Monitoring per-thread allocation using JRuby and java.lang.management.ThreadMXBean

check_thread_alloc.rb

require 'java'
require 'jruby'

thread_bean = java.lang.management.ManagementFactory.thread_mx_bean

t1 = Thread.new do
  a = nil
  loop do
    a = 'foo'
  end
end
t1_thread = JRuby.reference(t1).native_thread

main = Thread.current
main_thread = JRuby.reference(main).native_thread

loop do
  sleep 1
  t1_alloc = thread_bean.get_thread_allocated_bytes([t1_thread.id].to_java(:long))[0]
  main_alloc = thread_bean.get_thread_allocated_bytes([main_thread.id].to_java(:long))[0]

  puts "main allocated: #{main_alloc}"
  puts "t1 allocated: #{t1_alloc}"
end