从源代码级别看懂MinIO对象存储网关的实现

  nas    Network-attached storage (NAS)
  azure  Microsoft Azure Blob Storage
  s3     Amazon Simple Storage Service (S3)
  hdfs   Hadoop Distributed File System (HDFS)
  gcs    Google Cloud Storage

minio gateway nas PATH

 minio gateway nas /tmp/nas/

package main
import (
   "os"
   
   minio "github.com/minio/minio/cmd"
   // Import gateway
   _ "github.com/minio/minio/cmd/gateway"
)
func main() {
   minio.Main(os.Args)
}

func newApp(name string) *cli.App {
   // Collection of minio commands currently supported are.
   commands := []cli.Command{}
   //省略无关代码
   // registerCommand registers a cli command.
   registerCommand := func(command cli.Command) {
      commands = append(commands, command)
   }
    //省略无关代码
   // Register all commands.
   registerCommand(serverCmd)
   registerCommand(gatewayCmd)//注册的网关命令。
   app := cli.NewApp()
   app.Name = name
   //省略无关代码
   app.Commands = commands
   app.CustomAppHelpTemplate = minioHelpTemplate
   //省略无关代码
   return app
}
// Main main for minio server.
func Main(args []string) {
   // Set the minio app name.
   appName := filepath.Base(args[0])
   // Run the app - exit on error.
   if err := newApp(appName).Run(args); err != nil {
      os.Exit(1)
   }
}

➜  minio                      
NAME:
  minio - High Performance Object Storage
USAGE:
  minio [FLAGS] COMMAND [ARGS...]
COMMANDS:
  server   start object storage server
  gateway  start object storage gateway

var (
   gatewayCmd = cli.Command{
      Name:            "gateway",
      Usage:           "start object storage gateway",
      Flags:           append(ServerFlags, GlobalFlags...),
      HideHelpCommand: true,
   }
)

package gateway
import (
   // Import all gateways please keep the order
   // NAS
   _ "github.com/minio/minio/cmd/gateway/nas"
   // Azure
   _ "github.com/minio/minio/cmd/gateway/azure"
   // S3
   _ "github.com/minio/minio/cmd/gateway/s3"
   // HDFS
   _ "github.com/minio/minio/cmd/gateway/hdfs"
   // GCS (use only if you must, GCS already supports S3 API)
   _ "github.com/minio/minio/cmd/gateway/gcs"
   // gateway functionality is frozen, no new gateways are being implemented
   // or considered for upstream inclusion at this point in time. if needed
   // please keep a fork of the project.
)

func init() {
   const nasGatewayTemplate = `NAME:`//省略很多字符串
   minio.RegisterGatewayCommand(cli.Command{
      Name:               minio.NASBackendGateway,
      Usage:              "Network-attached storage (NAS)",
      Action:             nasGatewayMain,
      CustomHelpTemplate: nasGatewayTemplate,
      HideHelpCommand:    true,
   })
}

// RegisterGatewayCommand registers a new command for gateway.
func RegisterGatewayCommand(cmd cli.Command) error {
   cmd.Flags = append(append(cmd.Flags, ServerFlags...), GlobalFlags...)
   gatewayCmd.Subcommands = append(gatewayCmd.Subcommands, cmd)
   return nil
}

 minio gateway nas /tmp/nas/

func init() {
   const nasGatewayTemplate = `NAME:`//省略很多字符串
   minio.RegisterGatewayCommand(cli.Command{
      Name:               minio.NASBackendGateway,
      Usage:              "Network-attached storage (NAS)",
      Action:             nasGatewayMain,
      CustomHelpTemplate: nasGatewayTemplate,
      HideHelpCommand:    true,
   })
}

// Handler for 'minio gateway nas' command line.
func nasGatewayMain(ctx *cli.Context) {
   // Validate gateway arguments.
   if !ctx.Args().Present() || ctx.Args().First() == "help" {
      cli.ShowCommandHelpAndExit(ctx, minio.NASBackendGateway, 1)
   }
   minio.StartGateway(ctx, &NAS{ctx.Args().First()})
}

// StartGateway - handler for 'minio gateway <name>'.
func StartGateway(ctx *cli.Context, gw Gateway) {
  //为了分析过程，我先省略这个函数的逻辑
}

// Gateway represents a gateway backend.
type Gateway interface {
   // Name returns the unique name of the gateway.
   Name() string
   // NewGatewayLayer returns a new  ObjectLayer.
   NewGatewayLayer(creds auth.Credentials) (ObjectLayer, error)
   // Returns true if gateway is ready for production.
   Production() bool
}

// NAS implements Gateway.
type NAS struct {
   path string
}
// Name implements Gateway interface.
func (g *NAS) Name() string {
   return minio.NASBackendGateway
}
// NewGatewayLayer returns nas gatewaylayer.
func (g *NAS) NewGatewayLayer(creds auth.Credentials) (minio.ObjectLayer, error) {
   var err error
   newObject, err := minio.NewFSObjectLayer(g.path)
   if err != nil {
      return nil, err
   }
   return &nasObjects{newObject}, nil
}
// Production - nas gateway is production ready.
func (g *NAS) Production() bool {
   return true
}

// StartGateway - handler for 'minio gateway <name>'.
func StartGateway(ctx *cli.Context, gw Gateway) {
    //省略无关很多紧要的代码
   // Handle common command args.
   handleCommonCmdArgs(ctx)
   // Handle gateway specific env
   gatewayHandleEnvVars()
   // Set when gateway is enabled
   globalIsGateway = true
   // Initialize router. `SkipClean(true)` stops gorilla/mux from
   // normalizing URL path minio/minio#3256
   // avoid URL path encoding minio/minio#8950
   router := mux.NewRouter().SkipClean(true).UseEncodedPath()
   // operations such as profiling, server info etc.
   registerAdminRouter(router, enableConfigOps, enableIAMOps)
   
   // Add API router.
   registerAPIRouter(router)
   // Use all the middlewares
   router.Use(registerMiddlewares)
   newObject, err := gw.NewGatewayLayer(globalActiveCred)
   newObject = NewGatewayLayerWithLocker(newObject)
   // Once endpoints are finalized, initialize the new object api in safe mode.
   globalObjLayerMutex.Lock()
   globalObjectAPI = newObject //关键代码，使用网关接口生成的ObjectLayer
   globalObjLayerMutex.Unlock()
   
   handleSignals()
}