Magento – Optimizing app/etc/local.xml – caching like Redis

adminhtmlbackendlocal.xmlmagento-1.7performance

This is an interesting one. I've been looking into methods of improving the performance of the Magento backend. I stumbled across this module:

colinmollenhour/Cm_Cache_Backend_File

Which looks quite promising. I believe there was a presentation about this at Imagine 2012. In any case, in the instructions to install, I read this:

Edit app/etc/local.xml changing global/cache/backend to Cm_Cache_Backend_File

In other words:

<config>
<global>
    <cache>
        <backend>Cm_Cache_Backend_File</backend>
    </cache>
    ...
</global>
...

For the life of me however, I couldn't find the <cache>...</cache> tags.

Doing a quick search on Google for

optimize app/etc/local.xml

I found:

pagodabox/magento-install-optimized

Which lists the following changes:

<config>
<global>
    <session_save><![CDATA[]]></session_save> <!-- db / memcache / empty=files -->
    <session_save_path><![CDATA[]]></session_save_path><!-- e.g. for memcache session save handler tcp://10.0.0.1:11211?persistent=1&weight=2&timeout=10&retry_interval=10 -->
    <session_cache_limiter><![CDATA[]]></session_cache_limiter><!-- see http://php.net/manual/en/function.session-cache-limiter.php#82174 for possible values -->
    <cache>
        <backend></backend><!-- apc / memcached / xcache / empty=file -->
        <slow_backend></slow_backend> <!-- database / file (default) - used for 2 levels cache setup, necessary for all shared memory storages -->
        <slow_backend_store_data></slow_backend_store_data> <!-- 1 / 0 (default) - used for 2 levels cache setup, sets whether store data in db slow cache backend -->
        <auto_refresh_fast_cache></auto_refresh_fast_cache> <!-- 1 / 0 (default) - used for 2 levels cache setup, sets whether refresh data in fast cache backend -->
        <memcached><!-- memcached cache backend related config -->
            <servers><!-- any number of server nodes can be included -->
                <server>
                    <host><![CDATA[]]></host>
                    <port><![CDATA[]]></port>
                    <persistent><![CDATA[]]></persistent>
                    <weight><![CDATA[]]></weight>
                    <timeout><![CDATA[]]></timeout>
                    <retry_interval><![CDATA[]]></retry_interval>
                    <status><![CDATA[]]></status>
                </server>
            </servers>
            <compression><![CDATA[0]]></compression>
            <cache_dir><![CDATA[]]></cache_dir>
            <hashed_directory_level><![CDATA[]]></hashed_directory_level>
            <hashed_directory_umask><![CDATA[]]></hashed_directory_umask>
            <file_name_prefix><![CDATA[]]></file_name_prefix>
        </memcached>
    </cache>

    <!-- example of two level cache setup with slow backend at files. -->
    <full_page_cache>
        <backend_options>
             <cache_dir>full_page_cache</cache_dir>
         </backend_options>
         <slow_backend_options>
             <hashed_directory_level>1</hashed_directory_level>
             <hashed_directory_umask>0777</hashed_directory_umask>
             <file_name_prefix>fpc</file_name_prefix>
             <cache_dir><![CDATA[full_page_cache]]></cache_dir>
         </slow_backend_options>
     </full_page_cache>

    <remote_addr_headers><!-- list headers that contain real client IP if webserver is behind a reverse proxy -->
        <header1>HTTP_X_REAL_IP</header1>
        <header2>HTTP_X_FORWARDED_FOR</header2>
    </remote_addr_headers>
</global>

My questions are as follows:

Has anybody made ANY of these modifications to the local.xml file before?
If so, what was the result thereof?
Are there perhaps any other tips regarding this file which could help improve performance?

Edit:

Looking at a local.xml.template in stock Magento CE 1.9.0.1, I see no mention of the <cache>...</cache> tags.

Best Answer

If you are looking to improve the performance of the backend, neither Redis or Memcached (or any other backend) will make much of a difference.

In the admin, the cache is rarely accessed (config/layout only), both of which are infrequently hit and not particularly demanding anyway.

Memcached/Redis improve server concurrency under load, but do not improve individual user page load time.

Ultimately, if your admin is slow, its almost certainly caused by insufficient/incorrectly configured hosting. Its an environment that will highlight and accentuate any performance bottlenecks in the server config itself (that can't be hidden behind the block cache/fpc/varnish in the frontend).

But a quick tip would be to remove the admin notifications altogether. This can make the admin really slow.

Using APC as an OPCode Cache

Simply install the module on your server

pecl install apc

And enable it in your php.ini

echo "extension=apc.so" >> /usr/lib/local/php.ini       (RedHat/Centos)
echo "extension=apc.so" >> /etc/php5/conf.d/20apc.ini   (Debian)

You then enable and fine-tune the runtime configuration to suit, eg.

apc.enabled
apc.shm_segments
apc.shm_size
apc.optimization
apc.num_files_hint
apc.user_entries_hint
apc.ttl
apc.user_ttl
...

Then restart PHP/Apache

/etc/init.d/httpd restart                               (RedHat/Centos)
/etc/init.d/apache2 restart                             (Debian)

After that, there is nothing else to do. Confirm APC is enabled with a quick phpinfo() - but otherwise, at this point, the OPCode cache portion of APC is active.

Nothing needs to be configured on Magento's side.

Using APC as a Fast Backend

You need to add the following to your ./app/etc/local.xml

<global>
  ...
  <cache>
    <backend>apc</backend>
      <prefix>mystore_</prefix>
  </cache>
  ...
</global>

Then flush your existing store caches. To verify it is working, load a page in the front-end and the ./var/cache directory should remain empty.

Using Memcache as a Fast Backend

You'll need to install Memcache as a PHP extension, and install the respective Memcache Daemon (Memcached) on your server.

pecl install memcache

And enable it in your php.ini

echo "extension=memcache.so" >> /usr/lib/local/php.ini            (RedHat/Centos)
echo "extension=memcache.so" >> /etc/php5/conf.d/20memcache.ini   (Debian)

/etc/init.d/httpd restart                               (RedHat/Centos)
/etc/init.d/apache2 restart                             (Debian)

Then install Memcached on the server. For RH/Centos, adjust the URL to suit your release version and CPU architecture.

rpm -Uhv http://apt.sw.be/redhat/el6/en/x86_64/rpmforge/RPMS/rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm
yum --enablerepo=rpmforge install memcached

apt-get install memcached                               (Debian)

Then modify Magento to use Memcache as a fast backend, change the socket path to a TCP/IP connection to suit.

<cache>
  <slow_backend>database</slow_backend>
  
  <fast_backend>memcached</fast_backend>
  <fast_backend_options>
    <servers>
      <server>
        <host>unix:///tmp/memcached.sock</host>
        <port>0</port>
        <persistent>0</persistent>
      </server>
    </servers>
  </fast_backend_options>
  
  <backend>memcached</backend>
  <memcached>
  <servers>
    <server>
      <host>unix:///tmp/memcached.sock</host>
      <port>0</port>
      <persistent>0</persistent>
    </server>
  </servers>
</cache>

The caveats of Memcache and tagging - what is it storing

Memcache only supports a single level of key-value relationships, so it cannot store the Magento cache tags (that are used to flush cache data independently). As a result, you either need to specify a slow_backend to maintain the cache content tag relationship, or don't define one at all.

If you define a slow_backend, you run the risk of the cache tags growing so large that performance is negated; there is also the inherent problem that you cannot scale across multiple servers if each server is maintaining their own cache tags.

So when using Memcache, the better approach (with the caveat you cannot flush caches independently), is to not bother using the slow_backend.

In which case, we suggest removing <slow_backend>database</slow_backend> and replacing it with:

  <slow_backend>Memcached</slow_backend>
  <slow_backend_options>
    <servers>
      <server>
        <host>unix:///tmp/memcached.sock</host>
        <port>0</port>
        <persistent>0</persistent>
      </server>
    </servers>
  </slow_backend_options>

This will break/disable the 2nd level of caching (and prevent tag storage), but still allow the performance of Memcache.

Which to use

If its a single server deployment - there's no harm just using APC for everything.

If its a distributed set-up - then you'll need to use Memcache as the fast backend (so that all machines can access the common store).

More concerning is that if your hosting provider can't tell you the right set up to use, you are certainly with the wrong host.

Attributions: sonassi.com, php.net, repoforge.org

Magento 1.6 XML Configuration – Explain app/etc/local.xml File

In Local.xml file magento store the database information host details of the site while installing.

Just have look on your local.xml file.

You need to change the following

<default_setup>
    <connection>
        <host><![CDATA[localhost]]></host>
        <username><![CDATA[root]]></username>
        <password><![CDATA[]]></password>
        <dbname><![CDATA[magento-tdmes]]></dbname>
        <initStatements><![CDATA[SET NAMES utf8]]></initStatements>
        <model><![CDATA[mysql4]]></model>
        <type><![CDATA[pdo_mysql]]></type>
        <pdoType><![CDATA[]]></pdoType>
        <active>1</active>
    </connection>
</default_setup>

Host tag your host name

username tag DataBase User Name

password tag DataBase password

dbname tag Site DataBase Name

Change these things for your dev server.

NOTE: If this file readable to all then Hackers can easily hack your site

Best Answer

Related Solutions

Magento – Improving Speed with APC and Memcached

Using APC as an OPCode Cache

Using APC as a Fast Backend

Using Memcache as a Fast Backend

Which to use

Magento 1.6 XML Configuration – Explain app/etc/local.xml File

Related Topic