Elasticsearch学习笔记

这篇博客用于记录学习和使用Elasticsearch的过程，主要内容包括安装配置和通过Python访问Elasticsearch。Tips: Elasticsearch安装在一台Linux服务器上。

• Elasticsearch学习笔记
  • 安装配置Elasticsearch
  • 通过Python访问Elasticsearch
  • 参考资料：

安装配置Elasticsearch

1. 下载安装包：Download Elasticsearch;

2. 解压缩：tar -xvf elasticsearch-7.15.2-linux-x86_64.tar.gz;

3. 修改config目录下的elasticsearch.yml文件，配置局域网访问：network.host: 0.0.0.0;

4. 切换到bin目录，敲击命令./elasticsearch启动Elasticsearch，出现以下错误信息：

   ERROR: [2] bootstrap checks failed. You must address the points described in the following [2] lines before starting Elasticsearch.
   bootstrap check failure [1] of [2]: max virtual memory areas vm.max_map_count [65530] is too low, increase to at least [262144]
   bootstrap check failure [2] of [2]: the default discovery settings are unsuitable for production use; at least one of [discovery.seed_hosts, discovery.seed_providers, cluster.initial_master_nodes] must be configured
   

5. 由于当前用户拥有的内存权限太小，Elasticsearch不能正常启动，需要修改系统配置文件/etc/sysctl.conf，设置vm.max_map_count=262144，重启系统（或执行sysctl -w vm.max_map_count=262144）;

6. 另外，由于没有指定以下配置项，Elasticsearch不能正常启动：

   • discovery.seed_hosts: 集群主机列表；
   • discovery.seed_providers: 基于配置文件配置集群主机列表；
   • cluster.initial_master_nodes: 启动时初始化的参与选主的node，生产环境必填。

   修改配置文件elasticsearch.yml，设置discovery.seed_hosts: ["192.168.1.xx"]和cluster.initial_master_nodes: ["192.168.1.xx:9300"];

7. 重新启动Elasticsearch，浏览器访问http://192.168.1.xx:9200/：

   {
   "name" : "xxxx",
   "cluster_name" : "elasticsearch",
   "cluster_uuid" : "4urQVMKyQgGl0oTM_wvgjQ",
   "version" : {
   	"number" : "7.15.2",
   	"build_flavor" : "default",
   	"build_type" : "tar",
   	"build_hash" : "93d5a7f6192e8a1a12e154a2b81bf6fa7309da0c",
   	"build_date" : "2021-11-04T14:04:42.515624022Z",
   	"build_snapshot" : false,
   	"lucene_version" : "8.9.0",
   	"minimum_wire_compatibility_version" : "6.8.0",
   	"minimum_index_compatibility_version" : "6.0.0-beta1"
   },
   "tagline" : "You Know, for Search"
   }
   

8. 安装、配置成功！

通过Python访问Elasticsearch

1. 安装Elasticsearch的Python客户端：conda install elasticsearch;

2. 连接Elasticsearch:

   from elasticsearch import Elasticsearch
   
   es = Elasticsearch(hosts=['192.168.1.xx'])
   result = es.indices.create(index='news_and_events', ignore=400)  # 状态码400表示由于已经存在同名Index，创建失败
   print(result)
   

3. 安装插件elasticsearch-analysis-ik，使Elasticsearch具备中文分词的能力：

   ./elasticsearch-plugin install https://github.com/medcl/elasticsearch-analysis-ik/releases/download/v7.15.2/elasticsearch-analysis-ik-7.15.2.zip
   

   安装成功后，重启Elasticsearch；

4. 填充数据：

   from elasticsearch import Elasticsearch
   from tqdm import tqdm
   
   # 导入本地的模块
   from database import SessionLocal
   from models import Record
   
   es = Elasticsearch(hosts=['192.168.1.xx'])
   mapping = {
   	'properties': {
   		'title': {
   			'type': 'text',
   			'analyzer': 'ik_max_word',
   			'search_analyzer': 'ik_max_word'
   		},
   		'content': {
   			'type': 'text',
   			'analyzer': 'ik_max_word',
   			'search_analyzer': 'ik_max_word'
   		}
   	}
   }
   es.indices.create(index='news_and_events', ignore=400)  # Elasticsearch中的index可以类比关系型数据库里面的database
   es.indices.put_mapping(index='news_and_events', doc_type='records', body=mapping, include_type_name=True)  # doc_type类比关系模式
   
   # 查询数据库，导出所有的新闻和公告
   db = SessionLocal()
   result_set = db.query(Record).all()
   
   for record in tqdm(result_set):
   	data = {
   		'record_id': record.record_id,
   		'title': record.title,
   		'content': record.content
   	}
   	es.create(index='news_and_events', doc_type='records', id=record.record_id, document=data)
   
   # 关闭数据库和Elasticsearch连接
   db.close()
   es.close()
   

5. 查询数据：

   q = {
   		'query': {
   			'multi_match': {
   				'query': '成都重庆双城经济圈',
   				'fields': ['title^2', 'content']
   			}
   		}
   	}
   results = es.search(q, index='news_and_events', doc_type='records')
   

   Elasticsearch返回的结果：

   {
   	"took": 10,
   	"timed_out": false,
   	"_shards": {
   		"total": 1,
   		"successful": 1,
   		"skipped": 0,
   		"failed": 0
   	},
   	"hits": {
   		"total": {
   			"value": 623,
   			"relation": "eq"
   		},
   		"max_score": 57.087215,
   		"hits": [
   			{
   				"_index": "news_and_events",
   				"_type": "records",
   				"_id": "2508",
   				"_score": 57.087215,
   				"_source": {
   					"record_id": 2508,
   					"title": "关于成渝地区双城经济圈创新创业峰会的通知",
   					"content": "各学院，各位老师和同学：\n现转发重庆市教育委员会和四川省教育厅等六部门联合发布的《关于举办\"智创巴蜀\"首届成渝地区双城经济圈创新创业峰会的通知》，详见附件。欢迎积极参加。\n联系人：x老师\n联系电话：xxxxxxxx\n教务处\nxxxx年xx月xx日\n附件1-川渝6部门联合发峰会正式文件"
   				}
   			}
   		]
   	}
   }
   

参考资料：

• Important system configuration / Virtual memory
• 启动elasticsearch报错：max virtual memory areas vm.max_map_count
• ES启动异常：the default discovery settings are unsuitable for production use...
• master not discovered yet, this node has not...
• Elasticsearch基本介绍及其与Python的对接实现
• Python Elasticsearch Client