Terraform if

Manage your infrastructure as it grows with a flexible, robust workflow, drift detection and reconciliation, terraform if, and policies for security and compliance. Conditional expressions are a key part of any programming language.

Sign up. Sign in. Yevgeniy Brikman. This is Part 5 of the Comprehensive Guide to Terraform series. In previous parts, you learned why we picked Terraform , how to use the basic syntax and features of Terraform , how to manage Terraform state , and how to create reusable infrastructure with Terraform modules. Terraform is a declarative language.

Terraform if

Today we are going to dive into both of those scenarios and see how we can conditionally do things within Terraform. This allows us to do a range of things as engineers from simply checking if something has a value to more complex logic such as if multiple things exist within a network or have permissions to another thing. We are now going to dive into an example where we will be using the conditional as a way to feature flag some Terraform resource. In this example we are going to create a virtual machine that is significantly more powerful for our production environment than any other. It is also possible to nest these expressions to allow for checking more and more conditions, ideally you wouldn't do this unless you had no other choice however. It is obvious to see here that the more conditions we add the harder the code becomes to read and the more brittle it becomes too. But it certainly is possible. The second conditional type to touch on is the if within the for expression, which we are going to look at now. In this article we looked at the ternary operator which allows us to return a true value or a false value based on the result of a condition. These are exceptionally powerful and allow us to create logic such as what size of a resource to provision in different environments, or if a resource should even be provisioned at all. We then took a dive into the if expression on the for expression which allows us to filter out data before returning it to the consumer. These are some fantastic concepts that you can apply to your Terraform code today! Developer Resources. Integrations Blog Release Notes.

Read more about conditional expressions in Terraform.

A conditional expression uses the value of a boolean expression to select one of two values. Hands-on: Try the Create Dynamic Expressions tutorial. The syntax of a conditional expression is as follows:. A common use of conditional expressions is to define defaults to replace invalid values:. If var.

You can create conditions that produce custom error messages for several types of objects in a configuration. For example, you can add a condition to an input variable that checks whether incoming image IDs are formatted properly. Custom conditions can capture assumptions, helping future maintainers understand the configuration design and intent. They also return useful information about errors earlier and in context, helping consumers more easily diagnose issues in their configurations. Try the Validate Modules with Custom Conditions tutorial to learn how to use other custom conditions. This page explains the following:.

Terraform if

Manage your infrastructure as it grows with a flexible, robust workflow, drift detection and reconciliation, and policies for security and compliance. Conditional expressions are a key part of any programming language. Conditional expressions return a value based on whether an expression evaluates to true or false. In most modern languages, conditional expressions are represented by the if…else statement. Here is an example of a conditional expression: If this article is engaging, then people will continue reading it, else, no one will see it.

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This gives you the expected output:. Terraform uses conditional expression logic to build If statements. The second one, which attaches the CloudWatch read-only permissions, has a conditional expression that does the exact opposite, evaluating to 0 if var. An output block can include a precondition block. Learn more about Terraform count vs. We recommend writing error messages as one or more full sentences in a style similar to Terraform's own error messages. Example 3. In Terraform, you can accomplish the same thing by using count along with the following:. When creating a conditional expression, the two result types can be of any type. Text to speech. In this example we are going to create a virtual machine that is significantly more powerful for our production environment than any other. We could do a lot more with the for expression especially in how we return information but that is not the scope of this article, instead we focus on the power of the if. Use the contains function to test whether a given value is one of a set of predefined valid values. If the value of var.

Terraform provides conditional statement-type logic using Ternary Operators and there is so much you can do with it. In the above example, we can define the instance type to use as per the environment type while creating an aws instance. Suppose you want to create an AWS instance only when it is explicitly told to do so.

You can create conditions that produce custom error messages for several types of objects in a configuration. The problem, of course, is that an IAM user with that name already exists. To accomplish the same thing in Terraform, you can use count. Lesson 2: If you have existing infrastructure, use the import command. See all from Gruntwork. Each assertion requires a condition argument , a boolean expression that should return true if the intended assumption or guarantee is fulfilled or false if it does not. Any part of the expression can also be wrapped within parentheses which allows us to multiple checks or return values via complex expressions. To avoid this, writing the condition with a specific conversion function is recommended see below using the toString function :. The preceding code hardcodes a single tag, but you might want to allow users to pass in custom tags. Yup, you guessed it: downtime. Terraform evaluates custom conditions as early as possible, but must defer conditions that depend on unknown values until the apply phase. You should also consider the following questions when creating preconditions and postconditions. Therefore, Terraform may check conditions during apply for initial creation and then check them during planning for subsequent updates.