terraform-plugin-go provides low-level Go bindings for the Terraform plugin protocol, for integrations to be built upon. It strives to be a minimal possible abstraction on top of the protocol, only hiding the implementation details of the protocol while leaving its semantics unchanged.
terraform-plugin-go is a Go module versioned using semantic versioning.
The module is currently on a v0 major version, indicating our lack of confidence in the stability of its exported API. Developers depending on it should do so with an explicit understanding that the API may change and shift until we hit v1.0.0, as we learn more about the needs and expectations of developers working with the module.
We are confident in the correctness of the code and it is safe to build on so long as the developer understands that the API may change in backwards incompatible ways and they are expected to be tracking these changes.
Providers built on terraform-plugin-go will only be usable with Terraform v0.12.0 and later. Developing providers for versions of Terraform below 0.12.0 is unsupported by the Terraform Plugin SDK team.
This project follows the support policy of Go as its support policy. The two latest major releases of Go are supported by the project.
Currently, that means Go 1.21 or later must be used when including this project as a dependency.
terraform-plugin-go is targeted towards experienced Terraform developers. Familiarity with the Resource Instance Change Lifecycle is required, and it is the provider developer's responsibility to ensure that Terraform's requirements and invariants for responses are honored.
Provider developers are expected to create a type that implements the
tfprotov5.ProviderServer
interface. This type should be passed to
tfprotov5server.Serve
along with the name (like "hashicorp/time").
Resources and data sources can be handled in resource-specific or data
source-specific functions by using implementations of the
tfprotov5.ResourceServer
and
tfprotov5.DataSourceServer
interfaces, using the provider-level implementations of the interfaces to route
to the correct resource or data source level implementations using
req.TypeName.
When handling requests,
tfprotov5.DynamicValue
types should always have their
Unmarshal
methods called; their properties should not be inspected directly. The
tftypes.Value
returned from Unmarshal can be inspected to check whether it is
known
and subsequently converted to a plain Go type using its
As
method. As will return an error if the Value is not known.
The Terraform Plugin SDK's helper/resource package can be used to test providers written using terraform-plugin-go. While we are working on a testing framework for terraform-plugin-go providers that is independent of the Plugin SDK, this may take some time, so we recommend writing tests in the meantime using the plugin SDK, which will not be a runtime dependency of your provider.
You must supply a factory for your provider server by setting ProtoV5ProviderFactories on each TestCase. For example:
package myprovider
import (
"regexp"
"testing"
"github.com/hashicorp/terraform-plugin-go/tfprotov5"
"github.com/hashicorp/terraform-plugin-sdk/v2/helper/resource"
)
func TestAccDataSourceFoo(t *testing.T) {
resource.UnitTest(t, resource.TestCase{
ProtoV5ProviderFactories: map[string]func() (tfprotov5.ProviderServer, error){
"myprovider": func() (tfprotov5.ProviderServer, error) {
return Server(), nil
},
},
Steps: []resource.TestStep{
{
Config: `"data" "myprovider_foo" "bar" {}`,
Check: resource.ComposeTestCheckFunc(
resource.TestMatchResourceAttr("data.myprovider_foo.bar", "current", regexp.MustCompile(`[0-9]+`)),
),
},
},
})
}Provider servers can be instrumented with debugging tooling, such as delve, by using the WithManagedDebug() and WithDebug() ServeOpt. In this mode, Terraform CLI no longer manages the server lifecycle and instead connects to the running provider server via a reattach configuration supplied by the TF_REATTACH_PROVIDERS environment variable. The WithDebug() implementation is meant for advanced use cases which require manually handling the reattach configuration, such as managing providers with terraform-exec, while the WithManagedDebug() implementation is suitable for provider main() functions. For example:
func main() {
debugFlag := flag.Bool("debug", false, "Start provider in debug mode.")
flag.Parse()
opts := []tf6server.ServeOpt{}
if *debugFlag {
opts = append(opts, tf6server.WithManagedDebug())
}
tf6server.Serve("registry.terraform.io/namespace/example", /* Provider function */, opts...)
}To write raw protocol MessagePack or JSON data to disk, set the TF_LOG_SDK_PROTO_DATA_DIR environment variable. During Terraform execution, this directory will get populated with {TIME}_{RPC}_{MESSAGE}_{FIELD}.{EXTENSION} named files. Tooling such as jq can be used to inspect the JSON data. Tooling such as fq or msgpack2json can be used to inspect the MessagePack data.
Documentation is a work in progress. The GoDoc for packages, types, functions, and methods should have complete information, but we're working to add a section to terraform.io with more information about the module, its common uses, and patterns developers may wish to take advantage of.
Please bear with us as we work to get this information published, and please open issues with requests for the kind of documentation you would find useful.
This module is intentionally limited in its scope. It serves as the foundation for the provider ecosystem, so major breaking changes are incredibly expensive. By limiting the scope of the project, we're limiting the choices it needs to make, making it less likely that breaking changes will be required once we've hit version 1.0.0.
To that end, terraform-plugin-go's scope is limited to providing a common gRPC server interface and an implementation of Terraform's type system. It specifically is not trying to be a framework, nor is it attempting to provide any utility or helper functions that only a subset of provider developers will rely on. Its litmus test for whether something should be included is "will every Terraform provider need this functionality or can this functionality only be added if it's in this module?" All other functionality should be considered out of scope and should live in a separate module.
Please see .github/CONTRIBUTING.md.
Run go test ./... or make test after any changes.
Ensure the following tooling is installed:
- `golangci-lint: Aggregate Go linting tool.
Run golangci-lint run ./... or make lint after any changes.
Ensure the following tooling is installed:
protoc: Protocol Buffers compiler. This isn't Go specific tooling, so follow this installation guideprotoc-gen-go: Go plugin for Protocol Buffers compiler. Install by runningmake toolsprotoc-gen-go-grpc: Go gRPC plugin for Protocol Buffers compiler. Install by runningmake tools
The Protocol Buffers definitions can be found in tfprotov5/internal/tfplugin5 and tfprotov6/internal/tfplugin6.
Run make protoc to recompile the Protocol Buffers files after any changes.
This module is licensed under the Mozilla Public License v2.0.
