nginx ip_hash vs sticky: Load Balancing Quiz & Flashcards

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Questions and Answers

What is the primary goal of load balancing in a network?

To ensure no single server becomes a bottleneck and to increase availability and reliability.

What is the primary difference between Layer 4 and Layer 7 load balancers?

Layer 4 load balancers operate at the transport layer, while Layer 7 load balancers operate at the application layer.

What is the main advantage of using a weighted round robin algorithm in load balancing?

It allows for servers with different capacities to be utilized effectively.

When would a least connections algorithm be most useful in load balancing?

When traffic is varied and some requests may take longer to process. Signup and view all the answers

What is the purpose of IP hash load balancing algorithm?

To ensure that the same client is always directed to the same server. Signup and view all the answers

What is the main advantage of using load balancing in a network?

It improves response time and performance, and provides fault tolerance and redundancy. Signup and view all the answers

What is the role of a load balancer in a network?

To distribute incoming network traffic across multiple servers. Signup and view all the answers

What is the main difference between a Layer 4 load balancer and a router?

A Layer 4 load balancer routes traffic based on IP address and TCP/UDP port, while a router routes traffic based on IP address only. Signup and view all the answers

What is the main advantage of using a Layer 7 load balancer?

It can handle more sophisticated routing rules and provide features like SSL termination. Signup and view all the answers

What is the main difference between a round robin and weighted round robin algorithm?

Weighted round robin assigns a weight to each server based on its capacity. Signup and view all the answers

When would a round robin algorithm be most useful in load balancing?

When servers have similar capacity and the goal is simple traffic distribution. Signup and view all the answers

What is the primary goal of Least Response Time load balancing algorithm in ensuring faster service delivery?

To choose the least busy server to send requests, ensuring faster service delivery. Signup and view all the answers

What is the main difference between Hardware Load Balancers and Software Load Balancers?

Hardware Load Balancers are specialized devices, while Software Load Balancers run on standard servers. Signup and view all the answers

What is the purpose of Health Checks in Load Balancers?

To regularly monitor the health of backend servers and remove unresponsive servers from the pool. Signup and view all the answers

What is the benefit of using Session Persistence (Sticky Sessions) in Load Balancers?

Ensures that a user is consistently directed to the same server for the duration of a session. Signup and view all the answers

How does Automatic Scaling integrate with Load Balancers?

It adds or removes servers based on traffic load, providing elasticity to handle varying traffic demands. Signup and view all the answers

What is the benefit of using Content-based Routing in Load Balancers?

Directs traffic based on the content of the request, such as URL path or query parameters. Signup and view all the answers

What is the main challenge of using Load Balancers?

Cost, complexity, latency, and single point of failure. Signup and view all the answers

What is the advantage of using Load Balancers in high-traffic e-commerce websites?

Traffic is evenly distributed, response times improve, and the site remains available even if one of the servers goes down. Signup and view all the answers

What is the role of a Load Balancer in ensuring high availability?

Reroutes traffic if a server fails, ensuring continuous availability. Signup and view all the answers

Why is Load Balancing essential for modern web applications?

Provides a scalable, reliable, and high-performance infrastructure. Signup and view all the answers

Study Notes

Load Balancing

Load balancing is critical for large-scale applications, distributing workload across multiple servers to optimize resource use, maximize throughput, and avoid overload.
Primary goals: increase availability and reliability, improve response time and performance, and provide fault tolerance and redundancy.

Types of Load Balancers

Layer 4 (Transport Layer) Load Balancers:
- Operate at the transport layer (TCP/UDP)
- Route traffic based on IP address and TCP/UDP port
- Less CPU intensive as they do not inspect packet contents
Layer 7 (Application Layer) Load Balancers:
- Operate at the application layer (HTTP/HTTPS)
- Route traffic based on detailed application-level data (e.g., URL, HTTP headers)
- Can handle more sophisticated routing rules and provide features like SSL termination

Load Balancing Algorithms

Round Robin:
- Distributes requests sequentially across the pool of servers
- Simple and works well when servers have similar capacity
Weighted Round Robin:
- Assigns a weight to each server based on its capacity
- Servers with higher weights receive more requests
Least Connections:
- Directs traffic to the server with the fewest active connections
- Useful when traffic is varied and some requests may take longer to process
IP Hash:
- Routes requests based on the hash of the client’s IP address
- Ensures that the same client is always directed to the same server, useful for session persistence
Least Response Time:
- Sends requests to the server with the quickest response time
- Ensures faster service delivery by choosing the least busy server
Random:
- Distributes traffic randomly
- Simple and works well for evenly distributed traffic patterns

Implementation of Load Balancing

Hardware Load Balancers:
- Specialized devices designed for high-performance load balancing
- Examples: F5 Networks, Citrix NetScaler
Software Load Balancers:
- Run on standard servers and can be deployed on-premises or in the cloud
- Examples: Nginx, HAProxy, Apache Traffic Server
Cloud-based Load Balancers:
- Managed services provided by cloud providers
- Examples: AWS Elastic Load Balancing (ELB), Google Cloud Load Balancing, Azure Load Balancer

Features of Modern Load Balancers

Health Checks:
- Regularly monitor the health of backend servers
- Remove unresponsive servers from the pool and reintroduce them when they recover
SSL Termination:
- Decrypts incoming SSL traffic and forwards it as plain HTTP to backend servers
Session Persistence (Sticky Sessions):
- Ensures that a user is consistently directed to the same server for the duration of a session
Automatic Scaling:
- Integrates with auto-scaling groups to add or remove servers based on traffic load
- Provides elasticity to handle varying traffic demands
Content-based Routing:
- Directs traffic based on the content of the request, such as URL path or query parameters

Benefits of Load Balancing

Improved Performance:
- Distributes workload evenly, reducing latency and improving user experience
Increased Availability:
- Ensures continuous availability by rerouting traffic if a server fails
Scalability:
- Allows easy addition of new servers to handle increased traffic
Redundancy and Fault Tolerance:
- Provides a failover mechanism in case of server outages

Challenges and Considerations

Cost:
- Hardware load balancers can be expensive
- Cloud load balancing services have ongoing operational costs
Complexity:
- Configuration and management can be complex, especially for advanced features
Latency:
- Additional layer in the network can introduce latency, though typically minimal
Single Point of Failure:
- The load balancer itself can become a single point of failure if not properly managed