ElasticSearch interview questions

ElasticSearch interview questions Download ElasticSearch interview questions PDF

ElasticSearch interview questions

Elasticsearch is a search engine that is based on Lucene.It offers a distributed, multitenant – capable full-text search engine with as HTTP (Hyper Text Transfer Protocol) web interface and Schema-free JSON (JavaScript Object Notation) documents.It is developed in Java and is an open source released under Apache License.
As on March 2018, the version 6.2.2 is the latest and stable version of Elasticsearch.
Since Elasticsearch is built using Java, we require any of the following software to run Elasticsearch on our device.
  • The latest version of Java 8 series
  • Java version 1.8.0_131 is recommended.
Run Following command on your terminal to start Elasticsearch server:
cd elasticsearch
./bin/elasticsearch

curl ‘http://localhost:9200/?pretty’ command is used to check ElasticSearch server is running or not.

Some of the companies that use Elasticsearch along with Logstash and Kibana are:
  • Wikipedia
  • Netflix
  • Accenture
  • Stack Overflow
  • Fujitsu
  • Tripwire
  • Medium
  • Swat.io
  • Hip chat
  • IFTTT
It is a set or a collection of one or more than one nodes or servers that hold your complete data and offers federated indexing and search capabilities across all the nodes.It is identified by a different and unique name that is “Elasticsearch” by default.
This name is considered to be important because a node can be a part of a cluster only if it is set up to join the cluster by its name.
Each and every instance of Elasticsearch is a node.And, a collection of multiple nodes which can work in harmony form an Elasticsearch cluster.
An index in Elasticsearch is similar to a table in relational databases.The only difference lies in storing the actual values in the relational database, whereas that is optional in Elasticsearch.
An index is capable of storing actual or analyzed values in an index.
A type in Elasticsearch is a logical category of the index whose semantics are completely up to the user.
Mapping is a process which defines how a document is mapped to the search engine, searchable characteristics are included such as which fields are tokenized as well as searchable.
In Elasticsearch an index created may contain documents of all “mapping types”.
A document in Elasticsearch is similar to a row in relational databases.The only difference is that every document in an index can have a different structure or fields but having the same data type for common fields is mandatory.Each field with different data types can occur multiple times in a document.
The fields can also contain other documents.