Support additional catalogs

* add an --additional-catalog option
* --catalog can also override default catalogs with multiple other
  catalogs
* catalogs are merged in order catalogs first and additional-catalogs
  second

Author: slimslenderslacks

cmd/docker-mcp/commands/gateway.go

@@ -18,10 +18,11 @@ func gatewayCommand(docker docker.Client) *cobra.Command {
 
 	// Have different defaults for the on-host gateway and the in-container gateway.
 	var options gateway.Config
+	var additionalCatalogs []string
 	if os.Getenv("DOCKER_MCP_IN_CONTAINER") == "1" {
 		// In-container.
 		options = gateway.Config{
-			CatalogPath: catalog.DockerCatalogURL,
+			CatalogPath: []string{catalog.DockerCatalogURL},
 			SecretsPath: "docker-desktop:/run/secrets/mcp_secret:/.env",
 			Options: gateway.Options{
 				Cpus:             1,
@@ -36,7 +37,7 @@ func gatewayCommand(docker docker.Client) *cobra.Command {
 	} else {
 		// On-host.
 		options = gateway.Config{
-			CatalogPath:  "docker-mcp.yaml",
+			CatalogPath:  []string{"docker-mcp.yaml"},
 			RegistryPath: "registry.yaml",
 			ConfigPath:   "config.yaml",
 			SecretsPath:  "docker-desktop",
@@ -60,12 +61,15 @@ func gatewayCommand(docker docker.Client) *cobra.Command {
 				options.Port = 8811
 			}
 
+			// Append additional catalogs to the main catalog path
+			options.CatalogPath = append(options.CatalogPath, additionalCatalogs...)
 			return gateway.NewGateway(options, docker).Run(cmd.Context())
 		},
 	}
 
 	runCmd.Flags().StringSliceVar(&options.ServerNames, "servers", nil, "names of the servers to enable (if non empty, ignore --registry flag)")
-	runCmd.Flags().StringVar(&options.CatalogPath, "catalog", options.CatalogPath, "path to the docker-mcp.yaml catalog (absolute or relative to ~/.docker/mcp/catalogs/)")
+	runCmd.Flags().StringSliceVar(&options.CatalogPath, "catalog", options.CatalogPath, "paths to docker catalogs (absolute or relative to ~/.docker/mcp/catalogs/)")
+	runCmd.Flags().StringSliceVar(&additionalCatalogs, "additional-catalog", nil, "additional catalog paths to append to the default catalogs")
 	runCmd.Flags().StringVar(&options.RegistryPath, "registry", options.RegistryPath, "path to the registry.yaml (absolute or relative to ~/.docker/mcp/)")
 	runCmd.Flags().StringVar(&options.ConfigPath, "config", options.ConfigPath, "path to the config.yaml (absolute or relative to ~/.docker/mcp/)")
 	runCmd.Flags().StringVar(&options.SecretsPath, "secrets", options.SecretsPath, "colon separated paths to search for secrets. Can be `docker-desktop` or a path to a .env file (default to using Docker Deskop's secrets API)")

cmd/docker-mcp/internal/catalog/catalog.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"log"
 	"net/http"
 	"os"
 	"path/filepath"
@@ -15,20 +16,29 @@ import (
 )
 
 func Get(ctx context.Context) (Catalog, error) {
-	return ReadFrom(ctx, "docker-mcp.yaml")
+	return ReadFrom(ctx, []string{"docker-mcp.yaml"})
 }
 
-func ReadFrom(ctx context.Context, fileOrURL string) (Catalog, error) {
-	servers, err := readMCPServers(ctx, fileOrURL)
-	if err != nil {
-		return Catalog{}, err
-	}
-	if servers == nil {
-		servers = map[string]Server{}
+func ReadFrom(ctx context.Context, fileOrURLs []string) (Catalog, error) {
+	mergedServers := map[string]Server{}
+
+	for _, fileOrURL := range fileOrURLs {
+		servers, err := readMCPServers(ctx, fileOrURL)
+		if err != nil {
+			return Catalog{}, err
+		}
+
+		// Merge servers into the combined map, checking for overlaps
+		for key, server := range servers {
+			if _, exists := mergedServers[key]; exists {
+				log.Printf("Warning: overlapping key '%s' found in catalog '%s', overwriting previous value", key, fileOrURL)
+			}
+			mergedServers[key] = server
+		}
 	}
 
 	return Catalog{
-		Servers: servers,
+		Servers: mergedServers,
 	}, nil
 }
 

cmd/docker-mcp/internal/gateway/config.go

@@ -3,7 +3,7 @@ package gateway
 type Config struct {
 	Options
 	ServerNames  []string
-	CatalogPath  string
+	CatalogPath  []string
 	ConfigPath   string
 	RegistryPath string
 	SecretsPath  string

cmd/docker-mcp/internal/gateway/configuration.go

@@ -86,7 +86,7 @@ func (c *Configuration) Find(serverName string) (*catalog.ServerConfig, *map[str
 }
 
 type FileBasedConfiguration struct {
-	CatalogPath  string
+	CatalogPath  []string
 	ServerNames  []string // Takes precedence over the RegistryPath
 	RegistryPath string
 	ConfigPath   string