3.1.5. Custom Jinja functions.md

Custom Jinja functions

With Jinja you get to inject your own custom functions to be used in templating, so of course we do.

The variable function

With the variable function you can fetch any variable value off any other layer in your repository.

Example 1: fetching a vpc_id variable from the same layer in a different stack

# stacks/ec2/stack.tfvars.jinja:
vpc_id = "{{ variable("vpc_id", stack="vpc") }}"

Example 2: fetching a vpc_id variable from a different environment in a different stack

# stacks/ec2/layers/development/layer.tfvars.jinja:
vpc_id = "{{ variable("vpc_id", stack="vpc", environment="production") }}"

Example 3: full example

# stacks/ec2/layers/development@us-east-1_foo/layer.tfvars.jinja:
vpc_id = "{{ variable("vpc_id", stack="vpc", environment="development", subenvironment="us-east-1", instance="foo") }}"  # stack/environment/subenvironment/instance all default to the caller's

The output function

With the output function you can fetch any output value off the state of any other layer in your repository.

Example 1: fetching a vpc_id output from the same layer in a different stack

# stacks/ec2/stack.tfvars.jinja:
vpc_id = "{{ output("vpc_id", stack="vpc") }}"

The resource function

With the resource function you can fetch any resource attributes off the state of any other layer in your repository.

Example 1: fetching a aws_vpc.main resource from the same layer in a different stack

# stacks/ec2/stack.tfvars.jinja:
vpc_id = "{{ resource("aws_vpc.main", stack="vpc")["id"] }}"

The md5, sha1, sha256 and sha512 functions

With these functions you can generate the MD5, SHA-1, SHA-256 and SHA-512 checksums respectively of a given string.

Example

# stacks/ec2/stacks.tfvars.jinja
foo_md5 = "{{ md5("foo") }}"