Terraform count and for_each

count

The count parameter in Terraform allows you to create a specified number of identical resources. It is an integral part of a resource block that defines how many instances of a particular resource should be created.

Pros:

• Simple to use: The count parameter is straightforward for creating multiple instances of a resource.
• Suitable for homogeneous resources: When all the resources you’re creating are identical except for an identifier, count is likely a good fit.

Cons:

• Lacks key-based identification: count doesn’t include a way to address a resource with a unique key directly; you have to rely on an index.
• Immutable: If you remove an item from the middle of the count list, Terraform marks all subsequent resources for recreation which can be disruptive in certain scenarios.

count = 3 is added.

One EC2 had already been created, therefore it added 2 more. This feature is called… ” “.

Screenshot from aws console.

for_each

The for_each loop in Terraform, used within the for_each argument, iterates over a map or a set of strings, allowing you to create resources that correspond to the given elements.

Pros:

• Detailed declaration: for_each provides greater control when creating resources that require specific attributes or configurations.
• Key-based identification: Resources created with for_each can be directly identified and accessed by their keys, making modifications more manageable.
• Non-destructive updates: If you remove an item from the map or set, only that specific resource will be affected.

Cons:

• Complexity: for_each is more complex to use than count and requires more planning.
• Requires a set or map: You must provide a set or map of items to iterate over, which might not be necessary or straightforward for all situations.

When to Use Count vs. For_each

Both constructs are powerful, but they shine in different situations. Here’s a quick reference to determine which to use:

Use Count when:

• You need to create a fixed number of similar resources.
• Resource differences can be represented by an index.

Use For_each when:

• You’re dealing with a collection of items that have unique identifiers.
• Your resources are not perfectly identical and require individual configurations.
• You plan to make future modifications that should not affect all resources.