update docs for configuration_aliases

Remove references to the "proxy configuration block" concept, and add
examples showing the usage of `configuration_aliases`.
This commit is contained in:
James Bardin 2021-02-12 11:44:26 -05:00
parent 4e12ba3d75
commit 1bb602859a
3 changed files with 57 additions and 44 deletions

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@ -36,9 +36,10 @@ module "example" {
## Default Behavior: Inherit Default Providers
The `providers` argument is optional. If you omit it, a child module inherits
all of the _default_ provider configurations from its parent module. (Default
provider configurations are ones that don't use the `alias` argument.)
If the child module does not declare any configuration aliases, the `providers`
argument is optional. If you omit it, a child module inherits all of the
_default_ provider configurations from its parent module. (Default provider
configurations are ones that don't use the `alias` argument.)
If you specify a `providers` argument, it cancels this default behavior, and the
child module will _only_ have access to the provider configurations you specify.

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@ -22,18 +22,9 @@ within a `module` block. These two options are discussed in more detail in the
following sections.
A module intended to be called by one or more other modules must not contain
any `provider` blocks, with the exception of the special
"proxy provider blocks" discussed under
_[Passing Providers Explicitly](#passing-providers-explicitly)_
below.
For backward compatibility with configurations targeting Terraform v0.10 and
earlier Terraform does not produce an error for a `provider` block in a shared
module if the `module` block only uses features available in Terraform v0.10,
but that is a legacy usage pattern that is no longer recommended. A legacy
module containing its own provider configurations is not compatible with the
`for_each`, `count`, and `depends_on` arguments that were introduced in
Terraform v0.13. For more information, see
any `provider` blocks. A module containing its own provider configurations is
not compatible with the `for_each`, `count`, and `depends_on` arguments that
were introduced in Terraform v0.13. For more information, see
[Legacy Shared Modules with Provider Configurations](#legacy-shared-modules-with-provider-configurations).
Provider configurations are used for all operations on associated resources,
@ -82,6 +73,25 @@ settings come from provider _configurations_, and a particular overall Terraform
configuration can potentially have
[several different configurations for the same provider](/docs/language/providers/configuration.html#alias-multiple-provider-configurations).
To declare multiple configuration names for a provider within a module, add the
`configuration_aliases` argument:
```hcl
terraform {
required_providers {
aws = {
source = "hashicorp/aws"
version = ">= 2.7.0"
configuration_aliases = [ aws.alternate ]
}
}
}
```
The above requirements are identical to the previous, with the addition of the
alias provider configuration name `aws.alternate`, which can be referenced by
resources using the `provider` argument.
If you are writing a shared Terraform module, constrain only the minimum
required provider version using a `>=` constraint. This should specify the
minimum version containing the features your module relies on, and thus allow a
@ -201,17 +211,18 @@ module "tunnel" {
}
```
The subdirectory `./tunnel` must then contain _proxy configuration blocks_ like
the following, to declare that it requires its calling module to pass
configurations with these names in its `providers` argument:
The subdirectory `./tunnel` must then declare the configuration aliases for the
provider to pass configurations with these names in its `providers` argument:
```hcl
provider "aws" {
alias = "src"
}
provider "aws" {
alias = "dst"
terraform {
required_providers {
aws = {
source = "hashicorp/aws"
version = ">= 2.7.0"
configuration_aliases = [ aws.src, aws.dest ]
}
}
}
```
@ -219,20 +230,6 @@ Each resource should then have its own `provider` attribute set to either
`aws.src` or `aws.dst` to choose which of the two provider configurations to
use.
## Proxy Configuration Blocks
A proxy configuration block is one that contains only the `alias` argument. It
serves as a placeholder for provider configurations passed between modules, and
declares that a module expects to be explicitly passed an additional (aliased)
provider configuration.
-> **Note:** Although a completely empty proxy configuration block is also
valid, it is not necessary: proxy configuration blocks are needed only to
establish which _aliased_ provider configurations a child module expects.
Don't use a proxy configuration block if a module only needs a single default
provider configuration, and don't use proxy configuration blocks only to imply
[provider requirements](/docs/language/providers/requirements.html).
## Legacy Shared Modules with Provider Configurations
In Terraform v0.10 and earlier there was no explicit way to use different
@ -282,13 +279,10 @@ its provider configurations from the calling module, by using the "providers"
argument in the calling module block.
```
To make a module compatible with the new features, you must either remove all
of the `provider` blocks from its definition or, if you need multiple
configurations for the same provider, replace them with
_proxy configuration blocks_ as described in
[Passing Providers Explicitly](#passing-providers-explicitly).
To make a module compatible with the new features, you must remove all of the
`provider` blocks from its definition
If the new version of the module uses proxy configuration blocks, or if the
If the new version of the module declares `configuration_aliases`, or if the
calling module needs the child module to use different provider configurations
than its own default provider configurations, the calling module must then
include an explicit `providers` argument to describe which provider

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@ -103,6 +103,24 @@ provider "aws" {
}
```
To declare a configuration alias within a module in order to receive an
alternate provider configuration from the parent module, add the
`configuration_aliases` argument to that provider's `required_providers`
entry. The following example declares both the `mycloud` and
`mycloud.alternate` provider configuration names within the containing module:
```hcl
terraform {
required_providers {
mycloud = {
source = "mycorp/mycloud"
version = "~> 1.0"
configuration_alaises = [ mycloud.alternate ]
}
}
}
```
### Default Provider Configurations
A `provider` block without an `alias` argument is the _default_ configuration