Create Scaling,_ Networking, _and _Automation.md

Author: radhikam04

DBMS Module/Scaling,_ Networking, _and _Automation.md

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+# Scaling, Networking, and Automation Notes
+
+## **1. Horizontal vs Vertical Scaling**
+
+### **Understanding Scaling Through a Real-World Analogy**
+- **Scenario**: Imagine a restaurant during a festive season.
+  - The restaurant adds tables (e.g., increasing from 4 to 6) to accommodate more guests.
+  - **Drawback**: Despite additional seating, delays in service occur due to overloading of the kitchen and staff.
+  - **Solution**:
+    - Expand physical space by adding new floors or outlets.
+    - Hire more staff and upgrade the kitchen.
+- **Relation to DevOps**:
+  - This reflects the two primary scaling strategies:
+    1. Adding capacity by expanding resources (Vertical Scaling).
+    2. Adding more units to share the load (Horizontal Scaling).
+
+
+### **Concept of Scaling in DevOps**
+Scaling ensures that applications can handle increased traffic and workload efficiently.
+
+1. **Horizontal Scaling** (Scaling Out):
+   - Adds multiple servers to distribute traffic.
+   - A load balancer is used to direct incoming requests to these servers.
+   - Example: A web application serving thousands of users by distributing requests across multiple instances.
+
+2. **Vertical Scaling** (Scaling Up):
+   - Upgrades the existing server’s capacity (e.g., more RAM, CPU).
+   - Ideal for monolithic applications that are not designed for distributed environments.
+
+
+### **Comparison Between Horizontal and Vertical Scaling**
+
+| **Aspect**              | **Horizontal Scaling**                            | **Vertical Scaling**                              |
+|-------------------------|--------------------------------------------------|--------------------------------------------------|
+| **Scaling Method**      | Adds multiple servers to share the load          | Increases resources (CPU, RAM) on one server    |
+| **Limitation**          | Complexity in management and synchronization     | Physical hardware limits                        |
+| **Cost**                | Higher initial setup cost, scales well          | Expensive with diminishing returns             |
+| **Use Case**            | Distributed apps, high-read volume databases    | Smaller apps with balanced read/write needs    |
+
+
+### **Traditional vs. Modern Scaling**
+- **Traditional Approach**:
+  - Companies managed physical data centers with limited scalability options.
+  - Scaling required manual intervention, including migrations to larger hardware.
+- **Modern Approach**:
+  - Cloud providers (AWS, GCP) simplify scaling with:
+    - Auto-scaling groups for Horizontal Scaling.
+    - On-demand instance upgrades for Vertical Scaling.
+  - Tools like Docker and Kubernetes enable easy Horizontal Scaling by running applications in containers.
+
+
+- Why are modern databases more suited to Horizontal Scaling?
+  - **Answer**: Containers (via Docker and Kubernetes) allow applications to be easily replicated and deployed in distributed environments, ensuring fault tolerance and scalability.
+
+## **2. Load Balancing: Nginx vs. HAProxy**
+
+### **Load Balancer Functionality Overview**
+Load balancers distribute incoming traffic across servers to ensure:
+- High availability.
+- Fault tolerance.
+- Optimized performance.
+
+---
+
+### **Nginx**
+- **Analogy**: Think of Nginx as a multitasking station manager who directs trains to platforms while handling various administrative duties.
+- **Features**:
+  - Optimized for HTTP/HTTPS (Layer 7) traffic.
+  - Performs basic TCP load balancing but lacks advanced routing capabilities.
+  - Efficient for handling low-to-moderate traffic.
+- **Limitations**:
+  - Less robust health checks compared to specialized tools.
+  - Struggles with large-scale traffic management.
+
+---
+
+### **HAProxy**
+- **Analogy**: HAProxy is like a dedicated railway traffic controller, specializing in efficiently routing trains (traffic) during peak times.
+- **Features**:
+  - Optimized for TCP (Layer 4) load balancing with advanced algorithms.
+  - Supports robust health checks for backend servers.
+  - Handles high-traffic scenarios efficiently.
+- **Advantages Over Nginx**:
+  - Prioritizes reliability in large-scale setups.
+  - Better suited for applications requiring fine-grained traffic control.
+
+---
+
+### **Key Insight**
+Both tools have unique strengths:
+- **Nginx** excels at Layer 7 traffic and web server integration.
+- **HAProxy** is better for Layer 4 traffic and high-demand environments.
+
+---
+
+## **3. Practical Demonstration: Setting Up HAProxy for MySQL Load Balancing**
+
+### **Overview**
+- **Objective**: Set up HAProxy to distribute MySQL traffic across backend servers.
+- **Setup**:
+  - Frontend Server: Runs HAProxy (no MySQL installed).
+  - Backend Server: Hosts MySQL database(s).
+
+---
+
+### **Step-by-Step Guide**
+
+#### 1. **Server Setup**
+- Log into two servers:
+  - **Frontend Server**: Dedicated for HAProxy installation.
+  - **Backend Server**: Running MySQL for database operations.
+- Verify MySQL installation on the backend:
+  ```bash
+  sudo mysql
+  ```
+
+---
+
+#### 2. **Installing HAProxy**
+- Update the frontend server:
+  ```bash
+  sudo apt update
+  sudo apt install haproxy -y
+  ```
+
+---
+
+#### 3. **Configuring HAProxy**
+- Open HAProxy configuration file:
+  ```bash
+  sudo nano /etc/haproxy/haproxy.cfg
+  ```
+- Add the following configuration:
+  ```haproxy
+  frontend mysql_front
+      bind *:3306
+      default_backend mysql_servers
+
+  backend mysql_servers
+      mode tcp
+      option tcplog
+      balance roundrobin
+      server mysql_backend <backend-server-ip>:3306 check
+  ```
+- **Explanation**:
+  - `frontend`: Defines the entry point for MySQL traffic (port 3306).
+  - `backend`: Lists MySQL servers with IP addresses for traffic distribution.
+
+---
+
+#### 4. **Creating a MySQL User for HAProxy**
+- Create a user for HAProxy to perform health checks:
+  ```sql
+  CREATE USER 'haproxy_check'@'%' IDENTIFIED BY 'password';
+  GRANT REPLICATION CLIENT ON *.* TO 'haproxy_check'@'%';
+  FLUSH PRIVILEGES;
+  ```
+
+---
+
+#### 5. **Testing Connectivity**
+- Test connectivity between HAProxy and the backend server:
+  ```bash
+  ping <backend-server-ip>
+  telnet <backend-server-ip> 3306
+  ```
+
+---
+
+#### 6. **Installing MySQL Client on HAProxy**
+- Install the MySQL client utility:
+  ```bash
+  sudo apt install mysql-server
+  sudo systemctl status mysql
+  ```
+
+---
+
+#### 7. **Testing the Setup**
+- Connect to the MySQL backend through HAProxy:
+  ```bash
+  mysql -h localhost -u haproxy_check -p
+  ```
+
+---
+
+#### 8. **Adding More Backend Servers**
+- Update the HAProxy configuration to include additional backend servers:
+  ```haproxy
+  server mysql_backend_2 <new-server-ip>:3306 check
+  ```
+- Create the `haproxy_check` user on each new server.
+
+---
+
+### **Advantages of HAProxy Load Balancing**
+- Distributes load effectively, reducing the risk of server overloading.
+- Simplifies scaling by allowing new servers to be added with minimal changes.
+- Provides robust health checks to monitor backend server availability.