Load Balancing
Introduction
The term load balancing is a technique used in computing and networking to spread the income load or traffic of the network to multiple or a different server to handle the resources. Load balancing helps to enhance the capacity and reliability of application. Load balancer act as a “traffic controller” for your servers and it redirect the request to an active or available servers. It distributes user traffic across the multiple instances of your application by distributing the load. Load balancer decides where to send the request that comes from the end user or a client. It helps us to improve performance, stability and capacity while lowering latency therefore the demand is divided across the multiple servers. During the processing time if one server fails to operate then a load balancer rapidly shifts it’s workload to another server, reducing the impact on end users. Load balancer can easily scale up or scale down the servers according to the request made by the client. When the demand for a service increase, new servers can add to the system and when the demand decreases servers or resources can be taken offline which also helps to save the cost. Nowadays many modern cloud platforms provide auto scaling features which can automatically adjust the number based on the predefined rules such as CPU uses and network traffic.
Working Mechanism of load balancer
The working mechanism of load balancer involves the following steps: –
1. Monitoring the servers:
Load balancer continuously monitor the performance or the work performed by the individual servers in the system. It also includes the different parameters like server status, response time and current load.
2. Distributing incoming request: –
Whenever a client sends a request then the load balancer intercepts it before the request is forwarded to the available servers. Load balancer uses the different algorithm to analyze which server is free or which server can easily handle the request.
3. Selection of an algorithm:
Selection of a server is done in the basis of different criteria. Different algorithm is as follow: i. Round Robin: In round robin it distributes the incoming request equally in a circular form among servers. In round robin it does not check the capacity of the server to perform task it just sends the request equally among the available resources.
ii. Least Connection: In least connection it distributes the incoming request to the servers which has the least active connections.
iii. Weighted Round Robin: It is similar to the round robin but the one major difference is that it assigns different weights to server based on their capacity to perform the task.
iv. Least Response time: In this algorithm it sends request to the server with the quick response time.
4. Dynamic Adjustment:
Load balancer has the ability to dynamically adjust the distribution of the incoming traffic based on load to the server and it’s performance capacity. Some load balancer support auto scaling which means when the request is high it increases the number to server to hold the request and when the request it low is decreases the number of servers.
5. Failover and Redundancy:
The main advantages of using load balancer is that whenever the servers goes down it will automatically redirect the request to the another server which ensure the high availability.
6. Session persistence:
Load balancer also can be configured to ensure that the request come from the particular client always directed to the same server.
Types of Load balancer
Load balancer is categorized into the various types each designed to meet the specific needs and requirement.
1. Application Load Balancer (ALB):
It operates under the application layer which is Layer 7 of the OSI model and they are capable of making the routing decision based on the basis of content. They are able to distribute the traffic to different endpoint within an application.
Use cases: Microservices, web application
2. Network Load Balancer (NLB):
It operates under the Network layer which is Layer 4 of the OSI model and distributes the incoming network based on IP protocol. They are used for handling TCP/UDP traffic and provide high performance load balancing.
Use cases: TCP/UDP based service, TCP/UDP load balancing
3. Global Server Load Balancer (GSLB):
It is designed to balance traffic across multiple servers or data centers in various geographic location. They use the network-based method to direct client to the optimal server.
Use cases: Disaster recovery, global server distribution.
4. DNS Load Balancer:
It distributes the traffic by managing DNS response. They return multiple IP address for single domain and client use DNS to connect one of the available IP addresses.
Use cases: Load balancing at the DNs level, simple distribution of traffic.
5. Hardware Load Balancer:
They are the physical devices specially used for load balancing purpose. They come with the specialized hardware components optimized for network traffic management.
Use cases: High performance requirement, dedicated hardware infrastructure.
6. Software Load Balancer:
They are implemented as a software service that run-on general-purpose servers or a virtual machine.
Use cases: Virtualized environment, cloud deployment
7. Cloud Load Balancer:
They are load balancing solutions provided by the cloud service providers. They are designed to use in cloud environment and often integrate with other cloud services.
Use cases: Cloud based application, auto scaling.
Different Hardware load balancer:
1. F5 BIG-IP Series:
Vendor: F5 Networks. F5 BIG-IP devices are known for their advance application delivery. They also offer a wide range of models catering to different performance and feature requirement. Many world’s biggest company uses F5.
2. Citrix ADC (formerly NetScaler):
Vendor: Citrix. Citrix ADC provides load balancing, security features. It is designed to optimize the delivery of application and ensuring high performance.
3. A10 Network Thunder Series:
Vendor: A10 Networks. It includes with the advance features such as application delivery, SSL offloading. They cater to high performance networking requirements.
4. Nginx plus:
It is the popular open-source web server and reverse proxy server. It has a high performance and provide a redundancy.
Different software load balancer:
1. Nginx:
Nginx is a popular open-source web server and reverse proxy. Nginx is widely used in distributing web traffic and managing application delivery.
2. HAProxy:
It is a free, open-source software that provides high availability, load balancing and proxying TCP and HTTP based application. It is widely used in front of web servers to distribute incoming traffic.
3. Traefik:
It is a modern and a dynamic reverse proxy and load balancer designed for microservices and containerized application.
4. Envoy:
It is a open-source edge and service proxy designed for cloud-native application. It is often used as a sidecar proxy in microservices and also can perform load balancing among services.
5. Docker Swarm (Built in load balancing):
It is a container orchestration platform which includes built in load balancing for distributing traffic among containers.
6. AWS Elastic Load Balancer:
It is essentially a software load balancer provided by amazon web services. It automatically distributes incoming application traffic across multiple targets such as EC2 instances.
What are the popular cloud load balancer?
Popular cloud load balancers include:
1. AWS Elastic Load Balancer:
Cloud provider: Amazon Web service (AWS).
2. Azure Load Balancer:
Cloud provider: Microsoft Azure.
3. Google Cloud Load Balancing:
Cloud provider: Google Cloud Platform (GCP)
4. Alibaba Cloud Service Load Balancer (SLB)
Cloud provider: Alibaba Cloud
5. IBM Cloud Load Balancer:
Cloud provider: IBM Cloud
6. Oracle Cloud Infrastructure Load Balancer:
Cloud provider: Oracle Cloud Infrastructure
Popular trend in Load Balancing
Some popular trend in Load balancing is:
1. Application-Aware Load Balancing:
Load balancers are increasingly becoming more application- aware, user behavior. This allows for more intelligent routing decisions based on application-specific needs.
2. Automation:
Load balancers are embracing automation to simplify configuration and deployment. Integration with infrastructure as code tools and automation framework allows for more efficient management of load balancing.
3. AI and ML:
The integration of AI and ML into load balancing solutions allows for more intelligent decision making.
4. Serverless Load Balancing:
Serverless architectures are gaining popularity and load balancer are adapting to provide serverless load balancing solutions.
5. Edge Load Balancing:
Load balancing are deployed at the edge of network to effectively distribute traffic and reduce latency.
How to secure Load Balancer
Some key practices and consideration to enhance the security of a load balancer:
1. Limited access controls:
Restrict access to the load balancer management interface. Always use the strong authentication mechanism like multi factor authentication and give configuration access control to authorized person only.
2. SSL/TLS Encryption:
Enable SSL/TLS encryption for communication between load balancer and clients as well as load balancer and backend servers. Should regularly update SSL/TLS certificates.
3. Regular software update:
Should keep software up to date by applying patches and updates provided by the vendors. This helps to address security vulnerabilities.
4. Network Security:
Must use firewall to restrict unnecessary traffic to the load balancer. Configure network security group to control traffic flow.
5. DDoS protection:
Deploy Distributed Denial of Service protection mechanism to migrate the risk of DDoS attack. This includes rate limiting, traffic filtering.
6. Regular security audits:
Must conduct regular security audits of the load balancer configuration and settings. Should perform vulnerability assessments and penetration testing to identify and address potential security weaknesses.
Pradip Poudel