debug a process using strace/gdb

debug.rb

# collect information about a running process
# ruby debug.rb <pid>

begin
  raise ArgumentError unless pid = ARGV[0]
  pid = pid.to_i
  raise ArgumentError unless pid > 0
  Process.kill(0,pid)
rescue TypeError, ArgumentError
  raise 'pid required'
rescue Errno::ESRCH
  raise 'invalid pid'
rescue Errno::EPERM
  raise 'could not signal process (run as root)'
end

require 'fileutils'
dir = FileUtils.mkdir_p "/tmp/debug-#{pid}"
puts "Debugging process #{pid}, results in #{dir}."

File.open("#{dir}/proc-status.txt",'w'){ |f| f.write File.read("/proc/#{pid}/status") }

10.times do |i|
  out = File.open("#{dir}/gdb-backtrace-#{i}.txt",'w')
  r,w = IO.pipe
  child = fork{ $stdin.reopen(r); $stdout.reopen(out); $stderr.reopen(out); exec "gdb /proc/#{pid}/exe" }
  w.puts "attach #{pid}"
  w.puts "set height 0"
  w.puts "backtrace"
  w.puts "detach"
  w.puts "quit"
  Process.wait
  out.close

  sleep 1
end

out = File.open("#{dir}/lsof.txt",'w')
child = fork{ $stdout.reopen(out); $stderr.reopen(out); exec "lsof -nPp #{pid}" }
Process.wait
out.close

out = File.open("#{dir}/strace-summary.txt",'w')
child = fork{ $stdout.reopen(out); $stderr.reopen(out); exec "strace -cp #{pid}" }
sleep 5
Process.kill 'HUP', child
Process.wait
out.close

out = File.open("#{dir}/strace-log.txt",'w')
child = fork{ $stdout.reopen(out); $stderr.reopen(out); exec "strace -ttTp #{pid}" }
sleep 5
Process.kill 'HUP', child
Process.wait
out.close