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 199                         <h2>Chapters</h2>
 200                         <ol>
 201                                         <li>
 202                                         <a href="#_basic_caching">Basic Caching</a>
 203                                                 <ul>
 204
 205                                                         <li><a href="#_page_caching">Page Caching</a></li>
 206
 207                                                         <li><a href="#_action_caching">Action Caching</a></li>
 208
 209                                                         <li><a href="#_fragment_caching">Fragment Caching</a></li>
 210
 211                                                         <li><a href="#_sweepers">Sweepers</a></li>
 212
 213                                                         <li><a href="#_sql_caching">SQL Caching</a></li>
 214
 215                                                         <li><a href="#_cache_stores">Cache stores</a></li>
 216
 217                                                 </ul>
 218                                         </li>
 219                                         <li>
 220                                         <a href="#_advanced_caching">Advanced Caching</a>
 221                                         </li>
 222                         </ol>
 223                 </div>
 224
 225                 <div id="content">
 226                                 <h1>Caching with Rails: An overview</h1>
 227                         <div id="preamble">
 228 <div class="sectionbody">
 229 <div class="para"><p>Everyone caches. This guide will teach you what you need to know about
 230 avoiding that expensive round-trip to your database and returning what you
 231 need to return to those hungry web clients in the shortest time possible.</p></div>
 232 </div>
 233 </div>
 234 <h2 id="_basic_caching">1. Basic Caching</h2>
 235 <div class="sectionbody">
 236 <div class="para"><p>This is an introduction to the three types of caching techniques that Rails
 237 provides by default without the use of any third party plugins.</p></div>
 238 <div class="para"><p>To get started make sure config.action_controller.perform_caching is set
 239 to true for your environment. This flag is normally set in the
 240 corresponding config/environments/*.rb and caching is disabled by default
 241 there for development and test, and enabled for production.</p></div>
 242 <div class="listingblock">
 243 <div class="content"><!-- Generator: GNU source-highlight 2.9
 244 by Lorenzo Bettini
 245 http://www.lorenzobettini.it
 246 http://www.gnu.org/software/src-highlite -->
 247 <pre><tt>config<span style="color: #990000">.</span>action_controller<span style="color: #990000">.</span>perform_caching <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #0000FF">true</span></span>
 248 </tt></pre></div></div>
 249 <h3 id="_page_caching">1.1. Page Caching</h3>
 250 <div class="para"><p>Page caching is a Rails mechanism which allows the request for a generated
 251 page to be fulfilled by the webserver, without ever having to go through the
 252 Rails stack at all. Obviously, this is super-fast. Unfortunately, it can't be
 253 applied to every situation (such as pages that need authentication) and since
 254 the webserver is literally just serving a file from the filesystem, cache
 255 expiration is an issue that needs to be dealt with.</p></div>
 256 <div class="para"><p>So, how do you enable this super-fast cache behavior?  Simple, let's say you
 257 have a controller called ProductsController and a <em>list</em> action that lists all
 258 the products</p></div>
 259 <div class="listingblock">
 260 <div class="content"><!-- Generator: GNU source-highlight 2.9
 261 by Lorenzo Bettini
 262 http://www.lorenzobettini.it
 263 http://www.gnu.org/software/src-highlite -->
 264 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> ProductsController <span style="color: #990000">&lt;</span> ActionController
 265
 266   caches_page <span style="color: #990000">:</span>index
 267
 268   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> index<span style="color: #990000">;</span> <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 269
 270 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 271 </tt></pre></div></div>
 272 <div class="para"><p>The first time anyone requests products/index, Rails will generate a file
 273 called index.html and the webserver will then look for that file before it
 274 passes the next request for products/index to your Rails application.</p></div>
 275 <div class="para"><p>By default, the page cache directory is set to Rails.public_path (which is
 276 usually set to RAILS_ROOT + "/public") and this can be configured by
 277 changing the configuration setting ActionController::Base.page_cache_directory. Changing the
 278 default from /public helps avoid naming conflicts, since you may want to
 279 put other static html in /public, but changing this will require web
 280 server reconfiguration to let the web server know where to serve the
 281 cached files from.</p></div>
 282 <div class="para"><p>The Page Caching mechanism will automatically add a .html exxtension to
 283 requests for pages that do not have an extension to make it easy for the
 284 webserver to find those pages and this can be configured by changing the
 285 configuration setting ActionController::Base.page_cache_extension.</p></div>
 286 <div class="para"><p>In order to expire this page when a new product is added we could extend our
 287 example controler like this:</p></div>
 288 <div class="listingblock">
 289 <div class="content"><!-- Generator: GNU source-highlight 2.9
 290 by Lorenzo Bettini
 291 http://www.lorenzobettini.it
 292 http://www.gnu.org/software/src-highlite -->
 293 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> ProductsController <span style="color: #990000">&lt;</span> ActionController
 294
 295   caches_page <span style="color: #990000">:</span>list
 296
 297   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> list<span style="color: #990000">;</span> <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 298
 299   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> create
 300     expire_page <span style="color: #990000">:</span>action <span style="color: #990000">=&gt;</span> <span style="color: #990000">:</span>list
 301   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 302
 303 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 304 </tt></pre></div></div>
 305 <div class="para"><p>If you want a more complicated expiration scheme, you can use cache sweepers
 306 to expire cached objects when things change. This is covered in the section on Sweepers.</p></div>
 307 <h3 id="_action_caching">1.2. Action Caching</h3>
 308 <div class="para"><p>One of the issues with Page Caching is that you cannot use it for pages that
 309 require to restrict access somehow. This is where Action Caching comes in.
 310 Action Caching works like Page Caching except for the fact that the incoming
 311 web request does go from the webserver to the Rails stack and Action Pack so
 312 that before filters can be run on it before the cache is served, so that
 313 authentication and other restrictions can be used while still serving the
 314 result of the output from a cached copy.</p></div>
 315 <div class="para"><p>Clearing the cache works in the exact same way as with Page Caching.</p></div>
 316 <div class="para"><p>Let's say you only wanted authenticated users to edit or create a Product
 317 object, but still cache those pages:</p></div>
 318 <div class="listingblock">
 319 <div class="content"><!-- Generator: GNU source-highlight 2.9
 320 by Lorenzo Bettini
 321 http://www.lorenzobettini.it
 322 http://www.gnu.org/software/src-highlite -->
 323 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> ProductsController <span style="color: #990000">&lt;</span> ActionController
 324
 325   before_filter <span style="color: #990000">:</span>authenticate<span style="color: #990000">,</span> <span style="color: #990000">:</span>only <span style="color: #990000">=&gt;</span> <span style="color: #990000">[</span> <span style="color: #990000">:</span>edit<span style="color: #990000">,</span> <span style="color: #990000">:</span>create <span style="color: #990000">]</span>
 326   caches_page <span style="color: #990000">:</span>list
 327   caches_action <span style="color: #990000">:</span>edit
 328
 329   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> list<span style="color: #990000">;</span> <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 330
 331   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> create
 332     expire_page <span style="color: #990000">:</span>action <span style="color: #990000">=&gt;</span> <span style="color: #990000">:</span>list
 333     expire_action <span style="color: #990000">:</span>action <span style="color: #990000">=&gt;</span> <span style="color: #990000">:</span>edit
 334   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 335
 336   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> edit<span style="color: #990000">;</span> <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 337
 338 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 339 </tt></pre></div></div>
 340 <div class="para"><p>And you can also use :if (or :unless) to pass a Proc that specifies when the
 341 action should be cached. Also, you can use :layout &#8658; false to cache without
 342 layout so that dynamic information in the layout such as logged in user info
 343 or the number of items in the cart can be left uncached. This feature is
 344 available as of Rails 2.2.</p></div>
 345 <div class="para"><p>[More: more examples? Walk-through of Action Caching from request to response?
 346        Description of Rake tasks to clear cached files? Show example of
 347        subdomain caching? Talk about :cache_path, :if and assing blocks/Procs
 348        to expire_action?]</p></div>
 349 <h3 id="_fragment_caching">1.3. Fragment Caching</h3>
 350 <div class="para"><p>Life would be perfect if we could get away with caching the entire contents of
 351 a page or action and serving it out to the world. Unfortunately, dynamic web
 352 applications usually build pages with a variety of components not all of which
 353 have the same caching characteristics. In order to address such a dynamically
 354 created page where different parts of the page need to be cached and expired
 355 differently Rails provides a mechanism called Fragment Caching.</p></div>
 356 <div class="para"><p>Fragment Caching allows a fragment of view logic to be wrapped in a cache
 357 block and served out of the cache store when the next request comes in.</p></div>
 358 <div class="para"><p>As an example, if you wanted to show all the orders placed on your website
 359 in real time and didn't want to cache that part  of the page, but did want
 360 to cache the part of the page which lists all products available, you
 361 could use this piece of code:</p></div>
 362 <div class="listingblock">
 363 <div class="content"><!-- Generator: GNU source-highlight 2.9
 364 by Lorenzo Bettini
 365 http://www.lorenzobettini.it
 366 http://www.gnu.org/software/src-highlite -->
 367 <pre><tt><span style="color: #FF0000">&lt;% Order.find_recent.each do |o| %&gt;</span>
 368   <span style="color: #FF0000">&lt;%= o.buyer.name %&gt;</span> bought <span style="color: #FF0000">&lt;% o.product.name %&gt;</span>
 369 <span style="color: #FF0000">&lt;% end %&gt;</span>
 370
 371 <span style="color: #FF0000">&lt;% cache do %&gt;</span>
 372   All available products<span style="color: #990000">:</span>
 373   <span style="color: #FF0000">&lt;% Product.find(:all).each do |p| %&gt;</span>
 374     <span style="color: #FF0000">&lt;%= link_to p.name, product_url(p) %&gt;</span>
 375   <span style="color: #FF0000">&lt;% end %&gt;</span>
 376 <span style="color: #FF0000">&lt;% end %&gt;</span>
 377 </tt></pre></div></div>
 378 <div class="para"><p>The cache block in our example will bind to the action that called it and is
 379 written out to the same place as the Action Cache, which means that if you
 380 want to cache multiple fragments per action, you should provide an action_suffix to the cache call:</p></div>
 381 <div class="listingblock">
 382 <div class="content"><!-- Generator: GNU source-highlight 2.9
 383 by Lorenzo Bettini
 384 http://www.lorenzobettini.it
 385 http://www.gnu.org/software/src-highlite -->
 386 <pre><tt><span style="color: #FF0000">&lt;% cache(:action =&gt;</span> <span style="color: #FF0000">'recent'</span><span style="color: #990000">,</span> <span style="color: #990000">:</span>action_suffix <span style="color: #990000">=&gt;</span> <span style="color: #FF0000">'all_products'</span><span style="color: #990000">)</span> <span style="font-weight: bold"><span style="color: #0000FF">do</span></span> <span style="color: #990000">%&gt;</span>
 387   All available products<span style="color: #990000">:</span>
 388 </tt></pre></div></div>
 389 <div class="para"><p>and you can expire it using the expire_fragment method, like so:</p></div>
 390 <div class="listingblock">
 391 <div class="content"><!-- Generator: GNU source-highlight 2.9
 392 by Lorenzo Bettini
 393 http://www.lorenzobettini.it
 394 http://www.gnu.org/software/src-highlite -->
 395 <pre><tt>expire_fragment<span style="color: #990000">(:</span>controller <span style="color: #990000">=&gt;</span> <span style="color: #FF0000">'producst'</span><span style="color: #990000">,</span> <span style="color: #990000">:</span>action <span style="color: #990000">=&gt;</span> <span style="color: #FF0000">'recent'</span><span style="color: #990000">,</span> <span style="color: #990000">:</span>action_suffix <span style="color: #990000">=&gt;</span> 'all_products<span style="color: #990000">)</span>
 396 </tt></pre></div></div>
 397 <h3 id="_sweepers">1.4. Sweepers</h3>
 398 <div class="para"><p>Cache sweeping is a mechanism which allows you to get around having a ton of
 399 expire_{page,action,fragment} calls in your code by moving all the work
 400 required to expire cached content into a ActionController::Caching::Sweeper
 401 class that is an Observer and looks for changes to an object via callbacks,
 402 and when a change occurs it expires the caches associated with that object n
 403 an around or after filter.</p></div>
 404 <div class="para"><p>Continuing with our Product controller example, we could rewrite it with a
 405 sweeper such as the following:</p></div>
 406 <div class="listingblock">
 407 <div class="content"><!-- Generator: GNU source-highlight 2.9
 408 by Lorenzo Bettini
 409 http://www.lorenzobettini.it
 410 http://www.gnu.org/software/src-highlite -->
 411 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> StoreSweeper <span style="color: #990000">&lt;</span> ActionController<span style="color: #990000">::</span>Caching<span style="color: #990000">::</span>Sweeper
 412   observe Product <span style="font-style: italic"><span style="color: #9A1900"># This sweeper is going to keep an eye on the Post model</span></span>
 413
 414   <span style="font-style: italic"><span style="color: #9A1900"># If our sweeper detects that a Post was created call this</span></span>
 415   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> after_create<span style="color: #990000">(</span>product<span style="color: #990000">)</span>
 416           expire_cache_for<span style="color: #990000">(</span>product<span style="color: #990000">)</span>
 417   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 418
 419   <span style="font-style: italic"><span style="color: #9A1900"># If our sweeper detects that a Post was updated call this</span></span>
 420   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> after_update<span style="color: #990000">(</span>product<span style="color: #990000">)</span>
 421           expire_cache_for<span style="color: #990000">(</span>product<span style="color: #990000">)</span>
 422   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 423
 424   <span style="font-style: italic"><span style="color: #9A1900"># If our sweeper detects that a Post was deleted call this</span></span>
 425   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> after_destroy<span style="color: #990000">(</span>product<span style="color: #990000">)</span>
 426           expire_cache_for<span style="color: #990000">(</span>product<span style="color: #990000">)</span>
 427   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 428
 429   private
 430   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> expire_cache_for<span style="color: #990000">(</span>record<span style="color: #990000">)</span>
 431     <span style="font-style: italic"><span style="color: #9A1900"># Expire the list page now that we added a new product</span></span>
 432     expire_page<span style="color: #990000">(:</span>controller <span style="color: #990000">=&gt;</span> <span style="color: #FF0000">'#{record}'</span><span style="color: #990000">,</span> <span style="color: #990000">:</span>action <span style="color: #990000">=&gt;</span> <span style="color: #FF0000">'list'</span><span style="color: #990000">)</span>
 433
 434     <span style="font-style: italic"><span style="color: #9A1900"># Expire a fragment</span></span>
 435     expire_fragment<span style="color: #990000">(:</span>controller <span style="color: #990000">=&gt;</span> <span style="color: #FF0000">'#{record}'</span><span style="color: #990000">,</span> <span style="color: #990000">:</span>action <span style="color: #990000">=&gt;</span> <span style="color: #FF0000">'recent'</span><span style="color: #990000">,</span> <span style="color: #990000">:</span>action_suffix <span style="color: #990000">=&gt;</span> <span style="color: #FF0000">'all_products'</span><span style="color: #990000">)</span>
 436   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 437 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 438 </tt></pre></div></div>
 439 <div class="para"><p>Then we add it to our controller to tell it to call the sweeper when certain
 440 actions are called. So, if we wanted to expire the cached content for the
 441 list and edit actions when the create action was called, we could do the
 442 following:</p></div>
 443 <div class="listingblock">
 444 <div class="content"><!-- Generator: GNU source-highlight 2.9
 445 by Lorenzo Bettini
 446 http://www.lorenzobettini.it
 447 http://www.gnu.org/software/src-highlite -->
 448 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> ProductsController <span style="color: #990000">&lt;</span> ActionController
 449
 450   before_filter <span style="color: #990000">:</span>authenticate<span style="color: #990000">,</span> <span style="color: #990000">:</span>only <span style="color: #990000">=&gt;</span> <span style="color: #990000">[</span> <span style="color: #990000">:</span>edit<span style="color: #990000">,</span> <span style="color: #990000">:</span>create <span style="color: #990000">]</span>
 451   caches_page <span style="color: #990000">:</span>list
 452   caches_action <span style="color: #990000">:</span>edit
 453   cache_sweeper <span style="color: #990000">:</span>store_sweeper<span style="color: #990000">,</span> <span style="color: #990000">:</span>only <span style="color: #990000">=&gt;</span> <span style="color: #990000">[</span> <span style="color: #990000">:</span>create <span style="color: #990000">]</span>
 454
 455   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> list<span style="color: #990000">;</span> <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 456
 457   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> create
 458     expire_page <span style="color: #990000">:</span>action <span style="color: #990000">=&gt;</span> <span style="color: #990000">:</span>list
 459     expire_action <span style="color: #990000">:</span>action <span style="color: #990000">=&gt;</span> <span style="color: #990000">:</span>edit
 460   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 461
 462   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> edit<span style="color: #990000">;</span> <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 463
 464 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 465 </tt></pre></div></div>
 466 <h3 id="_sql_caching">1.5. SQL Caching</h3>
 467 <div class="para"><p>Query caching is a Rails feature that caches the result set returned by each
 468 query so that if Rails encounters the same query again for that request, it
 469 will used the cached result set as opposed to running the query against the
 470 database again.</p></div>
 471 <div class="para"><p>For example:</p></div>
 472 <div class="listingblock">
 473 <div class="content"><!-- Generator: GNU source-highlight 2.9
 474 by Lorenzo Bettini
 475 http://www.lorenzobettini.it
 476 http://www.gnu.org/software/src-highlite -->
 477 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> ProductsController <span style="color: #990000">&lt;</span> ActionController
 478
 479   before_filter <span style="color: #990000">:</span>authenticate<span style="color: #990000">,</span> <span style="color: #990000">:</span>only <span style="color: #990000">=&gt;</span> <span style="color: #990000">[</span> <span style="color: #990000">:</span>edit<span style="color: #990000">,</span> <span style="color: #990000">:</span>create <span style="color: #990000">]</span>
 480   caches_page <span style="color: #990000">:</span>list
 481   caches_action <span style="color: #990000">:</span>edit
 482   cache_sweeper <span style="color: #990000">:</span>store_sweeper<span style="color: #990000">,</span> <span style="color: #990000">:</span>only <span style="color: #990000">=&gt;</span> <span style="color: #990000">[</span> <span style="color: #990000">:</span>create <span style="color: #990000">]</span>
 483
 484   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> list
 485     <span style="font-style: italic"><span style="color: #9A1900"># Run a find query</span></span>
 486     Product<span style="color: #990000">.</span>find<span style="color: #990000">(:</span>all<span style="color: #990000">)</span>
 487
 488     <span style="color: #990000">...</span>
 489
 490     <span style="font-style: italic"><span style="color: #9A1900"># Run the same query again</span></span>
 491     Product<span style="color: #990000">.</span>find<span style="color: #990000">(:</span>all<span style="color: #990000">)</span>
 492   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 493
 494   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> create
 495     expire_page <span style="color: #990000">:</span>action <span style="color: #990000">=&gt;</span> <span style="color: #990000">:</span>list
 496     expire_action <span style="color: #990000">:</span>action <span style="color: #990000">=&gt;</span> <span style="color: #990000">:</span>edit
 497   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 498
 499   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> edit<span style="color: #990000">;</span> <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 500
 501 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
 502 </tt></pre></div></div>
 503 <div class="para"><p>In the <em>list</em> action above, the result set returned by the first
 504 Product.find(:all) will be cached and will be used to avoid querying the
 505 database again the second time that finder is called.</p></div>
 506 <div class="para"><p>Query caches are created at the start of an action and destroyed at the end of
 507 that action and thus persist only for the duration of the action.</p></div>
 508 <h3 id="_cache_stores">1.6. Cache stores</h3>
 509 <div class="para"><p>Rails provides different stores for the cached data for action and fragment
 510 caches. Page caches are always stored on disk.</p></div>
 511 <div class="para"><p>The cache stores provided include:</p></div>
 512 <div class="para"><p>1) Memory store: Cached data is stored in the memory allocated to the Rails
 513                  process, which is fine for WEBrick and for FCGI (if you
 514                  don't care that each FCGI process holds its own fragment
 515                  store). It's not suitable for CGI as the process is thrown
 516                  away at the end of each request. It can potentially also
 517                  take up a lot of memory since each process keeps all the
 518                  caches in memory.</p></div>
 519 <div class="listingblock">
 520 <div class="content"><!-- Generator: GNU source-highlight 2.9
 521 by Lorenzo Bettini
 522 http://www.lorenzobettini.it
 523 http://www.gnu.org/software/src-highlite -->
 524 <pre><tt>ActionController<span style="color: #990000">::</span>Base<span style="color: #990000">.</span>cache_store <span style="color: #990000">=</span> <span style="color: #990000">:</span>memory_store
 525 </tt></pre></div></div>
 526 <div class="para"><p>2) File store: Cached data is stored on the disk, this is the default store
 527                and the default path for this store is: /tmp/cache. Works
 528                well for all types of environments and allows all processes
 529                running from the same application directory to access the
 530                cached content.</p></div>
 531 <div class="listingblock">
 532 <div class="content"><!-- Generator: GNU source-highlight 2.9
 533 by Lorenzo Bettini
 534 http://www.lorenzobettini.it
 535 http://www.gnu.org/software/src-highlite -->
 536 <pre><tt>ActionController<span style="color: #990000">::</span>Base<span style="color: #990000">.</span>cache_store <span style="color: #990000">=</span> <span style="color: #990000">:</span>file_store<span style="color: #990000">,</span> <span style="color: #FF0000">"/path/to/cache/directory"</span>
 537 </tt></pre></div></div>
 538 <div class="para"><p>3) DRb store: Cached data is stored in a separate shared DRb process that all
 539               servers communicate with. This works for all environments and
 540               only keeps one cache around for all processes, but requires
 541               that you run and manage a separate DRb process.</p></div>
 542 <div class="listingblock">
 543 <div class="content"><!-- Generator: GNU source-highlight 2.9
 544 by Lorenzo Bettini
 545 http://www.lorenzobettini.it
 546 http://www.gnu.org/software/src-highlite -->
 547 <pre><tt>ActionController<span style="color: #990000">::</span>Base<span style="color: #990000">.</span>cache_store <span style="color: #990000">=</span> <span style="color: #990000">:</span>drb_store<span style="color: #990000">,</span> <span style="color: #FF0000">"druby://localhost:9192"</span>
 548 </tt></pre></div></div>
 549 <div class="para"><p>4) MemCached store: Works like DRbStore, but uses Danga's MemCache instead.
 550                     Requires the ruby-memcache library:
 551                     gem install ruby-memcache.</p></div>
 552 <div class="listingblock">
 553 <div class="content"><!-- Generator: GNU source-highlight 2.9
 554 by Lorenzo Bettini
 555 http://www.lorenzobettini.it
 556 http://www.gnu.org/software/src-highlite -->
 557 <pre><tt>ActionController<span style="color: #990000">::</span>Base<span style="color: #990000">.</span>cache_store <span style="color: #990000">=</span> <span style="color: #990000">:</span>mem_cache_store<span style="color: #990000">,</span> <span style="color: #FF0000">"localhost"</span>
 558 </tt></pre></div></div>
 559 <div class="para"><p>5) Custom store: You can define your own cache store (new in Rails 2.1)</p></div>
 560 <div class="listingblock">
 561 <div class="content"><!-- Generator: GNU source-highlight 2.9
 562 by Lorenzo Bettini
 563 http://www.lorenzobettini.it
 564 http://www.gnu.org/software/src-highlite -->
 565 <pre><tt>ActionController<span style="color: #990000">::</span>Base<span style="color: #990000">.</span>cache_store <span style="color: #990000">=</span> MyOwnStore<span style="color: #990000">.</span>new<span style="color: #990000">(</span><span style="color: #FF0000">"parameter"</span><span style="color: #990000">)</span>
 566 </tt></pre></div></div>
 567 </div>
 568 <h2 id="_advanced_caching">2. Advanced Caching</h2>
 569 <div class="sectionbody">
 570 <div class="para"><p>Along with the built-in mechanisms outlined above, a number of excellent
 571 plugins exist to help with finer grained control over caching. These include
 572 Chris Wanstrath's excellent cache_fu plugin (more info here:
 573 <a href="http://errtheblog.com/posts/57-kickin-ass-w-cachefu">http://errtheblog.com/posts/57-kickin-ass-w-cachefu</a>) and Evan Weaver's
 574 interlock plugin (more info here:
 575 <a href="http://blog.evanweaver.com/articles/2007/12/13/better-rails-caching/">http://blog.evanweaver.com/articles/2007/12/13/better-rails-caching/</a>). Both
 576 of these plugins play nice with memcached and are a must-see for anyone
 577 seriously considering optimizing their caching needs.</p></div>
 578 </div>
 579
 580                 </div>
 581         </div>
 582 </body>
 583 </html>