terraform check if variable is null or emptyterraform check if variable is null or empty

To see what that means, remove the original all_arns and first_arn output variables, and add a new all_users output variable: Heres what happens when you run terraform apply: You can see that Terraform created three IAM users and that the all_users output variable contains a map where the keys are the keys in for_each (in this case, the usernames) and the values are all the outputs for that resource. If try exhausts all of the given expressions The end result, of course, is exactly what you requested (i.e., two IAM users named morpheus and neo), but deleting resources is probably not how you want to get there, as you may lose availability (you cant use the IAM user during the apply), and, even worse, you may lose data (if the resource youre deleting is a database, you may lose all the data in it!). Making statements based on opinion; back them up with references or personal experience. We can also use try to deal with situations where a value might be provided How do I figure out what size drill bit I need to hang some ceiling hooks? constant "12" instead of the type conversion in this case, but shows how to I'm trying to use Terraform 0.13's custom variable validation to ensure that the value is either null or between a specified range. Although Terraform is a declarative language, it includes a large number of tools, such as variables and modules, which you saw in Part 4 of this series, and count, for_each, for, and built-in functions, which you saw in this blog post, that give the language a surprising amount of flexibility and expressive power. To learn more, see our tips on writing great answers. Terraform's coalesce () function can com handy when we have optional arguments coming from several sources and we want to pick one using some preference. For an expanded version of this blog post series, pick up a copy of the book Terraform: Up & Running (3rd edition available now!). The allowance of converting those particular string values is mainly motivated by backward compatibility: prior to Terraform 0.12, there was no boolean type and thus strings containing those values were the only way to represent booleans. I'll update my answer to be more complete, although I see you already accepted the other answer so I'm just doing this so as not to leave an incomplete answer here. If you want to check if a variable is null, use "null" in the conditional expression and if you want to check if a variable is an empty string, use "" in the conditional expression. How to assign default values to map(object()) input in Terraform? Do US citizens need a reason to enter the US? Terraform custom validation for variable that can be null And if the declarative language doesnt support if-statements, how can you conditionally configure resources, such as creating a Terraform module that can create certain resources for some users of that module but not for others? A common use of conditional expressions is to define defaults to replace description = The IP ranges to whitelist for incoming traffic to the masters Terraform attempts to select a result type that all of the arguments can convert to, so mixing argument types may produce surprising . Update, July 8, 2019: Weve updated this blog post series for Terraform 0.12 and released the 2nd edition of Terraform: Up & Running! Please set proper title and also format your code enclosing it within triple backticks. The first step is to add a Boolean input variable in modules/services/webserver-cluster/variables.tf that you can use to specify whether the module should enable auto scaling: Now, if you had a general-purpose programming language, you could use this input variable in an if-statement: Terraform doesnt support if-statements, so this code wont work. As discussed in Part 1 of this series, infrastructure-as-code in a declarative language tends to provide a more accurate view of what's actually deployed than a procedural language, so it's easier to reason about and makes it easier to keep the codebase small. Another refactor that you might be tempted to do is to change a Terraform identifier. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. . How can I make Terraform replace a null value with a default value? How to fetch a value from list of maps in terraform 0.12 based on condition, How to use null with a different value in place of default value. For example, heres how you can create the same three IAM users using for_each on a resource: Note the use of toset to convert the var.user_names list into a set. 3 Answers Sorted by: 79 Seems these days you can also use try to check if something is set. However, if we correct that to the opposite then it will expose a second problem: Terraform's logical operators don't have the "short circuit" behavior in some other languages, where the result of the first operand can prevent any attempt to evaluate the second operand. terraform cannot compare `[]` to an empty list; requires `tolist OK, maybe not too wild, as someone still needs to maintain your code, but just wild enough that you can create clean, beautiful APIs for your modules. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. The "bar" variable is defaulted to "HelloWorld". At the time of writing, I work on Terraform at HashiCorp.). For example, recall the way the webserver-cluster module in modules/services/webserver-cluster/main.tf sets tags: If var.custom_tags is empty, the for_each expression will have nothing to loop over, so no tags will be set. Now, what if you want to deploy one EC2 Instance per Availability Zone (AZ) in the current AWS region? Putting these two together, and combining them with a splat expression, you get the following: Depending on the outcome of the if/else conditional, either full_access will be empty and read_only will contain one element or vice versa, so once you concatenate them together, youll have a list with one element, and the one function will return that element. @GregHensley you can set a validation on the input var to allow either null or a non empty string, @GregHensley I updated the example to include. Lets see what happens if you try to use the result output from this resource in the count parameter of your aws_instance resource: If you run terraform plan on this code, youll get the following error: Terraform requires that it can compute count and for_each during the plan phase, before any resources are created or modified. This will fail if the value is null with the following error: Error during operation: argument must not be null. This means that count and for_each can reference hardcoded values, variables, data sources, and even lists of resources (so long as the length of the list can be determined during plan), but not computed resource outputs. Earlier in this blog post, you created several IAM users with read-only access to EC2. Configuration Language Functions try v1.5.x (latest) try Function try evaluates all of its argument expressions in turn and returns the result of the first one that does not produce any errors. Ahh yes, with fresh eyes today I see that there were two different things going on here and I focused only one the first one I saw. amazing. reference or a reference to a top-level object that has not been declared: Centralized secrets lifecycle management for developers. Connect and share knowledge within a single location that is structured and easy to search. Checks; Import. false : true}", https://discuss.hashicorp.com/t/how-do-write-an-if-else-block/2563. Could ChatGPT etcetera undermine community by making statements less significant for us? Asking for help, clarification, or responding to other answers. Can somebody be charged for having another person physically assault someone for them? For example, to capture that the aws_security_group resource was renamed from instance to cluster_instance, you would add the following moved block: Now, whenever anyone runs apply on this code, Terraform will automatically detect if it needs to update the state file: If you enter yes, Terraform will update the state automatically, and as the plan shows no resources to add, change, or destroy, Terraform will make no other changes which is exactly what you want! How do you manage the impact of deep immersion in RPGs on players' real-life? If the variable pg_slave01_db_ebs_snapshot_id is not empty and the Terraform Workspace is prod, it should create the resource. The syntax of a conditional expression is as follows: condition ? Is it possible to have null value conditional variables? so if I dont set a variable, it should not enable api_server_authorized_ip_ranges Trigger when bar is being used. The preferred way to check for an empty set or series of . For example, if var.example were set to {} then it could be converted to as a malformed resource reference. This is a slightly contrived example, but a useful one to demonstrate a simple type of if-else-statement. First, to allow users to specify custom tags, add a new map input variable called custom_tags in modules/services/webserver-cluster/variables.tf: Next, set some custom tags in the production environment, in live/prod/services/webserver-cluster/main.tf, as follows: The preceding code sets a couple of useful tags: the Owner tag specifies which team owns this ASG, and the ManagedBy tag specifies that this infrastructure is managed using Terraform (indicating that this infrastructure shouldnt be modified manually). Consider the following Terraform code, which should live in live/global/iam/main.tf: This code uses the aws_iam_user resource to create a single new IAM user. However, this is a workaround for me. Name = "$ {var.name}-$ {var.branch}" variable branch {default = null} Would something like this work? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. variable k8s_api_server_authorized_ip_ranges { Lets first walk through how to use for_each to create multiple copies of a resource. You can use the if string directive to fix this issue as follows: There are a few changes here from the original version: Whoops. Invalid value for "str" parameter: argument must not be null. Similarly, if the resource you are deleting happens to be a security group, your servers will reject all network traffic until the new security group is created. attempt to find a type that they can both convert to, and make those The syntax of a conditional expression is as follows: If condition is true then the result is true_val. Instead, the string values "true" and "false" map to true and false respectively, and any other string will produce a conversion error. There are two main lessons to take away from this: Lesson #1: After you start using Terraform, you should only use Terraform. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing. Every whitespace you put in a HEREDOC ends up in the final string. The second conditional expression is always getting evaluated with the. So considering both of those things and assuming that your goal was for this value to be just a plain empty list in the case where the given list is empty, perhaps the following: Powered by Discourse, best viewed with JavaScript enabled. One thing the module did not create was the scheduled action. The import command takes two arguments. then only concatenate like this: To deal with null and empty strings, you could use the coalesce function, which: takes any number of arguments and returns the first one that isn't null or an empty string. Below are the three ways of defining variables in Terraform: Command-line Flags: Pass variable values directly through command-line flags. Connect and share knowledge within a single location that is structured and easy to search. Perhaps someone created that resource manually or via CLI commands, but either way, some identifier is the same, and that leads to a conflict. Best way for "if null then default else value" - Terraform - HashiCorp Discuss I was using the following pattern often in my code: abc = something == null ? can refer to local.normalized_value attributes without the need to repeatedly When for_each loops over this set, it makes each username available in each.value. Find centralized, trusted content and collaborate around the technologies you use most. Perhaps you were doing a refactor and you thought it would be clearer to change this name to cluster_instance: Whats the result? In other words, you already have some conditional logic here. Is there way to ignore optional field in terraform module when value is not specified? For example, you can add a condition to an input variable that checks whether incoming image IDs are formatted properly. If you created infrastructure before you started using Terraform, you can use the terraform import command to add that infrastructure to Terraforms state file so that Terraform is aware of and can manage that infrastructure. For example, if youre renaming an aws_security_group group from instance to cluster_instance, you could run the following: This instructs Terraform that the state that used to be associated with aws_security_group.instance should now be associated with aws_security_group.cluster_instance. where COLLECTION is a set or map to loop over (lists are not supported when using for_each on a resource) and CONFIG consists of one or more arguments that are specific to that resource. Are there any practical use cases for subtyping primitive types? It fails becasue when your target_group_stickiness_duration is null, the. 1 Hi all, I'm trying to conditionally create a resource based on a variable. Note that if you have a lot of existing resources that you want to import into Terraform, writing the Terraform code for them from scratch and importing them one at a time can be painful, so you might want to look into tools such as terraformer and terracognita, which can import both code and state from supported cloud environments automatically. It defaults to true to preserve the existing behavior. but how to check it later that it is unset ? The module created an Auto Scaling Group (ASG), Application Load Balancer (ALB), security groups, and a number of other resources. We strongly suggest using try only in special local values whose expressions How to avoid conflict of interest when dating another employee in a matrix management company? Using tostring() to ensure functional conditionals in Terraform? Is saying "dot com" a valid clue for Codenames? By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. rev2023.7.24.43543. You could update your code to fetch the list of AZs using the aws_availability_zones data source and use the count parameter and array lookups to loop over each AZ and create an EC2 Instance in it: Again, this code works just fine, since count can reference data sources without problems. Now that you know how to do an if-statement, what about an if-else-statement? Youre now deleting solely the exact resource you want, without shifting all of the other ones around. The try function can only catch and handle dynamic errors resulting from Making statements based on opinion; back them up with references or personal experience. If youre clever, you can use the same mechanism to do a basic conditional. How to pass blank value of a map? : r/Terraform - Reddit Developer Terraform Configuration Language Expressions Custom Conditions v1.5.x (latest) Custom Conditions You can create conditions that produce custom error messages for several types of objects in a configuration. Is there a word for when someone stops being talented? Not the answer you're looking for? The solution I'm using is to put the modules in sequence calling each, i.e. Unfortunately, count has two limitations that significantly reduce its usefulness. Couldnt find a solution, so had to do this instead: var.pg_slave01_create && (terraform.workspace == "prod") ? Refactoring is an essential coding practice that you should do regularly. You can try the following which uses coalesce: It looks like there are two different things going on here. The for_each expression allows you to loop over lists, sets, and maps to create (a) multiple copies of an entire resource, (b) multiple copies of an inline block within a resource, or (c) multiple copies of a module. How do I figure out what size drill bit I need to hang some ceiling hooks? For example, consider how tags are set in the aws_autoscaling_group resource: Each tag requires you to create a new inline block with values for key, value, and propagate_at_launch. What I think I want is to say if the value was not passed, consider it null and pass that to the conditional. 3 6 comments Add a Comment absdevops 5 yr. ago Terraform is a declarative language. Warning: The try function is intended only for concise testing of the 1 : 0, Powered by Discourse, best viewed with JavaScript enabled, Conditionally creating a resource if variable is not empty. Can consciousness simply be a brute fact connected to some physical processes that dont need explanation? Is there a way to speak with vermin (spiders specifically)? Expressions. Why the ant on rubber rope paradox does not work in our universe or de Sitter universe? If you pass a for_each expression an empty collection, the result will be zero copies of the resource, inline block, or module where you have the for_each; if you pass it a nonempty collection, it will create one or more copies of the resource, inline block, or module. @lpossamai you cant combine two conditional expressions like that, you need to combine the two tests into a single conditional expression like this: count = var.pg_slave01_db_ebs_snapshot_id != "" && terraform.workspace == "prod" ? I have two different list(maps) inside a local block, named boot_disk and add_disk. terraform coalesce() function Does this definition of an epimorphism work? For example, here is the Terraform code to convert the list of names in var.names to uppercase: If you run terraform apply on this code, you get the following output: Just as with Pythons list comprehensions, you can filter the resulting list by specifying a condition: Running terraform apply on this code gives you this: Terraforms for expression also allows you to loop over a map using the following syntax: Here, MAP is a map to loop over, KEY and VALUE are the local variable names to assign to each key-value pair in MAP, and OUTPUT is an expression that transforms KEY and VALUE in some way. This will a string. As discussed in Part 1 of this series, infrastructure-as-code in a declarative language tends to provide a more accurate view of whats actually deployed than a procedural language, so its easier to reason about and makes it easier to keep the codebase small. The problem was that there was an extra trailing comma and space at the end of the string. In the following example, the .value part contains a set of attributes. Source: https://www.terraform.io/language/functions/coalesce Then to decide on the concatenation, you could use a conditional expression. What is the equivalent of "" for booleans in terraform? Lets first look at the terraform state mv command, which has the following syntax: where ORIGINAL_REFERENCE is the reference expression to the resource as it is now and NEW_REFERENCE is the new location you want to move it to. Allow "count" for non-null check on resource attributes that - GitHub The try function will not catch errors relating to constructs that are The preceding code hardcodes a single tag, but you might want to allow users to pass in custom tags. It won't actually work in Terraform. operators. I previously hinted at an approach of using a complex type (I said specifically a list at the time, but any collection or structural type will work) to allow separating the null-ness of the collection itself from the unknown-ness of the value inside it. When laying trominos on an 8x8, where must the empty square be? The for string directive uses the following syntax: where COLLECTION is a list or map to loop over, ITEM is the local variable name to assign to each item in COLLECTION, and BODY is what to render each iteration (which can reference ITEM). conversions automatically if so. Terraform conditionals - if variable does not exist. In How to create reusable infrastructure with Terraform modules, you created a Terraform module that could be used as a blueprint for deploying web server clusters. Thanks for filing the issue. Circlip removal when pliers are too large, How to automatically change the name of a file on a daily basis, Line integral on implicit region that can't easily be transformed to parametric region. Heres how you use count to create three IAM users: One problem with this code is that all three IAM users would have the same name, which would cause an error, since usernames must be unique. Terraform if statement with true or false, Terraform custom validation for variable that can be null, Consistent type in terraform true and false expressions. Connect and share knowledge within a single location that is structured and easy to search. invalid values: If var.a is an empty string then the result is "default-a", but otherwise The coalesce function takes any number of arguments and returns the first one that isn't null nor empty. Anyhoo, my solution is it check a variable in the for_each statement, run once if not null, otherwise run no times. true_val : false_val If condition is true then the result is true_val. If you set an argument of a resource or module to null, Terraform behaves as though you had completely omitted it it will use the argument's default value if it has one, or raise an error if the argument is mandatory. Lesson #2: If you have existing infrastructure, use the import command. How high was the Apollo after trans-lunar injection usually? Co-founder of Gruntwork, Author of Hello, Startup and Terraform: Up & Running. but here its enabling it, but adding IPs from this bit However, when it comes to Terraform, or any IaC tool, you have to be careful about what defines the external behavior of a piece of code, or you will run into unexpected problems. I have not found it explicitly stated either way.