Scaling

Sometimes in life we have to face good problems -- problems that we are happy to have. One such problem is scaling. And it is only really thought about when your website is doing well and receiving a lot of traffic. Thus it is a good problem.

Here are some tips to scaling well and enabling your website to grow large, easily. (By the way, I am assuming a LAMP configuration.)

• 1. Be very careful using session data (e.g., $_SESSION['varname']), because if you ever need to expand to multiple web servers, this wont work. Session data is stored in memory and will not be present if the web visitor would happen to use a different server for a second request.


• 2. I know this is common practice, but I will repeat it anyway: Use library and include files for your scripts. In these files include common functions and common parts of your rendered pages (e.g., headers, menus and footers). This makes updating your entire website as simple as editing one file.


• 3. Plan ahead for major traffic spikes by using grid hosting (e.g., Media Temple's "Grid Service"). Grid hosting is a deal where server resources are pooled together and used for whatever site needs them. This way, when you get a major spike in traffic (e.g., you get slashdotted), you have ample processing power and bandwidth to handle it. You may have to pay a bit more when you get traffic spikes, but it is better than being suspended by your host.


• 4. Deliver your media content on another set of servers. Media files like movies and audio can take up a lot of bandwidth and file space. Whenever possible offload these files on to someone else's site and you'll save some cash and be more scalable. For example, upload your movies to YouTube or Vimeo and then embed their flash players in your own site. Alternatively, you can use a Content Delivery Network or something like Amazon's S3. When you host content with any one of these solutions you also gain in the area of speed and quality of delivery.

There is a lot more that can be said in this area, but these are the things I've come across that have helped me.

jQuery's getJSON

I recently had a struggle getting jQuery's $.getJSON function to work on Internet Explorer (IE6 & IE7). I tried and tried to debug the javascript, but was getting no where. After giving up for a while and coming back to it the next day, I thought of checking the target file—the file jQuery was fetching asynchronously—for problems.

It turns out that IE doesn't like JSON encoded documents that are specified as UTF-8. Not sure what the problem is, but the document has to be returned in a format IE likes. If not, IE will not allow jQuery to process it. Now, I had a header on this file that specified the content-type and charset. But, I changed it and instead I put only the content-type at the top of my JSON-returning PHP files:

<?PHP
header("Content-Type: application/json");
?>

Why does IE balk at UTF-8 specified charsets for JSON-encoded responses?? Who knows. But, from the research I've done, specifying the charset in the HTTP header is not something that is required. I am sure there are good reasons to specify the charset, but this (above) works great for me.