Round Robin is a simple load balancing algorithm that evenly distributes incoming network or server requests among a group of servers. It operates on a cyclical basis, where each server in the group takes a turn in receiving requests. Once all servers have received a request, the cycle starts again.
Here’s how the Round Robin algorithm works:
- Order of Servers: Servers are listed in a sequential order, such as Server A, Server B, Server C, and so on.
- Incoming Requests: When a new request arrives, the load balancer forwards the request to the next server in the list. For example, if the last request was sent to Server B, the next request will be sent to Server C.
- Cyclic Behavior: The load balancer keeps track of which server received the last request. It then cycles through the list of servers in order, distributing incoming requests one by one.
- Equal Distribution: Round Robin ensures that each server receives an equal share of incoming requests over time, assuming that all servers have the same capabilities and resources.
- Predictable Pattern: The distribution of requests follows a predictable pattern, making it straightforward to implement and manage.
While Round Robin provides a simple way to balance the load among servers, it has limitations:
- Uneven Load: Servers may have different capabilities or workloads, leading to an unequal distribution of load. For example, if one server is more powerful than the others, it may complete requests faster, resulting in an imbalance.
- Server Health: Round Robin doesn’t consider the health or responsiveness of servers. If a server becomes slow or unresponsive, it will still receive requests, potentially degrading the overall performance of the application.
- Session Persistence: If the application requires maintaining session states, Round Robin might not be suitable, as each request is directed to a different server, potentially leading to inconsistent user experiences.
To address these limitations, more advanced load balancing algorithms such as Weighted Round Robin, Least Connections, and Least Response Time are often used. These algorithms consider factors like server capacity, responsiveness, and health, providing a more intelligent distribution of requests.