🏰 Watch-Tower

📌 Overview

Watch-Tower is a Kubernetes controller written in Go that:

• Monitors an AutomationController Custom Resource (CRD).
• Checks the PostgreSQL database role (Primary/Standby).
• Automatically scales the AutomationController based on:
  • If the DB is Primary, it sets spec.replicas = watch-tower/replicas annotation.
  • If the DB is Standby, it sets spec.replicas = 0.

🚀 Features

✅ Continuously monitors AutomationController CRD
✅ Detects PostgreSQL role (Primary/Standby)
✅ Reads watch-tower/replicas annotation for scaling
✅ Uses Kubernetes API to patch spec.replicas
✅ Runs in an infinite loop for real-time updates

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⚙️ Setup & Installation

1️⃣ Prerequisites

Ensure you have the following installed:

• Go 1.20+ (go version)
• Kubernetes CLI (kubectl) (kubectl version --client)
• OpenShift CLI (oc) (if using OpenShift) (oc version)
• PostgreSQL running in Kubernetes

2️⃣ Clone the Repository

git clone https://github.com/your-org/watch-tower.git
cd watch-tower

3️⃣ Install Dependencies

go mod tidy

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⚡ Running the Controller

1️⃣ Set Environment Variables

export DB_CREDENTIAL_PATH="/srv/db_credential"
export AAP_NAMESPACE="aap"
export KUBECONFIG=~/.kube/config

2️⃣ Run the Controller

go run main.go

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🔄 How It Works

1. Loops every 30 seconds to check:

   • PostgreSQL role (Primary or Standby).
   • AutomationController resources in the namespace.

2. Reads the watch-tower/replicas annotation:

   • If missing, it skips the resource.
   • If invalid, it logs a warning.

3. Decides the correct replica count:

   • If Primary, it uses the annotation value.
   • If Standby, it scales down to 0.

4. Checks the current spec.replicas:

   • ✅ If already correct, it skips patching.
   • 🔄 If different, it patches the CRD.

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📄 Example YAML (AutomationController)

Here’s an example AutomationController CRD with the required annotation:

apiVersion: automationcontroller.ansible.com/v1beta1
kind: AutomationController
metadata:
  name: example
  namespace: aap
  annotations:
    watch-tower/replicas: "3"
spec:
  replicas: 3

• The annotation watch-tower/replicas: "3" tells Watch-Tower how many replicas to use if the DB is Primary.

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📌 Expected Output

If the database is Primary

✅ Using local Kubeconfig
🚀 Starting Watch Loop for AutomationController...

🔄 Checking AutomationController and Database Role...
✅ Successfully connected to PostgreSQL!
🔍 Database Role: Primary
✅ No update needed for example (replicas already set to 3)

If the database is Standby

✅ Using local Kubeconfig
🚀 Starting Watch Loop for AutomationController...

🔄 Checking AutomationController and Database Role...
✅ Successfully connected to PostgreSQL!
🔍 Database Role: Standby
✅ Successfully patched example: spec.replicas = 0

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