Add backend deploy script (#89)

* Add backend deploy script

To save costs, backend services are spun down most of the time. This was manually done by changing the desired number of tasks to 0 manually. Let's create a bash script to simplify the process.

* Document backend deploy

* Elaborate on access key process

* Fix formatting

* Clarify expired env variables

Author: samuelim01

devops/README.md

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+# Backend Deployment
+
+This script allows you to set the desired number of tasks for each backend service.
+
+## Prerequisites
+
+Before using this script, ensure that you have the following:
+
+1. **AWS CLI**: You must have the AWS CLI installed on your machine to interact with AWS services. You may install AWS CLI [here](https://docs.aws.amazon.com/cli/latest/userguide/getting-started-install.html).
+
+2. **Access Keys**: You may obtain the AWS environment variables from the AWS Access Portal.
+
+## Running the Script
+
+1. Open a terminal and navigate to the `devops/` directory where the script is located.
+
+2. Obtain your AWS Access Keys:
+- Log in to the **AWS Access Console**.
+- Click on **Access keys**.
+- Copy the AWS environment variables into your terminal:
+
+```bash
+export AWS_ACCESS_KEY_ID=<AccessKeyId>
+export AWS_SECRET_ACCESS_KEY=<SecretAccessKey>
+export AWS_SESSION_TOKEN=<SessionToken>
+```
+
+3. To scale the services to **1 task** (i.e., start the services), run the following command:
+
+```bash
+./deploy-backend.sh 1
+```
+
+4. To scale the services to **0 tasks** (i.e., stop the services), run the following command:
+
+```bash
+./deploy-backend.sh 0
+```
+
+## Troubleshooting
+
+**Q: Why doesn't the script work when I try to run it?**
+
+**A:** Ensure you are using the correct IAM user with sufficient permissions to update ECS services.
+
+---
+
+**Q: The script won't run due to a permission error**
+
+**A:** This could be due to the script not having the correct execution permissions. Run the following command to give the script execute permissions:
+
+```bash
+chmod +x deploy-backend.sh
+```
+
+---
+
+**Q: The script worked before but doesn't work anymore**
+
+**A:** This could be due to the environment variables expiring. Copy a new set of environment variables as shown above.

devops/deploy-backend.sh

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+#!/bin/bash
+
+# Configuration
+AWS_REGION="ap-southeast-1"
+ECS_CLUSTER="backend-cluster"
+SERVICES=("question" "user" "match" "collaboration" "history")
+
+# Validate the user input for desired number of tasks
+if [[ "$1" != "0" && "$1" != "1" ]]; then
+  echo "Error: The desired number of tasks must be either 0 or 1."
+  echo "Usage: $0 <desired_tasks>"
+  echo "Example: $0 1  # Scale each service to 1 task"
+  echo "Example: $0 0  # Scale each service to 0 tasks"
+  exit 1
+fi
+
+DESIRED_TASKS=$1  # Desired number of tasks (0 or 1)
+
+# Function to update ECS service
+update_service() {
+  local service=$1
+
+  echo "Updating ECS service for $service..."
+
+  # Update ECS Service to trigger deployment with the desired number of tasks
+  aws ecs update-service \
+    --cluster "$ECS_CLUSTER" \
+    --service "$service-service" \
+    --desired-count "$DESIRED_TASKS" \
+    --force-new-deployment \
+    --region "$AWS_REGION" \
+    --output text > /dev/null 2>&1
+
+  if [[ $? -eq 0 ]]; then
+    echo "Service $service updated successfully with desired task count: $DESIRED_TASKS"
+  else
+    echo "Error updating service $service"
+    exit 1
+  fi
+}
+
+# Main script execution
+for service in "${SERVICES[@]}"; do
+  update_service "$service"
+done
+
+echo "All services have been updated."