Bicep | Use parameters optionally in template

Alok Maheshwari 1

Hi team,

I create a bicep template for backup policy, the template i have created has all 4 types of retention configured (daily, weekly, monthly, yearly). all of the required inputs for all 4 retentions are parameterized (i.e. backup retention, schedule etc. ).

now if i want to use the same template to only configure a policy that has daily backups or Weekly backups how can i use the same template?

I tried using existing template and it was obvious that i didnt provide inputs for monthly and yearly retention, i got an error.

if i want to do the same with powershell, i can mark those parameters optional. that way i dont have to provide an input for those.

1 answer

AnuragSingh-MSFT 21,361 Reputation points

2021-11-15T09:53:39.45+00:00

Hi @Alok Maheshwari ,

Welcome to Microsoft Q&A! Thanks for posting the question.

You may use a combination of following features of Bicep to add conditional logic to your template:
1. Deploy Conditon - This helps you to conditionally deploy resource.
2. Default Values of Parameters - The default value is used when a value is not provided during deployment.

Here are some Microsoft learn modules to help you understand it in detail:

1. Build flexible Bicep templates by using conditions and loops
2. Add flexibility by using parameters and variables

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AnuragSingh-MSFT 21,361 Reputation points

2021-11-18T07:15:54.883+00:00

Hi @Alok Maheshwari , I wanted to check if you had a chance to review my answer above. Please let me know if you have any queries or concerns.
Please 'Accept as answer' if it helped so that it can help others in the community looking for help on similar topics

Alok Maheshwari 1 Reputation point

2022-01-23T06:31:04.39+00:00

Hi Anurag,

Thanks for the response.

i reviewed the options you suggested but i am not clear about them how they can help me. taking another example to explain:

Requirement of the template:

should create two VM's

either these Vm's should be a part of availability set or zone <depends on user input>

so i create a template with parameters
param avzonerequired string
param avsetrequired string

with this requirement, what are my options to have both the parameters specified in the same template. currently, if i specify both the parameters in the tempalate and run the templateand provide input only for one parameter, deploymet ask me value for another parameter.

if i specify a default value for one of the parameters or in my case i have to specify a default value for both the parameters, template will still fail coz a vm can either be a part of avs or avz.

i come across this situation in many examples however now sure how this can be achieved. currently i have created two different templates and a powershell script on top of it.

powershell script will read the value of the input provided by user for following parameters and will execute the relevant template that has code only for avz or avs.

param avzonerequired string
param avsetrequired string

AnuragSingh-MSFT 21,361 Reputation points

2022-01-28T08:38:38.473+00:00

@Alok Maheshwari , thank you for the clarification.
The conditional deployment feature of Bicep can help here. For example, consider the New or Existing resource scenario available here. A similar parameter specifying the deployment criteria (either Aavailability Zone OR Availability Set) can be used and only that resource gets deployed.

In the scenario mentioned in your post above, I can foresee that the generated template would have a couple of hundred lines. To be able to maintain it modularly, the current solution of branching using PowerShell script also looks good.
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