docs: add OpenTelemetry example

.github/dependabot.yaml

@@ -20,6 +20,15 @@ updates:
         patterns:
           - "*"
 
+  - package-ecosystem: "gradle"
+    directory: "/examples/opentelemetry"
+    schedule:
+      interval: "monthly"
+    groups:
+      dependencies:
+        patterns:
+          - "*"
+
   - package-ecosystem: "github-actions"
     directory: "/"
     schedule:

.gitignore

@@ -30,3 +30,9 @@ VERSION.txt
 
 # VSCode IDE
 /.vscode
+
+# env files
+.env
+
+# mac
+.DS_Store

examples/README.md

@@ -0,0 +1,11 @@
+## Examples of using the OpenFGA Java SDK
+
+A collection of examples demonstrating how to use the OpenFGA Java SDK in different scenarios.
+
+### Available Examples
+
+#### Basic Examples (`basic-examples/`)
+A simple example that creates a store, runs a set of calls against it including creating a model, writing tuples and checking for access. This example is implemented in both Java and Kotlin.
+
+#### OpenTelemetry Examples
+- `opentelemetry/` - Demonstrates OpenTelemetry integration both via manual code configuration, as well as no-code instrumentation using the OpenTelemetry java agent

examples/opentelemetry/.env.example

@@ -0,0 +1,19 @@
+# OpenFGA Configuration (REQUIRED)
+FGA_API_URL=api_url_here
+FGA_STORE_ID=store_id_here
+FGA_MODEL_ID=model_id_here
+
+# Authentication (optional - for authenticated OpenFGA instances)
+FGA_CLIENT_ID=client_id_here
+FGA_CLIENT_SECRET=client_secret_here
+FGA_API_AUDIENCE=api_audience_here
+FGA_API_TOKEN_ISSUER=api_issuer_here
+
+# OpenTelemetry Configuration (for manual configuration mode - ./gradlew run)
+# These are used when running with manual OpenTelemetry setup
+# Note: When using the Java agent (./gradlew runWithAgent), 
+# these values are overridden by the JVM arguments in build.gradle
+OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4317
+OTEL_SERVICE_NAME=openfga-java-sdk-example
+OTEL_SERVICE_VERSION=1.0.0
+

examples/opentelemetry/Makefile

@@ -0,0 +1,16 @@
+all: build
+
+openfga_version=latest
+
+build:
+	./gradlew build
+
+run:
+	./gradlew run
+
+run-with-agent:
+	./gradlew runWithAgent
+
+run-openfga:
+	docker pull docker.io/openfga/openfga:${openfga_version} && \
+		docker run -p 8080:8080 docker.io/openfga/openfga:${openfga_version} run

examples/opentelemetry/README.md

@@ -0,0 +1,206 @@
+# OpenTelemetry Example for OpenFGA Java SDK
+
+This example demonstrates two approaches for using OpenTelemetry metrics with the OpenFGA Java SDK:
+
+1. **Manual Configuration** (`./gradlew run`) - Code-based OpenTelemetry setup
+2. **Java Agent** (`./gradlew runWithAgent`) - Zero-code automatic instrumentation
+
+Both approaches generate the same metrics:
+- `fga-client.request.duration` - Total request time for FGA requests
+- `fga-client.query.duration` - Time taken by FGA server to process requests
+- `fga-client.credentials.request` - Number of token requests (if using client credentials)
+
+## SDK Version Configuration
+
+**By default**, this example uses a published version of the OpenFGA Java SDK. 
+
+If you're contributing to the SDK or testing unreleased features:
+
+1. **Enable local SDK** in `settings.gradle`:
+   ```gradle
+   // Uncomment this line:
+   includeBuild '../..'
+   ```
+
+2. **Update dependency** in `build.gradle`:
+   ```gradle
+   // Comment out the versioned dependency:
+   // implementation("dev.openfga:openfga-sdk:$fgaSdkVersion")
+
+   // Uncomment the local dependency:
+   implementation("dev.openfga:openfga-sdk")
+   ```
+
+3. **Build the main SDK first** (from repository root):
+   ```bash
+   cd ../..
+   ./gradlew build
+   cd examples/opentelemetry
+   ```
+
+## Prerequisites
+
+- Java 11 or higher
+- Docker and Docker Compose
+- OpenFGA server running (or use the provided docker-compose setup)
+
+## Quick Start
+
+### 1. Start the OpenTelemetry Stack
+
+```bash
+# Clone the OpenTelemetry Collector setup
+git clone https://github.com/ewanharris/opentelemetry-collector-dev-setup.git otel-collector
+cd otel-collector
+
+# Start the services
+docker-compose up -d
+```
+
+This provides:
+- **Jaeger** at http://localhost:16686 - Distributed tracing UI
+- **Prometheus** at http://localhost:9090 - Metrics collection and querying  
+- **Grafana** at http://localhost:3001 - Metrics visualization (admin:admin)
+
+### 2. Configure OpenFGA Connection
+
+Copy and edit the environment file:
+```bash
+cp .env.example .env
+# Edit .env with your OpenFGA store details
+```
+
+### 3. Choose Your Approach
+
+#### Option A: Manual Configuration (./gradlew run)
+```bash
+./gradlew run
+```
+
+**Pros:**
+- Full control over OpenTelemetry configuration
+- Can customize metrics, exporters, and resources in code
+- No external dependencies beyond your application
+
+**Cons:**
+- Requires OpenTelemetry SDK dependencies in your application
+- More code to write and maintain
+
+#### Option B: Java Agent (./gradlew runWithAgent)  
+```bash
+./gradlew runWithAgent
+```
+
+**Pros:**
+- Zero code changes required - completely automatic
+- No OpenTelemetry dependencies needed in your application
+- Easy to enable/disable by adding/removing the agent
+
+**Cons:**
+- Less control over configuration
+- Requires downloading and managing the agent JAR
+
+## Viewing Metrics
+
+Both approaches export metrics to the same OTLP endpoint. View them in:
+
+- **Prometheus**: http://localhost:9090/graph
+  - Query: `fga_client_request_duration_bucket`
+  - Query: `fga_client_query_duration_bucket`  
+  - Query: `fga_client_credentials_request_total`
+
+- **Grafana**: http://localhost:3001 (admin:admin)
+  - Import dashboard from `grafana/` directory
+  - Or create custom dashboards with the FGA metrics
+
+## Architecture
+
+### Manual Configuration Mode
+```
+Your App → OpenTelemetry SDK → OTLP Exporter → Collector → Prometheus/Jaeger
+```
+
+The application code:
+1. Configures OpenTelemetry SDK with OTLP exporter
+2. Creates OpenFGA client with default telemetry enabled
+3. Performs FGA operations which generate metrics
+4. Metrics are exported to the OTLP collector
+
+### Java Agent Mode  
+```
+Your App → OpenTelemetry Agent → OTLP Exporter → Collector → Prometheus/Jaeger
+```
+
+The OpenTelemetry agent:
+1. Automatically detects and instruments the OpenFGA SDK
+2. Configures exporters based on system properties
+3. Collects metrics without any code changes
+4. Exports to the same OTLP collector
+
+## Troubleshooting
+
+### No Metrics Appearing
+1. Verify OTLP collector is running on localhost:4317
+2. Check the application logs for OpenTelemetry initialization messages
+3. Ensure FGA operations are actually being performed
+
+### Manual Configuration Issues
+- Verify all OpenTelemetry dependencies are included
+- Check that `buildAndRegisterGlobal()` is called before creating the FGA client
+
+### Java Agent Issues  
+- Verify the agent JAR was downloaded successfully
+- Check that OTEL system properties are set correctly
+- Ensure the agent is being loaded (look for agent startup messages)
+
+### Connection Issues
+- Verify your `.env` file has correct FGA_STORE_ID and FGA_MODEL_ID
+- Check that your OpenFGA server is accessible
+- Verify authentication credentials if using a protected OpenFGA instance
+
+## Observing Metrics
+
+### Prometheus (http://localhost:9090)
+
+Query for OpenFGA metrics:
+- `fga_client_request_duration_bucket` - Request duration histogram
+- `fga_client_query_duration_bucket` - Query duration histogram  
+- `fga_client_credentials_request_total` - Credentials request counter
+
+Example queries:
+```promql
+# Average request duration by method
+rate(fga_client_request_duration_sum[5m]) / rate(fga_client_request_duration_count[5m])
+
+# Request rate by HTTP status code
+rate(fga_client_request_duration_count[5m])
+
+# 95th percentile request duration
+histogram_quantile(0.95, rate(fga_client_request_duration_bucket[5m]))
+```
+
+### Grafana (http://localhost:3001)
+
+Login with `admin:admin`. The collector setup includes pre-configured dashboards for OpenFGA metrics.
+
+## Next Steps
+
+- Explore the metrics in Grafana with custom dashboards
+- Try different telemetry configurations to see what works best for your use case
+- Consider which approach (manual vs agent) fits better with your deployment strategy
+
+## Cleanup
+
+To stop the OpenTelemetry stack:
+
+```bash
+cd otel-collector
+docker-compose down
+```
+
+## Learn More
+
+- [OpenFGA Documentation](https://openfga.dev/docs)
+- [OpenFGA Java SDK Documentation](../../README.md)
+- [OpenTelemetry Java Documentation](https://opentelemetry.io/docs/languages/java/)
+- [OpenFGA Telemetry Documentation](../../docs/OpenTelemetry.md)

examples/opentelemetry/build.gradle

@@ -0,0 +1,115 @@
+plugins {
+    id 'application'
+    id 'com.diffplug.spotless' version '7.2.1'
+}
+
+application {
+    mainClass = 'dev.openfga.sdk.example.opentelemetry.OpenTelemetryExample'
+}
+
+// Override the default run task to pass manual config flag
+run {
+    args = ['--mode=manual']
+}
+
+// Task to download OpenTelemetry Java agent if not present
+task downloadAgent {
+    group = 'setup'
+    description = 'Download OpenTelemetry Java agent if not present'
+
+    doLast {
+        def agentFile = file('opentelemetry-javaagent.jar')
+        if (!agentFile.exists()) {
+            println "Downloading OpenTelemetry Java agent..."
+            def agentUrl = 'https://github.com/open-telemetry/opentelemetry-java-instrumentation/releases/latest/download/opentelemetry-javaagent.jar'
+            try {
+                new URL(agentUrl).withInputStream { i ->
+                    agentFile.withOutputStream { it << i }
+                }
+                println "Downloaded opentelemetry-javaagent.jar"
+            } catch (Exception e) {
+                throw new GradleException("Failed to download OpenTelemetry agent: ${e.message}", e)
+            }
+            println "Downloaded opentelemetry-javaagent.jar"
+        } else {
+            println "OpenTelemetry agent already exists"
+        }
+    }
+}
+
+// Task to run with OpenTelemetry agent (no-code approach)
+task runWithAgent(type: JavaExec) {
+    group = 'application'
+    description = 'Run the OpenTelemetry example with Java agent (no-code approach)'
+    dependsOn downloadAgent
+    classpath = sourceSets.main.runtimeClasspath
+    mainClass = 'dev.openfga.sdk.example.opentelemetry.OpenTelemetryExample'
+
+    // Add JVM arguments for OpenTelemetry agent with configuration
+    jvmArgs = [
+        '-javaagent:opentelemetry-javaagent.jar',
+        '-Dotel.service.name=openfga-java-sdk-agent-example',
+        '-Dotel.service.version=1.0.0',
+        '-Dotel.exporter.otlp.endpoint=http://localhost:4317',
+        '-Dotel.exporter.otlp.protocol=grpc'
+    ]
+
+    // Pass agent mode flag to the application
+    args = ['--mode=agent']
+
+    doFirst {
+        println "🤖 Running with OpenTelemetry Java agent (no-code approach)..."
+        println "Service Name: openfga-java-sdk-agent-example"
+        println "Service Version: 1.0.0"
+        println "Exporter Endpoint: http://localhost:4317"
+        println "Exporter Protocol: grpc"
+        println ""
+        println "Make sure you have an OTLP collector running on localhost:4317"
+        println "The agent automatically instruments the application - no code changes needed!"
+    }
+}
+
+repositories {
+    mavenCentral()
+}
+
+ext {
+    fgaSdkVersion = "0.9.0"
+    openTelemetryVersion = "1.53.0"
+    openTelemetryAlphaVersion = "1.53.0-alpha"
+}
+
+dependencies {
+    // Core FGA SDK (always required)
+    // By default, uses the published SDK from Maven Central
+    implementation("dev.openfga:openfga-sdk:$fgaSdkVersion")
+
+    // For local development using the SDK source code:
+    // 1. Uncomment the includeBuild line in settings.gradle
+    // 2. Comment out the line above and uncomment the line below:
+    // implementation("dev.openfga:openfga-sdk")
+
+    // OpenTelemetry SDK dependencies - ONLY NEEDED FOR MANUAL CONFIGURATION (./gradlew run)
+    // When using the Java agent (./gradlew runWithAgent), these dependencies are not required
+    // The agent provides all OpenTelemetry functionality automatically
+    implementation("io.opentelemetry:opentelemetry-sdk:$openTelemetryVersion")
+    implementation("io.opentelemetry:opentelemetry-exporter-prometheus:$openTelemetryAlphaVersion")
+    implementation("io.opentelemetry:opentelemetry-exporter-otlp:$openTelemetryVersion")
+    implementation("io.opentelemetry:opentelemetry-sdk-extension-autoconfigure:$openTelemetryVersion")
+    implementation("io.opentelemetry.semconv:opentelemetry-semconv:1.34.0")
+
+    // Environment variables for this example
+    implementation("io.github.cdimascio:dotenv-java:3.2.0")
+}
+
+// Use spotless plugin to automatically format code
+spotless {
+    enforceCheck false
+    java {
+        palantirJavaFormat()
+        removeUnusedImports()
+        importOrder()
+    }
+}
+
+