Custom Retriever

Simple retriever

To create a custom retriever you must have a struct that implements the Retriever interface.

type Retriever interface {
	Retrieve(ctx context.Context) ([]byte, error)
}

The Retrieve function is supposed to load the file and to return a []byte of your flag configuration file.

You can check existing Retriever (file, s3, ...) to have an idea on how to do build your own.

Initializable retriever

Sometimes you need to initialize your retriever before using it. For example, if you want to connect to a database, you need to initialize the connection before using it.

To help you with that, you can use the InitializableRetriever interface.

The only difference with the Retriever interface is that the Init func of your retriever will be called at the start of the application and the Shutdown func will be called when closing GO Feature Flag.

type InitializableRetriever interface {
	Retrieve(ctx context.Context) ([]byte, error)
	Init(ctx context.Context, logger *fflog.FFLogger) error
	Shutdown(ctx context.Context) error
	Status() retriever.Status
}

To avoid any issue to call the Retrieve function before the Init function, you have to manage the status of your retriever. GO Feature Flag will try to call the Retrieve function only if the status is RetrieverStatusReady.