CakePHP 2.1 HTTP cache - cakephp

Question

I'm trying to speed up my site by taking advantage of the new HTTP cache features in CakePHP 2.1:
class ArticlesController extends AppController {
public function view($id) {
$article = $this->Article->find(
'first',
array('conditions' => array('Article.id' => $id))
);
$this->response->modified($article['Article']['modified']);
$this->set(compact('article'));
}
}
Caching works fine, but does not distinguish between different users (i.e. if a user logs in and visits a page that was already cached, the previously cached page is displayed, and user-specific content is not shown). I'd like one of the following to happen:
Cache discriminates between different users and stores a separate cache for each user
Caching is disabled if a user is logged in (the user login is only used for admin purposes)
I've tried adding
if (AuthComponent::user('id')) {
$this->disableCache();
}
But this doesn't seem to solve the problem
Does anyone know how to get this to work, or am I doing something fundamentally wrong?

Answer 1

You could try the etag caching method and generate a hash based on the article id and user id.
See http://book.cakephp.org/2.0/en/controllers/request-response.html#the-etag-header
The Etag header (called entity tag) is string that uniquely identifies the requested resource. It is very much like the checksum of a file, caching will compare checksums to tell whether they match or not.
To actually get advantage of using this header you have to either call manually CakeResponse::checkNotModified() method or have the RequestHandlerComponent included in your controller:
<?php
public function index() {
$articles = $this->Article->find('all');
$this->response->etag($this->Article->generateHash($articles));
if ($this->response->checkNotModified($this->request)) {
return $this->response;
}
...
}

Answer 2

I thought I'd post the solution(s) I eventually used, in case it helps anyone.
To disable caching completely for logged in users:
class ArticlesController extends AppController {
public function view($id) {
$article = $this->Article->find(
'first',
array('conditions' => array('Article.id' => $id))
);
if (!AuthComponent::user('id')) {
$this->response->etag($this->Article->generateHash($article));
}
$this->set(compact('article'));
}
}
To have a separate cache for each user (and for the case when no-one is logged in):
class Article extends AppModel {
public function generateHash($article) {
if (AuthComponent::user('id')) {
return md5(AuthComponent::user('id') . '-' . $article['Article']['modified']);
} else {
return md5($article['Article']['modified']);
}
}
}
class ArticlesController extends AppController {
public function view($id) {
$article = $this->Article->find(
'first',
array('conditions' => array('Article.id' => $id))
);
$this->response->etag($this->Article->generateHash($article));
$this->set(compact('article'));
}
}