数据获取

Gemfile

# 不指定用master的会遇到命令无法执行的问题，所以指定master分支

gem 'rbtrace', git: 'https://github.com/tmm1/rbtrace', branch: 'master'

例如：某controller.rb中

def index
  if params[:rbtrace] = "go"
    require 'rbtrace'
    pid = Process.pid
    system("nohup bundle exec rbtrace -p #{pid} -e 'load \"/tmp/heap_dump.rb\"' &")
  end
end

/tmp/heap_dump.rb文件

Thread.new do
  require "objspace"
  ObjectSpace.trace_object_allocations_start
  GC.start
  ObjectSpace.dump_all(output: File.open("/tmp/heap.json", "w"))
end.join

分三个时段分别生成一个heap.json文件（触发第二步index内的代码执行）

数据分析

在bundle exec rails console内执行分析的代码输出到log文件(或者你可以写个脚本执行单独保存或者使用文章开始使用的数据分析工具）

first_addrs = []
third_addrs = []

# Get a list of memory addresses from the first dump
File.open("/tmp/heap1.json", "r").each_line do |line|
parsed = JSON.parse(line)
first_addrs << parsed["address"] if parsed && parsed["address"]
end

# Get a list of memory addresses from the last dump
File.open("/tmp/heap3.json", "r").each_line do |line|
parsed = JSON.parse(line)
third_addrs << parsed["address"] if parsed && parsed["address"]
end

diff = []

# Get a list of all items present in both the second and
# third dumps but not in the first.
File.open("/tmp/heap2.json", "r").each_line do |line|
  parsed = JSON.parse(line)
  if parsed && parsed["address"] && !first_addrs.include?(parsed["address"]) && third_addrs.include?(parsed["address"])
  puts diff.count
  puts parsed
    diff << parsed
  end
end


# Group items

diff.group_by do |x|

[x["type"], x["file"], x["line"]]

end.map do |x,y|

# Collect memory size

[x, y.count, y.inject(0){|sum,i| sum + (i['bytesize'] || 0) }, y.inject(0){|sum,i| sum + (i['memsize'] || 0) }]

end.sort do |a,b|

b[1] <=> a[1]

end.each do |x,y,bytesize,memsize|

# Output information about each potential leak

Rails.logger.info "Leaked #{y} #{x[0]} objects of size #{bytesize}/#{memsize} at: #{x[1]}:#{x[2]}"

end


# Also output total memory usage, because why not?
memsize = diff.inject(0){|sum,i| sum + (i['memsize'] || 0) }
bytesize = diff.inject(0){|sum,i| sum + (i['bytesize'] || 0) }
puts "\n\nTotal Size: #{bytesize}/#{memsize}"