The extensionResourceId function is available in Bicep files, but typically you don't need it. Currently only user-assigned managed identities are supported. When the value is false, the resource isn't created. Updating an Azure API Management instance after initial creation will lock your API Management against any updates. You access the existing resource's properties through its symbolic name. The value can only be applied to the whole resource or module. Need the ability to check if a secret exists and use it if it does, if it doesn't, want to create it with a default value and use it (rather than fail the deployment) The most succinct way to reference a child resource is by specifying childs full type and including parents name like shown in the code snippet below. If your script fails the role assignments will not be properly cleaned up. The process of finding a specific item within an array of objects should be straightforward in any programming language. Just note that we as always use existing keyword and the name consists of two sections separated by slash /. It was, however, difficult to perform, Azure Virtual Desktops gold Image windows update automation was one of the most interesting challenges I got within the last few months. For explicit dependencies, Azure Resource Manager automatically removes it from the required dependencies when the resource isn't deployed. Having a stack of VMs (Virtual Machines) unnecessarily, This article describes how to add authentication for a Vimeo account to an Azure AD B2C custom policy. contains contains (container, itemToFind) Checks whether an array contains a value, an object contains a key, or a string contains a substring. Use the existing keyword when you're deploying a resource that needs to get a value from an existing resource. The first two sections cover important information which will be used throughout the post, In order to authorise access to the Key Vault assets, you apply RBAC on the Key Vault and grant access to API Managements managed identity. The code above is equivalent to the bicep code we already discussed. For example, the DNS name for a v1 or v2 storage account will be the same, such as contoso.blob.core.windows.net . I think theres no doubt that referencing resources through symbolic names is easier and handier. Not surprisingly, we often want similar capabilities while working with Azure Bicep. New or existing resource Runtime functions Complete mode Next steps Sometimes you need to optionally deploy a resource in an Azure Resource Manager template (ARM template). It checks if the given tag exists on the resource group. In the following example stg is a symbolic name. Here is a slight variation of the previous case which leverages Biceps feature of declaring child resources inside of a parent. The properties are available through the symbolic name. PowerShell, bash) or tooling (e.g. Use the condition element to specify whether the resource is deployed. The next example conditionally deploys a module. Build the ARM template from the bicep file. However, when testing if an object contains a key, the comparison is case-insensitive. Use the conditional expression ? The following example shows how to either deploy a new storage account or use an existing storage account. Use the if keyword to specify whether the resource or module is deployed. A solution is to wire multiple deployment steps together in scripts or deployment pipelines, and use Azure CLI or other means to check whether resources exist. resource secret 'Microsoft.KeyVault/vaults/secrets@2019-09-01' = if (!contains (resourceGroup ()).tags, 'keyVaultSecretName')) { . My biggest objection against baking in all this logic into pipelines is portability. When the value is true, the resource is created. Although not so much related to idempotency, in this case you want to be able to check API Management exists prior to any Azure resource deployments. Use the existing keyword when you're deploying a resource that needs to get a value from an existing resource. Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. The same holds for Azure Web Apps (formerly Azure Web Sites), where you would have a DNS name such as contoso.azurewebsites.net . Solution 1: Bicep template requiring user-assigned managed identity The script below requires you to provide the resource ID of the user-assigned managed identity which sufficient (Reader) permissions in the resource group to check for resource -existence. Creating an App Service or Function App instance via ARM or Bicep templates is easy. Examples The following example shows how to use the if function. But what happens if you (accidentally) deploy your template again after an actual application has been deployed into your App Service? In new resource group, we can create new Vnet and other resources. The last section is about using the well-known reference function in Bicep, just in case you really want to. The following example template shows how to use this function with expressions that are only conditionally valid. In Bicep referencing existing resource in the same resource group is easy and clean: If we have another template which is deployed in the scope of another resource group but still in the same subscription, then we can use resourceGroup function to specify the correct scope. The basic format of the resource ID returned by this function is: JSON {scope}/providers/ {extensionResourceProviderNamespace}/ {extensionResourceType}/ {extensionResourceName} ARM template reference function can also be used, however, it is less recommended. If exists, then retrieve the NSG using existing keyword and pass it to SQLMI. Not surprisingly, we often want similar capabilities while working with Azure Bicep. This chicken and egg problem arises in many situations where a system-assigned managed identity is used in combination with a Key Vault. Regardless of whether youre using ARM templates or the intermediate language Bicep, resource management operations will result in the same state of your resources time after time you deploy them. Some of the following sections will use scope property to correctly reference an existing resource. Ill present you with two different options for the check if resource exists solutions. Architecture The following diagram illustrates the authentication, Arinco trades as Arinco (VIC) Pty Ltdand Arinco (NSW) Pty Ltd, Level 9, 360 Collins Street,Melbourne VIC 3000. ARM does not have the ability to check if a resource exists, despite some. This comes into play when we want to reference a resource in a different scope. This could lead to undesirable behaviour, like accidentally wiping your App Configuration settings and thereby taking your whole application offline as a result. In the case of Windows PowerShell, executing az appservice plan list lists all the App Service Plan under your current . This does not work, because the resourceId function does not actually check if a resource exists, it simply returns what the ID would be for the given resource group, type and name. The idempotency of your ARM templates does not form any issue, but the fact your API Management instance is temporarily unavailable for your API developers might cause some upset developers and lead to unnecessary loss of productivity. When creating an Azure API Management instance, its possible to reference Key Vault certificates for the purpose of TLS encryption on your own custom domains. You access the existing resource's properties through its symbolic name. I'll present you with two different options for the 'check if resource exists' solutions. This article describes the Bicep functions for working with objects. Check the name and scope of the resource you're trying to reference. This leads to execution errors upon the next time youll deploy the template. The script returns a boolean value indicating if the resource exists, or not. The storage account is deployed. The value for the condition resolves to true or false. You get an error if the function refers to a resource that doesn't exist. Reader to check if a resource exists) for this identity in your target subscription or resource group. As a result, we want to return secretUriWithVersion in template deployment output. There are some cases where you may want to desire a different outcome depending on current state. Note that there are no [] around function invocation. This approach leverages parent property which can be passed when declaring symbolic name for the child resource. For example, you can reference a resource that exists under one condition but not under the other condition. In this section we will explore multiple ways how to reference an existing child resource in Bicep. After being declared, stg can be used to retrieve information about the resource. If you have no issue with having a user-assigned managed identity floating around in your Azure subscription I tend to opt for solution 1. Moreover, under the hood Bicep just compiles all the examples above to the correct use of reference function. When the value is true, the resource is created. Conditions may be used with dependency declarations. Use the if keyword to specify whether the resource or module is deployed. The value for the condition resolves to true or false. This is required when we want to make incremental changes to an existing instance. Lets illustrate this on an example of a Key Vault and a secret. However, when newOrExisting is set to existing, the condition evaluates to false and the storage account isn't deployed. Conditional deployment doesn't cascade to child resources. symbolic names along with existing keyword and scope property allow working with resources not defined in the same template and also enable advanced scenarios which are discussed later. Instead, use the symbolic name for the resource and access the id property. Ive written a post about reference function and theres a dedicated section to referencing existing resources. As we will see, Bicep not only allows using the existing reference function but provides even more convenient and clear syntax to achieve that. Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. The resulting ARM template is similar to the one from the previous section but now we specify subscriptionId explicitly. Not only does the script run faster than solution 2, but it proved to be more reliable than solution 2. We can use the output of these scripts within the ARM template itself. Although this behaviour is desirable most of the time, there are always exceptions to the rule. For the syntax to deploy a resource, see Resource declaration in Bicep. The resource isn't redeployed when referenced with the existing keyword. Now, lets assume that we deploy a separate template in the scope of the same resource group and want to get blob primary endpoint. The script below operates similarly to the script above, with the exception of not having to provide an identity. The following example gets an existing storage account in the same resource group as the current deployment. Set up necessary authentication and authorization so that script can access information about resources in Azure. Deployment scripts run in Azure container instances; its lifecycle is fully managed by Azure so theres no additional infrastructure required to be set up. The string comparison is case-sensitive. Azure/bicep (github.com), At the end of the script, set pipeline variable to hold the information if resource exists, see, Use the pipeline variable from the previous step to pass value for the parameter. As of May 2022, Azure Bicep does not provide a built-in way to check if a resource exists, however, the approaches described in this post provide a workaround which can be helpful in your use case. In the previous section we deployed a simple storage account. One of the many benefits of Azure Resource Manager operations is the fact theyre idempotent. When executing Azure CLI or PowerShell commands, your script will have to authenticate itself to Azure again since deployment scripts dont run under the identity of the execution host (theyre running remotely in ACI). I hope the solutions above provide you with a workable solution whilst a native ARM/Bicep solution isnt around. The downside to this is that it will lead to very lengthy deployment times when you run your templates for the second time, which is common in IaC CI/CD scenarios. If you would rather learn about conditions through step-by-step guidance, see Build flexible Bicep templates by using conditions and loops. The script created a managed identity and pauses for a minute in order for the user-assigned managed identity becomes available for role assignment. Please find an example below. Lets start with the most basic and simple case where we want to retrieve properties of a resource which is deployed in the same template. More info about Internet Explorer and Microsoft Edge, Build flexible Bicep templates by using conditions and loops, For recommendations about creating Bicep files, see, To create multiple instances of a resource, see. An example of conditionally evaluating expressions is shown in the following section. Get started on the right path to cloud success today. See the docs for more - learn.microsoft.com/en-us/azure/azure-resource-manager/ - David Gard Sep 5, 2019 at 10:04 4 You can pass in a parameter value that indicates whether a resource is deployed. Small notes: As already mentioned, each resource in Bicep has a symbolic name which is used to reference the resource. The exists keyword is to get a symbolic reference to a known, previously deployed resource and one that you do not intend to update as part of this deployment. To reference an existing resource that isn't deployed in your current Bicep file, declare the resource with the existing keyword. Code can be foundhereThe module can be incorporated into your Bicep template in the same way as the script outlined in Solution 1. Sometimes you need to optionally deploy a resource or module in Bicep. Below is an example how to get the primary endpoint for blob of a storage account that we just deployed. Referencing existing resources in Bicep is achieved by declaring a symbolic name for the existing resource and using it to retrieve needed properties. Share Improve this answer Follow answered Jan 11 at 19:51 Ihor Indyk 1 1 1 Add a comment Your Answer Instead of a simple, single deployment template that can be deployed from anywhere, youre now composing a solution that consists of several dependent components and needs to be wired up by a language (e.g. This might be useful to get FQDNs, properties, managed identity info. I wont go into great detail on deployment scripts in this blog (more info here), but in essence they allow you to perform Azure PowerShell or Azure CLI scripts within an ARM resource deployment. The following examples assume that we have a Key Vault kv-contoso and a secret someSecret in it. Property scope allows specifying where this existing resource lives. To illustrate this, take a look at the following example where reference function is directly used to retrieve needed property. The script returns a boolean value indicating if the >resource exists, or not. The value for the condition resolves to true or false. The bicep file above mainly boils down to the following expression which is significantly harder to understand. Using the module in your Bicep template is demonstrated in below parent and dependent template snippets: In order to test your Bicep template simply perform a resource deployment on your resource group, e.g.az deployment group create resource-group myresourcegroup template-file test.bicep, Solution 2: Bicep template with automatic user-assigned managed identity lifecycle management. Microsoft.Storage/storageAccounts@2021-02-01, // Using stg to get property of a resource, "[reference(resourceId('Microsoft.Storage/storageAccounts', 'stcontoso'), '2021-02-01', 'full').kind]", // Returns https://stcontosoo.blob.core.windows.net/, // Creating a symbolic name for an existing resource, // Resource group where the storage account exists, "[reference(extensionResourceId(format('/subscriptions/{0}/resourceGroups/{1}', subscription().subscriptionId, parameters('storageResourceGroupName')), 'Microsoft.Storage/storageAccounts', parameters('storageAccountName')), '2021-02-01').primaryEndpoints.blob]", Microsoft.KeyVault/vaults/secrets@2019-09-01, // https://kv-contoso.vault.azure.net/secrets/someSecret/2cdd92336f0a4a0a80bbbbdf9af8407d, Symbolic Name and State Object of a Resource, Reference Resource Deployed In The Same Template, Reference Existing Resource In The Same Resource Group, Reference Existing Resource In a Different Resource Group, Reference Existing Resource In a Different Resource Group and Subscription, declaring child resources inside of a parent, Parameters In Azure Bicep - Ultimate Guide With Examples, Variables In Azure Bicep - From Basics To Advanced, Learn Modules In Azure Bicep - Basics To Advanced, How It Works, Nested Modules, Outputs, Scopes, Child Resources In Azure Bicep - 3 Ways To Declare, Loops, Conditions, Create Resource Group With Azure Bicep and Deploy Resources In It, 5 Ways To Deploy Bicep File With Parameters - Azure DevOps, PowerShell, CLI, Portal, Cloud Shell, Using Key Vault Secrets As Secure Parameters In Azure Bicep - Template & Module Inputs, Deploy Azure Bicep In YAML and Classic Release Pipelines (CI/CD) - Azure DevOps, Reference() Function Explained With Examples - ARM Template, Symbolic name declaration from Bicep doesnt have any equivalent in the ARM template, It is optional, if not specified, default value will be applied, Each resource type has its permitted scope, for example, storage account only accepts, Symbolic name declaration contains keyword. Reference New Or Existing Resource In Azure Bicep In a traditional ARM template reference function provides capability to retrieve runtime state object of a resource. The following example references an existing storage account in a different resource group. Set the scope property to access a resource in a different scope. This is obvious when we deploy the resource in the same Bicep file. When the value is false, the resource isn't created. It might come in handy when we want to retrieve some properties both from parent and child resources like shown in the example below. There is no concept of an "existence check" in bicep. Note that to access child resource symbolic name, we need to use :: operator. The above code gets compiled into the ARM template section below. For more information about setting the scope, see Scope functions for Bicep. 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