143 lines
4.7 KiB
Markdown
143 lines
4.7 KiB
Markdown
# Adding a new resource type to driftctl
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## 1 Defining the resource
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First step is to implement a new resource will be to define a go struct representing all fields that needs to be monitored for this kind of resource.
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You can find example in already implemented resource like aws.S3Bucket
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```go
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type AwsS3Bucket struct {
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AccelerationStatus *string `cty:"acceleration_status"`
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Acl *string `cty:"acl" diff:"-"`
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Arn *string `cty:"arn"`
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Bucket *string `cty:"bucket"`
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...
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```
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Your new type will need to implement `resource.Resource` interface in order for driftctl to retrieve its type and a unique identifier for it.
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```go
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type Resource interface {
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TerraformId() string
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TerraformType() string
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}
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```
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Some resources are read differently by the terraform state reader and the supplier. You can optionally implement `resource.NormalizedResource` to add a normalization step before the comparison is made.
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```go
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type NormalizedResource interface {
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NormalizeForState() (Resource, error)
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NormalizeForProvider() (Resource, error)
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}
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```
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For example S3Bucket policy is encoded in json but the formatting (newline and tabs) differs when read using the state reader. S3Bucket implements `resource.NormalizedResource`:
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```go
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func (s S3Bucket) NormalizeForState() (resource.Resource, error) {
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err := normalizePolicy(&s)
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return &s, err
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}
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func (s S3Bucket) NormalizeForProvider() (resource.Resource, error) {
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err := normalizePolicy(&s)
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return &s, err
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}
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func normalizePolicy(s *S3Bucket) error {
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if s.Policy.Policy != nil {
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jsonString, err := structure.NormalizeJsonString(*s.Policy.Policy)
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if err != nil {
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return err
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}
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s.Policy.Policy = &jsonString
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}
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return nil
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}
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```
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You can implement different normalization for the state representation and the supplier one.
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## 2 Supplier and Deserializer
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Then you will have to implement two interfaces:
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- `resource.supplier` is used to read resources list. It will call the cloud provider sdk to get the list of resources, and
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the terraform provider to get the details for each of these resources.
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- `remote.CTYDeserializer` is used to transform terraform cty output into your resource
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### Supplier
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This is used to read resources list. It will call the cloud provider sdk to get the list of resources, and the
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terraform provider to get the details for each of these resources.
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You can use an already implemented resource as example.
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Supplier constructor could use these arguments:
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- an instance of `ParallelRunner` that you will use to parallelize your call to the supplier:
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```go
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results := make(map[string][]cty.Value)
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for _, bucket := range response.Buckets {
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b := *bucket
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s.runner.Run(func() error {
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return s.readBucket(b, results)
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})
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}
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if err := s.runner.Wait(); err != nil {
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return nil, err
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}
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```
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- an instance of `terraform.ResourceReader` that you can use to read resource using the supplier:
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```go
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s3Bucket, err := s.reader.ReadResource(aws.AwsS3BucketResourceType, name)
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if err != nil {
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logrus.Warnf("Error reading bucket %s[%s]: %+v", name, aws.AwsS3BucketResourceType, err)
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return err
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}
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appendValueIntoMap(results, aws.AwsS3BucketResourceType, s3Bucket)
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```
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- an instance of the cloud provider sdk that you will use to retrieve resources list.
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### Deserializer
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The deserializer is used when reading resource from the terraform provider or from the state.
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The interface contains a `Deserialize(values []cty.Value) ([]resource.Resource, error)` method that you'll implement.
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You should then deserialize the obtained cty values into your resource and return the list.
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Example: [aws_s3_bucket_deserializer.go](https://github.com/cloudskiff/driftctl/blob/master/pkg/resource/aws/deserializer/s3_bucket_deserializer.go)
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## 3 Adding your resource
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There are two files you are going to edit to make driftctl aware of your new resource.
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For the state reader you will need to add your `CTYDeserializer` implementation into `iac/deserializers.go`
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Just add an instance in the list:
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```go
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func Deserializers() []remote.CTYDeserializer {
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return []remote.CTYDeserializer{
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aws.NewS3BucketDeserializer(),
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...
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}
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}
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```
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Then in the cloud provider's init file (e.g. in `remote/aws/init.go`) add your new implementation for `resource.Supplier`:
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```go
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func Init() error {
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provider, err := NewTerraFormProvider()
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if err != nil {
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return err
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}
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terraform.AddProvider(terraform.AWS, provider)
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resource.AddSupplier(NewS3BucketSupplier(provider.Runner().SubRunner(), s3.New(provider.session)))
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...
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}
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```
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Don't forget to add unit tests after adding a new resource.
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You can also add acceptance test if you think it makes sense.
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