@ -25,7 +25,7 @@ since Terraform loads all files ending in `.tf` in a directory.
variable "access_key" {}
variable "secret_key" {}
variable "region" {
default = "us-east-1"
default = "us-east-1"
}
```
@ -41,9 +41,9 @@ Next, replace the AWS provider configuration with the following:
```
provider "aws" {
access_key = "${var.access_key}"
secret_key = "${var.secret_key}"
region = "${var.region}"
access_key = "${var.access_key}"
secret_key = "${var.secret_key}"
region = "${var.region}"
}
```
@ -57,11 +57,6 @@ There are multiple ways to assign variables. Below is also the order
in which variable values are chosen. If they're found in an option first
below, then the options below are ignored.
**UI Input:** If you execute `terraform plan` or apply without doing
anything, Terraform will ask you to input the variables interactively.
These variables are not saved, but provides a nice user experience for
getting started with Terraform.
**Command-line flags:** You can set it directly on the command-line with the
`-var` flag. Any command in Terraform that inspects the configuration
accepts this flag, such as `apply` , `plan` , and `refresh` :
@ -107,38 +102,51 @@ $ terraform plan \
-var-file="production.tfvars"
```
**UI Input:** If you execute `terraform plan` or apply without doing
anything, Terraform will ask you to input the variables interactively.
These variables are not saved, but provides a nice user experience for
getting started with Terraform. (UI Input is only supported for string
variables - list and map variables must be populated via one of the
other mechanisms.
**Variable Defaults**: If no value is assigned to a variable via any of these
methods and the variable has a `default` key in its declaration, that value
will be used for the variable.
< a id = "mappings" > < / a >
## Mappings
< a id = "maps" > < / a >
## Maps
We've replaced our sensitive strings with variables, but we still
are hardcoding AMIs. Unfortunately, AMIs are specific to the region
that is in use. One option is to just ask the user to input the proper
AMI for the region, but Terraform can do better than that with
_mappings_.
_maps_.
Mappings are a way to create variables that are lookup tables. An example
will show this best. Let's extract our AMIs into a mapping and add
Maps are a way to create variables that are lookup tables. An example
will show this best. Let's extract our AMIs into a map and add
support for the "us-west-2" region as well:
```
variable "amis" {
type = "map"
default = {
us-east-1 = "ami-13be557e"
us-west-2 = "ami-06b94666"
}
type = "map"
default = {
us-east-1 = "ami-13be557e"
us-west-2 = "ami-06b94666"
}
}
```
A variable becomes a mapping when it has a type of "map" assigned, or has a
default value that is a map like above.
A variable can have a "map" type assigned explicitly, or it can be implicitly
declared as a map by specifying a default value that is a map. The above
demonstrates both.
Then, replace the "aws\_instance" with the following:
```
resource "aws_instance" "example" {
ami = "${lookup(var.amis, var.region)}"
instance_type = "t2.micro"
ami = "${lookup(var.amis, var.region)}"
instance_type = "t2.micro"
}
```
@ -148,39 +156,40 @@ key is `var.region`, which specifies that the value of the region
variables is the key.
While we don't use it in our example, it is worth noting that you
can also do a static lookup of a mapping directly with
can also do a static lookup of a map directly with
`${var.amis["us-east-1"]}` .
< a id = "assigning-map ping s"> < / a >
## Assigning Mapping s
< a id = "assigning-map s"> < / a >
## Assigning Maps
We set defaults above, but mappings can also be set using the `-var` and
`-var-file` values. For example, if the user wanted to specify an alternate AMI
for us-east-1:
We set defaults above, but maps can also be set using the `-var` and
`-var-file` values. For example:
```
$ terraform plan -var 'amis.us-east-1=foo '
$ terraform plan -var 'amis={ us-east-1 = "foo", us-west-2 = "bar" } '
...
```
**Note**: even if every key will be assigned as input, the variable must be
established as a mapping by setting its default to `{}` .
established as a map by setting its default to `{}` .
Here is an example of setting a mapping 's keys from a file. Starting with these
Here is an example of setting a map's keys from a file. Starting with these
variable definitions:
```
variable "region" {}
variable "amis" {
default = {}
type = "map"
}
```
You can specify keys in a `terraform.tfvars` file:
```
amis.us-east-1 = "ami-abc123"
amis.us-west-2 = "ami-def456"
amis = {
us-east-1 = "ami-abc123"
us-west-2 = "ami-def456"
}
```
And access them via `lookup()` :
@ -207,7 +216,7 @@ Outputs:
## Next
Terraform provides variables for parameterizing your configurations.
Mapping s let you build lookup tables in cases where that makes sense.
Maps let you build lookup tables in cases where that makes sense.
Setting and using variables is uniform throughout your configurations.
In the next section, we'll take a look at
Paul Hinze
10 years ago
committed by
GitHub