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From Bill Stoddard <b...@wstoddard.com>
Subject Re: Altogether Broken OtherChild logic
Date Thu, 30 Jan 2003 18:37:21 GMT
William A. Rowe, Jr. wrote:

>I belive I've deciphered the "RotateLogs doesn't work for access logs
>on Windows" Apache 2.0.44 bug.  It's actually many bugs in conformance.
>
>First, rbb's reorg of the WinNT pipe logic (apr/file_io/win32/pipe.c rev 1.46) 
>causes server/log.c ap_open_piped_log() to create an async (nonblocking) 
>pipe.  This was very cool for internal pipes.  However, console apps that are
>unprepared for Overlapped IO (read: all of them) will die given an Overlapped 
>pipe handle.  Even APR doesn't assume (and shouldn't) that a pipe handle
>passed as stdin/stdout is an Async handle.  However, Async handles are
>the only way to do timeouts.
>
>Unix ap_file_pipe_create() always creates the pipes blocking.  In fixing the
>bug, by creating blocking handles (that can't be timed out) for Win32, I also
>discovered our nonblocking pipe logic was reversed for parent/child handles 
>of the child stdin process. I've just committed all those fixes, so this aspect 
>was patched as well.  If you look at the new apr_create_nt_pipe() API, it 
>might be worth renaming and exporting it as apr_file_pipe_create_ex().
>It's similar to apr_file_pipe_create() with the added blocking mode argument
>(APR_FULL_BLOCK, APR_FULL_NONBLOCK, APR_READ_BLOCK and
>APR_WRITE_BLOCK).  APR_PARENT/CHILD_BLOCK only makes sense
>to a function like apr_procattr_io_set.  In fact, for safety, that creation call
>should never create NONBLOCK child pipes, but that's another discussion.
>
>So part one was fixed, now we create the access log's rotatelogs process
>with a good stdin stream.  It survives to log an entry, but only until we call 
>apr_proc_other_child_check within the WinNT MPM's *maintenence* loop.
>
>It seems that apr_proc_other_child_check is only being used during teardown
>of the Unix children.  It also seems that the 'correct' flag passed to the maint
>function for your registered otherchild is APR_OC_REASON_RESTART when
>the process is still running.
>
>Now mod_log_config kills the child process on APR_OC_REASON_RESTART.
>Because Win32 doesn't call the function in maintenance like unix, but in a one 
>second health-check loop, we are blowing away our access logger process.
>
>Finally, it looks like apr_proc_other_child_read is the function we *really* wanted
>to use within the health check.  But it seems all of these apr_proc_other_child
>functions are really misdocumented within APR.  Would someone step up and
>spell out exactly what they are *supposed* to be doing within unix, and then we
>can discuss how to make them portable to Win32?  It seems we have too much
>bubblegum and bailing wire holding them together, and the fixes that I made to
>do *exactly* what Unix was doing has killed the WinNT mpm.
>
>Bill
>
This stuff kinda worked on Windows in the past.  I need to dig some but 
I seem to recall that it was basically impossible to do the exact same 
thing in Windows as you do in Unix. The other_child_read in Unix will 
not (and cannot) work the same way under Unix.

Bill

>  
>


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