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Elasticsearch是一个分布式、RESTful风格的搜索和数据分析引擎。目前已被各大公司广泛的引入生产使用，也已成为大数据生态的重要组成部分。本篇简单介绍一下Elasticsearch的本地安装和一些常用操作。
Elasticsearch使用Java构建，不同版本的Elasticsearch对Java版本要求略有差异，可参考下图来选择Elasticsearch和Java的版本（下图来自官网Support Matrix JVM）。
Elasticsearch本地安装
本地安装Elasticsearch非常简单，首先到官网下载Elasticsearch到本地指定目录，然后解压，进入到Elasticsearch的解压目录下，执行./bin/elasticsearch或.inelasticsearch.bat(Windows)，可以加上-d参数让Elasticsearch在后台运行。至此，Elasticsearch就安装好了，可以通过curl http://localhost:9200或者用浏览器打开http://localhost:9200/检查是否正常启动，下图这样就表示正常启动了。
常见问题
Elasticsearch的安装非常简单，通常在安装过程中会遇到一些问题，下面这几个问题是在Ubuntu操作系统安装时经常遇到的问题。
问题一：
ERROR: [1] bootstrap checks failed
[1]: max virtual memory areas vm.max_map_count [65530] is too low, increase to at least [262144]
解决办法：
切换到root用户修改配置/etc/sysctl.conf
添加下面配置并执行命令：
vm.max_map_count=655360
sysctl -p
然后，重新启动elasticsearch，即可启动成功。
问题二：
ERROR: [1] bootstrap checks failed
[1]: max number of threads [1024] for user [elasticsearch] is too low, increase to at least [2048]
解决办法：
修改/etc/security/limits.d/90-nproc.conf
* soft nproc 1024 修改成 * soft nproc 2048
Elasticsearch常用操作
问题三：
ERROR: [1] bootstrap checks failed
[1]: max file descriptors [4096] for elasticsearch process likely too low, increase to at least [65536]
解决办法：
切换到root用户，编辑/etc/security/limits.conf添加如下内容（其实切换到root用户直接执行ulimit -n 65536即可）
* soft nofile 65536
* hard nofile 131072
* soft nproc 2048
* hard nproc 4096
新增一个索引
curl -X PUT 'http://localhost:9200/index_name' -H 'Content-Type: application/json' -d '{
"settings": {
...
},
"mappings": {
"one": {...},
"two": {...},
...
}
}'
删除一个索引
curl -X DELETE "http://localhost:9200/index_name"
删除多个索引
curl -X DELETE "http://localhost:9200/index_name1,index_name2"
删除所有索引
curl -X DELETE "http://localhost:9200/_all"
curl -X DELETE "http://localhost:9200/*"
添加一条数据
curl -X PUT 'http://localhost:9200/index_name/type_name/id' -H 'Content-Type: application/json' -d '{
"title": "The title",
"text": "The text ...",
"date": "2019/01/01"
}'
删除单条数据
curl -X DELETE "http://localhost:9200/index_name/type_name/id"
批量删除多条数据
curl -X POST "http://localhost:9200/_bulk" -H 'Content-Type: application/json' -d '
{"delete":{"_index":"index_name","_type":"main","_id":"1"}}
{"delete":{"_index":"index_name","_type":"main","_id":"2"}}
'
删除所有数据
curl -X POST "http://localhost:9200/index_name/type_name/_delete_by_query?conflicts=proceed" -H 'Content-Type: application/json' -d '{"query": {"match_all": {}}}'
修改索引setting
curl -X POST 'http://localhost:9200/index_name' -H 'Content-Type: application/json' -d '{
"settings": {
"number_of_shards": 3,
"number_of_replicas": 0,
"index.mapping.total_fields.limit": 5000
}
}'
索引重命名
curl -X POST 'http://localhost:9200/_reindex' -H 'Content-Type: application/json' -d '{
"source": {
"index": "index_name_old"
},
"dest": {
"index": "index_name_new"
}
}'
手动迁移分片
curl -X PUT 'http://localhost:9200/_cluster/settings' -H 'Content-Type: application/json' -d'{
"transient": {
"cluster.routing.allocation.enable": "none"
}
}'
curl -X PUT 'http://localhost:9200/_cluster/settings' -H 'Content-Type: application/json' -d'{
"transient": {
"cluster.routing.allocation.enable": "all"
}
}'
curl -X POST 'http://localhost:9200/_cluster/reroute' -H 'Content-Type: application/json' -d '{
"commands" : [
{
"move" : {
"index" : "reindex-resharding-test",
"shard" : 0,
"from_node" : "192.168.0.101",
"to_node" : "192.168.0.102"
}
}
]
}'
查看集群状态
curl -X GET 'http://localhost:9200/_cluster/health?pretty'
查看所有索引
curl -X GET 'http://localhost:9200/_cat/indices?v'
查看所有shards
curl -X GET 'http://localhost:9200/_cat/shards'
查看unassigned shards
curl -X GET 'http://localhost:9200/_cat/shards' | grep UNASSIGNED