terraform/terraform/resource_provider.go

package terraform

import (
	"fmt"

	multierror "github.com/hashicorp/go-multierror"
	"github.com/hashicorp/terraform/plugin/discovery"
)

// ResourceProvider is an interface that must be implemented by any
// resource provider: the thing that creates and manages the resources in
// a Terraform configuration.
//
// Important implementation note: All returned pointers, such as
// *ResourceConfig, *InstanceState, *InstanceDiff, etc. must not point to
// shared data. Terraform is highly parallel and assumes that this data is safe
// to read/write in parallel so it must be unique references. Note that it is
// safe to return arguments as results, however.
type ResourceProvider interface {
	/*********************************************************************
	* Functions related to the provider
	*********************************************************************/

	// ProviderSchema returns the config schema for the main provider
	// configuration, as would appear in a "provider" block in the
	// configuration files.
	//
	// Currently not all providers support schema. Callers must therefore
	// first call Resources and DataSources and ensure that at least one
	// resource or data source has the SchemaAvailable flag set.
	GetSchema(*ProviderSchemaRequest) (*ProviderSchema, error)

	// Input is called to ask the provider to ask the user for input
	// for completing the configuration if necesarry.
	//
	// This may or may not be called, so resource provider writers shouldn't
	// rely on this being available to set some default values for validate
	// later. Example of a situation where this wouldn't be called is if
	// the user is not using a TTY.
	Input(UIInput, *ResourceConfig) (*ResourceConfig, error)

	// Validate is called once at the beginning with the raw configuration
	// (no interpolation done) and can return a list of warnings and/or
	// errors.
	//
	// This is called once with the provider configuration only. It may not
	// be called at all if no provider configuration is given.
	//
	// This should not assume that any values of the configurations are valid.
	// The primary use case of this call is to check that required keys are
	// set.
	Validate(*ResourceConfig) ([]string, []error)

	// Configure configures the provider itself with the configuration
	// given. This is useful for setting things like access keys.
	//
	// This won't be called at all if no provider configuration is given.
	//
	// Configure returns an error if it occurred.
	Configure(*ResourceConfig) error

	// Resources returns all the available resource types that this provider
	// knows how to manage.
	Resources() []ResourceType

	// Stop is called when the provider should halt any in-flight actions.
	//
	// This can be used to make a nicer Ctrl-C experience for Terraform.
	// Even if this isn't implemented to do anything (just returns nil),
	// Terraform will still cleanly stop after the currently executing
	// graph node is complete. However, this API can be used to make more
	// efficient halts.
	//
	// Stop doesn't have to and shouldn't block waiting for in-flight actions
	// to complete. It should take any action it wants and return immediately
	// acknowledging it has received the stop request. Terraform core will
	// automatically not make any further API calls to the provider soon
	// after Stop is called (technically exactly once the currently executing
	// graph nodes are complete).
	//
	// The error returned, if non-nil, is assumed to mean that signaling the
	// stop somehow failed and that the user should expect potentially waiting
	// a longer period of time.
	Stop() error

	/*********************************************************************
	* Functions related to individual resources
	*********************************************************************/

	// ValidateResource is called once at the beginning with the raw
	// configuration (no interpolation done) and can return a list of warnings
	// and/or errors.
	//
	// This is called once per resource.
	//
	// This should not assume any of the values in the resource configuration
	// are valid since it is possible they have to be interpolated still.
	// The primary use case of this call is to check that the required keys
	// are set and that the general structure is correct.
	ValidateResource(string, *ResourceConfig) ([]string, []error)

	// Apply applies a diff to a specific resource and returns the new
	// resource state along with an error.
	//
	// If the resource state given has an empty ID, then a new resource
	// is expected to be created.
	Apply(
		*InstanceInfo,
		*InstanceState,
		*InstanceDiff) (*InstanceState, error)

	// Diff diffs a resource versus a desired state and returns
	// a diff.
	Diff(
		*InstanceInfo,
		*InstanceState,
		*ResourceConfig) (*InstanceDiff, error)

	// Refresh refreshes a resource and updates all of its attributes
	// with the latest information.
	Refresh(*InstanceInfo, *InstanceState) (*InstanceState, error)

	/*********************************************************************
	* Functions related to importing
	*********************************************************************/

	// ImportState requests that the given resource be imported.
	//
	// The returned InstanceState only requires ID be set. Importing
	// will always call Refresh after the state to complete it.
	//
	// IMPORTANT: InstanceState doesn't have the resource type attached
	// to it. A type must be specified on the state via the Ephemeral
	// field on the state.
	//
	// This function can return multiple states. Normally, an import
	// will map 1:1 to a physical resource. However, some resources map
	// to multiple. For example, an AWS security group may contain many rules.
	// Each rule is represented by a separate resource in Terraform,
	// therefore multiple states are returned.
	ImportState(*InstanceInfo, string) ([]*InstanceState, error)

	/*********************************************************************
	* Functions related to data resources
	*********************************************************************/

	// ValidateDataSource is called once at the beginning with the raw
	// configuration (no interpolation done) and can return a list of warnings
	// and/or errors.
	//
	// This is called once per data source instance.
	//
	// This should not assume any of the values in the resource configuration
	// are valid since it is possible they have to be interpolated still.
	// The primary use case of this call is to check that the required keys
	// are set and that the general structure is correct.
	ValidateDataSource(string, *ResourceConfig) ([]string, []error)

	// DataSources returns all of the available data sources that this
	// provider implements.
	DataSources() []DataSource

	// ReadDataDiff produces a diff that represents the state that will
	// be produced when the given data source is read using a later call
	// to ReadDataApply.
	ReadDataDiff(*InstanceInfo, *ResourceConfig) (*InstanceDiff, error)

	// ReadDataApply initializes a data instance using the configuration
	// in a diff produced by ReadDataDiff.
	ReadDataApply(*InstanceInfo, *InstanceDiff) (*InstanceState, error)
}

// ResourceProviderError may be returned when creating a Context if the
// required providers cannot be satisfied. This error can then be used to
// format a more useful message for the user.
type ResourceProviderError struct {
	Errors []error
}

func (e *ResourceProviderError) Error() string {
	// use multierror to format the default output
	return multierror.Append(nil, e.Errors...).Error()
}

// ResourceProviderCloser is an interface that providers that can close
// connections that aren't needed anymore must implement.
type ResourceProviderCloser interface {
	Close() error
}

// ResourceType is a type of resource that a resource provider can manage.
type ResourceType struct {
	Name       string // Name of the resource, example "instance" (no provider prefix)
	Importable bool   // Whether this resource supports importing

	// SchemaAvailable is set if the provider supports the ProviderSchema,
	// ResourceTypeSchema and DataSourceSchema methods. Although it is
	// included on each resource type, it's actually a provider-wide setting
	// that's smuggled here only because that avoids a breaking change to
	// the plugin protocol.
	SchemaAvailable bool
}

// DataSource is a data source that a resource provider implements.
type DataSource struct {
	Name string

	// SchemaAvailable is set if the provider supports the ProviderSchema,
	// ResourceTypeSchema and DataSourceSchema methods. Although it is
	// included on each resource type, it's actually a provider-wide setting
	// that's smuggled here only because that avoids a breaking change to
	// the plugin protocol.
	SchemaAvailable bool
}

// ResourceProviderResolver is an interface implemented by objects that are
// able to resolve a given set of resource provider version constraints
// into ResourceProviderFactory callbacks.
type ResourceProviderResolver interface {
	// Given a constraint map, return a ResourceProviderFactory for each
	// requested provider. If some or all of the constraints cannot be
	// satisfied, return a non-nil slice of errors describing the problems.
	ResolveProviders(reqd discovery.PluginRequirements) (map[string]ResourceProviderFactory, []error)
}

// ResourceProviderResolverFunc wraps a callback function and turns it into
// a ResourceProviderResolver implementation, for convenience in situations
// where a function and its associated closure are sufficient as a resolver
// implementation.
type ResourceProviderResolverFunc func(reqd discovery.PluginRequirements) (map[string]ResourceProviderFactory, []error)

// ResolveProviders implements ResourceProviderResolver by calling the
// wrapped function.
func (f ResourceProviderResolverFunc) ResolveProviders(reqd discovery.PluginRequirements) (map[string]ResourceProviderFactory, []error) {
	return f(reqd)
}

// ResourceProviderResolverFixed returns a ResourceProviderResolver that
// has a fixed set of provider factories provided by the caller. The returned
// resolver ignores version constraints entirely and just returns the given
// factory for each requested provider name.
//
// This function is primarily used in tests, to provide mock providers or
// in-process providers under test.
func ResourceProviderResolverFixed(factories map[string]ResourceProviderFactory) ResourceProviderResolver {
	return ResourceProviderResolverFunc(func(reqd discovery.PluginRequirements) (map[string]ResourceProviderFactory, []error) {
		ret := make(map[string]ResourceProviderFactory, len(reqd))
		var errs []error
		for name := range reqd {
			if factory, exists := factories[name]; exists {
				ret[name] = factory
			} else {
				errs = append(errs, fmt.Errorf("provider %q is not available", name))
			}
		}
		return ret, errs
	})
}

// ResourceProviderFactory is a function type that creates a new instance
// of a resource provider.
type ResourceProviderFactory func() (ResourceProvider, error)

// ResourceProviderFactoryFixed is a helper that creates a
// ResourceProviderFactory that just returns some fixed provider.
func ResourceProviderFactoryFixed(p ResourceProvider) ResourceProviderFactory {
	return func() (ResourceProvider, error) {
		return p, nil
	}
}

func ProviderHasResource(p ResourceProvider, n string) bool {
	for _, rt := range p.Resources() {
		if rt.Name == n {
			return true
		}
	}

	return false
}

func ProviderHasDataSource(p ResourceProvider, n string) bool {
	for _, rt := range p.DataSources() {
		if rt.Name == n {
			return true
		}
	}

	return false
}

// resourceProviderFactories matches available plugins to the given version
// requirements to produce a map of compatible provider plugins if possible,
// or an error if the currently-available plugins are insufficient.
//
// This should be called only with configurations that have passed calls
// to config.Validate(), which ensures that all of the given version
// constraints are valid. It will panic if any invalid constraints are present.
func resourceProviderFactories(resolver ResourceProviderResolver, reqd discovery.PluginRequirements) (map[string]ResourceProviderFactory, error) {
	ret, errs := resolver.ResolveProviders(reqd)
	if errs != nil {
		return nil, &ResourceProviderError{
			Errors: errs,
		}
	}

	return ret, nil
}