feat: Azure Blob Storage Retriever

README.md

@@ -299,6 +299,7 @@ The available retrievers are:
 - **MongoDB**
 - **Redis**
 - **BitBucket**
+- **AzBlobStorage**
 - ...
 
 _[See the full list and more information.](https://gofeatureflag.org/docs/configure_flag/store_your_flags)_
@@ -620,4 +621,4 @@ These are our really cool sponsors!
 
 If you are using `go-feature-flag`, we encourage you to include your company's name in this list. This simple act significantly boosts the project's visibility and credibility, making a substantial contribution to its advancement. To do so, kindly add yourself to [adopters](./ADOPTERS.md).
 
-Here is the list of [adopters](./ADOPTERS.md).
+Here is the list of [adopters](./ADOPTERS.md).

cmd/relayproxy/config/retriever.go

@@ -32,6 +32,9 @@
 	Collection   string              `mapstructure:"collection" koanf:"collection"`
 	RedisOptions *redis.Options      `mapstructure:"redisOptions" koanf:"redisOptions"`
 	RedisPrefix  string              `mapstructure:"redisPrefix" koanf:"redisPrefix"`
+	AccountName  string              `mapstructure:"accountName" koanf:"accountname"`
+	AccountKey   string              `mapstructure:"accountKey" koanf:"accountkey"`
+	Container    string              `mapstructure:"container" koanf:"container"`
 }
 
 // IsValid validate the configuration of the retriever
@@ -67,6 +70,9 @@
 	if c.Kind == RedisRetriever {
 		return c.validateRedisRetriever()
 	}
+	if c.Kind == AzBlobStorageRetriever {
+		return c.validateAzBlobStorageRetriever()
+	}
 	return nil
 }
 
@@ -113,6 +119,19 @@
 	return nil
 }
 
+func (c *RetrieverConf) validateAzBlobStorageRetriever() error {
+	if c.AccountName == "" {
+		return fmt.Errorf("invalid retriever: no \"accountName\" property found for kind \"%s\"", c.Kind)
+	}
+	if c.Container == "" {
+		return fmt.Errorf("invalid retriever: no \"container\" property found for kind \"%s\"", c.Kind)
+	}
+	if c.Object == "" {
+		return fmt.Errorf("invalid retriever: no \"object\" property found for kind \"%s\"", c.Kind)
+	}
+	return nil
+}
+
 // RetrieverKind is an enum containing all accepted Retriever kind
 type RetrieverKind string
 
@@ -127,13 +146,15 @@
 	MongoDBRetriever       RetrieverKind = "mongodb"
 	RedisRetriever         RetrieverKind = "redis"
 	BitbucketRetriever     RetrieverKind = "bitbucket"
+	AzBlobStorageRetriever RetrieverKind = "azureBlobStorage"
 )
 
 // IsValid is checking if the value is part of the enum
 func (r RetrieverKind) IsValid() error {
 	switch r {
 	case HTTPRetriever, GitHubRetriever, GitlabRetriever, S3Retriever, RedisRetriever,
-		FileRetriever, GoogleStorageRetriever, KubernetesRetriever, MongoDBRetriever, BitbucketRetriever:
+		FileRetriever, GoogleStorageRetriever, KubernetesRetriever, MongoDBRetriever,
+		BitbucketRetriever, AzBlobStorageRetriever:
 		return nil
 	}
 	return fmt.Errorf("invalid retriever: kind \"%s\" is not supported", r)

cmd/relayproxy/config/retriever_test.go

@@ -122,6 +122,39 @@ func TestRetrieverConf_IsValid(t *testing.T) {
 			wantErr:  true,
 			errValue: "invalid retriever: no \"bucket\" property found for kind \"googleStorage\"",
 		},
+		{
+			name: "kind azureBlobStorage without object",
+			fields: config.RetrieverConf{
+				Kind:        "azureBlobStorage",
+				Container:   "testcontainer",
+				AccountName: "devstoreaccount1",
+				AccountKey:  "Eby8vdM02xNOcqFlqUwJPLlmEtlCDXJ1OUzFT50uSRZ6IFsuFq2UVErCz4I6tq",
+			},
+			wantErr:  true,
+			errValue: "invalid retriever: no \"object\" property found for kind \"azureBlobStorage\"",
+		},
+		{
+			name: "kind azureBlobStorage without accountName",
+			fields: config.RetrieverConf{
+				Kind:       "azureBlobStorage",
+				Container:  "testcontainer",
+				Object:     "flag-config.yaml",
+				AccountKey: "Eby8vdM02xNOcqFlqUwJPLlmEtlCDXJ1OUzFT50uSRZ6IFsuFq2UVErCz4I6tq",
+			},
+			wantErr:  true,
+			errValue: "invalid retriever: no \"accountName\" property found for kind \"azureBlobStorage\"",
+		},
+		{
+			name: "kind azureBlobStorage without container",
+			fields: config.RetrieverConf{
+				Kind:        "azureBlobStorage",
+				Object:      "flag-config.yaml",
+				AccountName: "devstoreaccount1",
+				AccountKey:  "Eby8vdM02xNOcqFlqUwJPLlmEtlCDXJ1OUzFT50uSRZ6IFsuFq2UVErCz4I6tq",
+			},
+			wantErr:  true,
+			errValue: "invalid retriever: no \"container\" property found for kind \"azureBlobStorage\"",
+		},
 		{
 			name: "valid s3",
 			fields: config.RetrieverConf{

cmd/relayproxy/service/gofeatureflag.go

@@ -26,6 +26,7 @@
 	"github.com/thomaspoignant/go-feature-flag/notifier/slacknotifier"
 	"github.com/thomaspoignant/go-feature-flag/notifier/webhooknotifier"
 	"github.com/thomaspoignant/go-feature-flag/retriever"
+	"github.com/thomaspoignant/go-feature-flag/retriever/azblobstorageretriever"
 	"github.com/thomaspoignant/go-feature-flag/retriever/bitbucketretriever"
 	"github.com/thomaspoignant/go-feature-flag/retriever/fileretriever"
 	"github.com/thomaspoignant/go-feature-flag/retriever/gcstorageretriever"
@@ -186,6 +187,13 @@
 		return &mongodbretriever.Retriever{Database: c.Database, URI: c.URI, Collection: c.Collection}, nil
 	case config.RedisRetriever:
 		return &redisretriever.Retriever{Options: c.RedisOptions, Prefix: c.RedisPrefix}, nil
+	case config.AzBlobStorageRetriever:
+		return &azblobretriever.Retriever{
+			Container:   c.Container,
+			Object:      c.Object,
+			AccountName: c.AccountName,
+			AccountKey:  c.AccountKey,
+		}, nil
 	default:
 		return nil, fmt.Errorf("invalid retriever: kind \"%s\" "+
 			"is not supported", c.Kind)

retriever/azblobstorageretriever/README.md

@@ -0,0 +1,105 @@
+# Azure Blob Storage Feature Flag Retriever
+
+This retriever is used to retrieve data from a Container on Azure Blob Storage.
+
+## Installation
+
+```bash
+go get github.com/thomaspoignant/go-feature-flag/retriever/azblobstorageretriever
+```
+
+## Usage
+
+### Configuration
+
+Create a `Retriever` struct with the following fields:
+
+- `Container`: Name of the Azure Blob Storage container
+- `AccountName`: Azure Storage Account Name
+- `AccountKey`: (Optional) Storage Account Key
+- `ServiceURL`: (Optional) Custom service URL
+- `Object`: Name of the feature flag file in the container
+
+### Authentication Methods
+
+#### 1. Shared Key Authentication
+
+```go
+retriever := &azblobretriever.Retriever{
+    Container:    "your-container",
+    AccountName:  "your-account-name",
+    AccountKey:   "your-account-key",
+    Object:       "feature-flags.json",
+}
+```
+
+#### 2. Microsoft Entra ID (Recommended)
+
+```go
+retriever := &azblobretriever.Retriever{
+    Container:    "your-container",
+    AccountName:  "your-account-name",
+    Object:       "feature-flags.json",
+}
+```
+
+### Retrieving Feature Flags
+
+```go
+package main
+
+import (
+    "context"
+    "fmt"
+    "log"
+    "time"
+
+    "github.com/thomaspoignant/go-feature-flag/retriever/azblobstorageretriever"
+)
+
+func main() {
+    retriever := &azblobretriever.Retriever{
+        Container:   "feature-flags",
+        AccountName: "mystorageaccount",
+        AccountKey:  "your-account-key",
+        Object:      "flags.json",
+    }
+
+    ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+    defer cancel()
+
+    err := retriever.Init(ctx, nil)
+    defer func() { _ = r.Shutdown(ctx) }()
+    if err != nil {
+        log.Fatalf("Failed to initialize retriever:", err)
+    }
+
+    data, err := retriever.Retrieve(ctx)
+    if err != nil {
+        log.Fatalf("Failed to retrieve feature flags: %v", err)
+    }
+
+    fmt.Println("Retrieved feature flags:")
+    fmt.Println(string(data))
+}
+```
+
+## Key Features
+
+- Supports both shared key and default Azure credential authentication
+- Automatic retry mechanism for blob downloads
+- Flexible configuration with optional custom service URL
+
+## Error Handling
+
+The `Retrieve` method returns an error if:
+- `AccountName` is empty
+- `Container` or `Object` is not specified
+- There's an issue initializing the Azure client.
+- There's a problem downloading or reading the file from Azure Blob Storage.
+
+## Best Practices
+
+- **Security** Never hard-code your `AccountKey` in your source code. Use environment variables or a secure secret management system.
+- **Error Handling**: Always check for errors returned by the `Retrieve` method.
+- **Context**: Use a context with timeout for better control over the retrieval process.

retriever/azblobstorageretriever/retriever.go

@@ -0,0 +1,113 @@
+package azblobretriever
+
+import (
+	"context"
+	"fmt"
+	"io"
+
+	"github.com/Azure/azure-sdk-for-go/sdk/azidentity"
+	"github.com/Azure/azure-sdk-for-go/sdk/storage/azblob"
+	"github.com/thomaspoignant/go-feature-flag/retriever"
+	"github.com/thomaspoignant/go-feature-flag/utils/fflog"
+)
+
+type Retriever struct {
+	// Container is the name of your Azure Blob Storage Container.
+	Container string
+
+	// Storage Account Name and Key
+	AccountName string
+	AccountKey  string
+
+	// ServiceURL is the URL of the storage account e.g. https://<account>.blob.core.windows.net/
+	// It can be overridden by the user to use a custom URL.
+	// Default: https://<account>.blob.core.windows.net/
+	ServiceURL string
+
+	// Object is the name of your file in your container.
+	Object string
+
+	// client is a pointer to an Azure Blob Storage client.
+	// It provides access to Azure Blob Storage services for operations like
+	// creating, reading, updating, and deleting blobs.
+	client *azblob.Client
+	status retriever.Status
+}
+
+func (r *Retriever) Init(_ context.Context, _ *fflog.FFLogger) error {
+	if r.AccountName == "" {
+		return fmt.Errorf("unable to connect to Azure Blob Storage, \"AccountName\" cannot be empty")
+	}
+
+	url := r.ServiceURL
+	if url == "" {
+		url = fmt.Sprintf("https://%s.blob.core.windows.net/", r.AccountName)
+	}
+
+	var client *azblob.Client
+	var err error
+
+	if r.AccountKey == "" {
+		var cred *azidentity.DefaultAzureCredential
+		cred, err = azidentity.NewDefaultAzureCredential(nil)
+		if err != nil {
+			r.status = retriever.RetrieverError
+			return err
+		}
+		client, err = azblob.NewClient(url, cred, nil)
+	} else {
+		var cred *azblob.SharedKeyCredential
+		cred, err = azblob.NewSharedKeyCredential(r.AccountName, r.AccountKey)
+		if err != nil {
+			r.status = retriever.RetrieverError
+			return err
+		}
+		client, err = azblob.NewClientWithSharedKeyCredential(url, cred, nil)
+	}
+
+	if err != nil {
+		r.status = retriever.RetrieverError
+		return err
+	}
+
+	r.client = client
+	r.status = retriever.RetrieverReady
+	return nil
+}
+
+func (r *Retriever) Shutdown(_ context.Context) error {
+	r.client = nil
+	r.status = retriever.RetrieverNotReady
+	return nil
+}
+
+func (r *Retriever) Status() retriever.Status {
+	return r.status
+}
+
+func (r *Retriever) Retrieve(ctx context.Context) ([]byte, error) {
+	if r.client == nil {
+		r.status = retriever.RetrieverError
+		return nil, fmt.Errorf("client is not initialized")
+	}
+
+	if r.Object == "" || r.Container == "" {
+		return nil, fmt.Errorf("missing mandatory information object=%s, repositorySlug=%s", r.Object, r.Container)
+	}
+
+	fileStream, err := r.client.DownloadStream(ctx, r.Container, r.Object, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	retryReader := fileStream.NewRetryReader(ctx, nil)
+	defer func() { _ = retryReader.Close() }()
+
+	body, err := io.ReadAll(retryReader)
+	if err != nil {
+		return nil,
+			fmt.Errorf("unable to read from Azure Blob Storage Object %s in Container %s, error: %s", r.Object, r.Container, err)
+	}
+
+	return body, nil
+}