Differences

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--- v5:userguide:memcached [2016/01/17 03:39] – ↷ Page moved from v5:reference:memcached to v5:userguide:memcached mnewnham
+++ v5:userguide:memcached [2022/03/20 18:07] – [Adding Weighted Server Groups] fix syntax error in code sample dregad
@@ Line 1: / Line 1: @@
 ====== Memcached Setup ======
-<WRAP tip>
-There are 2 pear modules for connection to a Memcached server, the older [[https://pecl.php.net/package/memcache|PEAR Memcache library]] and the newer [[https://pecl.php.net/package/memcached|PEAR Memcached library]].
-  * Windows support is only available for the older Memcache library.
-  * ADOdb has only been tested against the older library
-</WRAP>
 ===== Description =====
-This section describes connection to an already configured Memcache server. Information about installation and configuration of Memcached servers can be found [[https://memcached.org/|here]].
+This section describes connecting to an already configured Memcache server. Information about installation and configuration of Memcached servers can be found [[https://memcached.org/|here]].
 ===== The Memcache Library =====
+There are 2 distinct PEAR modules for connecting to a [[wp>Memcached]] server: the [[https://pecl.php.net/package/memcache|Memcache]] library and the [[https://pecl.php.net/package/memcached|Memcached]] library.
+<WRAP tip>
+  * Windows support is only available for the //Memcache// library.
+  * //Memcache// should be used in PHP 5.x environments on UNIX platforms.
+  * //Memcached// should be used in PHP 7.x environments on UNIX platforms.
+  * If both libraries are available, //Memcache// will be used.
+</WRAP>
+===== Why can't I use the memcached library under Windows? =====
+The memcached library is much more heavily featured, more modern and better maintained. The problem with it is not a problem with ADOdb, nor a problem with PHP. The PHP module is dependent on the 3rd party library **libmemcache**, which has no Windows support. Any Windows DLLs you might find floating around the web will __always__ be built on the memcache library.
@@ Line 14: / Line 20: @@
 $db = NewADOConnection($driver='mysqli');
 /*
-* Enable memcache
+ * Enable memcache
-*/
+ */
 $db->memCache = true;
 /*
-* Add one or more servers, for use in distributed systems
+ * Add one or more servers, for use in distributed systems
-*/
+ */
 $db->memCacheHost = array('192.168.0.78', '192.168.0.79', '192.168.0.80');
 /*
-* Optionally add the server port if it differs from the default
+ * Optionally add the server port if it differs from the default
-*/
+ */
 $db->memCachePort = 11211;
 /*
-* Use 'true' to store the item compressed (uses zlib)
+ * Use 'true' to store the item compressed (uses zlib)
-*/
+ * Note; Compression is only supported using the memcache library. This
-$db->memCacheCompress = false;
+ *       parameter will be ignored when using the memcached library
+ */
+$db->memCacheCompress = false;
 /*
-* We connect to the database, not the memcache server
+ * We connect to the database, not the memcache server
-*/
+ */
 $db->Connect('localhost','mysql-user','mysql-password','employees');
 /*
-* look for a cached query with a life of 2400 seconds
+ * look for a cached query with a life of 2400 seconds
-*/
+ */
 $sql = 'SELECT code,description FROM xref_table';
 $db->cacheExecute(2400,$sql);
 </code>
+===== Adding Weighted Server Groups =====
+From ADOdb version 5.22, the **memcached** library supports the use of **//Weighted server groups//**, in which a specific server can be forced to return a result a specific percentage of the time.
+If the feature is used, the total weighting of the server group must equal 100%.  To achieve this, the configuration of the servers must be defined in a different way to the default. Each host is defined as an array:
+<code php>
+array(
+ 'host'=> The host name,
+ 'port'=> The port, defaults to 11211,
+ 'weight'=> A percentage, up to 100,
+);
+</code>
+The host arrays are then combined together. In this example 86.91 serves 70% of requests and 86.92 serves 30%
+<code php>
+$hosts = array(
+    array('host'=>'192.168.86.91','port'=>'11211','weight'=>70),
+    array('host'=>'192.168.86.92','port'=>'11211','weight'=>30),
+    );
+$db = NewADOConnection($driver='mysqli');
+/*
+ * Enable memcache
+ */
+$db->memCache = true;
+/*
+ * Add the weighted servers in $memCacheHosts. All other parameters are ignored.
+ */
+$db->memCacheHost = $hosts
+</code>
+===== Adding options to the memcached server =====
+From ADOdb version 5.22, [[https://www.php.net/manual/en/memcached.setoption.php|server options]] can be set on the **Memcached** connection by use of the **memCacheOptions** array
+<code php>
+$hosts = array(
+    array('host'=>'192.168.86.91','port'=>'11211','weight'=>70)
+    array('host'=>'192.168.86.92','port'=>'11211','weight'=>30)
+    );
+$db = NewADOConnection($driver='mysqli');
+/*
+ * Enable memcache
+ */
+$db->memCache = true;
+/*
+ * Add the weighted servers in $memCacheHosts
+ */
+$db->memCacheHost = $hosts;
+/*
+* Set some options
+*/
+$db->memCacheOptions = array(Memcached::OPT_HASH=>Memcached::HASH_MURMUR);
+</code>
 ===== Using Debug Mode  =====
-The size of query results that can be cached by the memcached server is limited by server configuration. The default is quite small. If the query is too large, and [[v5:reference:debug|debugging]] is enabled, then an error is displayed.
+The size of query results that can be cached by the memcached server is limited by server configuration. The default is quite small. If the query is too large, and [[v5:userguide:debug|debugging]] is enabled, then an error is displayed.
+<code>
+3849805e4e026b9e7c485999a24a95c6 cache failure: Item with such key doesn't exists on the memcached server.
+(this is a notice and not an error)
+-----<hr>
+(mysqli): SELECT * FROM employees
+------<hr>
+Notice: MemcachePool::set(): Server 192.168.0.78 (tcp 11211, udp 0) failed with:
+SERVER_ERROR object too large for cache
+(3) in C:\dev\github\mssqlnative-fixes\adodb-memcache.lib.inc.php on line 94
+Failed to save data at the memcached server!
+Cache write error
+PHP Notice:  MemcachePool::set(): Server 192.168.0.78 (tcp 11211, udp 0) failed with:
+SERVER_ERROR object too large for cache (3)
+in C:\dev\github\mssqlnative-fixes\adodb-memcache.lib.inc.php on line 94
+</code>
-  3849805e4e026b9e7c485999a24a95c6 cache failure: Item with such key doesn't exists on the memcached server.
-  (this is a notice and not an error)
-  -----<hr>
-  (mysqli): SELECT * FROM employees
-  -----<hr>
-  Notice: MemcachePool::set(): Server 192.168.0.78 (tcp 11211, udp 0) failed with:
-  SERVER_ERROR object too large for cache
-  (3) in C:\dev\github\mssqlnative-fixes\adodb-memcache.lib.inc.php on line 94
-  Failed to save data at the memcached server!
-  Cache write error
-  PHP Notice:  MemcachePool::set(): Server 192.168.0.78 (tcp 11211, udp 0) failed with:
-  SERVER_ERROR object too large for cache (3)
-  in C:\dev\github\mssqlnative-fixes\adodb-memcache.lib.inc.php on line 94
 ADOdb currently has no mechanism for splitting large queries into smaller chunks.
 {{tag>[memcached cache]}}