{"id":16286,"date":"2018-03-20T06:30:47","date_gmt":"2018-03-20T12:30:47","guid":{"rendered":"http:\/\/vanseodesign.com\/?p=16286"},"modified":"2018-01-26T15:28:57","modified_gmt":"2018-01-26T22:28:57","slug":"apache-web-server","status":"publish","type":"post","link":"https:\/\/vanseodesign.com\/web-design\/apache-web-server\/","title":{"rendered":"Apache—Server Software With Process-Based Architecture"},"content":{"rendered":"

You may or not think about it much, or even at all, but your choice of server software has an impact on the performance of your site. It isn\u2019t that one application is always better than the others, but rather they each have their own strengths and weaknesses and depending on the particulars of your site, one application might work better for you than another.<\/p>\n

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About a month ago I revisited an ongoing series about website performance<\/a>. I spent a week talking about hosting plans<\/a> and another talking about server hardware<\/a>. Over the next few weeks I want to talk about server software, particularly Apache, NGINX, IIS, and LiteSpeed. I\u2019ll talk about Apache today and continue with the others starting next week.<\/p>\n

Odds are the software running your website is Apache, which still runs on close to 50% of all the servers across the web. It\u2019s been the most commonly used server software for as long as I can remember and it\u2019s all I\u2019ve ever used. It\u2019s 50\/50 that the same is true for you as well.<\/p>\n

There are a lot of Server Software Options<\/h2>\n

Apache, while popular, has never been the only application you could use to run a server. Internet Information Services (IIS) from Microsoft has also been popular throughout much of the life of the internet. For years your choice probably came down to which combination of server side programming language and database you wanted to use. If those were .Net and MSSQL, you went with IIS, otherwise you chose Apache and worked with open source languages and databases.<\/p>\n

NGINX and LiteSpeed are additional applications that have grown in popularity in recent years and both offer performance benefits Apache and IIS don\u2019t.<\/p>\n

It doesn\u2019t stop there. Wikipedia lists 36 different options for server software<\/a>, assuming I counted correctly. I\u2019m not going to talk about, or even mention, any besides the four I\u2019ve already called out, but know there are a lot more options.<\/p>\n

To understand why you might choose one or the other let\u2019s talk about each of the four in turn, specifically how they handle HTTP requests and connections<\/a>. We\u2019ll start with Apache.<\/p>\n

How Apache Handles HTTP Requests and Connections<\/h2>\n

Apache<\/a> was developed with a process-based architecture<\/a> in that each request for a connection is handled by a single process. The way it generally works is a parent process for the server receives connection requests and when it does, it creates (spawns) a child process to handle it. When another request comes in the parent process spawns a new child process to handle the new request and so on.<\/p>\n

Unfortunately, each child (worker) process is heavy on server resources, particularly RAM, so the more requests and open connections, the more resources are taxed. To help, Apache developers used a prefork model, which creates a pool of worker processes in advance that are able and ready to take connections. When all the processes in the pool are busy with connections, Apache will create additional worker processes to be ready for future requests.<\/p>\n

On the positive side, this setup makes it easy to insert additional code into the overall process that are incorporated in the form of modules and plenty of third party developers took advantage of that ability to write all sorts of modules to extend Apache\u2019s basic functionality.<\/p>\n

Aside<\/strong>: If your server runs Apache and you want to see what modules your server is currently running, you can create a very simple PHP file to show you. Here’s all the code you need.<\/p>\n

[code type=php]
\n
\n[\/code]<\/p>\n

Save the code and name the file whatever you want (as long as it has a .php extension) and visit its URL in a browser and you\u2019ll get all sorts of information. When you\u2019re done remove the file, since you\u2019d rather no one with malicious intent know the information.<\/p>\n

Again, workers processes use a lot of RAM and even using mpm_prefork only helps so much. When the number of requests is less than the number of available processes, Apache is very fast, but when the reverse is true, Apache performance degrades and the less powerful the hardware, the more quickly the degradation.<\/p>\n

As traffic increases, particularly during a spike, all the spawned processes eat into the available RAM until there\u2019s little or none left. The server can come to a complete halt until existing connections are closed and resources are freed for new ones. Cloud servers that can share resources can combat this because there are more resources to share temporarily when one site has a traffic spike.<\/p>\n

Part of the problem is that Apache processes are blocking processes<\/a>. That is each is handled one at a time as the others wait in a queue. One request needs to complete before the next one can start, which makes inefficient use of resources.<\/p>\n

Heavy traffic wasn\u2019t a problem in the early days of the web, which helps account for Apache being process-driven, but as we know web traffic increased and increased and increased and Apache developers added two more multi-processing modules (MPMs)\u00a0<\/a>mpm_worker and mpm_event.<\/p>\n