Scheduling Azure DevOps Pipelines with YAML

I had the pleasure of presenting some thoughts about developing apps for SaaS with James Crowter to the Dutch Dynamics Community yesterday. We were sharing some of our experiences of the maintenance challenge that comes with having published apps on AppSource.

How can you continuously test your apps against past, current and upcoming versions of Business Central? Perhaps two ways:

1. Slowly drive yourself to despair with the monotony of creating different versions of Business Central environments and testing manually
2. Automate as much of the tedious infrastructure and repetitive testing work as possible so you can concentrate on some fun stuff instead

We have two main reasons to trigger the execution of the pipeline for a given branch of an app in Azure DevOps:

1. We have changed some code
2. Microsoft have changed some code that we depend on

If we have changed some of our own code we should run it through the pipeline to ensure that it passes our checks, the automated tests run and that the resulting .app files are versioned and signed correctly. It is easy to overlook some of these tasks and/or inadvertently break some existing functionality when making our changes. The pipeline is there to have our back.

At the same time, Microsoft are making changes to the base and system applications that we rely on. Even if we don’t have any planned changes for our apps we may need to make some code changes to accommodate what Microsoft have done to the ground underneath our feet.

With a bit of luck we’ll see this sort of thing:

warning AL0432: Method 'FilterReservFor' is marked for removal. Reason: Replaced by ProdOrderLine.SetReservationFilters(FilterReservEntry)

warning AL0432: Method 'CreateReservEntryFor' is marked for removal. Reason: Replaced by CreateReservEntryFor(ForType, ForSubtype, ForID, ForBatchName, ForProdOrderLine, ForRefNo, ForQtyPerUOM, Quantity, QuantityBase, ForReservEntry)

We’re using a method that Microsoft are making obsolete and will be removed at some point in the future. No need to panic, but be aware that you should switch to the new method. Very civilised. Thanks.

With less luck we’ll find that Microsoft have introduced a change that breaks our app in some way – with a compilation error or unintended behaviour. Either way, it’s something that we want to know about.

Scheduling pipelines can help with that.

Typically we:

• Develop against a W1 version of the latest sandbox image, run pipelines against our latest commits against mcr.microsoft.com/businesscentral/sandbox with a continuous integration trigger
• Migrate changes backwards to BC14 and BC13 compatible versions of our apps, run pipelines against appropriate Docker images for those versions
• Have separate branches which we rebase onto the latest commit to run pipelines against bcinsider.azurecr.io/bcsandbox and bcinsider.azurecr.io/bcsandbox-master with a schedule

The continuous integration trigger is straightforward enough. At the top of our .azure-pipelines.yml we have:

trigger:
  - '*'

The schedule is defined in a separate section of the yml file, like this:

schedules:
  - cron: 0 3 * * Sun
    displayName: Schedule insider builds
    branches:
      include: ['build/insider', 'build/insider-master']
    always: true

Those branches are the ones that are set to build against the insider Docker images. I hadn’t come across cron before, but it’s pretty simple. The schedule is defined as:

• Minute
• Hour
• Day of month
• Month
• Day of week

Our schedule comes out as 03:00 every Sunday. Asterisks stand for any value. https://crontab.guru/ is useful for getting your head around the format.

The branches key defines which branches are included in the schedule and the always indicates that we always want to run the pipeline, even if there haven’t been any code changes since it was last run.