Add Terraform files to deploy Envoy RateLimiter

examples/terraform/envoy-ratelimiter/README.md

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+<!--
+    Licensed to the Apache Software Foundation (ASF) under one
+    or more contributor license agreements.  See the NOTICE file
+    distributed with this work for additional information
+    regarding copyright ownership.  The ASF licenses this file
+    to you under the Apache License, Version 2.0 (the
+    "License"); you may not use this file except in compliance
+    with the License.  You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+    Unless required by applicable law or agreed to in writing,
+    software distributed under the License is distributed on an
+    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+    KIND, either express or implied.  See the License for the
+    specific language governing permissions and limitations
+    under the License.
+-->
+
+# Envoy Rate Limiter on GKE (Terraform)
+This directory contains a production-ready Terraform module to deploy a scalable **Envoy Rate Limit Service** on Google Kubernetes Engine (GKE) Autopilot.
+
+## Architectures:
+- **GKE Autopilot**: Fully managed, serverless Kubernetes environment.
+  - **Private Cluster**: Nodes have internal IPs only.
+  - **Cloud NAT (Prerequisite)**: Allows private nodes to pull Docker images.
+- **Envoy Rate Limit Service**: A stateless Go/gRPC service that handles rate limit logic.
+- **Redis**: Stores the rate limit counters.
+- **StatsD Exporter**: Sidecar container that converts StatsD metrics to Prometheus format, exposed on port `9102`.
+- **Internal Load Balancer**: A Google Cloud TCP Load Balancer exposing the Rate Limit service internally within the VPC.
+
+## Prerequisites:
+### Following items need to be setup for Envoy Rate Limiter deployment on GCP:
+1. [GCP project](https://cloud.google.com/resource-manager/docs/creating-managing-projects)
+
+2. [Tools Installed](https://cloud.google.com/sdk/docs/install):
+   - [Terraform](https://www.terraform.io/downloads.html) >= 1.0
+   - [Google Cloud SDK](https://cloud.google.com/sdk/docs/install) (`gcloud`)
+   - [kubectl](https://kubernetes.io/docs/tasks/tools/)
+
+3. APIs Enabled:
+   ```bash
+   gcloud services enable container.googleapis.com compute.googleapis.com
+   ```
+
+4. **Network Configuration**:
+   - **Cloud NAT**: Must exist in the region to allow Private Nodes to pull images and reach external APIs. Follow [this](https://docs.cloud.google.com/nat/docs/gke-example#create-nat) for more details.
+     **Helper Command** (if you need to create one):
+     ```bash
+     gcloud compute routers create nat-router --network <VPC_NAME> --region <REGION>
+     gcloud compute routers nats create nat-config \
+         --router=nat-router \
+         --region=<REGION> \
+         --auto-allocated-nat-external-ips \
+         --nat-all-subnet-ip-ranges
+     ```
+   - **Validation via Console**:
+     1. Go to **Network Services** > **Cloud NAT** in the Google Cloud Console.
+     2. Verify a NAT Gateway exists for your **Region** and **VPC Network**.
+     3. Ensure it is configured to apply to **Primary and Secondary ranges** (or at least the ranges GKE will use).
+
+# Prepare deployment configuration:
+1. Create a `terraform.tfvars` file to define variables specific to your environment:
+
+* `terraform.tfvars` environment variables:
+```
+project_id            = "my-project-id"             # GCP Project ID
+region                = "us-central1"               # GCP Region for deployment
+cluster_name          = "ratelimit-cluster"         # Name of the GKE cluster
+deletion_protection   = true                        # Prevent accidental cluster deletion (set "true" for prod)
+control_plane_cidr    = "172.16.0.0/28"             # CIDR for GKE control plane (must not overlap with subnet)
+ratelimit_replicas    = 1                           # Initial number of Rate Limit pods
+min_replicas          = 1                           # Minimum HPA replicas
+max_replicas          = 5                           # Maximum HPA replicas
+hpa_cpu_target_percentage        = 75                          # CPU utilization target for HPA (%)
+hpa_memory_target_percentage     = 75                          # Memory utilization target for HPA (%)
+vpc_name              = "default"                   # Existing VPC name to deploy into
+subnet_name           = "default"                   # Existing Subnet name (required for Internal LB IP)
+ratelimit_image       = "envoyproxy/ratelimit:e9ce92cc" # Docker image for Rate Limit service
+redis_image           = "redis:6.2-alpine"          # Docker image for Redis
+ratelimit_resources   = { requests = { cpu = "100m", memory = "128Mi" }, limits = { cpu = "500m", memory = "512Mi" } }
+redis_resources       = { requests = { cpu = "250m", memory = "256Mi" }, limits = { cpu = "500m", memory = "512Mi" } }
+```
+
+* Custom Rate Limit Configuration (Must override in `terraform.tfvars`):
+```
+ratelimit_config_yaml = <<EOF
+domain: mongo_cps
+descriptors:
+  - key: database
+    value: users
+    rate_limit:
+      unit: second
+      requests_per_unit: 500
+EOF
+```
+
+# Deploy Envoy Rate Limiter:
+1. Initialize Terraform to download providers and modules:
+```bash
+terraform init
+```
+
+2. Plan and apply the changes:
+```bash
+terraform plan -out=tfplan
+terraform apply tfplan
+```
+
+3. Connect to the service:
+After deployment, get the **Internal** IP address:
+```bash
+terraform output load_balancer_ip
+```
+The service is accessible **only from within the VPC** (e.g., via Dataflow workers or GCE instances in the same network) at `<INTERNAL_IP>:8081`.
+
+4. **Test with Dataflow Workflow**:
+   Verify connectivity and rate limiting logic by running the example Dataflow pipeline.
+
+   ```bash
+   # Get the Internal Load Balancer IP
+   export RLS_IP=$(terraform output -raw load_balancer_ip)
+
+   python sdks/python/apache_beam/examples/rate_limiter_simple.py \
+     --runner=DataflowRunner \
+     --project=<YOUR_PROJECT_ID> \
+     --region=<YOUR_REGION> \
+     --temp_location=gs://<YOUR_BUCKET>/temp \
+     --staging_location=gs://<YOUR_BUCKET>/staging \
+     --job_name=ratelimit-test-$(date +%s) \
+     # Point to the Terraform-provisioned Internal IP
+     --rls_address=${RLS_IP}:8081 \
+     # REQUIRED: Run workers in the same private subnet
+     --subnetwork=regions/<YOUR_REGION>/subnetworks/<YOUR_SUBNET_NAME> \
+     --no_use_public_ips
+   ```
+
+
+# Clean up resources:
+To destroy the cluster and all created resources:
+```bash
+terraform destroy
+```
+*Note: If `deletion_protection` was enabled, you must set it to `false` in `terraform.tfvars` before destroying.*
+
+# Variables description:
+
+|Variable               |Description                                          |Default                          |
+|-----------------------|:----------------------------------------------------|:--------------------------------|
+|project_id             |**Required** Google Cloud Project ID                 |-                                |
+|vpc_name               |**Required** Existing VPC name to deploy into        |-                                |
+|subnet_name            |**Required** Existing Subnet name                    |-                                |
+|ratelimit_config_yaml  |**Required** Rate Limit configuration content        |-                                |
+|region                 |GCP Region for deployment                            |us-central1                      |
+|control_plane_cidr     |CIDR block for GKE control plane                     |172.16.0.0/28                    |
+|cluster_name           |Name of the GKE cluster                              |ratelimit-cluster                |
+|deletion_protection    |Prevent accidental cluster deletion                  |false                            |
+|ratelimit_replicas     |Initial number of Rate Limit pods                    |1                                |
+|min_replicas           |Minimum HPA replicas                                 |1                                |
+|max_replicas           |Maximum HPA replicas                                 |5                                |
+|hpa_cpu_target_percentage         |CPU utilization target for HPA (%)                   |75                               |
+|hpa_memory_target_percentage      |Memory utilization target for HPA (%)                |75                               |
+|ratelimit_image        |Docker image for Rate Limit service                  |envoyproxy/ratelimit:e9ce92cc    |
+|redis_image            |Docker image for Redis                               |redis:6.2-alpine                 |
+|ratelimit_resources    |Resources for Rate Limit service (map)               |requests/limits (CPU/Mem)        |
+|redis_resources        |Resources for Redis container (map)                  |requests/limits (CPU/Mem)        |
+

examples/terraform/envoy-ratelimiter/gke.tf

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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Provision the Kubernetes cluster.
+resource "google_container_cluster" "primary" {
+  name     = var.cluster_name
+  location = var.region
+
+  enable_autopilot    = true
+  deletion_protection = var.deletion_protection
+
+  network    = data.google_compute_network.default.id
+  subnetwork = data.google_compute_subnetwork.default.id
+
+  ip_allocation_policy {}
+
+  # Private Cluster Configuration
+  private_cluster_config {
+    enable_private_nodes    = true            # Nodes have internal IPs only
+    enable_private_endpoint = false           # Master is accessible via Public IP (required for Terraform from outside VPC)
+    master_ipv4_cidr_block  = var.control_plane_cidr
+  }
+}

examples/terraform/envoy-ratelimiter/network.tf

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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
+resource "google_compute_address" "ratelimit_ip" {
+  name         = var.ip_name != "" ? var.ip_name : "${var.cluster_name}-ratelimit-ip"
+  region       = var.region
+  address_type = "INTERNAL"
+  subnetwork   = data.google_compute_subnetwork.default.id
+}

examples/terraform/envoy-ratelimiter/outputs.tf

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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+output "cluster_name" {
+  description = "The name of the GKE cluster."
+  value       = google_container_cluster.primary.name
+}
+
+output "load_balancer_ip" {
+  description = "The IP address of the load balancer."
+  value       = google_compute_address.ratelimit_ip.address
+}

examples/terraform/envoy-ratelimiter/prerequisites.tf

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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+resource "google_project_service" "required" {
+  for_each = toset([
+    "container",
+    "iam",
+    "compute",
+  ])
+
+  service            = "${each.key}.googleapis.com"
+  disable_on_destroy = false
+}
+
+// Query the VPC network to make sure it exists.
+data "google_compute_network" "default" {
+  name       = var.vpc_name
+  depends_on = [google_project_service.required]
+}
+
+// Query the VPC subnetwork to make sure it exists in the region specified.
+data "google_compute_subnetwork" "default" {
+  name       = var.subnet_name
+  region     = var.region
+  depends_on = [google_project_service.required]
+  lifecycle {
+    postcondition {
+      condition     = self.private_ip_google_access
+      error_message = <<EOT
+fatal: ${self.id} misconfigured: private Google access disabled.
+See https://cloud.google.com/vpc/docs/configure-private-google-access for details.
+EOT
+    }
+  }
+}

examples/terraform/envoy-ratelimiter/provider.tf

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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+terraform {
+  required_providers {
+    google = {
+      source  = "hashicorp/google"
+      version = "~> 5.0"
+    }
+    kubernetes = {
+      source  = "hashicorp/kubernetes"
+      version = "~> 2.0"
+    }
+  }
+}
+
+provider "google" {
+  project = var.project_id
+  region  = var.region
+}
+
+# Configure kubernetes provider to use the GKE cluster
+provider "kubernetes" {
+  host                   = "https://${google_container_cluster.primary.endpoint}"
+  token                  = data.google_client_config.default.access_token
+  cluster_ca_certificate = base64decode(google_container_cluster.primary.master_auth[0].cluster_ca_certificate)
+}
+
+data "google_client_config" "default" {}