This is a quick follow up to this post. If you want an intro to building AL apps for Business Central you might want to check that out first.

In order to build your apps you need a build agent running somewhere which will listen for new jobs and run the scripts, create the Docker containers, run the tests or do whatever else you define in the build file.

You can install an agent on your own server somewhere and authenticate with a personal access token. You’re in charge of the hardware, install agents and scale the performance as you see fit.

Hosting

The alternative is to choose one of the hosted agents that Microsoft provide. The obvious attraction is that you don’t need to maintain any hardware. You just specify the type of machine (Ubuntu, Mac, Windows) that you want the job to run on and pay-as-you-go. Or possibly, don’t pay at all.

With the free tier of Azure DevOps you get:

  • One build job running at a time (other jobs will be queued until that has finished)
  • 1,800 minutes of build time per month

That’s cool. You can keep tabs on your usage and purchase more parallel jobs from here: https://dev.azure.com/<your organisation>/settings/buildqueue?_a=concurrentJobs

If you hit the limits of the free tier you can check out the cost of more jobs here: https://azure.microsoft.com/en-us/pricing/details/devops/azure-devops-services/. At the time of writing 40 USD gets you a second concurrent job and lifts the build minutes per month restriction to unlimited.

Self-Hosting

So…why would you not run on hosted agents? Cost is a consideration. Additional parallel jobs on self-hosted agents are only 15 USD per month. But, what’s 25 dollars per month between friends? That’s assuming you can’t live within the limits of the free tier. If you can then using hosted agents is free.

The main consideration as far as I can see is performance. If you are going to create a Docker container as part of your build (and if you aren’t then I’m not sure what you’re doing) then self-hosted agents are always going to have an advantage. You can have the right Docker image ready downloaded before the build begins but a hosted agent will always needs to download it first.

Our builds, running on a self-hosted agent, typically take between 8 and 15 minutes to complete, depending on how many tests are included in the build. Using the “Hosted Windows 2019 with VS2019” agent pool a test build (which just creates the downloads the Docker image and creates the container) takes around 18 minutes – pulling the latest production sandbox image.

NavContainerHelper is version 0.6.2.3
Host is Microsoft Windows Server 2019 Datacenter - ltsc2019
Docker Client Version is 18.09.6
Docker Server Version is 18.09.6
Pulling image mcr.microsoft.com/businesscentral/sandbox:latest-ltsc2019
latest-ltsc2019: Pulling from businesscentral/sandbox

Add in some time to actually build and publish the app, run the tests and upload the results and we’re probably looking closer to 25 minutes for the whole thing.

I’ll leave it up to you to decide whether you care enough about that performance difference to host build agents yourself. Then again, 1800 / 25 = 72 builds per month before you need to consider paying for more. Maybe that’s all you need? Especially if you’re just getting started with Azure DevOps, builds, YAML and all that jazz…