I was working with a CloudFormation i want to use multiple intrinsic function together so i tried and shared bellow:
Introduction:
AWS CloudFormation is a powerful infrastructure-as-code service that allows you to define and deploy cloud resources in a repeatable and automated manner One unique feature that CloudFormation offers is Fn::Sub, It allows you to replace variables in a string with their corresponding values. This is very useful for dynamically generating resource names, URLs, and other values based on the current context of the CloudFormation stack.
Fn::Sub Function
The Fn::Sub function replaces variables in the input string with specified values. You can use the Fn::Sub function to replace supported functions such as Fn::FindInMap, Fn::ImportValue, or to replace variables in the input string. The syntax for the Fn::Sub function is:
{ "Fn::Sub" : [ String, { Var1Name: Var1Value, Var2Name: Var2Value } ] }The first parameter is a string containing the variables to be assigned. The second parameter is an object that specifies the name and value of each variable to be assigned. Let's take a look at some examples of using the Fn::Sub function in functions that support it.
Usage of Fn::Sub with Fn::FindInMap function
The Fn::FindInMap function returns the value corresponding to the specified key in the specified map. The Fn::FindInMap function has the following syntax:
{ "Fn::FindInMap" : [ MapName, TopLevelKey, SecondLevelKey ] }In the following example, the Fn::Sub and Fn::FindInMap functions are used to substitute the variable log_group_name with the value of the mapping result:
{
"Mappings": {
"LogGroupMapping": {
"Test": {
"Name": "test_log_group"
},
"Prod": {
"Name": "prod_log_group"
}
}
},
"Resources": {
"myLogGroup": {
"Type": "AWS::Logs::LogGroup",
"Properties": {
"LogGroupName": {
"Fn::Sub": [
"cloud_watch_${log_group_name}",
{
"log_group_name": {
"Fn::FindInMap": [
"LogGroupMapping",
"Test",
"Name"
]
}
}
]
}
}
}
}
}This example uses the Fn::FindInMap function to find the "Name" value in the "LogGroupMapping" map. Then use the Fn::Sub function to replace the log_group_name variable with the resulting value of the mapping.
Usage of Fn::Sub with Fn::ImportValue function
The Fn::ImportValue function returns the value of an exported output from another CloudFormation stack. The syntax for the Fn::ImportValue function is:
{ "Fn::ImportValue" : "exported-output-name" }
The following example uses the Fn::Sub function with the Fn::ImportValue function to replace the Domain variable with a value derived from the imported value.
{
"Resources": {
"DNS": {
"Type": "AWS::Route53::HostedZone",
"Properties": {
"Name": {
"Fn::Sub": [
"www.${Domain}",
{
"Domain": {
"Fn::ImportValue": "DomainName"
}
}
]
}
}
}
}
}
``Reference:
https://aws.amazon.com/premiumsupport/knowledge-center/cloudformation-fn-sub-function/
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