-655B-4BC3-8F2A-DF06B7AAB7E9}
 		{782E4DC1-8186-4BAC-B2F4-89E6DF22A4DD} = {AAD39891-0B70-47FA-A212-43E1AAE5DF56}
 		{B1CA9165-89D9-4D6E-AFEF-5434A8D8A672} = {E622CFF2-C6C4-40FB-BE42-7C4F2B38B75A}
+		{21E61166-2640-4E38-8108-1BA510C07110} = {4E95C87B-655B-4BC3-8F2A-DF06B7AAB7E9}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {573B2B5F-8CBB-4D52-A55A-4E65E282AAFB}

examples/Example.AspNetCore.Mvc/Dockerfile

@@ -0,0 +1,25 @@
+FROM mcr.microsoft.com/dotnet/aspnet:8.0 AS base
+USER $APP_UID
+WORKDIR /app
+EXPOSE 8080
+EXPOSE 8081
+
+FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build
+ARG BUILD_CONFIGURATION=Release
+WORKDIR /src
+COPY ["examples/Example.AspNetCore.Mvc/Example.AspNetCore.Mvc.csproj", "examples/Example.AspNetCore.Mvc/"]
+COPY ["src/Elastic.OpenTelemetry/Elastic.OpenTelemetry.csproj", "src/Elastic.OpenTelemetry/"]
+COPY ["examples/ServiceDefaults/ServiceDefaults.csproj", "examples/ServiceDefaults/"]
+RUN dotnet restore "examples/Example.AspNetCore.Mvc/Example.AspNetCore.Mvc.csproj"
+COPY . .
+WORKDIR "/src/examples/Example.AspNetCore.Mvc"
+RUN dotnet build "Example.AspNetCore.Mvc.csproj" -c $BUILD_CONFIGURATION -o /app/build
+
+FROM build AS publish
+ARG BUILD_CONFIGURATION=Release
+RUN dotnet publish "Example.AspNetCore.Mvc.csproj" -c $BUILD_CONFIGURATION -o /app/publish /p:UseAppHost=false
+
+FROM base AS final
+WORKDIR /app
+COPY --from=publish /app/publish .
+ENTRYPOINT ["dotnet", "Example.AspNetCore.Mvc.dll"]

examples/Example.AspNetCore.Mvc/Example.AspNetCore.Mvc.csproj

@@ -4,6 +4,7 @@
     <TargetFramework>net8.0</TargetFramework>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
+    <DockerDefaultTargetOS>Linux</DockerDefaultTargetOS>
   </PropertyGroup>
 
   <ItemGroup>
@@ -15,4 +16,10 @@
     <PackageReference Include="OpenTelemetry.Instrumentation.AspNetCore" Version="1.9.0" />
   </ItemGroup>
 
+  <ItemGroup>
+    <Content Include="..\..\.dockerignore">
+      <Link>.dockerignore</Link>
+    </Content>
+  </ItemGroup>
+
 </Project>

examples/k8s/README.md

@@ -0,0 +1,128 @@
+# Run Elastic Distribution of OpenTelemetry .NET on k8s
+
+The following documents how to auto instrument using the OpenTelemetry k8s Operator.
+
+First create a namespace for your k8s deployment:
+
+```bash
+kubectl create namespace my-dotnet-ns
+```
+
+Next up we'll set our Elastic Cloud endpoint and key as k8s secrets.
+
+```bash
+kubectl create secret generic elastic-otel -my-dotnet-ns \
+  "--from-literal=endpoint=<cloud_endpoint>" \
+  "--from-literal=apiKey=Authorization=Bearer <api_key>"
+```
+
+Next create an `Instrumentation` resource by creating an [`elastic-otel-dotnet.yml`](elastic-otel-dotnet.yml) file.
+
+Then apply it to create it in our namespace
+
+```bash
+kubectl apply -f elastic-otel-dotnet.yml -n my-dotnet-ns
+```
+
+We then edit the namespace to make sure our Instrumentation annotations get applied always:
+
+```bash
+kubectl edit namespace my-dotnet-ns
+```
+ensure the following `instrumentation` gets added under `metadata>annotations`
+
+```yml
+apiVersion: v1
+kind: Namespace
+metadata:
+  annotations:
+    instrumentation.opentelemetry.io/inject-dotnet: elastic-otel-dotnet
+```
+
+We can now create our pod containing our dotnet image.
+
+To add your containerized image create a new `my-dotnet-application.yml` file
+
+```yml
+apiVersion: v1
+kind: Pod
+metadata:
+  name: my-dotnet-application
+  namespace: my-dotnet-application
+  labels:
+    app: my-dotnet-application
+spec:
+  containers:
+    - image: _YOUR_APPLICATIONS_DOCKER_URL_
+      imagePullPolicy: Always
+      name: my-dotnet-application
+```
+
+We can then spin up this pod by applying the template
+
+```bash
+kubectl apply -f my-dotnet-application.yml -n my-dotnet-ns
+```
+
+Once spun up we can query the logs with 
+
+```bash
+kubectl logs my-dotnet-application -n my-dotnet-ns
+```
+
+It should print the Elastic Distribution of OpenTelemetry .NET preamble 
+
+```log
+[2024-09-06 18:49:36.011][00001][------][Information]  Elastic Distribution of OpenTelemetry .NET: 1.0.0-alpha.6.1
+```
+
+TIP: You can expose this pod locally to your host using:
+
+```bash
+kubectl port-forward -n my-dotnet-ns pods/my-dotnet-application 8081:8080
+```
+
+Here we forward the container port `8080` to your local port `8081` allowing you to browse your application.
+
+
+
+
+### Use a local image as pod image
+
+Useful when developing.
+
+```bash
+docker build . -t asp-net-example -f examples/Example.AspNetCore.Mvc/Dockerfile
+minikube image load asp-net-example:latest --daemon
+```
+
+This ensures minikube can resolve `asp-net-example:latest`, you can now update your 
+application spec section to:
+
+```yml
+spec:
+  containers:
+    - image: asp-net-example:latest
+      imagePullPolicy: Never
+      name: asp-net-example
+```
+
+NOTE: Make sure `imagePullPolicy` is set to `Never`
+
+
+### Debug deployments 
+
+The `describe` command is great to validate the init-container ran and exposed
+all the necessary environment variables.
+
+```bash
+kubectl describe pod my-dotnet-application -n my-dotnet-ns
+```
+
+You can use `exec` to inspect the container to see if it matches your expectations.
+```log
+kubectl exec my-dotnet-application -n my-dotnet-ns -- ls -la /otel-auto-instrumentation-dotnet
+```
+
+
+

examples/k8s/elastic-otel-dotnet.yml

@@ -0,0 +1,35 @@
+apiVersion: opentelemetry.io/v1alpha1
+kind: Instrumentation
+metadata:
+  name: elastic-otel-dotnet
+  namespace: my-dotnet-application
+spec:
+  env:
+    - name: OTEL_EXPORTER_OTLP_ENDPOINT
+      valueFrom:
+        secretKeyRef:
+          name: elastic-otel
+          key: endpoint
+  exporter:
+    endpoint: $OTEL_EXPORTER_OTLP_ENDPOINT
+  propagators:
+    - tracecontext
+    - baggage
+    - b3
+  sampler:
+    type: parentbased_traceidratio
+    argument: "1.0"
+  dotnet:
+    image: docker.elastic.co/observability/elastic-otel-dotnet:edge
+    env:
+      - name: OTEL_EXPORTER_OTLP_HEADERS
+        valueFrom:
+          secretKeyRef:
+            name: elastic-otel
+            key: apiKey
+      - name: OTEL_LOG_LEVEL
+        value: "info"
+      - name: ELASTIC_OTEL_LOG_TARGETS
+        value: "stdout"
+
+

examples/k8s/my-dotnet-application.yml

@@ -0,0 +1,12 @@
+apiVersion: v1
+kind: Pod
+metadata:
+  name: my-dotnet-application
+  namespace: my-dotnet-application
+  labels:
+    app: my-dotnet-application
+spec:
+  containers:
+    - image: asp-net-example:latest
+      imagePullPolicy: Never
+      name: asp-net-example