TeamCity

Precompiling ASP.NET MVC applications with Teamcity & Octopus

  • February 7, 2017

Notice the first time you open a page or view in your ASP.NET MVC application, it’s takes quite a bit longer, and subsequent loads are faster? This is because they are compiled on-demand by IIS the first time someone tries to access them – dynamically being turned into an alpha-numerically named DLL. There are quite a few problems with this process:

  • Some errors in your razor code won’t be made apparent until the view is compiled after being accessed for the first time. If you follow the principle of “crash early”, then you’ll agree the web server is much too late for this to happen!
  • Web servers are meant to serve web requests, not compile code. Compiling views comes with a performance overhead that may affect the performance of concurrent requests.
  • If a user is unlucky enough to be the first to access a view they will be met with a long load time, giving a poor impression that something may be wrong.

In this post I will show you how to setup true precompilation for your ASP.NET application. The goal is to package our entire web application, including views, into one or more DLL files. This comes with many benefits:

  • Any compilation errors in your razor code are found well before any code is deployed to a web server.
  • Compilation is done on your build server, allowing you to create a deployment package that requires no additional compiling on the web servers.
  • Users are no longer victim to long load times the first time a view is accessed.

I am assuming that you already have a build and deploy process setup using Teamcity and Octopus. I will be showing you the small tweaks necessary to that process to make precompilation work.

Setup a Publishing Profile

We’re going to leverage publishing profiles as a way of instructing MSBuild on how to compile our project.

  1. Start by right clicking your web project in Visual Studio and clicking Publish…
  2. You will be asked to select a publish target. Select Custom and enter a profile name when prompted
  3. Under publish method select File System
  4. Under target location enter $(ProjectDir)precompiled and click next
  5. Select the build configuration you want to apply, and under File Publish Options make sure both options to delete all existing files prior to publish and precompile during publishing are both checked
  6. Click the Configure button that is next to the precompile during publishing option. Details on all the options in this window are documented on MSDN. For now we will make sure the allow precompiled site to be updatable option is unchecked. Select the option to Merge all outputs to a single assembly and enter a name for the DLL file, for example MyWebProject.Precompiled
  7. Close out of the dialogs. You can push the publish button to test your profile. Once the compile is complete, you should be able to go into your project directory and see a new folder called precompiled. Inside of it you will find the bin folder where you will see some new compiled DLL’s that weren’t there before. Those are your precompiled views.

If you look in the Properties folder in your project you should have a new folder called PublishProfiles containing an xml file with the profile configuration. Here is a sample of what it may look like:

<?xml version="1.0" encoding="utf-8"?>
<!--
This file is used by the publish/package process of your Web project. You can customize the behavior of this process
by editing this MSBuild file. In order to learn more about this please visit http://go.microsoft.com/fwlink/?LinkID=208121. 
-->
<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
 <PropertyGroup>
 <WebPublishMethod>FileSystem</WebPublishMethod>
 <LastUsedBuildConfiguration>Release</LastUsedBuildConfiguration>
 <LastUsedPlatform>Any CPU</LastUsedPlatform>
 <SiteUrlToLaunchAfterPublish />
 <LaunchSiteAfterPublish>True</LaunchSiteAfterPublish>
 <PrecompileBeforePublish>True</PrecompileBeforePublish>
 <EnableUpdateable>False</EnableUpdateable>
 <DebugSymbols>False</DebugSymbols>
 <WDPMergeOption>MergeAllOutputsToASingleAssembly</WDPMergeOption>
 <UseMerge>True</UseMerge>
 <SingleAssemblyName>MyWebProject.Precompiled</SingleAssemblyName>
 <ExcludeApp_Data>False</ExcludeApp_Data>
 <publishUrl>$(ProjectDir)precompiled</publishUrl>
 <DeleteExistingFiles>True</DeleteExistingFiles>
 </PropertyGroup>
</Project>

MSBuild Precompiling Views in Teamcity

Now that we have a publishing profile setup, the next step is to automate the precompilation step in Teamcity.

  1. Add a new MSBuild step to your current build configuration (you do have one setup already to compile your project, right?). We will want this to be one of the last steps in our configuration.
  2. Give it a name, point the build file path to your solution file, and set the command line parameters to the following:
/p:DeployOnBuild=true
/p:PublishProfile=<YourPublishProfileName>.pubxml
/p:VisualStudioVersion=14.0
/p:Configuration=Release
/p:AspnetMergePath="C:\Program Files (x86)\Microsoft SDKs\Windows\v8.1A\bin\NETFX 4.5.1 Tools"

And that’s it, Teamcity will invoke MSBuild using the publishing profile we created earlier, and generate the precompiled DLL’s.

If you are going to be deploying using Octopus, make sure the Run OctoPack option is checked in the build step.

Creating an Octopus Package

The last step is to take our precompiled application and package it up for octopus to deploy. The first thing we need to do is create a .nuspec file in our project, make sure it has a build action property of Content. This will tell OctoPack how and what to package in our project. Name the .nuspec file the same as your web project and enter the following:

<?xml version="1.0"?>
<package xmlns="http://schemas.microsoft.com/packaging/2010/07/nuspec.xsd">
 <metadata>
  <id>MyWebProject</id>
  <title>MyWebProject</title>
  <version>0.0.0.0</version>
  <authors>Me</authors>
  <description>The MyWebProject deployment package</description>
  <releaseNotes></releaseNotes>
 </metadata>
 <files>
  <file src="precompiled\**\*.*" target=""/>
  <file src="Web.*.config" target=""/>
 </files>
</package>

Basically we’re telling OctoPack some basic information about our project, and to include everything in the precompiled folder into our package. We are also asking Octopack to include any extra config transformations, this is optional but necessary if you wish to perform config transformation during your Octopus deploy process.

That should be it. Now when TeamCity runs, it will tell MSBuild to precompile all your views into one or more DLL’s using the publishing profile you created. Once that is done it will invoke OctoPack which will look at the nuspec file in your project and create an Octopus package containing the contents of the precompiled folder. You can then push that package to your Octopus server where it can then be deployed to your web servers.

Compile Time View Validation in ASP.NET MVC

  • June 17, 2016

Open up your favorite .cshtml file, put the mouse cursor in the middle of some razor code, and have a cat walk across your keyboard. If you don’t have a cat nearby, rolling your face on your keyboard will also suffice. You should start seeing things highlighted and underlined in red. Now go ahead and build your project.

Build Succeeded – Really?

Unlike all the other code in your project, your view files are not compiled when you hit the Build button in your IDE. Instead, they are compiled on-demand by IIS the first time someone tries to access them – dynamically being turned into an alpha-numerically named DLL. The problem is that any errors you have in your views won’t be made apparent until IIS tries to compile them, at which point the user who requested the view would see an error page. So how do you protect yourself from this happening?

Pre-compilation To The Rescue

Pre-compiling Razor views is possible, there are projects out there that will allow you to turn your views into DLL files before they even touch an IIS server. However doing so in this case would be overkill, we just want to know if there are obvious errors in our views.

To let you find those compile-time bugs there’s a flag you can set in your .csproj file.

<MvcBuildViews>true</MvcBuildViews>

This will cause your views to be test compiled when your project is built. Why do I emphasize test compiled? Because they aren’t compiled in the traditional sense that you end up with resulting DLL files, they will still need to be dynamically compiled by IIS later on. It’s just a test to see if when they are compiled by IIS, if any errors will be thrown.

You will find that this setting is false by default, and there’s a good reason for that – view compilation takes time. In a large enough project it could take enough time to seriously annoy a developer who is used to those quick compiles. A medium sized project of around 70 views has the compile time grow by 36 seconds when this feature is enabled.

But there’s a compromise, instead of having your views test compile during every build, we can set it to only test compile when performing a release build. If you look in your .csproj file, you will find a PropertyGroup block for each build configuration in your project. Find your release build configuration and add the MvcBuildViews property. In this example my build configuration is simply called Release.

<PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
    <MvcBuildViews>true</MvcBuildViews>
    ...
</PropertyGroup>

This way the debug builds you do on your machine will run fast, while the builds that run on your build server will take a bit longer, while validating that all your views will compile. If a view can’t be compiled, the build fails, and the code will never be deployed to an IIS server.

Preventing accidental deployments in TeamCity

  • July 7, 2014

One-click deployments are exactly that – one click of the “Run” button, and the magic happens. But, if you have a particularly busy project list in TeamCity, you will find yourself constantly double checking which “Run” button you are pressing, for fear of accidently running a deployment into production. It’s an unfortunate consequence of making things too easy – one little misclick can become a big mistake.

In this post I will show you how to reduce the risk of accidently running a production deployment in TeamCity by introducing a simple safety switch into the build process. At the end, upon pressing the “Run” button you will be presented with a prompt that looks something like this:

oneclickteamcity

The prompt includes a checkbox asking you to confirm that you really want to run the build. If you check it – the build will run as it normally would. If you don’t – it will fail. Effectively turning a one-click deployment into a three-click deployment, with the added benefit of no added training or documentation to other users of your build server.

Step 1

Add a new build step to your build configuration – it should be the very first step that is run. In this example I’ll make it of type Powershell – you can use other script based build types (Gradle, command line, etc.), the script will simply verify if the user has checked the confirm checkbox before the build runs.

Give the build step a name like “Deployment Confirmation”.

Set the Script option to Source code and enter the following into the Script source box:

write-host "##teamcity[message text='Starting confirmation validation...']"
if("%env.Confirm%" -eq "false") {
	write-host "##teamcity[message text='Confirmation validation FAILED' errorDetails='This is a production deployment. The confirm checkbox must be checked to proceed with the deploy process.' status='ERROR']"
	throw "Confirmation validation FAILED"
} else {
	​write-host "##teamcity[message text='Confirmation validation SUCCESSFUL']"
}​

The script basically checks the value of the build parameter %env.Confirm% that is set by the checkbox in the build prompt. If it’s false (unchecked), throw an exception that will kill the rest of the build process. If it is true, don’t do anything, and the build will continue as usual.

The rest of the fields in this build step can be left with their default values. Now would also be a good time to make sure any subsequent steps in your build configuration are set to execute “Only if all previous steps were successful”.

Step 2

Add an environment variable to your build parameters. Name it env.Confirm (make sure if matches the name in the script above) and set the default value to false. Press the “Edit…” button to create a new variable specification. You will be presented with a form with the following fields:

  • Label – this is the text that appears to the left of the checkbox. I set it to something like “This is a production deployment”.
  • Description – this is the text that appears beneath the checkbox. I set it to something like “Are you sure?”.
  • Display – set this to “Prompt”, we want TeamCity to prompt for this value whenever a build is requested.
  • Type – set this to “Checkbox” with the checked value being true and unchecked value being false.

That’s it! From now on when you click the “Run” button, you should get the prompt above. Also note that the build log will contain the message output from the script above so that it becomes very clear why a build failed if someone doesn’t click the confirm checkbox.

One Catch

The only catch I have found with this approach is that despite the default value of our checkbox being set to false, TeamCity has a “feature” that stores the last value of the checkbox in some session state (cookies, session storage, etc.). So if you run a build, enable the checkbox, and five minutes later try to run the build again, the checkbox will already be checked for you. It seems only after twenty minutes or so, or however long it takes for your session to expire, will it reset back to the correct behaviour.

This isn’t a big deal, even if the checkbox is pre-enabled due to this “feature” in TeamCity, the prompt will still appear, so you’re still turning a one-click deployment into a two-click deployment.