Declarative, not good enough. Imperative, not enough. #18330
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Off the top:
I'll keep it straight to the point:
Just 4 limitations that makes it impossible to dynamically deploy resources that have dependencies without just spitting every aspect of each resource in the parameter or the Bicep file. And if that's the case, what use do we have of the imperative aspect of Bicep?
I know what this sounds like, and I'm sure a lot of you feel this way one way or another or to some extent. And not to neglect all the effort put into it, but Bicep in its current state with all the extra fluff is a mild convenience over ARM templates. |
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Replies: 2 comments 4 replies
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All those scenarios are actually supported using the map function: Looping over modules and resources: module someModuleLoop ...
var someVariable = map(someModuleLoop, mod => {
outputs: mod.outputs
})
// Or
var storageAccountNames = [
'${uniqueString('stAccTest')}1'
'${uniqueString('stAccTest')}2'
'${uniqueString('stAccTest')}3'
'${uniqueString('stAccTest')}4'
]
resource storageAccountLoop 'Microsoft.Storage/storageAccounts@2021-04-01' = [for name in storageAccountNames: {
name: name
location: resourceGroup().location
sku: {
name: 'Standard_LRS'
}
kind: 'StorageV2'
properties: {
accessTier: 'Hot'
}
}]
var accountEndpoints = map(storageAccountLoop, (account) => account.properties.primaryEndpoints)
output endpoints array = accountEndpointsNested loops: var myNestedLoop = flatten(map(range(0, 5), x => map(range(1, 10), y => (x * 10 ) + y)))
//Outputs all numbers from 0 to 50 in an array
output result array = myNestedLoopAs for this:
This seems like it would be covered by using modules instead. This is just my personal preference, but I would rather have many modules doing one thing (one deploying containers, another deploying databases, another creating the cosmos DB, ...) rather than having everything in a humongous expression and template that's terrible to maintain. |
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You can easily compile a resource name dynamically from parameters, variables, and expressions for a single resource hierarchy such as a storage account, it doesn't have a parent that it needs to know its id before hand. The example I provided was Cosmos accounts, dbs, and containers. You cannot deploy a container without know the parent db before hand, and you cannot deploy the db in the first place before knowing the parent account before hand. After some good hours and our dear AI chat bots I got it working and I will post the answer shortly to what I was trying to achieve but the hurdle of using all these functions just to get around nested loops is a bit too much to the point where I genuinely asked myself: why do we even need Bicep at this point (or even ARM templates for that matter)? Because if you need imperative control, we have PowerShell and .NET SDK. If you need state, Bicep 100% is not it because if you are going to fully express your state (predetermined everything), we already have JSON ARM templates (although JSON was the best option for this either imo). Why add in functions and expressions and all this extra just it would feel like a hurdle track just to get around its limitations? I would put it this way, Bicep (in its current state) is an underbaked cupcake that requires a machine to eat instead of a simple fork. |
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Honestly, the only reason you have those massive complex expressions is because you are trying to do everything in the same file. I tried to modularise everything and it is much more readable: //main.bicep
param farm object = {
id: '1'
name: 'farmName123'
}
param environment object = {
id: '1'
name: 'envName123'
}
param ring object = {
id: '1'
name: 'ringName123'
}
param accounts array = [
{
databases: [
{
containers: [
{
indexes: [
{
path: '/id/?'
type: 'Hash'
}
{
path: '/timestamp/?'
type: 'Range'
}
]
}
{
indexes: [
{
path: '/category/?'
type: 'Hash'
}
{
path: '/createdAt/?'
type: 'Range'
}
]
}
]
}
{
containers: [
{
indexes: [
{
path: '/userId/?'
type: 'Hash'
}
{
path: '/score/?'
type: 'Range'
}
]
}
{
indexes: [
{
path: '/type/?'
type: 'Hash'
}
{
path: '/updatedAt/?'
type: 'Range'
}
]
}
]
}
]
}
{
databases: [
{
containers: [
{
indexes: [
{
path: '/id/?'
type: 'Hash'
}
{
path: '/value/?'
type: 'Range'
}
]
}
{
indexes: [
{
path: '/region/?'
type: 'Hash'
}
{
path: '/timestamp/?'
type: 'Range'
}
]
}
]
}
{
containers: [
{
indexes: [
{
path: '/user/?'
type: 'Hash'
}
{
path: '/eventTime/?'
type: 'Range'
}
]
}
{
indexes: [
{
path: '/tag/?'
type: 'Hash'
}
{
path: '/created/?'
type: 'Range'
}
]
}
]
}
]
}
]
var cosmosName = 'cosmos-${farm.name}-${environment.name}-${ring.name}'
module cosmosAccountModule 'caccount.module.bicep' = [for (account, i) in accounts: {
name: 'cosmosAccountModule-${i}'
params: {
cosmosIndex: i
cosmosName: '${cosmosName}-${i}'
databasesToCreate: account.databases
}
}]//caccount.module.bicep
param cosmosName string
param cosmosIndex int
param databasesToCreate array
resource cosmosAccount 'Microsoft.DocumentDB/databaseAccounts@2025-04-15' = {
name: cosmosName
}
module databaseModule 'cdb.module.bicep' = [for (database, i) in databasesToCreate: {
name: 'databaseModule-${i}'
params: {
databaseIndex: i
cosmosName: cosmosAccount.name
containersToCreate: database.containers
}
}]
//cdb.module.bicep
param containersToCreate array
param databaseIndex int
param cosmosName string
resource cosmosAccount 'Microsoft.DocumentDB/databaseAccounts@2025-04-15' existing = {
name: cosmosName
resource sqlDatabase 'sqlDatabases@2025-04-15' = {
// Use replace function here to replace "cosmos" with "sqldb"
name: '${cosmosName}-${databaseIndex}'
}
}
module containerModule 'ccontainer.module.bicep' = [for (container, i) in containersToCreate: {
name: 'containerModule-${i}'
params: {
containerIndex: i
databaseName: cosmosAccount::sqlDatabase.name
cosmosName: cosmosName
indexes: container.indexes
}
}]
//ccontainer.module.bicep
param containerIndex int
param databaseName string
param cosmosName string
param indexes array
var compositeIndexes = map(indexes, index => {
path: index.path
order: index.type == 'Range' ? 'ascending' : 'ascending'
})
resource cosmosAccount 'Microsoft.DocumentDB/databaseAccounts@2025-04-15' existing = {
name: cosmosName
resource sqlDatabase 'sqlDatabases@2025-04-15' existing = {
name: databaseName
resource container 'containers@2025-04-15' = {
// Use replace function here to replace "sqldb" with "container"
name: '${sqlDatabase.name}-${containerIndex}'
properties: {
resource: {
id: '${sqlDatabase.name}-${containerIndex}'
partitionKey: {
paths: [
'/partitionKey'
]
kind: 'Hash'
}
indexingPolicy: {
indexingMode: 'consistent'
automatic: true
includedPaths: [
{
path: '/*'
}
]
excludedPaths: [
{
path: '/"_etag"/?'
}
]
//
compositeIndexes: compositeIndexes
}
}
}
}
}}I don't really know if it is truly 1 to 1 to what you wrote, because I don't have all the context and the original template is unreadable. But this is why we have templates. Make several small readable blocks so that anyone can easily get on and understand what is going on at a first glance. The small deployment time gain you will have from everything in one file is definitely not as important as the time loss anyone else than you will have to debug this bicep file in the future. |
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Thank you. A better approach. To summarize it, what you can't do in nested for loops, spread the loops over nested modules instead. Appreciate the time. |
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main.parameters.json See attached files:
Here is the result of a |
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See @GABRIELNGBTUC 's response. That's a more modular and manageable approach. |
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main.parameters.json
main-bicep.txt
See attached files:
main-bicep.txtis the bicep filemain.parameters.jsonis a simple parameter file represents hierarchal mapping (nested arrays) of cosmos accounts, db, and containers.Here is the result of a
WhatIfDeployment which seems to be working: