3 files changed, 171 insertions, 0 deletions
diff --git a/f3s/tracing-demo/docker/frontend/Dockerfile b/f3s/tracing-demo/docker/frontend/Dockerfile
new file mode 100644
index 0000000..dd28e97
--- /dev/null
+++ b/f3s/tracing-demo/docker/frontend/Dockerfile
@@ -0,0 +1,16 @@
+FROM python:3.11-slim
+
+WORKDIR /app
+
+# Copy and install dependencies
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+# Copy application code
+COPY app.py .
+
+# Expose port for Flask application
+EXPOSE 5000
+
+# Run the application
+CMD ["python", "app.py"]
diff --git a/f3s/tracing-demo/docker/frontend/app.py b/f3s/tracing-demo/docker/frontend/app.py
new file mode 100644
index 0000000..65ab3f3
--- /dev/null
+++ b/f3s/tracing-demo/docker/frontend/app.py
@@ -0,0 +1,149 @@
+#!/usr/bin/env python3
+"""
+Tracing Demo - Frontend Service
+Receives user requests and forwards to middleware service.
+Demonstrates OpenTelemetry auto-instrumentation with Flask.
+"""
+from flask import Flask, jsonify, request
+import requests
+import os
+import logging
+
+# OpenTelemetry imports for distributed tracing
+from opentelemetry import trace
+from opentelemetry.sdk.trace import TracerProvider
+from opentelemetry.sdk.trace.export import BatchSpanProcessor
+from opentelemetry.exporter.otlp.proto.grpc.trace_exporter import OTLPSpanExporter
+from opentelemetry.instrumentation.flask import FlaskInstrumentor
+from opentelemetry.instrumentation.requests import RequestsInstrumentor
+from opentelemetry.sdk.resources import Resource
+
+# Configure logging
+logging.basicConfig(level=logging.INFO)
+logger = logging.getLogger(__name__)
+
+# Initialize OpenTelemetry tracing with resource attributes
+# These attributes identify this service in traces
+resource = Resource(attributes={
+    "service.name": "frontend",
+    "service.namespace": "tracing-demo",
+    "service.version": "1.0.0",
+    "deployment.environment": "production"
+})
+
+provider = TracerProvider(resource=resource)
+
+# Configure OTLP exporter to send traces to Alloy
+otlp_exporter = OTLPSpanExporter(
+    endpoint=os.getenv('OTEL_EXPORTER_OTLP_ENDPOINT',
+                      'http://alloy.monitoring.svc.cluster.local:4317'),
+    insecure=True
+)
+
+# Batch spans for efficient export
+processor = BatchSpanProcessor(otlp_exporter)
+provider.add_span_processor(processor)
+trace.set_tracer_provider(provider)
+
+# Get tracer for manual instrumentation if needed
+tracer = trace.get_tracer(__name__)
+
+# Create Flask application
+app = Flask(__name__)
+
+# Auto-instrument Flask to create spans for HTTP requests
+FlaskInstrumentor().instrument_app(app)
+
+# Auto-instrument requests library to propagate trace context
+RequestsInstrumentor().instrument()
+
+# Configuration for downstream services
+MIDDLEWARE_URL = os.getenv('MIDDLEWARE_URL',
+                          'http://middleware-service.services.svc.cluster.local:5001')
+
+@app.route('/')
+def index():
+    """
+    Health check and service information endpoint.
+    Returns service metadata.
+    """
+    return jsonify({
+        "service": "frontend",
+        "version": "1.0.0",
+        "message": "Tracing demo frontend service",
+        "trace_enabled": True,
+        "middleware_url": MIDDLEWARE_URL
+    })
+
+@app.route('/health')
+def health():
+    """
+    Kubernetes health check endpoint.
+    Used by readiness and liveness probes.
+    """
+    return jsonify({"status": "healthy"}), 200
+
+@app.route('/api/process', methods=['GET', 'POST'])
+def process():
+    """
+    Main processing endpoint that demonstrates distributed tracing.
+    Forwards request to middleware service and returns combined response.
+    Creates a custom span to track the processing logic.
+    """
+    # Create a custom span for the processing logic
+    with tracer.start_as_current_span("frontend-process") as span:
+        # Add custom attributes to the span for better observability
+        span.set_attribute("frontend.handler", "process")
+
+        # Get request data (supports both GET and POST)
+        if request.method == 'POST':
+            data = request.get_json() or {}
+        else:
+            data = {"source": "GET request"}
+
+        span.set_attribute("frontend.request.method", request.method)
+
+        try:
+            # Call middleware service
+            # The requests library auto-instrumentation will create a span
+            # and propagate the trace context via W3C Trace Context headers
+            logger.info(f"Calling middleware at {MIDDLEWARE_URL}/api/transform")
+
+            response = requests.post(
+                f'{MIDDLEWARE_URL}/api/transform',
+                json=data,
+                timeout=10
+            )
+
+            response.raise_for_status()
+            middleware_data = response.json()
+
+            # Record successful call in span
+            span.set_attribute("frontend.middleware.status", response.status_code)
+
+            return jsonify({
+                "service": "frontend",
+                "status": "success",
+                "request_data": data,
+                "middleware_response": middleware_data
+            }), 200
+
+        except requests.exceptions.RequestException as e:
+            # Log error and record in span
+            logger.error(f"Error calling middleware: {e}")
+            span.set_attribute("frontend.error", str(e))
+
+            # Set span status to error
+            span.set_status(trace.Status(trace.StatusCode.ERROR, str(e)))
+
+            return jsonify({
+                "service": "frontend",
+                "status": "error",
+                "error": str(e)
+            }), 500
+
+if __name__ == '__main__':
+    logger.info("Starting frontend service on port 5000")
+    logger.info(f"Middleware URL: {MIDDLEWARE_URL}")
+    logger.info(f"OTLP endpoint: {os.getenv('OTEL_EXPORTER_OTLP_ENDPOINT', 'default')}")
+    app.run(host='0.0.0.0', port=5000, debug=False)
diff --git a/f3s/tracing-demo/docker/frontend/requirements.txt b/f3s/tracing-demo/docker/frontend/requirements.txt
new file mode 100644
index 0000000..cb10687
--- /dev/null
+++ b/f3s/tracing-demo/docker/frontend/requirements.txt
@@ -0,0 +1,6 @@
+flask==3.0.0
+requests==2.31.0
+opentelemetry-distro==0.49b0
+opentelemetry-exporter-otlp==1.28.0
+opentelemetry-instrumentation-flask==0.49b0
+opentelemetry-instrumentation-requests==0.49b0