There's an article out there, Profiling LAMP Applications with Apache's Blackbox Logs, that describes how to create a log that records a lot of detailed information missing in the common and combined log formats. This information is supposed to help you resolve performance issues. As the author notes "While the common log-file format (and the combined format) are great for hit tracking, they aren't suitable for getting hardcore performance data."

The article describes a "blackbox" log format, like a blackbox flight recorder on an aircraft, that gathers information used to profile server performance, missing from the hit tracking log formats: Keep alive status, remote port, child processes, bytes sent, etc.

LogFormat "%a/%S %X %t \"%r\" %s/%>s %{pid}P/%{tid}P %T/%D %I/%O/%B" blackbox

I'm trying to recreate as much of the format for Nginx, and would like help filling in the blanks. Here's what Nginx blackbox format would look like, the unmapped Apache directives have question marks after their names.

access_log blackbox '$remote_addr/$remote_port X? [$time_local] "$request"'
                    's?/$status $pid/0 T?/D? I?/O?/B?'

Here's a table of the variables I've been able to map from the Nginx documentation.

%a = $remote_addr - The IP address of the remote client.
%S = $remote_port - The port of the remote client.
%X = ? - Keep alive status.
%t = $time_local - The start time of the request.
%r = $request - The first line of request containing method verb, path and protocol.
%s = ? - Status before any redirections.
%>s = $status - Status after any redirections.
%{pid}P = $pid - The process id.
%{tid}P = N/A - The thread id, which is non-applicable to Nignx.
%T = ? - The time in seconds to handle the request.
%D = ? - The time in milliseconds to handle the request.
%I = ? - The count of bytes received including headers. 
%O = ? - The count of bytes sent including headers.
%B = ? - The count of bytes sent excluding headers, but with a 0 for none instead of '-'.

Looking for help filling in the missing variables, or confirmation that the missing variables are in fact, unavailable in Nginx.