Learning Elasticsearch

Failure handling

Elasticsearch handles failures automatically. This section describes how the failures are handled internally. Let’s say we have an index with two shards and one replica. In the following diagram, the shards represented in solid line are primary shards, and the shards in the dotted line are replicas:

As shown in preceding diagram, we initially have a cluster with two nodes. Since the index has two shards and one replica, shards are distributed across the two nodes. To ensure availability, primary and replica shards never exist in the same node. If the node containing both primary and replica shards goes down, the data cannot ...