PHP script to be run at startup (APC variables initialization)

Question

Is it possible to have the PHP server (via php5-fpm) run a PHP script just after it started, and before clients have access to it, in order to perform the initialization of APC variables.

Basically some events are counted during the server life via apc_inc, like

apc_inc('event-xyz-happened');

the event-xyz-happened APC var is permanent (life span is server life, not request life).

The problem is, the event-xyz-happened APC var has to exist before it is incremented (unlike Perl) the first time. apc_inc being pretty fast, I want to avoid solutions like

if ( ! apc_exists('event-xyz-happened')) {
  apc_store('event-xyz-happened', 1);
}
else {
  apc_inc('event-xyz-happened');
}

which not only require a call to apc_exists('event-xyz-happened'), but may also suffer from a race condition when it doesn't exist yet.

--

Is there a solution to create some APC variables before clients have access to the server?

dunno about php5-fpm but I know that at work we have the following in our virtual host config in apache which looks to achieve a similar thing to what you're after: php_value auto_prepend_file /var/www/xhprof_gui/xhprof_session.php — Jason
– Jason, Commented Feb 13, 2013 at 9:23
@Jason this is to set configuration directives, not APC variables (plus, I'm using nginx) — Déjà vu
– Déjà vu, Commented Feb 13, 2013 at 9:25

Wing Lian · Accepted Answer · 2013-02-13 09:54:28Z

2

You can use apc_add followed by apc_inc (see http://www.php.net/manual/en/function.apc-add.php)

// if it doesn't exist, it gets created
// if it does exist, nothing happens, no race condition
apc_add('event-xyz-happened', 0); 
apc_inc('event-xyz-happened', 1);

answered Feb 13, 2013 at 9:54

Wing Lian

2,41818 silver badges14 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Déjà vu Over a year ago

Good idea indeed. I'd still prefer an initialization solution, that would avoid the apc_add overhead. But that's the best alternative so far.

SWilk · Accepted Answer · 2013-02-13 09:49:19Z

0

You should not use apc variables for this purpose.

APC is a cache engine, it is not a fast database engine. As a cache engine, it can and it will sooner or later remove your variables to clear some memory for other variables or opcode cache. The more memory you assinge to APC the less probable it is that your variable will get removed, but you cannot rely that the variable will be there.

All your php scripts have to check if the variable is in apc cache, and if it is not, initialize it.

If you need to store some variables with very quick access, you can setup a local mysql server and create a table with 'memory' engine. It will be almost as fast as apc, but i will be permament, as long as the server is running.

Good luck SWilk

answered Feb 13, 2013 at 9:49

SWilk

3,5068 gold badges33 silver badges52 bronze badges

3 Comments

Déjà vu Over a year ago

This is not true. If no ttl is specified, the variable will not expire (as long as there is memory available). As for creating a memory table in a DB, I'm after performance, and I doubt an inc+query+fetch... from a database can be even close to apc_inc (which returns the incremented value) in terms of performance.

SWilk Over a year ago

I am just saying that you cannot rely on the variable beeing in cache for sure. If you run out of memory and no variable ttl has run out then entire cache will be purged. See stackoverflow.com/questions/1053810/… As of mysql memory table performance, I might have exaggerated a bit ;)

Déjà vu Over a year ago

Sure, thanks, and I rely on the cache. This is why all precaution is taken - automatic checking scripts, plenty of mem - not to overflow the memory allocated to the cache. Memory will not be overflowed.

Collectives™ on Stack Overflow

PHP script to be run at startup (APC variables initialization)

2 Answers 2

1 Comment

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related