In Elasticsearch, a data node is a node in a cluster that stores data and serves search requests. Data nodes are responsible for holding a portion of the cluster’s data and for serving queries that involve that data.
When data is indexed into Elasticsearch, it is distributed across the nodes in the cluster using a process called sharding. Each shard of data is replicated across multiple nodes to ensure fault tolerance and high availability.
Data nodes are responsible for holding the primary or replica copy of one or more shards of data. When a search request is made, the data node retrieves the relevant shard from its local storage and returns the results.
In addition to storing and serving data, data nodes also perform other tasks, such as:
1. Query execution: Data nodes execute search queries and return the results to the client.
2. Indexing: Data nodes receive new documents and index them into the appropriate shard.
3. Aggregation: Data nodes perform aggregations, which involve summarizing and analyzing data across multiple documents or shards.
4. Document routing: Data nodes route new documents to the appropriate shard based on the document’s ID or routing value.
Overall, data nodes are an important component of an Elasticsearch cluster that store and serve data, perform search queries, and execute other tasks related to indexing and analysis.