Consistent hashing
Haithem Mihoubi
20k | Software Engineer | Java Spring Boot Developer | Devops enthusiast ??
Consistent Hashing is a technique used in computer science to distribute data across multiple nodes in a network. The goal of consistent hashing is to distribute data evenly and efficiently, while minimizing the number of changes required when a node is added or removed.
At a high level, consistent hashing works by mapping resources (such as data, keys, or files) to nodes using a hash function. The hash function maps the resource to a point on a ring, which is a continuous and infinite data structure. The nodes in the network are also assigned points on the same ring, and the resource is assigned to the node closest to its hash value.
One important aspect of consistent hashing is the use of virtual nodes, or replicas. Each node in the network can have multiple replicas on the ring, which helps to distribute the load evenly and improve fault tolerance. In the event of a node failure, its replicas can take over its load, ensuring that there is no disruption in the system.
When a node is added or removed, only a subset of the resources need to be re-assigned, as opposed to re-assigning the entire data set. This makes consistent hashing a more efficient and scalable solution compared to traditional methods of data distribution, where adding or removing a node requires the entire data set to be re-assigned to other nodes.
Consistent Hashing is widely used in various distributed systems, including databases, cache systems, and content delivery networks. For example, in a content delivery network, the resources are files or videos, and the nodes are servers. The consistent hashing algorithm assigns the files to the closest server, ensuring that the load is evenly distributed and the network is scalable.
In summary, consistent hashing is a crucial component in building scalable and highly-available systems. Its ability to minimize the number of changes required when a node is added or removed, and its ability to distribute data evenly across nodes, makes it an important tool in the design of future systems.
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