{"rowid": 107, "title": "Using Google App Engine as Your Own Content Delivery Network", "contents": "Do you remember, years ago, when hosting was expensive, domain names were the province of the rich, and you hosted your web pages on Geocities? It seems odd to me now that there was a time when each and every geek didn\u2019t have his own top-level domain and super hosting setup. But as the parts became more and more affordable a man could become an outcast if he didn\u2019t have his own slightly surreal-sounding TLD.\n\nAnd so it will be in the future when people realise with surprise there was a time before affordable content delivery networks.\n\nA content delivery network, or CDN, is a system of servers spread around the world, serving files from the nearest physical location. Instead of waiting for a file to find its way from a server farm in Silicon Valley 8,000 kilometres away, I can receive it from London, Dublin, or Paris, cutting down the time I wait. The big names \u2014 Google, Yahoo, Amazon, et al \u2014 use CDNs for their sites, but they\u2019ve always been far too expensive for us mere mortals. Until now.\n\nThere\u2019s a service out there ready for you to use as your very own CDN. You have the company\u2019s blessing, you won\u2019t need to write a line of code, and \u2014 best of all \u2014 it\u2019s free. The name? Google App Engine.\n\nIn this article you\u2019ll find out how to set up a CDN on Google App Engine. You\u2019ll get the development software running on your own computer, tell App Engine what files to serve, upload them to a web site, and give everyone round the world access to them.\n\nCreating your first Google App Engine project\n\nBefore we do anything else, you\u2019ll need to download the Google App Engine software development kit (SDK). You\u2019ll need Python 2.5 too \u2014 you won\u2019t be writing any Python code but the App Engine SDK will need it to run on your computer. If you don\u2019t have Python, App Engine will install it for you (if you use Mac OS X 10.5 or a Linux-based OS you\u2019ll have Python; if you use Windows you won\u2019t).\n\nDone that? Excellent, because that\u2019s the hardest step. The rest is plain sailing.\n\nYou\u2019ll need to choose a unique \u2018application id\u2019 \u2014 nothing more than a name \u2014 for your project. Make sure it consists only of lowercase letters and numbers. For this article I\u2019ll use 24ways2008, but you can choose anything you like.\n\nOn your computer, create a folder named after your application id. This folder can be anywhere you want: your desktop, your documents folder, or wherever you usually keep your web files. Within your new folder, create a folder called assets, and within that folder create three folders called images, css, and javascript. These three folders are the ones you\u2019ll fill with files and serve from your content delivery network. You can have other folders too, if you like.\n\nThat will leave you with a folder structure like this:\n\n24ways2008/\n\t\tassets/\n\t\t\tcss/\n\t\t\timages/\n\t\t\tjavascript/\n\nNow you need to put a few files in these folders, so we can later see our CDN in action. You can put anything you want in these folders, but for this example we\u2019ll include an HTML file, a style sheet, an image, and a Javascript library.\n\nIn the top-level folder (the one I\u2019ve called 24ways2008), create a file called index.html. Fill this with any content you want. In the assets/css folder, create a file named core.css and throw in a couple of CSS rules for good measure. In the assets/images directory save any image that takes your fancy \u2014 I\u2019ve used the silver badge from the App Engine download page. Finally, to fill the JavaScript folder, add in this jQuery library file. If you\u2019ve got the time and the inclination, you can build a page that uses all these elements.\n\nSo now we should have a set of files and folders that look something like this:\n\n24ways2008/\n\t\tassets/\n\t\t\t\tindex.html\n\t\t\t\tcss/\n\t\t\t\t\t\tcore.css\n\t\t\t\timages/\n\t\t\t\t\t\tappengine-silver-120x30.gif\n\t\t\t\tjavascript/\n\t\t\t\t\t\tjquery-1.2.6.min.js\n\nWhich leaves us with one last file to create. This is the important one: it tells App Engine what to do with your files. It\u2019s named app.yaml, it sits at the top-level (inside the folder I\u2019ve named 24ways2008), and it needs to include these lines:\n\napplication: 24ways2008\nversion: 1\nruntime: python\napi_version: 1\n\nhandlers:\n- url: /\n\tstatic_files: assets/index.html\n\tupload: assets/index.html\n\n- url: /\n\tstatic_dir: assets\n\nYou need to make sure you change 24ways2008 on the first line to whatever you chose as your application id, but otherwise the content of your app.yaml file should be identical. And with that, you\u2019ve created your first App Engine project. If you want it, you can download a zip file containing my project.\n\nTesting your project\n\nAs it stands, your project is ready to be uploaded to App Engine. But we couldn\u2019t call ourselves professionals if we didn\u2019t test it, could we? So, let\u2019s put that downloaded SDK to good use and run the project from your own computer.\n\nOne of the files you\u2019ll find App Engine installed is named dev_appserver.py, a Python script used to simulate App Engine on your computer. You\u2019ll find lots of information on how to do this in the documentation on the development web server, but it boils down to running the script like so (the space and the dot at the end are important):\n\ndev_appserver.py .\n\nYou\u2019ll need to run this from the command-line: Mac users can run the Terminal application, Linux users can run their favourite shell, and Windows users will need to run it via the Command Prompt (open the Start menu, choose \u2018Run\u2026\u2019, type \u2018cmd\u2018, and click \u2018OK\u2019). Before you run the script you\u2019ll need to make sure you\u2019re in the project folder \u2014 in my case, as I saved it to my desktop I can go there by typing \n\ncd ~/Desktop/24ways2008\n\nin my Mac\u2019s Terminal app; if you\u2019re using Windows you can type \n\ncd \"C:\\Documents and Settings\\username\\Desktop\\24ways2008\"\n\nIf that\u2019s successful, you\u2019ll see a few lines of output, the last looking something like this:\n\nINFO     2008-11-22 14:35:00,830 dev_appserver_main.py] Running application 24ways2008 on port 8080: http://localhost:8080\n\nNow you can power up your favourite browser, point it to http://localhost:8080/, and you\u2019ll see the page you saved as index.html. You\u2019ll also find your CSS file at http://localhost:8080/css/core.css. In fact, anything you put inside the assets folder in the project will be accessible from this domain. You\u2019re running our own App Engine web server!\n\nNote that no-one else will be able to see your files: localhost is a special domain that you can only see from your computer \u2014 and once you stop the development server (by pressing Control\u2013C) you\u2019ll not be able to see the files in your browser until you start it again.\n\nYou might notice a new file has turned up in your project: index.yaml. App Engine creates this file when you run the development server, and it\u2019s for internal App Engine use only. If you delete it there are no ill effects, but it will reappear when you next run the development server. If you\u2019re using version control (e.g. Subversion) there\u2019s no need to keep a copy in your repository.\n\nSo you\u2019ve tested your project and you\u2019ve seen it working on your own machine; now all you need to do is upload your project and the world will be able to see your files too.\n\nUploading your project\n\nIf you don\u2019t have a Google account, create one and then sign in to App Engine. Tell Google about your new project by clicking on the \u2018Create an Application\u2019 button. Enter your application id, give the application a name, and agree to the terms and conditions. That\u2019s it. All we need do now is upload the files.\n\nOpen your Mac OS X Terminal, Windows Command Prompt, or Linux shell window again, move to the project folder, and type (again, the space and the dot at the end are important):\n\nappcfg.py update .\n\nEnter your email address and password when prompted, and let App Engine do it\u2019s thing. It\u2019ll take no more than a few seconds, but in that time App Engine will have done the equivalent of logging in to an FTP server and copying files across. It\u2019s fairly understated, but you now have your own project up and running. You can see mine at http://24ways2008.appspot.com/, and everyone can see yours at http://your-application-id.appspot.com/. Your files are being served up over Google\u2019s content delivery network, at no cost to you!\n\nBenefits of using Google App Engine\n\nThe benefits of App Engine as a CDN are obvious: your own server doesn\u2019t suck up the bandwidth, while your visitors will appreciate a faster site. But there are also less obvious benefits.\n\nFirst, once you\u2019ve set up your site, updating it is an absolute breeze. Each time you update a file (or a batch of files) you need only run appcfg.py to see the changes appear on your site. To paraphrase Joel Spolsky, a good web site must be able to be updated in a single step. Many designers and developers can\u2019t make that claim, but with App Engine, you can.\n\nApp Engine also allows multiple people to work on one application. If you want a friend to be able to upload files to your site you can let him do so without giving him usernames and passwords \u2014 all he needs is his own Google account. App Engine also gives you a log of all actions taken by collaborators, so you can see who\u2019s made updates, and when.\n\nAnother bonus is the simple version control App Engine offers. Do you remember the file named app.yaml you created a while back? The second line looked like this:\n\nversion: 1\n\nIf you change the version number to 2 (or 3, or 4, etc), App Engine will keep a copy of the last version you uploaded. If anything goes wrong with your latest version, you can tell App Engine to revert back to that last saved version. It\u2019s no proper version control system, but it could get you out of a sticky situation.\n\nOne last thing to note: if you\u2019re not happy using your-application-id.appspot.com as your domain, App Engine will quite happily use any domain you own.\n\nThe weak points of Google App Engine\n\nIn the right circumstances, App Engine can be a real boon. I run my own site using the method I\u2019ve discussed above, and I\u2019m very happy with it. But App Engine does have its disadvantages, most notably those discussed by Aral Balkan in his post \u2018Why Google App Engine is broken and what Google must do to fix it\u2018.\n\nAral found the biggest problems while using App Engine as a web application platform; I wouldn\u2019t recommend using it as such either (at least for now) but for our purposes as a CDN for static files, it\u2019s much more worthy. Still, App Engine has two shortcomings you should be aware of.\n\nThe first is that you can\u2019t host a file larger than one megabyte. If you want to use App Engine to host that 4.3MB download for your latest-and-greatest desktop software, you\u2019re out of luck. The only solution is to stick to smaller files.\n\nThe second problem is the quota system. Google\u2019s own documentation says you\u2019re allowed 650,000 requests a day and 10,000 megabytes of bandwidth in and out (20,000 megabytes in total), which should be plenty for most sites. But people have seen sites shut down temporarily for breaching quotas \u2014 in some cases after inexplicable jumps in Google\u2019s server CPU usage. Aral, who\u2019s seen it happen to his own sites, seemed genuinely frustrated by this, and if you measure your hits in the hundreds of thousands and don\u2019t want to worry about uptime, App Engine isn\u2019t for you.\n\nThat said, for most of us, App Engine offers a fantastic resource: the ability to host files on Google\u2019s own content delivery network, at no charge.\n\nConclusion\n\nIf you\u2019ve come this far, you\u2019ve seen how to create a Google App Engine project and host your own files on Google\u2019s CDN. You\u2019ve seen the great advantages App Engine offers \u2014 an excellent content delivery network, the ability to update your site with a single command, multiple authors, simple version control, and the use of your own domain \u2014 and you\u2019ve come across some of its weaknesses \u2014 most importantly the limit on file sizes and the quota system. All that\u2019s left to do is upload those applications \u2014 but not before you\u2019ve finished your Christmas shopping.", "year": "2008", "author": "Matt Riggott", "author_slug": "mattriggott", "published": "2008-12-06T00:00:00+00:00", "url": "https://24ways.org/2008/using-google-app-engine-as-your-own-cdn/", "topic": "process"}