add cache docs

docs/components/cache.rst

@@ -1,4 +1,124 @@
 Cache
 #####
 
+Symfony makes heavy use of a filesystem cache. When developing for Mautic, clearing the cache is a regular occurrence. By default, Mautic instances have the cache located in ``var/cache/ENV`` where ``ENV`` is the environment currently accessed - ``dev`` or ``prod``. To rebuild the cache, delete the relevant ``ENV`` folder within the cache directory, or run the Symfony command ``php bin/console cache:clear --env=ENV``. If a specific environment isn't passed to the command via ``--env=ENV``, Mautic uses the ``dev`` environment by default.
+
+
+.. vale off
+
+In the ``dev`` environment, Mautic doesn't cache translations, views, and assets. However, changes to these files require clearing the cache for them to take effect in the ``prod`` environment. Changes to Mautic config files, Symfony config files, etc., require clearing of the cache regardless of the environment.
+
+.. vale on
+
+The typical rule of thumb is, if Mautic isn't acting as you expect after making changes, try clearing your cache. If you get ``class could not be found`` or ``cannot redeclare class`` errors when using the ``cache:clear`` command, manually delete the ``var/cache/ENV`` folder - replacing ENV with the environment e.g ``dev`` or ``prod`` - then run the command and/or browse to the site to rebuild.
+
+Cache bundle
+************
+
+Enables PSR-6 and PSR-16 caching. Check :xref:`Symfony Cache Component`
+
+Namespace versus tag
+====================
+
+This bundle introduces tags to the cache. All its adapters are fully tag aware which makes the use of namespace obsolete for daily use.
+
+Previously, if you wanted to keep control on cache section and didn't want to hold the index of all keys to clear, you would have to use namespace.
+
+The main disadvantage of this approach is that Mautic creates a new adapter for each namespace.
+
+From Symfony 3.4, the cache uses tag-aware adapters. If you want to clear all records related to your Bundle or Component, you just need to tag them.
+
+.. code-block:: php
+
+    /** @var CacheProvider $cache */
+    $cache = $this->get('mautic.cache.provider');
+    /** @var CacheItemInterface $item */
+    $item = $cache->getItem('test_tagged_Item');
+    $item->set('yesa!!!');
+    $item->tag(['firstTag', 'secondTag']);
+    $item->expiresAfter(20000);
+
+All you need to do now is to clear all tagged items:
+
+.. code-block:: php
+
+    $cache->invalidateTags(['firstTag']);
+Pools clearing
+==============
+
+Removing cache items
+--------------------
+
+Cache Pools include methods to delete a cache item, some of them, or all of them. The most common is ``Psr\\Cache\\CacheItemPoolInterface::deleteItem``, which deletes the cache item identified by the given key.
+
+.. code-block:: php
+
+    $isDeleted = $cache->deleteItem('user_'.$userId);
+Use the ``Psr\\Cache\\CacheItemPoolInterface::deleteItems`` method to delete several cache items simultaneously - it returns true only if all the items have been deleted, even when any or some of them don't exist.
+
+Configuration
+-------------
+
+Plugins come preconfigured to utilize filesystem caching.
+
+These are the default settings:
+
+.. code-block:: php
+
+    'cache_adapter' => 'mautic.cache.adapter.filesystem',
+    'cache_prefix' => 'app',
+    'cache_lifetime' => 86400
+They can be overridden in ``local.php`` like this:
+
+.. code-block:: php
+
+    'cache_adapter'  => 'mautic.cache.adapter.redis',
+    'cache_prefix'   => 'app_cache',
+    'cache_lifetime' => 86400,
+
+Delivered adapters
+------------------
+.. vale off
+
+- ``mautic.cache.adapter.filesystem``
+- ``mautic.cache.adapter.memcached``
+
+.. code-block:: php
+    'memcached' => [
+        'servers' => ['memcached://localhost'],
+        'options' => [
+            'compression' => true,
+            'libketama_compatible' => true,
+            'serializer' => 'igbinary',
+        ],
+    ],
+
+- ``mautic.cache.adapter.redis``
+
+Redis configuration in ``local.php``:
+
+.. code-block:: php
+
+    'redis' => [
+        'dsn' => 'redis://localhost',
+        'options' => [
+            'lazy' => false,
+            'persistent' => 0,
+            'persistent_id' => null,
+            'timeout' => 30,
+            'read_timeout' => 0,
+            'retry_interval' => 0,
+        ],
+    ],
+
+In order to use another adapter, just set it up as a service.
+
+Clearing the cache
+------------------
+
+The ``cache:clear`` command clears Mautic's cache. Use this command:
+
+.. code-block:: bash
+
+    bin/console mautic:cache:clear
 

docs/links/symfony_cache_component.py

@@ -0,0 +1,7 @@
+from . import link
+
+link_name = "Symfony Cache Component" 
+link_text = "Symfony Cache Component" 
+link_url = "https://symfony.com/doc/current/components/cache.html" 
+
+link.xref_links.update({link_name: (link_text, link_url)})