Monday, 23 July 2018

Creating VSTS Service Hooks with PowerShell using the REST API

Service Hooks are Visual Studio Team Services way of integrating with other web applications by automatically sending them events when specific things happen in VSTS, like a build completes or code is committed.

These are what I used in my earlier post about integrating VSTS with TeamCity. If you just have one service hook to set up then using the web UI is fine, but if you find yourself doing something again and again then finding a way to automate it can be really useful.

Interacting with service hooks via VSTS REST API is documented here. Web Hooks are a particular service hook 'consumer' suitable for sending HTTP messages to any web endpoint.

I'm going to create a PowerShell script which requires the following parameters

Param(
   [string]$vstsAccount,
   [string]$projectName,
   [string]$repositoryName,
   [string]$token
)

Using the VSTS APIs requires authentication, so the first thing is to encode a Personal Access Token (PAT) so it can be set as a HTTP header. (You create PATs from the Web UI by clicking on your profile picture and selecting Security)

$base64AuthInfo = [Convert]::ToBase64String([Text.Encoding]::ASCII.GetBytes(("{0}:{1}" -f "",$token)))

There's a whole lot of VSTS events that you can choose as a trigger when creating a service hook. In this example, I'm interested in being notified when a Git pull request is created. In order to use this particular API, I need to also know the ids of the VSTS Project and Repository that I want this service hook associated with. I'll use API calls to find those out.

$uri = "https://$($vstsAccount).visualstudio.com/_apis/projects?api-version=5.0-preview.1"
$result = Invoke-RestMethod -Uri $uri -Method Get -ContentType "application/json" -Headers @{Authorization=("Basic {0}" -f $base64AuthInfo)}

$projectId = $result.value | Where-Object { $_.name -eq $projectName } | Select-Object -ExpandProperty id

$uri = "https://$($vstsAccount).visualstudio.com/_apis/git/repositories?api-version=5.0-preview.1"
$result = Invoke-RestMethod -Uri $uri -Method Get -ContentType "application/json" -Headers @{Authorization=("Basic {0}" -f $base64AuthInfo)}

$repositoryId = $result.value | Where-Object { $_.name -eq "$repositoryName" } | Select-Object -ExpandProperty id

As far as the REST API is concerned, we're creating a new 'subscription'. Create operations use a POST and usually also require JSON data to be sent in the body. We'll use PowerShell to model the data and then convert it back to a JSON string:

$body = @{
    "publisherId" = "tfs"
    "eventType" = "git.pullrequest.created"
    "resourceVersion" = "1.0"
    "consumerId" = "webHooks"
    "consumerActionId" = "httpRequest"
    "publisherInputs" = @{
        "projectId" = $projectId
        "repository" = $repositoryId
        "branch" = ""
        "pullrequestCreatedBy" = ""
        "pullrequestReviewersContains" = ""
    }
    "consumerInputs" = @{
        "url" = "https://servicetonotify"
        "basicAuthUsername" = ""
        "basicAuthPassword" = ""
        "resourceDetailsToSend" = "all"
        "messagesToSend" = "none"
        "detailedMessagesToSend" = "none"
    }
}

$bodyJson = $body | ConvertTo-Json

Obviously you will need to customise the url value to point to your particular web service that should be notified. If that service requires authentication, you can supply a username and password in the basicAuthUsername and basicAuthPassword values. You can also control what detailed information VSTS will send to by setting the three *ToSend values. In my case I only needed resourceDetailsToSend but not the other two.

$uri = "https://$($vstsAccount).visualstudio.com/_apis/hooks/subscriptions?api-version=5.0-preview.1"
Invoke-RestMethod -Uri $uri -Method Post -ContentType "application/json" -Headers @{Authorization=("Basic {0}" -f $base64AuthInfo)} -Body $bodyJson

Using the VSTS REST API is pretty straight forward, and gives you great access to query and modify your VSTS environment.

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