The VP Geek Speaks

Optimize Magento Time To First Byte

When looking at the performance of your site, waterfall charts are one of the first places you should investigate. The first thing that is represented on these charts is that the HTML for the website is the first resource that is downloaded every time.

As a result of being the first resource downloaded every time, this is the logical first place to look to improve the performance of your Magento website. There are a few ways to make sure that the page downloads more quickly, and they all involve making sure that the file size is as small as possible.

Magento appending __SID to URLs

When trying to fully optimize a Magento website to run as fast as possible, I tend to opt for turning on all of the caching options in Magento, and then put the Varnish caching server in front of the web server with the Turpentine plugin. However, when you do this with some configurations, you start seeing the __SID query string parameter added to the end of the site’s url. Unfortunately, when the Turpentine plugin sees the __SID query string in the URL, it means that this page request will bypass the cache and load it directly from the server, slowing things down.

Magento Adminhtml and Relative Links to Static Resources

Relative links in URLs allow you to only specify the path to an resource that is in the same or subfolder of the current folder. Lets say the current page you are on is http://example.com/test/ and you want to reference an image at http://example.com/test/image.jpg. You could put the full http://example.com/test/image.jpg in the src attribute of the img tag, or you could use just image.jpg instead. This works well when you are not sure what the directory path is the parent directory of your code. However, it can cause some issues when your code is moved to another location, but some resources are not moved, such as image.jpg.

MySQL Deadlocks with Magento

One of the things that Magento, and specifically the Zend Framework provide developers is the ability to not have to think about database details as it should just handle all that for you. When it becomes obvious that there is a problem somehow with the production database getting some sort of SQL errors, its time for the developers to start caring about the implementation and architecture details of the database.

Top 5 Ways to Make a Developer Your Enemy

Developers are known to be some of the most finicky employees you will encounter in the workplace. However, this is a list of things that will annoy or infuriate developers and non-developers alike.

1. Have the IT Manager send an email to all staff saying that all computers will have a keylogger installed. – This one is wrong on so many levels, the least of which is that it shows how little faith the company has in its employees and breeds mistrust of authority.
2. As a Manager or Team Lead, take ideas and suggestions from meetings with your team, and pass them off to upper management as your own. – This just reeks of someone that is only in it to gain more and more power.
3. As a Manager, don’t take the heat when things go wrong and blame the lowest-level employee instead. – I’ve seen senior management that is supposed to keep track of projects, ignore the project, and when it is the due date, blame those doing actual work on the project, throwing them under the bus.
4. As a new employee, on your second day of work, tell anyone that will listen or is within earshot that you are able to rewrite the entire codebase in three short months. Bear in mind, this codebase is over 7 years old and has a team of more than 20 developers working on it, but of course the newbie can rewrite the entire thing in no time flat.
5. As Management, when a developer hands in his/her resignation, schedule a meeting to try to first place a guilt trip on said employee to convince them to stay. If that doesn’t seem to work, then threaten to give the employee negative referrals if they don’t rescind the resignation and continue working for the company. Keep in mind that this occurred in a right to work state, meaning that there is no agreement in place that the employer would not wait a day or week or month and fire the employee without cause, just out of spite for wanting to work elsewhere.

These are just some of the things that will anger a software developer, so, be aware to avoid these if it matters at all to you.

Varnish and Magento Performance Mystery

One of the things that you think you will solve when you implement a Varnish caching server in front of a Magento website is performance problems. However, this is not necessarily the case.

When I set Varnish up to cache content in front of my Magento website, I get what seems to be much improved performance. If I run a few tests in the developer tools of Chrome, it seems that the waterfall chart makes sense and the data is loaded appropriately and in a timely manner with the main HTML being downloaded in about 300ms.

How Not to Use SQL Transactions

SQL Transactions allow you to isolate atomic operations so that you can ensure that a third party does not update the data affected during the atomic operation protected by the transaction. An example of an operation that you would want to protect with a SQL Transaction would be transferring funds from one bank account to another. The first step of this operation would be to subtract the funds from bank account A. Once complete, we would then add the same amount of funds to bank account B. Assuming nothing fails, everything works as expected. However, if there is other database activity at the same time or an error occurs in one of the queries, without a transaction you could have the funds removed from bank account A or added to bank account B, but not both, causing a major balancing issue with your bank accounts.

Unexpected Results with SQL Server and Python pyodbc

Using the Microsoft SQL Server Management Studio (SSMS) with SQL Server hides many of the API complications that can sometimes arise when working with SQL Server. One specific example would be when using Python on Windows with the pyodbc driver. If you have an update statement that performs a simple update to a status column and a datetime column, you can have some unexpected results.

Lets say that the table you are running the update against has a before update trigger and an after update trigger configured on it. Both triggers effectively do the same thing, as they log the current affected row to a second, logging table, peforming separate insert statements to do so. When running this update statement in SSMS, it seems to behave as you would expect, with a single result set returned, but listing three sets of (1 row updated) for every row that was updated. When using Python’s pyodbc driver to run this exact same SQL update statement, it shows that only 1 row was updated when there should have been many updated.

SQL Server Transaction Log Exponential Growth

There are few things more frustrating than seemingly random issues that crop up in software when configuration changes occur. One such occurrence is when you migrate your databases from Microsoft SQL Server 2012 Standard Edition to Microsoft SQL Server 2012 Enterprise Edition with High Availability and the transaction log suddenly begins to experience exponential growth without ceasing.

It turns out that when using Python and pyodbc on Windows to access SQL Server, there can be some unpredictable results. If you have a long-running SQL query that you are running from Python and pyodbc, when you are running it against a Microsoft SQL Server 2012 Standard Edition database, it will fail and time out silently, making Python think that the query succeeded. On the other hand, if you run the same long-running SQL query from Python and pyodbc in Microsoft SQL Server 2012 Enterprise Edition with High Availability, it will fail and rollback the query, but will fill the transaction log.

WordPress and the Genesis Framework

It turns out that working with WordPress and the Genesis Framework is quite a bit different than working with Magento or other blogging platforms. Ghost is a blogging platform that runs on NodeJs that utilizes Handlebars templates for the layout of the content on the website itself. Similarly, Magento uses its own templating system in .phtml files for laying out content on the screen. However, WordPress, and specifically the Genesis Framework have taken this simple templating concept and added quite a few layers of abstraction to come to the end result. This does give WordPress a great deal of extensibility for the various plugins that have been written for WordPress. Unfortunately, this makes for a steeper learning curve for developers working on a WordPress website.