feat(config): specify to use in-memory database (#74)

<!-- Provide a brief summary of your changes -->
Add support for specifying database type (MongoDB or in-memory
database).

## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->
The README states that MCP Registry supports both MongoDB and in-memory
databases, but does not provide the capability to specify which database
type to use.


https://github.com/modelcontextprotocol/registry/blob/5d9171bdccf579398273806a7067cda29e88363c/README.md?plain=1#L19

This PR addresses this limitation by adding explicit database type
configuration through the `DATABASE_TYPE` environment variable, allowing
users to choose between `mongodb` and `memory` database types in a
standardized way.

## How Has This Been Tested?
<!-- Have you tested this in a real application? Which scenarios were
tested? -->
Yes

```console
$ export MCP_REGISTRY_DATABASE_TYPE="memory"
$ ./scripts/test_endpoints.sh
Testing health endpoint: http://localhost:8080/v0/health
Status Code: 200
Response:
{
  "status": "ok",
  "github_client_id": ""
}
Health check successful
-------------------------------------
Testing servers endpoint: http://localhost:8080/v0/servers
Status Code: 200
Response Summary:
Total registries: 0
servers Names:

Pagination Metadata:
{}

servers Details:
{
  "servers": [],
  "metadata": {}
}
servers request successful
-------------------------------------
Testing ping endpoint: http://localhost:8080/v0/ping
Status Code: 200
Response:
{
  "status": "ok",
  "version": "dev"
}
Ping successful
-------------------------------------
All tests passed successfully!
```

## Breaking Changes
<!-- Will users need to update their code or configurations? -->
No

## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [x] Documentation update

## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed

## Additional context
<!-- Add any other context, implementation notes, or design decisions
-->
Close #63

---------

Co-authored-by: Avinash Sridhar <[email protected]>
Co-authored-by: Copilot <[email protected]>

Author: 3 people

README.md

@@ -289,6 +289,7 @@ The service can be configured using environment variables:
 | Variable | Description | Default |
 |----------|-------------|---------|
 | `MCP_REGISTRY_APP_VERSION`           | Application version | `dev` |
+| `MCP_REGISTRY_DATABASE_TYPE`         | Database type | `mongodb` |
 | `MCP_REGISTRY_COLLECTION_NAME`       | MongoDB collection name | `servers_v2` |
 | `MCP_REGISTRY_DATABASE_NAME`         | MongoDB database name | `mcp-registry` |
 | `MCP_REGISTRY_DATABASE_URL`          | MongoDB connection string | `mongodb://localhost:27017` |

cmd/registry/main.go

@@ -15,6 +15,7 @@ import (
 	"github.com/modelcontextprotocol/registry/internal/auth"
 	"github.com/modelcontextprotocol/registry/internal/config"
 	"github.com/modelcontextprotocol/registry/internal/database"
+	"github.com/modelcontextprotocol/registry/internal/model"
 	"github.com/modelcontextprotocol/registry/internal/service"
 )
 
@@ -39,38 +40,48 @@ func main() {
 	// Initialize services based on environment
 	var registryService service.RegistryService
 
-	// Use MongoDB for real registry service in production/other environments
-	// Create a context with timeout for MongoDB connection
-	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
-	defer cancel()
-
-	// Connect to MongoDB
-	mongoDB, err := database.NewMongoDB(ctx, cfg.DatabaseURL, cfg.DatabaseName, cfg.CollectionName)
-	if err != nil {
-		log.Printf("Failed to connect to MongoDB: %v", err)
-		return
-	}
-
-	// Create registry service with MongoDB
-	registryService = service.NewRegistryServiceWithDB(mongoDB)
-	log.Printf("MongoDB database name: %s", cfg.DatabaseName)
-	log.Printf("MongoDB collection name: %s", cfg.CollectionName)
-
-	// Store the MongoDB instance for later cleanup
-	defer func() {
-		if err := mongoDB.Close(); err != nil {
-			log.Printf("Error closing MongoDB connection: %v", err)
-		} else {
-			log.Println("MongoDB connection closed successfully")
+	switch cfg.DatabaseType {
+	case config.DatabaseTypeMemory:
+		memoryDB := database.NewMemoryDB(map[string]*model.Server{})
+		registryService = service.NewRegistryServiceWithDB(memoryDB)
+	case config.DatabaseTypeMongoDB:
+		// Use MongoDB for real registry service in production/other environments
+		// Create a context with timeout for MongoDB connection
+		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+		defer cancel()
+
+		// Connect to MongoDB
+		mongoDB, err := database.NewMongoDB(ctx, cfg.DatabaseURL, cfg.DatabaseName, cfg.CollectionName)
+		if err != nil {
+			log.Printf("Failed to connect to MongoDB: %v", err)
+			return
 		}
-	}()
 
-	if cfg.SeedImport {
-		log.Println("Importing data...")
-		if err := database.ImportSeedFile(mongoDB, cfg.SeedFilePath); err != nil {
-			log.Printf("Failed to import seed file: %v", err)
+		// Create registry service with MongoDB
+		registryService = service.NewRegistryServiceWithDB(mongoDB)
+		log.Printf("MongoDB database name: %s", cfg.DatabaseName)
+		log.Printf("MongoDB collection name: %s", cfg.CollectionName)
+
+		// Store the MongoDB instance for later cleanup
+		defer func() {
+			if err := mongoDB.Close(); err != nil {
+				log.Printf("Error closing MongoDB connection: %v", err)
+			} else {
+				log.Println("MongoDB connection closed successfully")
+			}
+		}()
+
+		if cfg.SeedImport {
+			log.Println("Importing data...")
+			if err := database.ImportSeedFile(mongoDB, cfg.SeedFilePath); err != nil {
+				log.Printf("Failed to import seed file: %v", err)
+			} else {
+				log.Println("Data import completed successfully")
+			}
 		}
-		log.Println("Data import completed successfully")
+	default:
+		log.Printf("Invalid database type: %s; supported types: %s, %s", cfg.DatabaseType, config.DatabaseTypeMemory, config.DatabaseTypeMongoDB)
+		return
 	}
 
 	// Initialize authentication services

internal/config/config.go

@@ -4,18 +4,26 @@ import (
 	env "github.com/caarlos0/env/v11"
 )
 
+type DatabaseType string
+
+const (
+	DatabaseTypeMongoDB DatabaseType = "mongodb"
+	DatabaseTypeMemory  DatabaseType = "memory"
+)
+
 // Config holds the application configuration
 type Config struct {
-	ServerAddress      string `env:"SERVER_ADDRESS" envDefault:":8080"`
-	DatabaseURL        string `env:"DATABASE_URL" envDefault:"mongodb://localhost:27017"`
-	DatabaseName       string `env:"DATABASE_NAME" envDefault:"mcp-registry"`
-	CollectionName     string `env:"COLLECTION_NAME" envDefault:"servers_v2"`
-	LogLevel           string `env:"LOG_LEVEL" envDefault:"info"`
-	SeedFilePath       string `env:"SEED_FILE_PATH" envDefault:"data/seed.json"`
-	SeedImport         bool   `env:"SEED_IMPORT" envDefault:"true"`
-	Version            string `env:"VERSION" envDefault:"dev"`
-	GithubClientID     string `env:"GITHUB_CLIENT_ID" envDefault:""`
-	GithubClientSecret string `env:"GITHUB_CLIENT_SECRET" envDefault:""`
+	ServerAddress      string       `env:"SERVER_ADDRESS" envDefault:":8080"`
+	DatabaseType       DatabaseType `env:"DATABASE_TYPE" envDefault:"mongodb"`
+	DatabaseURL        string       `env:"DATABASE_URL" envDefault:"mongodb://localhost:27017"`
+	DatabaseName       string       `env:"DATABASE_NAME" envDefault:"mcp-registry"`
+	CollectionName     string       `env:"COLLECTION_NAME" envDefault:"servers_v2"`
+	LogLevel           string       `env:"LOG_LEVEL" envDefault:"info"`
+	SeedFilePath       string       `env:"SEED_FILE_PATH" envDefault:"data/seed.json"`
+	SeedImport         bool         `env:"SEED_IMPORT" envDefault:"true"`
+	Version            string       `env:"VERSION" envDefault:"dev"`
+	GithubClientID     string       `env:"GITHUB_CLIENT_ID" envDefault:""`
+	GithubClientSecret string       `env:"GITHUB_CLIENT_SECRET" envDefault:""`
 }
 
 // NewConfig creates a new configuration with default values