November 2002
Intermediate to advanced
640 pages
16h 33m
English
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8.27. Program: Abusive User Checker
Shared memory’s speed makes
it an ideal way to store data different web server processes need to
access frequently when a file or database would be too slow. Example 8-7 shows the
pc_Web_Abuse_Check class, which uses shared memory
to track accesses to web pages in order to cut off users that abuse a
site by bombarding it with requests.
Example 8-7. pc_Web_Abuse_Check class
class pc_Web_Abuse_Check { var $sem_key; var $shm_key; var $shm_size; var $recalc_seconds; var $pageview_threshold; var $sem; var $shm; var $data; var $exclude; var $block_message; function pc_Web_Abuse_Check() { $this->sem_key = 5000; $this->shm_key = 5001; $this->shm_size = 16000; $this->recalc_seconds = 60; $this->pageview_threshold = 30; $this->exclude['/ok-to-bombard.html'] = 1; $this->block_message =<<<END <html> <head><title>403 Forbidden</title></head> <body> <h1>Forbidden</h1> You have been blocked from retrieving pages from this site due to abusive repetitive activity from your account. If you believe this is an error, please contact <a href="mailto:webmaster@example.com?subject=Site+Abuse">webmaster@example.com</a>. </body> </html> END; } function get_lock() { $this->sem = sem_get($this->sem_key,1,0600); if (sem_acquire($this->sem)) { $this->shm = shm_attach($this->shm_key,$this->shm_size,0600); $this->data = shm_get_var($this->shm,'data'); } else { error_log("Can't acquire semaphore $this->sem_key"); } } function release_lock() { if (isset($this->data)) { shm_put_var($this->shm,'data',$this->data); ...Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.