概述
继续跟中华石杉老师学习ES，第48篇
课程地址： https://www.roncoo.com/view/55
官方说明
Percentiles Aggregation： 戳这里
示例
需求： 网站访问时延统计
为了演示该功能，我们先建个索引，模拟一批数据
#新建索引 PUT /website { "mappings": { "logs": { "properties": { "latency": { "type": "long" }, "province": { "type": "keyword" }, "timestamp": { "type": "date" } } } } }
#模拟数据 POST /website/logs/_bulk { "index": {}} { "latency" : 105, "province" : "江苏", "timestamp" : "2018-10-28" } { "index": {}} { "latency" : 83, "province" : "江苏", "timestamp" : "2018-10-29" } { "index": {}} { "latency" : 92, "province" : "江苏", "timestamp" : "2018-10-29" } { "index": {}} { "latency" : 112, "province" : "江苏", "timestamp" : "2018-10-28" } { "index": {}} { "latency" : 68, "province" : "江苏", "timestamp" : "2018-10-28" } { "index": {}} { "latency" : 76, "province" : "江苏", "timestamp" : "2018-10-29" } { "index": {}} { "latency" : 101, "province" : "新疆", "timestamp" : "2018-10-28" } { "index": {}} { "latency" : 275, "province" : "新疆", "timestamp" : "2018-10-29" } { "index": {}} { "latency" : 166, "province" : "新疆", "timestamp" : "2018-10-29" } { "index": {}} { "latency" : 654, "province" : "新疆", "timestamp" : "2018-10-28" } { "index": {}} { "latency" : 389, "province" : "新疆", "timestamp" : "2018-10-28" } { "index": {}} { "latency" : 302, "province" : "新疆", "timestamp" : "2018-10-29" }
DSL:
#网站访问时延统计（50% 95% 99%的请求） GET /website/logs/_search { "size": 0, "aggs": { "latency_percentiles": { "percentiles": { "field": "latency", "percents": [ 50, 95, 99 ] } }, "latency_avg": { "avg": { "field": "latency" } } } }
返回：
{ "took": 3, "timed_out": false, "_shards": { "total": 5, "successful": 5, "skipped": 0, "failed": 0 }, "hits": { "total": 12, "max_score": 0, "hits": [] }, "aggregations": { "latency_avg": { "value": 201.91666666666666 }, "latency_percentiles": { "values": { "50.0": 108.5, "95.0": 627.4999999999997, "99.0": 654 } } } }
可知,
- 50%的请求 在 108.5毫秒
- 95%的请求 在 627.5毫秒
- 99%的请求 在 654毫秒
- 平均时延 201.9毫秒
数值的最大的值是多少，不是完全准确的
需求二：按地区分组后看下每个地区的 网站访问时延统计
GET /website/_search { "size": 0, "aggs": { "group_by_province": { "terms": { "field": "province" }, "aggs": { "latency_percentiles": { "percentiles": { "field": "latency", "percents": [ 50, 95, 99 ] } }, "latency_avg": { "avg": { "field": "latency" } } } } } }
返回：
Percentiles优化 compression
compression 官方指导： 戳这里
TDigest算法，用很多节点来执行百分比的计算，近似估计，有误差，节点越多，越精准
compression ，限制节点数量最多 compression * 20 = 2000个node去计算 ，默认100
compression 越大，占用内存越多，越精准，性能越差
一个节点占用32字节，100 * 20 * 32 = 64KB
简单来说： 如果你想要percentile算法越精准，compression可以设置的越大
