Elasticsearch вопросы и ответы для интервью

Вопрос 41. How does Elasticsearch achieve high availability?

Elasticsearch achieves high availability through the concept of replication. Each shard has one or more replicas, and if a node fails, its shards can be served by replicas on other nodes.

Example:

PUT /my_index/_settings
{
  "number_of_replicas": 2
}

Вопрос 42. How can you improve the performance of Elasticsearch queries?

Performance can be improved by optimizing mappings, using proper analyzers, and scaling the cluster horizontally.

Вопрос 43. What is the purpose of the 'Query DSL' in Elasticsearch?

The Query DSL (Domain Specific Language) in Elasticsearch is used to define queries in a JSON format. It allows for complex and flexible querying of data.

Example:

{
  "query": {
    "match": {
      "field": "value"
    }
  }
}

Вопрос 44. What is the purpose of the 'Fielddata' cache in Elasticsearch?

Fielddata cache stores the data structures necessary for sorting and aggregating on fields, improving performance.

Вопрос 45. Explain the 'Bulk' API in Elasticsearch.

The Bulk API in Elasticsearch allows you to index, delete, or update multiple documents in a single request for better performance. It reduces the overhead of handling individual requests.

Example:

POST /my_index/_bulk
{ "index": { "_id": "1" } }
{ "field": "value1" }
{ "delete": { "_id": "2" } }
{ "create": { "_id": "3" } }
{ "field": "value3" }