Add observability

[tarun-google]

Export script metrics to Cloud Monitoring

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[gemini-code-assist]

Summary of Changes

Hello @tarun-google, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the observability of the Envoy Rate Limiter example by transitioning its metrics collection from StatsD to native Prometheus, with direct export to Google Cloud Monitoring. This change provides more robust and integrated monitoring capabilities. Additionally, the deployment experience has been improved through the introduction of an automated helper script, simplifying the setup and teardown of the rate limiter service.

Highlights

• Observability Integration: Integrated native Prometheus metrics with Google Cloud Monitoring for the Envoy Rate Limiter, replacing the previous StatsD exporter.
• Simplified Deployment: Introduced a new deploy.sh helper script to automate the Terraform deployment and destruction processes for the Envoy Rate Limiter.
• Metrics Enabled by Default: Changed the default setting for enable_metrics to true, ensuring observability is active out-of-the-box.
• Documentation Updates: Updated the README.md to reflect the new Prometheus metrics, the default enablement of metrics, and the streamlined deployment instructions.

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Changelog

• examples/terraform/envoy-ratelimiter/README.md
  • Updated the description of metrics to reflect Prometheus integration and export to Google Cloud Monitoring.
  • Changed the default value for enable_metrics in the example configuration to true.
  • Revised deployment instructions to recommend and detail the use of the new deploy.sh script.
  • Added a new section dedicated to 'Observability & Metrics', including sample metrics and viewing instructions for Google Cloud Console.
  • Updated cleanup instructions to include the deploy.sh destroy command.
• examples/terraform/envoy-ratelimiter/deploy.sh
  • Added a new shell script to automate the Terraform init, apply, and destroy commands for the Envoy Rate Limiter.
• examples/terraform/envoy-ratelimiter/prerequisites.tf
  • Added the monitoring Google Cloud service to the list of required project services.
• examples/terraform/envoy-ratelimiter/ratelimit.tf
  • Modified the kubernetes_deployment resource to expose a Prometheus metrics port (9090) dynamically when metrics are enabled.
  • Replaced USE_STATSD environment variable with USE_PROMETHEUS and configured PROMETHEUS_ADDR and PROMETHEUS_PATH.
  • Removed the STATSD_HOST and STATSD_PORT environment variables.
  • Removed the statsd-exporter sidecar container definition.
  • Added a kubernetes_manifest resource to create a PodMonitoring object for Google Cloud Monitoring, targeting the rate limit service's Prometheus endpoint.
• examples/terraform/envoy-ratelimiter/variables.tf
  • Changed the default value of the enable_metrics variable from false to true.

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