Book Image

Elasticsearch Server - Third Edition

By : Rafal Kuc
Book Image

Elasticsearch Server - Third Edition

By: Rafal Kuc

Overview of this book

ElasticSearch is a very fast and scalable open source search engine, designed with distribution and cloud in mind, complete with all the goodies that Apache Lucene has to offer. ElasticSearch’s schema-free architecture allows developers to index and search unstructured content, making it perfectly suited for both small projects and large big data warehouses, even those with petabytes of unstructured data. This book will guide you through the world of the most commonly used ElasticSearch server functionalities. You’ll start off by getting an understanding of the basics of ElasticSearch and its data indexing functionality. Next, you will see the querying capabilities of ElasticSearch, followed by a through explanation of scoring and search relevance. After this, you will explore the aggregation and data analysis capabilities of ElasticSearch and will learn how cluster administration and scaling can be used to boost your application performance. You’ll find out how to use the friendly REST APIs and how to tune ElasticSearch to make the most of it. By the end of this book, you will have be able to create amazing search solutions as per your project’s specifications.
Table of Contents (18 chapters)
Elasticsearch Server Third Edition
Credits
About the Authors
About the Reviewer
www.PacktPub.com
Preface
Index

The gateway and recovery modules


Apart from our indices and the data indexed inside them, Elasticsearch needs to hold the metadata, such as the type mappings, the index level settings, and so on. This information needs to be persisted somewhere so it can be read during cluster recovery. Of course, it could be stored in memory, but full cluster restart or a fatal failure would result in this information being lost, which is not something that we want. This is why Elasticsearch introduced the gateway module. You can think about it as a safe heaven for your cluster data and metadata. Each time you start your cluster, all the needed data is read from the gateway and, when you make a change to your cluster, it is persisted using the gateway module.

The gateway

In order to set the type of gateway we want to use, we need to add the gateway.type property to the elasticsearch.yml configuration file and set it to the local value. Currently, Elasticsearch recommends using the local gateway type (gateway...