Cloud computing platform (Search)-elasticsearch-Overview

Introduction

Elasticsearch is an open-source, distributed, and restful search engine built based on Lucene. Designed for cloud computing, it can achieve real-time search, stable, reliable, fast, and easy to install and use. JSON data indexing is supported through HTTP.

We create a website or application and add a search function, which makes it difficult to search. We hope that our search solution will be faster. We hope to have a Zero Configuration and a completely free search mode. We hope that we can simply use JSON to index data through HTTP, we hope that our search server will always be available. We hope that we can start with one server and expand it to several hundred. We need to search in real time, and we need simple multi-tenancy, we hope to build a cloud solution. Elasticsearch aims to solve all these problems and more.

Concept

Cluster

A cluster has multiple nodes, one of which is the master node. The master node can be elected and the master node is for the inside of the cluster. One concept of ES is decentralization. Literally, it is a non-central node. This is for the outside of the cluster, because the elasticsearch cluster is logically a whole, communication between you and any node is equivalent to communication with the entire elasticsearch cluster.

Shards

Elasticsearch divides a complete index into Multiple shards. This allows you to split a large index into Multiple shards and distribute them to different nodes. Create a distributed search. The number of shards can only be specified before the index is created and cannot be changed after the index is created.

Replicas

An elasticsearch instance represents an index copy. elasticsearch allows you to set multiple index copies. Replicas improve system fault tolerance. When a shard of a node is damaged or lost, it can be recovered from the replica. The second is to improve the query efficiency of elasticsearch. elasticsearch automatically performs load balancing on search requests.

Recovery

This indicates data recovery or data redistribution. When a node is added or exited, elasticsearch redistributes the index shards Based on the server load. When the node is restarted, the data is also restored.

River

It represents a data source of ES, and is also a method for synchronizing data from other storage methods (such as databases) to es. It is an es service that exists as a plug-in. It reads data from the river and indexes it into es. The official River has couchdb, rabbitmq, Twitter, and Wikipedia.

Gateway

Elasticsearch indexes represent the storage method of elasticsearch index snapshots. elasticsearch stores indexes in the memory by default. When the memory is full, the indexes are persisted to the local hard disk. Gateway stores index snapshots. When the elasticsearch cluster is disabled and restarted, it reads index backup data from the gateway. Elasticsearch supports multiple types of gateways, including local file systems (default), distributed file systems, hadoop HDFS, and Amazon S3 cloud storage services.

Discovery. Zen

It represents the automatic discovery node mechanism of ES. Es is a P2P-based system. It first searches for existing nodes through broadcast and then communicates between nodes through multicast protocol, it also supports point-to-point interaction.

Transport

It represents the interaction between es nodes or clusters and clients. By default, TCP is used internally for interaction, and HTTP protocol (JSON format) is supported), thrift, Servlet, memcached, zeromq and other transmission protocols (integrated through plug-ins ).