master: add master.follower to handle read file id lookup requests

weed/command/command.go

@@ -28,6 +28,7 @@ var Commands = []*Command{
 	cmdFuse,
 	cmdGateway,
 	cmdMaster,
+	cmdMasterFollower,
 	cmdMount,
 	cmdS3,
 	cmdIam,

weed/command/master_follower.go

@@ -0,0 +1,145 @@
+package command
+
+import (
+	"context"
+	"fmt"
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/chrislusf/seaweedfs/weed/glog"
+	"github.com/chrislusf/seaweedfs/weed/pb"
+	"github.com/chrislusf/seaweedfs/weed/pb/master_pb"
+	"github.com/chrislusf/seaweedfs/weed/security"
+	"github.com/chrislusf/seaweedfs/weed/server"
+	"github.com/chrislusf/seaweedfs/weed/util"
+	"github.com/gorilla/mux"
+	"google.golang.org/grpc/reflection"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+)
+
+var (
+	mf MasterOptions
+)
+
+func init() {
+	cmdMasterFollower.Run = runMasterFollower // break init cycle
+	mf.port = cmdMasterFollower.Flag.Int("port", 9334, "http listen port")
+	mf.ipBind = cmdMasterFollower.Flag.String("ip.bind", "", "ip address to bind to")
+	mf.peers = cmdMasterFollower.Flag.String("masters", "localhost:9333", "all master nodes in comma separated ip:port list, example: 127.0.0.1:9093,127.0.0.1:9094,127.0.0.1:9095")
+
+	mf.ip = aws.String(util.DetectedHostAddress())
+	mf.metaFolder = aws.String("")
+	mf.volumeSizeLimitMB = nil
+	mf.volumePreallocate = nil
+	mf.defaultReplication = nil
+	mf.garbageThreshold = aws.Float64(0.1)
+	mf.whiteList = nil
+	mf.disableHttp = aws.Bool(false)
+	mf.metricsAddress = aws.String("")
+	mf.metricsIntervalSec = aws.Int(0)
+	mf.raftResumeState = aws.Bool(false)
+}
+
+var cmdMasterFollower = &Command{
+	UsageLine: "master.follower -port=9333 -masters=<master1Host>:<master1Port>",
+	Short:     "start a master follower",
+	Long: `start a master follower to provide volume=>location mapping service
+
+	The master follower does not participate in master election. 
+	It just follow the existing masters, and listen for any volume location changes.
+
+	In most cases, the master follower is not needed. In big data centers with thousands of volume
+	servers. In theory, the master may have trouble to keep up with the write requests and read requests.
+
+	The master follower can relieve the master from from read requests, which only needs to 
+	lookup a fileId or volumeId.
+
+	The master follower currently can handle fileId lookup requests:
+		/dir/lookup?volumeId=4
+		/dir/lookup?fileId=4,49c50924569199
+	And gRPC API
+		rpc LookupVolume (LookupVolumeRequest) returns (LookupVolumeResponse) {}
+
+	This master follower is stateless and can run from any place.
+
+  `,
+}
+
+func runMasterFollower(cmd *Command, args []string) bool {
+
+	util.LoadConfiguration("security", false)
+	util.LoadConfiguration("master", false)
+
+	startMasterFollower(mf)
+
+	return true
+}
+
+func startMasterFollower(masterOptions MasterOptions) {
+
+	// collect settings from main masters
+	masters := strings.Split(*mf.peers, ",")
+	masterGrpcAddresses, err := pb.ParseServersToGrpcAddresses(masters)
+	if err != nil {
+		glog.V(0).Infof("ParseFilerGrpcAddress: %v", err)
+		return
+	}
+
+	grpcDialOption := security.LoadClientTLS(util.GetViper(), "grpc.master")
+	for i := 0; i < 10; i++ {
+		err = pb.WithOneOfGrpcMasterClients(masterGrpcAddresses, grpcDialOption, func(client master_pb.SeaweedClient) error {
+			resp, err := client.GetMasterConfiguration(context.Background(), &master_pb.GetMasterConfigurationRequest{})
+			if err != nil {
+				return fmt.Errorf("get master grpc address %v configuration: %v", masterGrpcAddresses, err)
+			}
+			masterOptions.defaultReplication = &resp.DefaultReplication
+			masterOptions.volumeSizeLimitMB = aws.Uint(uint(resp.VolumeSizeLimitMB))
+			masterOptions.volumePreallocate = &resp.VolumePreallocate
+			return nil
+		})
+		if err != nil {
+			glog.V(0).Infof("failed to talk to filer %v: %v", masterGrpcAddresses, err)
+			glog.V(0).Infof("wait for %d seconds ...", i+1)
+			time.Sleep(time.Duration(i+1) * time.Second)
+		}
+	}
+	if err != nil {
+		glog.Errorf("failed to talk to filer %v: %v", masterGrpcAddresses, err)
+		return
+	}
+
+
+	option := masterOptions.toMasterOption(nil)
+	option.IsFollower = true
+
+
+	r := mux.NewRouter()
+	ms := weed_server.NewMasterServer(r, option, masters)
+	listeningAddress := *masterOptions.ipBind + ":" + strconv.Itoa(*masterOptions.port)
+	glog.V(0).Infof("Start Seaweed Master %s at %s", util.Version(), listeningAddress)
+	masterListener, e := util.NewListener(listeningAddress, 0)
+	if e != nil {
+		glog.Fatalf("Master startup error: %v", e)
+	}
+
+	// starting grpc server
+	grpcPort := *masterOptions.port + 10000
+	grpcL, err := util.NewListener(*masterOptions.ipBind+":"+strconv.Itoa(grpcPort), 0)
+	if err != nil {
+		glog.Fatalf("master failed to listen on grpc port %d: %v", grpcPort, err)
+	}
+	grpcS := pb.NewGrpcServer(security.LoadServerTLS(util.GetViper(), "grpc.master"))
+	master_pb.RegisterSeaweedServer(grpcS, ms)
+	reflection.Register(grpcS)
+	glog.V(0).Infof("Start Seaweed Master %s grpc server at %s:%d", util.Version(), *masterOptions.ip, grpcPort)
+	go grpcS.Serve(grpcL)
+
+	go ms.MasterClient.KeepConnectedToMaster()
+
+	// start http server
+	httpS := &http.Server{Handler: r}
+	go httpS.Serve(masterListener)
+
+	select {}
+}