Picture a restaurant host seating incoming guests in different parts of the restaurant to distribute the workload among the waitstaff. The host aims to ensure that no single server feels overwhelmed or becomes responsible for more tables than they can handle. This process also means guests receive timely service.
In cloud services, load balancing algorithms work the same way. Network administrators and IT managers use load balancing software to portion out resources to websites and applications so they get the most from their resources.
Load balancers distribute network traffic across a pool of resources. They follow load balancing algorithms, or rules, to determine how to allocate network traffic between servers and identify which server will meet the needs of different user requests.
The primary goal is to prevent any single server from becoming overloaded, ensuring optimal performance, high availability, and efficient resource utilization.
Every day, billions of people access modern applications through the internet. Applications usually run on multiple servers. Load balancing tools facilitate task distribution to prevent any server from getting overwhelmed and slowing down or, worse, crashing. It helps disburse work evenly across multiple servers so users can access applications without delay or interruption.
To make this happen, developers created load balancers, devices, or software programs responsible for traffic distribution. Network administrators place them between users and servers. When a user attempts to connect to an application, the load balancer reviews the request and chooses the most suitable server.
The process works behind the screens, invisible to users so they don’t see their requests funneling through load balancers. Instead, they ask for various web pages and receive results while the load balancer works to present the pages they request – almost like magic.
You can compare load balancing to a traffic conductor’s responsibility (except that a traffic director is visible and load balancers aren’t). Think about a busy intersection that’s under construction with no operating stoplights. Without a traffic controller, cars might not take turns passing through the intersection, which will eventually lead to accidents and traffic jams.
The traffic director guides vehicles through the intersection at reasonable intervals, balancing the traffic load to make certain everything flows smoothly and to reduce the likelihood of accidents. In this example, the traffic director is the load balancer, the cars are the tasks that users request, and the roads are the servers.
Load balancing boosts the efficiency, dependability, and scalability of systems managing heavy traffic, resulting in an enhanced user experience. Load balancing algorithms offers several key benefits:
Load balancing algorithms fall into one of two types: static or dynamic. Let's learn more about the types of load balancing algorithms.
Static load balancing algorithms follow fixed rules to distribute traffic evenly across servers. Rather than considering the current state or load of the servers, they rely on predetermined rules. Due to their straightforwardness, static load balancing algorithms are generally easier to implement than dynamic ones. However, they don’t always handle various server loads efficiently.
Below are some of the standard static load balancing algorithms.
In round-robin distribution, load balancers distribute incoming user requests across servers in a rotational order. The load balancer works its way through a list of servers until it reaches the end. Then, the process starts over, and the load balancer starts assigning requests at the top of the list in the same order. Remember that all static algorithms, including the round-robin method, assume all servers are available, regardless of capacity.
Examples:
A weighted round-robin calls on more advanced methods than a traditional round-robin assignment. Instead of equal distribution, a weighted algorithm allows you to assign weights to each server, typically based on the server’s capacity. The load balancer uses the assigned weights to allocate requests accordingly.
Servers with higher weights receive a larger proportion of the incoming requests. The distribution is rotational, similar to the traditional round-robin technique, but servers receive requests proportional to their weight throughout the cycle.
Examples:
The load balancer uses the IP hash method to generate a hash value from the user’s IP address. It then takes the hash value and assigns the client to a specific server. All requests from that client are associated with their hash, and the load balancer will send the user to the same server with each new request.
Examples:
Unlike static load balancing algorithms, dynamic load balancing algorithms examine the current state of servers before distributing incoming network traffic. While more complex, these algorithms perform better for efficient resource distribution and server load handling. Below are some typical dynamic load balancing algorithms.
When clients connect to a server, they establish an active connection in order to communicate. When a load balancer uses the least connection method, it looks at the servers to determine which ones have the fewest active connections and sends incoming traffic to them. This method assumes that the servers with the least connections have the most available capacity.
Examples:
The weighted least connection method is an advanced configuration of least connection algorithms. Like the static version of the weighted round-robin method, you can assign weights to each server with this algorithm. The load balancer will distribute new requests to the server with the least connections by weighted capacity.
Examples:
Response time means the time a server takes to process an incoming request and send a response back to the user. The least response time method evaluates server response times so the load balancer routes incoming requests to the fastest-responding server.
Examples:
In the resource-based method, load balancers distribute traffic by analyzing current servers. The load balancers look for a server with sufficient resources before sending any data.
Examples:
Here are some factors to consider while choosing choosing types of load balancing algorithms that work best for your needs.
Load balancing software distributes resources and incoming traffic to applications and websites in order to help network administrators and IT managers control resources efficiently.
To qualify for inclusion in G2’s load balancing category, a product must:
Below are the top five leading load balancing platforms from G2’s Summer 2024 Grid® Report. Some reviews may be edited for clarity.
HAProxy powers modern application delivery at scale in any environment. It offers comprehensive load balancing methods, including round robin, least connections, and several hashing techniques. Users can turn on advanced routing decisions based on URL, domain name, file extension, IP address, or active connections.
“We migrated from Snapt load balancer (software based) to HAProxy Enterprise (software based). This also came with the HAProxy Fusion. HAProxy has been performant and stable across the multiple clients we service and allows configuration changes that do not impact our clients. This has been a huge step up for our stability and confidence in our solution. Since it is software-based, we have easily incorporated the solution into our disaster recovery solution.
The product is very competitively priced, and we have received phenomenal support. I would highly recommend this product.”
- HAProxy Review, Nathan H.
“Would love a more in-depth user interface (UI) from the open source version.”
- HAProxy Review, Colin C.
Cloudflare Application Security and Performance’s load-balancing solution guarantees high performance, uptime, and quality user experience by balancing traffic across geographically distributed servers and data centers. With this dynamic platform, users can manage traffic across multiple protocols to tailor the configuration and meet their business needs.
“Cloudflare's comprehensive features boost your site's speed and shield it from various online threats.
Cloudflare also provides free secure sockets layer (SSL) certificates for secure data transmission, optimizes images for faster loading, and streamlines files through minification. Browser caching, WebSockets for real-time communication, load balancing, rate limiting, optimized network routing, page rules for customization, and the AMP Real URL feature for maintaining your brand identity in Google AMP results are all part of Cloudflare's robust toolkit for optimizing and securing your website.”
- Cloudflare Application Security and Performance Review, Chandra Shekhar T.
“So far, there isn't anything that I dislike. However, they can improve the language in their UI, which is full of jargon for techies. Or they could offer a simple UI view for non-techies and an advanced view for techies.”
- Cloudflare Application Security and Performance Review, Jay K.
F5 NGINX Ingress Controller uses a universal Kubernetes tool for implementing application programming interface (API) gateways and load balancers. It provides app protection at scale through strong security controls and distributed environments, and prevents app downtime through advanced connectivity patterns and troubleshooting processes.
“It reduced the complexity of Kubernetes application traffic. F5 NGINX Ingress Controller simplifies the management and optimization of traffic flow to your Kubernetes applications and provides advanced networking and security features to ensure their reliability and security.”
- F5 NGINX Ingress Controller Review, Shubham S.
“When considering F5, weighing the benefits, such as advanced traffic management and security features, is important against potential downsides, such as cost and complexity. While it is a reliable solution for managing Kubernetes' ingress traffic, users may need to invest time and resources to learn and implement it effectively.”
- F5 NGINX Ingress Controller Review, Bhargav N.
Kemp LoadMaster offers load balancers for high-performance balancing and application delivery. It provides hardware, virtual, and cloud-native deployment load balancers to meet varying needs. Kemp LoadMaster solutions also come with an extensive library of application deployment templates.
“Kemp Loadmaster is a flexible, solid, and reliable system. The customer service support is tremendous, and I recommend getting good support maintenance.”
- Kemp LoadMaster Review, Anthony C.
“Kemp LoadMaster is a bit higher priced than other load-balancing solutions in the market.”
- Kemp LoadMaster Review, Tony W.
F5 NGINX Plus is an all-in-one API gateway, content cache, load balancer, and web server with enterprise-grade features. The NGINX Plus load balancer is high-performance and lightweight for various network and development operations needs.
“F5 NGINX Plus is one of the best API monitoring and security enhancing platforms that simplifies modernizing legacy applications, and delivering micro-services applications to enterprises undergoing digital transformation.”
- F5 NGINX Plus Review, Manya V.
“The current Trial is for 30 days for NGINX Plus and should have been at least 90 days for the platform to understand how the return on investment would be if it is purchased.”
- F5 NGINX Plus Review, Mohammad S.
The "random" algorithm distributes incoming requests randomly across available servers. It's a simple approach that can be effective in some situations, but it doesn't consider server load or other factors.
For imbalanced data, algorithms that consider server load or performance are generally preferred. Least connections and Least response time can be good choices, as they dynamically adapt to changing server conditions.
Session Affinity ensures that requests from the same user are always directed to the same server. Important for applications that rely on session data (e.g., online shopping carts, user logins).
Load balancers handle server failures by regular health checks, automatic removal of unhealthy servers, and failover.
There is no "best" algorithm. The optimal choice depends heavily on the specific needs and characteristics of your system. Factors to consider include: traffic patterns, server capabilities, and application requirements.
Load balancing algorithms fundamentally maintain the efficiency and reliability of modern applications and websites. They work hard to make sure no single server gets overloaded so companies can provide smooth and uninterrupted service for users worldwide. Whether you manage a cloud environment or run a bustling e-commerce business, load balancing will enrich the user experience.
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