Templating

awsdac supports the Go standard text/template package. To process templates in this format, enable the -t (--template) flag in awsdac command. When this flag is enabled, awsdac first expands the strings in the file as a template, and then processes it as a YAML file. Therefore, to create a template, you need to be aware of the expanded YAML format, so it is a slightly advanced feature. However, text/template allows repetition, variable expansion, and conditional branching, which can compress lines of code and we can provide more flexibility in custom functions. To use templating, run awsdac -t <template>

Custom functions

awsdac defines the following custom functions. The custom functions are defined in custom-func.go.

• seq a - Return an array containing the values 0 through a-1
• add a b - Returns the result of a + b
• mul a b - Returns the result of a × b
• mkarr a b ... - Returns an array of the given elements. [a, b, ...]

Examples

Repetition

You can execute a block repeatedly with index.

    {{- range $i := seq 3}}
    VPC{{$i}}:
      Type: AWS::EC2::VPC
      Title: "VPC"
      Children:
        - VPC{{$i}}AvailabilityZone0
        - VPC{{$i}}AvailabilityZone1
    {{- end}}

This template will expand to the following YAML:

    VPC0:
      Type: AWS::EC2::VPC
      Title: "VPC"
      Children:
        - VPC0AvailabilityZone0
        - VPC0AvailabilityZone1
    VPC1:
      Type: AWS::EC2::VPC
      Title: "VPC"
      Children:
        - VPC1AvailabilityZone0
        - VPC1AvailabilityZone1
    VPC2:
      Type: AWS::EC2::VPC
      Title: "VPC"
      Children:
        - VPC2AvailabilityZone0
        - VPC2AvailabilityZone1

if you want to use 1-indexed iteration, you can use below with add func

    {{- range $i := seq 3}}{{$vpc := (add $i 1)}}
    VPC{{$vpc}}:
      Type: AWS::EC2::VPC
      Title: "VPC"
      Children:
        - VPC{{$vpc}}AvailabilityZone1
        - VPC{{$vpc}}AvailabilityZone2
    {{- end}}