Posts tagged deployment

Dynamic Robots.txt in ASP MVC

0
128 days
by in .net, asp net mvc

I recently had the need to switch a robots.txt file dynamically, depending on whether a site was deployed to live or beta servers. The solution was very simple, ditch the real file and replace it with a controller action. This is a brief note on how I did this. I don’t pretend this is an ideal solution, it was something I knocked together before I went out for dinner.

The solution I went for was in three parts: a web.config transform, routing and the controller itself.

The web config transform for my live site looks like this:

<?xml version="1.0"?>
<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
    <appSettings>
        <add key="SiteStatus" value="live" xdt:Transform="SetAttributes" xdt:Locator="Match(key)"/>
    </appSettings>
</configuration>
view raw Web.live.config This Gist brought to you by GitHub.

The route is equally simple:

routes.MapRoute(
    "Robots.txt",
    "Robots.txt",
    new 
    { 
        controller = "Robots", 
        action = "RobotsText" 
    }
);

view raw routing.cs This Gist brought to you by GitHub.

And finally the actual controller:

public class RobotsController : Controller
{
    public FileContentResult RobotsText()
    {
        var content = "User-agent: *" + Environment.NewLine;

        if (string.Equals(ConfigurationManager.AppSettings["SiteStatus"], "live", StringComparison.InvariantCultureIgnoreCase))
        {
            content += "Disallow: /elmah.axd" + Environment.NewLine;
            content += "Sitemap: http://www.jacquelinewhite.co.uk/sitemap.xml";
        }
        else
        {
            content += "Disallow: /" + Environment.NewLine; 
        }

        return File(
                Encoding.UTF8.GetBytes(content),
                "text/plain"); 
    }
}
view raw RobotsController.cs This Gist brought to you by GitHub.

And there we have it, my robots.txt file now is customised on a per deployment basis.

An imperfect Hack to Keep App_Offline Showing When You Delete Your Web App

0
431 days
by in asp .net

In a simple world, a good solution for deploying web apps looks a bit like this:

  1. Remove server from load balancer
  2. Remove old site
  3. Install new site
  4. Verify installation locally
  5. Add server back into the load balancer

Nice and simple, now you just move onto the next server and repeat the process.

The problem I have is that I don’t have that kind of access to the load balancer; I have no mechanism for taking a given server out of action other than using the app_offline.htm file. This works tolerably, but it’s a dirty hack rather than an elegant solution. As part of my deployment process I always delete all files in the site, this is fine as all data is stored either in a database or in a different folder. This causes problems for asp.net as it stops seeing the site as an application and ignores the app_offline.htm file. That’s no good for users as they will start to see either the default 404 page, or a message about the directory listing not being found. A simple hack that I’ve put in is to add the app_offline.htm to the list of default documents; also I set the IIS 404 for that site to app_offline.htm. It’s safe to do this as my app sets its own 404 pages, so in normal operation the app_offline.htm is ignored. It’s not a perfect solution, but it is better than nothing and hopefully brings the number of users seeing duff pages down to a minimum.

What I really need now is a way for the app_offline.htm file to be ignored for requests coming to the local machine and then I can stop doing deployments in front of my users.

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