Terraform Modules/Workspaces

Question 1

What to use terraform modules?

Answer 1

Aimed at reducing repetition, reduce possible changes due to provider updates, lack of standardization, difficult to manage, and difficult for devs to use.

Question 2

How do you reference modules in Terraform?

Answer 2

module “name” {}

*The module block must contain source argument that contains location to the referenced module.

Question 3

Are there some infrastructure resources that you can directly use a module calling code and the entire infrastructure will be created for you? If so what’s an example

Answer 3

Yes

Ex: ec2-instance

Question 4

Whats an example of a module that requires additional input before completing?

Answer 4

module “eks” will throw an error because it requires additional details.

Ex: the EKS module requires subnet ID’s and a cluster name. Once submitted, the terraform plan will complete.

Question 5

Can module structures be different

Answer 5

Yes, some module pages in GitHub can contain multiple sets of modules together for different features.

Question 6

What’s the criteria on which module you should download/use?

Answer 6

1. Check the # of downloads.
2. Check GitHub Page of Modules for information related to contributors, recent changes, and pending issues being worked on.
3. Avoid modules maintained/written by individual participant (changes/updates might not be fixed in timely manner)
4. Analyze module documentation
5. Check version history of module (indicates updates occurring/not occurring)
6. Analyze the code (look for clean/well structured code)
7. Community feedback (# of stars and forks)
8. Modules maintained by hashicorp partner.

Question 7

Should you try random Terraform modules that arent actively maintained and look shady (primarily by sole individual contributors)

Answer 7

Absolutely not as it could contain malicious code that sends info about your environment to a hacker.

Question 8

What modules do orgs use?

Answer 8

They mostly have private modules, creating forks from strong modules , and modifying them to their use case.

Question 9

Whats the structure of a module if you create your own?

Answer 9

1. First, a base “modules” folder.
2. a sub-folder containing name for each module.
3. Each sub-folder contains the actual module terraform code that other projects can reference (ex. main.tf)

Question 10

How is a module referenced using a local path?

Answer 10

Local parts are used to reference to modules that are available in local file system.

A local path must begin with either ./ or ../ to indicate that its a local path.

module ec2 {}
source = “../modules/ec2”

Question 11

How is a module referenced using a git respository?

Answer 11

source = “git::https://example.com/vpc.git”

Question 12

Can a specific module have multiple versions?

Answer 12

Yes, you can reference specific versions with the version block

module “eks” {
source = ..
version = ..
}

Question 13

What are challenges with module code?

Answer 13

1. Hardcoded values (if dev is calling modules, he will have to stick with same values. AVOID if possible
   * Dev can’t override values
2. Provider improvements; avoid hardcoding region in the module code.
   Fix: use required_provider block with version constraints for module to work

Question 14

Whats the workout around for hardcoded values in modules?

Answer 14

Use variables to allow the value to be overrided.

Ex:
ami = var.ami
instance_type = var.instance_type

Question 15

Whats the workout around hardcoded provider blocks?

Answer 15

Make use of required_providers block
*In doing so you can set a version requirement where the current code is working.

Question 16

Module outputs, what are they?

Answer 16

They make info about your infra available on the cmd line, and can expose info for other terraform configs to use.

Question 17

If you want to create a source that has independency on an infrastructure created through a module, you won’t be able to implicitly it without what?

Answer 17

The use of output values.

Ensure to include output, values in the module code for better flexibility and integration with other resources and projects.

Format: module.module.outputnamee

Question 18

Whats the difference between root module and child module?

Answer 18

Root modules reside in the main working directory of your terraform configuration. this is the entry point for your infrastructure definition.

Child modules are modules that have been called by another module.

Question 19

What is the standard module structure?

Answer 19

The standard structure is a file and directory layout Hashicorp recommends for reusable modules.

Question 20

Whats the minimum recommended module structure?

Answer 20

$ tree minimal-module/
.
README.md
main.tf
variables.tf
outputs.tf

Question 21

Whats the best practice for writing modules for larger orgs?

Answer 21

After determining org’s requirements, split up into categories.

Ex: networking module, security, routing, web module, database, app module.