原書(shū)：Elasticsearch: the Definitive Guide source
https://github.com/elastic/elasticsearch
It's a distributed search engine built on Lucene, with a Java API and a JSON REST API. It's an indexed document-oriented database. You can do reasonably sophisticated searches with a query DSL.
Life inside a Cluster 原文
每一個(gè)cluster有一個(gè)master node爬范，用來(lái)管理加減node和產(chǎn)生或是刪除index净赴。用戶可以跟任意一個(gè)node溝通纫事，所有的node都知道每一個(gè)文件住在哪兒并且能夠?qū)⒂脩舻恼?qǐng)求轉(zhuǎn)發(fā)到正確的node要到該要的回復(fù)清钥。
An index is just a logical namespace that points to one or more physical shards.
A shard is a low-level worker unit that holds just a slice of all the data in the index--a single instance of Lucene.
Documents are stored in shards, and shards are allocated to nodes in your cluster, auto-balanced by Elasticsearch.
