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HTTP Response Header Size Limits

Published: January 24, 2017

A while back I published a post about HTTP request header size limits. At the time, I had just finished remediating an issue where requests were being blocked by a WAF for exceeding the “max header size” policy.

Recently, I’ve been dealing with a similar, but slightly different issue…requests failing due to the size of the response headers. Here, I’ll document my findings on this issue…

MySQL Query Cache Hit Rate

Published: January 22, 2017

MySQL’s query cache is a useful tool to improve performance and scalability. However, if not implemented correctly, it can do more harm than good…

The query cache offers the potential for substantial performance improvement, but do not assume that it will do so under all circumstances. With some query cache configurations or server workloads, you might actually see a performance decrease.

https://dev.mysql.com/doc/refman/5.7/en/query-cache.html

One critical data point to look at when measuring the effectiveness of query caching is the query cache hit rate. Let’s take a look at how to do that.

Enterprise_PageCache is Borked In 1.14.3.X

Published: January 20, 2017

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If you are thinking about installing or upgrading to Magento Enterprise 1.14.3.X read this post right now. Enterprise_PageCache is completely borked in both 1.14.3.0 and 1.14.3.1. The repro steps for the bug are not only dead simple, but also extremely common user behavior…


Steps To Reproduce

  1. Ensure that full page cache is turned on
  2. Navigate to a category page
  3. Apply any layered navigation filter
  4. Remove the filter you just applied

Expected result

Unfiltered category page is displayed

Actual result

Filtered category page continues to display


What’s worse, the cache for the unfiltered category page is now poisoned for any user who visits that page!

The good news it that there’s a patch available, SUPEE-9465. If that’s all you’re looking for I’ve posted it here.

However, because it’s interesting, let’s take at what went wrong starting in 1.14.3.0.

Help! I Can't Set A Catalog Product Collection's Page Size

Published: January 18, 2017

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I ran up against a pretty interesting issue recently. I was looking to render a custom block (descendant of Mage_Catalog_Block_Product_List) in a CMS block. You can do this with template variables…

{{block type="mpchadwick_customproductlist/list" template="mpchadwick/customproductlist/list.phtml"}}

Then, in my custom product list block I was setting up the collection in the constructor.

<?php

class Mpchadwick_CustomProductList_Block_List extends Mage_Catalog_Block_Product_List
{

    protected $helper;

    protected function _construct()
    {
    
        $this->helper = Mage::helper('mpchadwick_customproductlist');
        
        $collection = Mage::getModel('catalog/product')
            ->getCollection();
        
        $helper->filterCollection($collection);       
        
        $this->setCollection($collection);
         
        return parent::_construct();
    }
}

One of the things I was looking to do in the filterCollection was set the page size. However, no matter what I did (e.g. setPageSize, setPage, limit on the Varien_Db_Select object) it still wouldn’t work.

Finally, after an hour of pulling out my hair, I figured out why.

Aspell and Curly Quotes

Published: January 13, 2017

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aspell really doesn’t like curly quotes…

$ echo "This really shouldn’t fail" | aspell list
shouldn
$
$ echo "This really shouldn't fail" | aspell list
$

I ran up against this issue looking into adding a spell check featured for jekyll-pre-commit.

Understanding How A Magento 1 Module Works

Published: January 11, 2017

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As a developer, there’s a good chance you spend more time reading code than you do writing it. In the world of Magento, a lot of that time will be spent reading through the source code of custom and community modules.

In this post, I’ll provide some tips to help you understand how these modules work.