es 开启slowlog

在 Elasticsearch 中，slowlog（慢日志）是用来记录查询和索引操作的性能数据，帮助你诊断性能瓶颈。你可以为查询 (search slowlog) 和索引 (index slowlog) 配置慢日志。

数据准备

POST /products/_doc/1
{
  "product_name": "Apple iPhone 15",
  "price": 999.99,
  "category": "Smartphones",
  "rating": 4.5,
  "discount": 0.1,
  "availability": true,
  "stock": 50,
  "release_date": "2023-09-01"
}

POST /products/_doc/2
{
  "product_name": "Samsung Galaxy S24",
  "price": 899.99,
  "category": "Smartphones",
  "rating": 4.3,
  "discount": 0.05,
  "availability": true,
  "stock": 30,
  "release_date": "2023-10-10"
}

POST /products/_doc/3
{
  "product_name": "Dell XPS 13",
  "price": 1199.99,
  "category": "Laptops",
  "rating": 4.8,
  "discount": 0.15,
  "availability": true,
  "stock": 20,
  "release_date": "2023-08-20"
}

POST /products/_doc/4
{
  "product_name": "Sony WH-1000XM5",
  "price": 349.99,
  "category": "Headphones",
  "rating": 4.7,
  "discount": 0.2,
  "availability": false,
  "stock": 0,
  "release_date": "2023-06-15"
}

POST /products/_doc/5
{
  "product_name": "Apple MacBook Air",
  "price": 999.00,
  "category": "Laptops",
  "rating": 4.6,
  "discount": 0.1,
  "availability": true,
  "stock": 15,
  "release_date": "2023-11-01"
}

检索请求实现流程

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其中，query阶段的核心步骤如下。

❑客户端发送请求到协调节点。
❑协调节点转发请求到索引的每个主或副本分片。
❑分片本地查询完成后，将结果添加到本地的优先队列。
❑每个分片将本地结果返回给协调节点，协调节点合并完成后，形成全局排序列表。

fetch阶段的核心步骤如下。

❑协调节点接收到客户端请求后，将GET请求（query阶段形成的全局排序列表结果数据）转发给相关节点。
❑接收到请求的节点向协调节点返回结果数据。
❑待全部结果数据都返回后，协调节点将结果返回给客户端。

修改现有索引的慢日志配置 (动态配置)

你也可以通过 Elasticsearch 的 动态设置 API 来为已存在的索引启用慢日志配置，而不需要重启 Elasticsearch。

示例：动态配置查询慢日志

PUT /products/_settings
{
  "settings": {
    "index.search.slowlog.threshold.query.warn": "10s",  
    "index.search.slowlog.threshold.query.info": "5s",   
    "index.search.slowlog.threshold.query.debug": "0s",  
    "index.search.slowlog.threshold.query.trace": "500ms", 
    "index.search.slowlog.threshold.fetch.warn": "1s",   
    "index.search.slowlog.threshold.fetch.info": "500ms",
    "index.search.slowlog.threshold.fetch.debug": "0s",
    "index.indexing.slowlog.level": "debug"  
  }
}

GET /products/_search

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示例：动态配置索引慢日志

PUT /products/_settings
{
  "settings": {
    "index.indexing.slowlog.threshold.index.warn": "10s",
    "index.indexing.slowlog.threshold.index.info": "5s",
    "index.indexing.slowlog.threshold.index.debug": "0s",
    "index.indexing.slowlog.level": "trace"
  }
}