Guess that Apache received two POST requests at a same time. They would be normally logged by the dumpio module in the correct order like below. Where you can see that log 3 belongs to POST logged in the post 1 (/mypage_1/) and log 4 belongs to the post logged in log 2 (/mypage_2/).
[Thu Dec 13 11:28:01 2012] [debug] mod_dumpio.c(74): mod_dumpio: dumpio_in (data-HEAP): POST /mypage_1/ HTTP/1.1\r\n
[Thu Dec 13 11:28:01 2012] [debug] mod_dumpio.c(74): mod_dumpio: dumpio_in (data-HEAP): POST /mypage_2/ HTTP/1.1\r\n
[Thu Dec 13 11:28:01 2012] [debug] mod_dumpio.c(74): mod_dumpio: dumpio_in (data-HEAP): xml_request=I_Belong_To_mypage_1
[Thu Dec 13 11:28:01 2012] [debug] mod_dumpio.c(74): mod_dumpio: dumpio_in (data-HEAP): xml_request=I_Belong_To_mypage_2
I wonder if by any chance they could be logged in a different order like below. And in this case I would not know what request belongs to what POST. Is there any way for me to know the requests that belong to each POST?
[Thu Dec 13 11:28:01 2012] [debug] mod_dumpio.c (74): mod_dumpio: dumpio_in (data-HEAP): POST /mypage_1/ HTTP/1.1\r\n
[Thu Dec 13 11:28:01 2012] [debug] mod_dumpio.c (74): mod_dumpio: dumpio_in (data-HEAP): POST /mypage_2/ HTTP/1.1\r\n
[Thu Dec 13 11:28:01 2012] [debug] mod_dumpio.c (74): mod_dumpio: dumpio_in (data-HEAP): xml_request=I_Belong_To_mypage_2
[Thu Dec 13 11:28:01 2012] [debug] mod_dumpio.c (74): mod_dumpio: dumpio_in (data-HEAP): xml_request=I_Belong_To_mypage_1