Azure DevOps Hidden Gems #6 – Use the Manual Intervention Task to Pause a Stage of the Release Pipeline

Posted by Graham Smith on September 17, 2019No Comments (click here to comment)

I've been working with Azure DevOps quite a lot recently (having used its predecessors for many years) and I'm constantly amazed by features I never knew existed or which I vaguely knew existed but hadn't fully appreciated. In this blog post series I'm attempting to shine a light on some of these hidden gems for the benefit of others. The full list of posts is here and if you have any suggestions for other posts please leave a comment!

If you've created a release pipeline in Azure DevOps you probably know that there is rich functionality for approvals and gates to control a deployment between stages of the pipeline. Approvals are as you would imagine: a requirement for one or more people to approve either that a release stage is allowed to proceed or that a release stage has completed successfully. Gates are slightly different. From the docs: "Gates allow you to configure automated calls to external services, where the results are used to approve or reject a deployment. You can use gates to ensure that the release meets a wide range or criteria, without requiring user intervention.":

That's all well and good for controlling the deployment between stages of a pipeline. But what if you need to control the flow within a stage of a pipeline?

A colleague and I had this requirement recently when designing a release pipeline to manage the creation and updating of resources in Azure using Terraform, the cross-platform infrastructure as code technology from HashiCorp. One of the useful features of Terrafrom is the ability to call a command that will work out which resources are going to be created, destroyed or updated for a given Terraform configuration. A bit like the -WhatIf parameter in PowerShell if you are familiar with that. The problem in our scenario is that we need to halt the pipeline part way through a stage so someone can look at what Terraform is about to do and decide if it makes sense, and abort the stage if it doesn't. There is a solution of course, and it's the Manual Intervention task.

The task is simplicity itself to use, although it does need to run in the context of an Agentless job. Don't forget to add this or you will search in vain for the Manual Intervention task:

With the Manual Intervention task added to the Agentless job it's just a matter of setting a few properties:

When the pipeline is running it halts at the Manual Intervention task and waits for an intervention to either Resume or Reject the release:

If you weren't aware of this task you might be tempted to split a stage in to two stages to handle this scenario. Whilst this would probably work to my mind it's messy and inelegant and you should certainly check out the Manual Intervention task first.

Hope this helps!

Cheers -- Graham