Elasticsearch Cluster Architecture

Elasticsearch clusters are built to be highly scalable and fault–tolerant and allowing them to handle large volumes of data and queries efficiently. The architecture of an Elasticsearch cluster consists of several key components:

1. Nodes: Nodes are individual instances of Elasticsearch running on a server. Each node can be configured to perform specific roles within the cluster, such as master-eligible, data, ingest or coordinating-only.
2. Master Node: The master node is responsible for cluster-wide management tasks, such as creating or deleting indices, tracking which nodes are part of the cluster, and deciding which shards to allocate to which nodes.
3. Data Node: Data nodes are responsible for storing and managing the actual data in the cluster. They handle indexing requests, store data in shards and execute search queries. Data nodes can hold multiple primary and replica shards, distributing the data across the cluster for scalability and fault tolerance.
4. Ingest Node: Ingest nodes are used for pre-processing documents before they are indexed. They can apply transformations, enrichments, or other processing steps to the data. Ingest nodes help offload processing tasks from data nodes improving overall cluster performance.
5. Coordinating-Only Node: Coordinating-only nodes do not hold any data or participate in the master election process. Their main role is to act as a proxy for client requests, distributing search and indexing requests to the appropriate data nodes.
6. Shards: Shards are the basic units of data in Elasticsearch. Each index is divided into multiple shards, which can be distributed across the cluster. This allows Elasticsearch to parallelize operations and scale horizontally.
7. Replicas: Replicas are copies of shards that are distributed across the cluster. Replicas serve two main purposes: they improve search performance by allowing queries to be executed in parallel across multiple replicas and they provide fault tolerance by allowing data to be recovered from replicas if a primary shard fails.
8. Cluster State: The cluster state is a metadata repository that stores information about the cluster, including the index mapping settings and the location of shards. The cluster state is managed by the master node and is distributed to all nodes in the cluster.

Elasticsearch’s cluster architecture and node roles are fundamental to building scalable and fault-tolerant search infrastructures. A cluster comprises interconnected nodes, each serving specific roles like master, data, ingest, or coordinating-only. Understanding these components is crucial for efficient cluster management and performance.

In this article, We will learn about the Elasticsearch Cluster Architecture, Node Roles in Elasticsearch, and Practical Examples in detail.