Creating a yaml CI Build for .net application

One of the great announcements from this year's Microsoft Connect() conference was YAML support for VSTS build definitions. 

For me, it's a great way forward towards "codifying" the build pipeline. The current TFS builds technology, introduced in Team Foundation Server 2015, despite all the benefits of a loose and extensible mechanism is rather difficult to maintain as code and doesn't really fit "pipeline as a code" definition. If you remember, earlier versions of Team Foundation Server (TFS 2005 and TFS 2008) used an MSBuild file to run builds. Whilst this was easy to code and maintain, extensibility was rather limited. Then, Team Foundation Server 2010 introduced XAML builds with better support for workflows but was difficult to work with. TFS 2015 simplifies XAML but the whole logic is spread across different aspects of the build. Yaml solves this shortcoming nicely.

Enable YAML Builds Preview Feature

At the time of writing this post, support for YAML builds is still in preview in VSTS. To enable it for your account, click on your profile and select option "Preview Features" from the drop down menu

Select option "from this account [projectName]". Scroll down till you find the "Build Yaml definitions" feature and set it to On

We are now ready to use YAML builds.

Creating a Yaml Build 

There are two ways in which we can set up a Yaml build. 

1) Create a file called .vsts-ci.yaml. When you push your change with this file to TFS, a build definition, using this file is created for you.

2) Explicitly create a build definition using the YAML template, providing the path of YAML file that you have committed in the repo.

We will go with option 2.

Create build.yml file

YAML file format is the format of choice for configuration files and is used by some exciting technologies like docker, Ansible, etc. It's great that VSTS now supports it as well. 

For this demo, we are creating build for a simple .Net Web Application. For the purpose of building our application, we need to do the following

1) Restore all NuGet packages

2) Build the entire solution

Our very simple yaml file looks as below

steps:

- task: nugetrestore@1

displayName: NuGet Restore

inputs:

projects: "MyWebApplication.sln"

- task: MSBuild@1

displayName: Building solution

inputs:

command: build

projects: "MyWebApplication.sln"

The file is pretty much self descriptive. As you can see we we have two tasks. The first task uses nugetrestore passing the solution as input. The second task executes MSBuild passing the applicatino's solution.

Commit the file to your local Git Repo and push to commit to TFS.

Creating the Build definition

Now that our yaml file is committed, we will create a build definition to use it. To do this, click on the New button to create build definition. For the build template, select YAML and click Apply

We will then be asked to provide the build name, agent queue and path to Yaml file. Make sure, you have selected the correct repository and branch in the "Get Sources" option for the build definition.

Please note that YAML builds are only supported for Git are not supported when TFVC is used a version control repository.

Click on the Triggers tab to make sure that Continuous Integration is selected as option

Click save to save your build. Now this build is set up as a continuous integration build for your repository and is triggered with every commit.

Conclusion:

If you compare the amount of work you had to do to create yaml build, it's really a breeze as compare to TFSBuilds. There are many use cases of using YAML for your build definitions. You can set up a complete pipeline, decoratively executing each steps which can be developed and tested locally before being used in VSTS.

TFS 2017 Build - Partially succeed a build

At times, there is a need to explicitly set a Team build's result to be "Partially Successful". 

In Xaml, the way to forcibly build to set as partially successful is to set the build's "CompilationStatus" property to true and "TestStatus" to False, as shown below

<mtbwa:SetBuildProperties DisplayName="Set TestStatus to Failed so we get a PartiallySucceeded build" PropertiesToSet="TestStatus" TestStatus="[Microsoft.TeamFoundation.Build.Client.BuildPhaseStatus.Failed]" />

Setting a TFS 2017 build to partially succeed is a bit more intuitive. Simply add a powershell task with an inline script and set the task's result to "SucceededWithIssues". Make sure it's the last task in your build, so that it doesn't affect the flow of task execution. The Powershell statement is shown below

Write-Host "##vso[task.complete result=SucceededWithIssues;]DONE"

My build looks as follow

TFS 2017 Build System - Maintain last "N' builds

In my last blog post, I described retention policies in the TFS 2017 build system. I described how different it is from the the retention policies we get in XAML build system. 

One of the limitations I found in the new style retention policy is that I couldn't retain a specific number of builds for each status. We needed to do it for some builds that are triggered very frequently (once every couple of minutes) and check if there is some work to be done. If it found work, it would do it, otherwise it will reschedule a build for itself after a couple of minutes. Another scenario, where you might have a lot of builds is when you it is triggered by a commit of a very busy repository.

So, in order for us to retain only "N" builds for each status, we created a Powershell Module to clean up builds. In the module, we create a command-let that takes as parameter the name of the build, the number of builds to keep, the result filter and tag filter. Our command-let looks as following

***************************************************

.SYNOPSIS

 Cleans up all builds for the given build definition keeping the latest N number of builds where n is passed a parameter

 If a status is provided, it would only keep N builds with the given status

.DESCRIPTION

 PATCH https://{instance}/DefaultCollection/{project}/_apis/build/builds/{buildId}?api-version={version}

 Uses api-version 2.0 to update the build result

***************************************************

function Cleanup-Builds([string] $tfsCollection,

                    [string] $tfsProject,

                    [string] $buildDefinitionName,

                    [int] $numberOfBuildsToKeep = 10,

                    [string] $result="",

                    [string] $tagsFilter = "")

{

    if (${env:system.debug} -eq $true) {

        $VerbosePreference="Continue"

    }

    if ($status -eq ""){

        Write-Verbose "Deleting all but the latest $numberOfBuildsToKeep builds for definition $buildDefinitionName."

    }

    else{

        Write-Verbose "Deleting all but the latest $numberOfBuildsToKeep builds for definition $buildDefinitionName with status $status."

    }

    $buildDefinition = Find-BuildDefinition($buildDefinitionName)

    if ($buildDefinition -eq $null) {

        Write-Error "No build definition found $buildDefinitionName"

        return

    }

    $buildDefinitionId = $buildDefinition.id

    $query = [uri]::EscapeUriString("$tfsCollection$tfsProject/_apis/build/builds?api-version=2.0&definitions=$buildDefinitionId&queryOrder=2&resultFilter=$result&tagFilters=$tagsFilter&`$top=5000")

    $builds = Invoke-RestMethod -Method GET -UseDefaultCredentials -ContentType "application/json" -Uri $query

    $retainedBuild = 0

    $deletedBuildCount = 0

    for ($i = $builds.Count - 1; $i -gt -1; $i--) {

        $build = $builds.value[$i]

        $buildId = $build.id

        $buildNumber = $build.buildNumber

        

        try {

            $query = [uri]::EscapeUriString("$tfsCollection$tfsProject/_apis/build/builds/$buildId/tags?api-version=2.0")

            $tagFound = $false

            # Not delete the latest numberOfBuildsToKeep builds

            if ( ($retainedBuild -lt $numberOfBuildsToKeep)) {

                $retainedBuild = $retainedBuild + 1

            }

            else {

                Write-Verbose "Deleting build $buildNumber"

                $query = [uri]::EscapeUriString("$tfsCollection$tfsProject/_apis/build/builds/$buildId`?api-version=2.0")

                Invoke-RestMethod -Method DELETE -UseDefaultCredentials -ContentType "application/json" -Uri $query

                $deletedBuildCount = $deletedBuildCount + 1

            }

        }

        catch {

            Write-Error "StatusCode:" + $_.Exception.Response.StatusCode.value__ +

                        "`r`nStatusDescription:" + $_.Exception.Response.StatusDescription

        }

    }

        

    Write-Output "Deleted $deletedBuildCount builds for build definition $buildDefinitionName"

}

We create a PowerShell Module file for the above command let. To set up the Powershell module, we modified the PSModulePath environment variable as first step of our build to include the module path. Then to set-it all up we added a PowerShell task group calling the Cleanup-Builds command in an inline script as shown below

Our build definition looks like below

Retention Policies for TFS 2017 Build System

TFS build system has had a major overhaul since TFS 2015. For people working on team builds since TFS 2010, there is some major learning curve. One of the things the people often find confusing is the retention policy in the new build system. In earlier versions of TFS, you could specify how many builds you want to retain for each status as shown in the screenshot below

Retention Policies for Xaml Builds

The retention policy is quite obvious and you have a deterministic number of builds retained at each status. It's not quite the case in the new build system. A sample retention policy in the new system looks like following

Retention Policies for TFS Builds

So what does it mean? 

Well, to say it simply, it means exactly what it says on the tin!! In the example above, the build would keep all builds from the last 4 days and keep a minimum of 20 builds. That is if there are less than 20 builds present for the given build definition, it would keep older builds until there are a minimum of 20 builds. Lets ignore the options with the lock sign, we will come back to it later. Note there is are no maximum count. It means that you can't control how many builds you keep for your build definition. This is a major shift from earlier retention policy where the number of builds kept for a build definition was deterministic. 

When are builds actually cleaned up?

If you are using an on-premise version of TFS (I am using TFS 2017 Update 2), the builds are actually not cleaned until 3:00 AM every day. For VSTS, it happens several times in a day but the time is not deterministic. The actually explains why there is only a "Minimum to Keep" option in the retention policy.

If you have a build definitions that is triggered very frequently, you will need to find a solution of actually deleting the build definitions. I will explain it in the next post.

What about Keep For 356 days, 100 good builds?

This is the option you see below your policy in the screenshot shown above. This is in fact a TFS Project Collection wide policy and enforces the maximum retention policy. So, in the example above, you can't set "Days to Keep" to more than 365 and "Minimum to Keep" to more than 100. In fact, if you have appropriate permissions, you can change it for the entire Team Project Collection.

TFS Project Collection Retention Policy

Multiple Policies

If you want, you can add retention multiple policies for your build definition. It is very useful, if you have build definition that builds different code branches (release branches for instance). You can use the retention policies to keep different number of builds from each branch. 

Multiple Policies

If you have multiple retention policies for the same branch, the retention would be the most lenient of all the retention, so whatever retains the most builds.

In the next blog post, I will show how we are keeping a lid on the number of builds for builds which are build very frequently, every couple of minutes in our case.