memory_dump_diff.rb

# rbtrace -p PID -e 'Thread.new{require "objspace"; ObjectSpace.trace_object_allocations_start; GC.start(); ObjectSpace.dump_all(output: File.open("heap_#{Time.now.to_i}.json", "w"))}.join' 
# Gather three snapshots
# Remove common objects in snapshot 1 from snapshot 2
# Remove missing objects in snapshot 3 from snapshot 2
#!/usr/bin/env ruby

require 'set'  
require 'json'

if ARGV.length != 3  
  puts "Usage: detect_leaks [FIRST.json] [SECOND.json] [THIRD.json]"
  exit 1
end

first_addrs = Set.new  
third_addrs = Set.new

# Get a list of memory addresses from the first dump
File.open(ARGV[0], "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(ARGV[2], "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(ARGV[1], "r").each_line do |line|  
  parsed = JSON.parse(line)
  if parsed && parsed["address"]
    if !first_addrs.include?(parsed["address"]) && third_addrs.include?(parsed["address"])
      diff << parsed
    end
  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
  puts "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}"  


# OUTPUT
# Leaked 77 STRING objects of size 10947/10961 at: /Users/peterwagenet/.rvm/gems/ruby-2.1.3/gems/actionview-4.1.6/lib/action_view/template.rb:297  
# Leaked 15 DATA objects of size 0/51808 at: /Users/peterwagenet/.rvm/gems/ruby-2.1.3/gems/actionview-4.1.6/lib/action_view/template.rb:297  
# Leaked 1 FILE objects of size 0/216 at: /Users/peterwagenet/.rvm/gems/ruby-2.1.3/gems/puma-2.7.1/lib/puma/server.rb:290  
# Leaked 1 DATA objects of size 0/0 at: /Users/peterwagenet/.rvm/gems/ruby-2.1.3/gems/puma-2.7.1/lib/puma/client.rb:35

# Total Size: 11767/68771