How to handle dependencies in Bicep

Sajal Choudhary -

Bicep deploys resources in parallel. Which is what you might want as that is faster. However, there might be dependencies. I came across this while creating the environment needed for this exercise. It was basically a lab on vnet-peering.
What I needed to create was this:

In 2 regions,

    1. 3 VNets
    2. 3 VMs in these 3 VNets

In this scenario, there are dependencies. To create the VM you need the VNet, and the VNIC which would be attached to the VM, among other things.
When I started deploying it initially without defining dependencies, it failed to create the VNIC as the VNET was not deployed yet.

There are two ways to handle dependencies in bicep:

  1. Implicit
  2. Explicit

An implicit dependency is created when a resource declaration references another resource in its definition.
To specify an explicit dependency you use the dependsOn keyword.
PowerShell is a faster and simpler (at least to me) way to create these resources. But it is a better way in case of one-off things. If you want to deploy resources again and again IaC tools (bicep) are a better option. Using bicep would ensure that I could deploy the same resources with certainty. There would be no drift. Plus, I would get to learn Bicep.

So, I built the template from scratch. The code is kept here.