Updated the query cache overview document

git-svn-id: svn+ssh://kelev.kaltura.com/usr/local/kalsource/backend/server/trunk/core@62285 6b8eccd3-e8c5-4e7d-8186-e12b5326b719

doc/Query Cache Overview.htm

@@ -41,10 +41,9 @@ <h3>When do we update the invalidation keys ?</h3>
 Whenever a flavor asset object of entry_id x is saved, it will also update the time saved in the memcache
 under 'flavor_asset:entry_id=x', thus invalidating all the queries that contained entry_id=x.
 On single datacenter environments the invalidation keys can be updated automatically by the 'save'
-functions. On multi datacenter environments this won't work because it won't invalidate the queries
-that are cached on the remote DC. So, instead, we'll define UDFs (User Defined Functions) on the 
-database that will perform the invalidation - whether the database was modified locally or by the 
-replication.
+functions. On multi datacenter environments this won't work, because it won't invalidate the queries
+that are cached on the remote DC. So, instead, we'll define triggers on the database that will perform 
+the invalidation - whether the database was modified locally or by the replication.
 </p>
 <h3>What's needed to add a new query to the cache ?</h3>
 <p>
@@ -54,8 +53,31 @@ <h3>What's needed to add a new query to the cache ?</h3>
 $this object is saved.
 <li>&lt;peer&gt;::getCacheInvalidationKeys – returns a list of invalidation keys that should be checked before
 the supplied $criteria can be returned from the cache.
+</ul>
 See asset.php & assetPeer.php as an example.
+</p>
+<h3>What is the process for setting up the query cache ?</h3>
+<p>
+<h4>All environments</h4>
+Set up a single machine on each datacenter that will run the shared memcached. Configure the hostname and port
+of this memcache in kConfLocal (global_memcache_host / global_memcache_port).
+<h4>Single datacenter environment only</h4>
+On all servers, set query_cache_enabled and query_cache_invalidate_on_change to true in kConfLocal
+<h4>Multi datacenter environment only</h4>
+Perform the following on one of the mysql slaves in each datacenter:
+<ul>
+<li>Compile and install 'Memcached Functions for MySQL'. To install a precompiled version:
+<ul>
+<li>Copy /usr/lib64/mysql/plugin/libmemcached_functions_mysql.so and /usr/local/lib64/libmemcached.so.
+<li>Install the functions by running: mysql kaltura &lt; memcached_functions_mysql-1.0/sql/install_functions.sql
+</ul>
+<li>Configure the 'Memcached Functions for MySQL' library to use the shared memcache server by adding the
+command 'select memc_servers_set('&lt;global memcache host&gt;:&lt;global memcache port&gt;');' to the mysql init script.<br>
+<b>Note:</b> To add an init script for mysql, add the command line switch '--init-file=&lt;mysql init script path&gt;' to mysqld.
+<li>Restart mysql.
+<li>Install the triggers by running from deployment/base/scripts: php query_cache_triggers.php create &lt;host&gt; &lt;user&gt; &lt;password&gt;
 </ul>
+On all servers, set query_cache_enabled to true in kConfLocal (query_cache_invalidate_on_change should be left false).
 </p>
 </body>
-</html>
+</html>