Hello:
We have a very high-volume site that runs across a cluster of several
machines which needs to have access to our back end storage platform, which
needless to say is very busy. I have been given the task of reducing load to
the filer. Due to the fact that our application is rather large and includes
lots of files which reside on our filer, php would be a good place to cut down
load.
We currently have a rather unique setup. We are running php with
fast-cgi support via sapi/cgi/cgi_main.c as well as APC for opcode/user
caching**. This allows us to run php as a daemon which reduces system calls
and retains persistence with APC. Our setup has been working quite well.
However, there is one behavior that is less than optimal.
Whenever one of our pages is accessed, it appears*** that the requested
file and all included files are opened, which results in several open calls to
our filer. As I mentioned, we are running APC which seems to be doing a
nice job of op-code caching. It would be ideal if somehow I could modify php
to first check APC cache for the pre-compiled opcode before attempting to
open the file. This would be a huge win on our cluster, since each hit
currently generates 5-10 open calls.
Now please bear with me because I am new to the Zend / main tree of
the php source. If my understanding is correct, the basic flow of
cgi/php goes something like this:
request
some variable init.
module_init <-apc overide compile_file w/my_compile_file
php_fopen_primary_script(&file_handle TSRMLS_CC);
php_execute_script(&file_handle TSRMLS_CC);
VCWD_CHDIR_FILE(primary_file->filename);
# i think included_files gets opened here someplace
# i do not understand that magic yet.
zend_execute_scripts()
zend_compile_file()
compile_file || my_compile_file() <-- apc
# it looks like the std compile_file
# may do some zend_open cmds here via
# open_file_for_scaning()
zend_destroy_file_handle() <-- destroy before execute?
zend_execute()
php_request_shutdown()
FCGX_Finish_r;
I have a few questions:
1. When exactly do the files get opened/read? And is this a necessary
step if you already have the op-code.
2. Is it possible to check apc_cache before opening files? If it
is possible, how/where do you think it could be best implemented?
Is there some similar interface to the my_compile_file trick used
to override zend_compile_file by apc? Perhaps something like
my_open_file, which I could then add support for into the apc module?
3. would changing utility_functions->fopen_function; to point to
my_fopen_function in place of zend_open work.
Any input would be greatly appreciated.
-James
** ( mod_php and the likes are not an option for us as we have our own
custom web server which we cannot do without :) )
*** when i truss one of the php daemon process i can clearly see that
it opens and reads the requested file. It also opens all the
included/required files but does not seem read them.
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