Vendors of hardware‑based solutions load proprietary software onto the machine they provide, which often uses specialized processors. Load balancers typically come in two flavors: hardware‑based and software‑based. In such environments it greatly helps if the load balancer can dynamically add or remove servers from the group without interrupting existing connections. This is common in environments such as the Amazon Web Services (AWS) Elastic Compute Cloud (EC2), which enables users to pay only for the computing capacity they actually use, while at the same time ensuring that capacity scales up in response traffic spikes. Many fast‑changing applications require new servers to be added or taken down on a constant basis. Switching servers would cause that information to be fetched for the second time, creating performance inefficiencies. Another use case for session persistence is when an upstream server stores information requested by a user in its cache to boost performance. The best load balancers can handle session persistence as needed. In such cases, it is essential that all requests from a client are sent to the same server for the duration of the session. Changing which server receives requests from that client in the middle of the shopping session can cause performance issues or outright transaction failure. For example, in a shopping cart application the items in a user’s cart might be stored at the browser level until the user is ready to purchase them. Information about a user’s session is often stored locally in the browser. The Least Time algorithm, if so configured). One that is selected by then applying the Least Connections algorithm (or for NGINX Plus Random with Two Choices – Picks two servers at random and sends the request to the.IP Hash – The IP address of the client is used to determine which server receives the request.Of loads if the set of upstream servers changes. NGINX Plus can optionally apply a consistent hash to minimize redistribution Hash – Distributes requests based on a key you define, such as the client IP address or.Least Time – Sends requests to the server selected by a formula that combines theįastest response time and fewest active connections.The relative computing capacity of each server is factored into determining which one has the least connections. Least Connections – A new request is sent to the server with the fewest current connections to clients.Round Robin – Requests are distributed across the group of servers sequentially. Provides the flexibility to add or subtract servers as demand dictatesĭifferent load balancing algorithms provide different benefits the choice of load balancing method depends on your needs:.Ensures high availability and reliability by sending requests only to servers that are online.Distributes client requests or network load efficiently across multiple servers.In this manner, a load balancer performs the following functions: When a new server is added to the server group, the load balancer automatically starts to send requests to it. If a single server goes down, the load balancer redirects traffic to the remaining online servers. To cost‑effectively scale to meet these high volumes, modern computing best practice generally requires adding more servers.Ī load balancer acts as the “traffic cop” sitting in front of your servers and routing client requests across all servers capable of fulfilling those requests in a manner that maximizes speed and capacity utilization and ensures that no one server is overworked, which could degrade performance. Modern high‑traffic websites must serve hundreds of thousands, if not millions, of concurrent requests from users or clients and return the correct text, images, video, or application data, all in a fast and reliable manner. Load balancing refers to efficiently distributing incoming network traffic across a group of backend servers, also known as a server farm or server pool.
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