环境搭建

https://www.elastic.co/guide/en/apm/get-started/current/quick-start-overview.html

然后在项目里加入apm agent，并设置好apm server的地址即可

结构分析

span：通过 a.订阅rails事件、b.改写底层gem、c.用户with_span 来收集，代表一些特别关注的可能消耗性能的过程。内含transaction id。

transaction：在middleware中收集，代表整个请求响应的过程。可能带有trace id

trace id：调用其他服务时，在http header中加入trace id，以便分布式链路跟踪




elastic-apm ruby agent的源码分析




增加额外跟踪信息

https://www.elastic.co/guide/en/apm/agent/ruby/current/context.html



聚合查询


transaction和span存储在不同的索引里，不便于查询“哪些url的redis访问频繁”，“哪些url的IO时间占比低但总RT却很长”

require 'elasticsearch'

class Txns
  attr_reader :c

  def initialize(c)
    @c = c
  end

  def load
    res = c.search(
      index: 'apm-*-transaction-*',
      body: {
        size: 200,
        query: {match_all: {}},
        _source: {includes: [
          'transaction.duration.us',
          'transaction.id',
          'url.path'
        ]}
      }
    )

    res['hits']['hits'].map{ |r| Txn.new(c, r['_source']) }
  end
end

class Txn
  attr_reader :conn, :src, :id, :duration, :path
  def initialize(conn, src)
    @conn = conn
    @src = src
  end

  def id
    @id ||= src.dig('transaction', 'id')
  end

  def duration
    @duration ||= src.dig('transaction', 'duration', 'us')
  end

  def path
    @path ||= src.dig('url', 'path')
  end

  def spans
    res = conn.search(
      index: 'apm-*-span-*',
      body: {
        size: 0,
        query: {terms: {'transaction.id' => [id]}},
        aggs: {
          by_subtype: {
            terms: {field: 'span.subtype'},
            aggs: {
              duration_sum: {
                stats: {field: 'span.duration.us'}
              }
            }
          }
        }
      }
    )
    buckets = res.dig('aggregations', 'by_subtype', 'buckets')
    buckets.map do |b|
      b['duration_sum'].merge!(
        'percentage' => (b['duration_sum']['sum'] / duration),
        'subtype' => b['key'],
      )
    end
  end

  def to_doc
    {txn_id: id, path: path, duration: duration, spans: spans}
  end

  def index
    conn.index index: 'txn_stats_001', id: id, body: to_doc
  end
end

client = Elasticsearch::Client.new log: true

Txns.new(client).load.each &:index




聚合统计图