1 files changed, 143 insertions, 0 deletions
diff --git a/weed/server/master_grpc_server_admin.go b/weed/server/master_grpc_server_admin.go
new file mode 100644
index 000000000..93c9e4e4e
--- /dev/null
+++ b/weed/server/master_grpc_server_admin.go
@@ -0,0 +1,143 @@
+package weed_server
+
+import (
+	"context"
+	"fmt"
+	"github.com/chrislusf/seaweedfs/weed/glog"
+	"math/rand"
+	"sync"
+	"time"
+
+	"github.com/chrislusf/seaweedfs/weed/pb/master_pb"
+)
+
+/*
+How exclusive lock works?
+-----------
+
+Shell
+------
+When shell lock,
+  * lease an admin token (lockTime, token)
+  * start a goroutine to renew the admin token periodically
+
+When shell unlock
+  * stop the renewal goroutine
+  * sends a release lock request
+
+Master
+------
+Master maintains:
+  * randomNumber
+  * lastLockTime
+When master receives the lease/renew request from shell
+  If lastLockTime still fresh {
+    if is a renew and token is valid {
+      // for renew
+      generate the randomNumber => token
+      return
+    }
+    refuse
+    return
+  } else {
+    // for fresh lease request
+    generate the randomNumber => token
+    return
+  }
+
+When master receives the release lock request from shell
+  set the lastLockTime to zero
+
+
+The volume server does not need to verify.
+This makes the lock/unlock optional, similar to what golang code usually does.
+
+*/
+
+const (
+	LockDuration = 10 * time.Second
+)
+
+type AdminLock struct {
+	accessSecret   int64
+	accessLockTime time.Time
+	lastClient     string
+}
+
+type AdminLocks struct {
+	locks map[string]*AdminLock
+	sync.RWMutex
+}
+
+func NewAdminLocks() *AdminLocks {
+	return &AdminLocks{
+		locks: make(map[string]*AdminLock),
+	}
+}
+
+func (locks *AdminLocks) isLocked(lockName string) (clientName string, isLocked bool) {
+	locks.RLock()
+	defer locks.RUnlock()
+	adminLock, found := locks.locks[lockName]
+	if !found {
+		return "", false
+	}
+	glog.V(4).Infof("isLocked %v", adminLock.lastClient)
+	return adminLock.lastClient, adminLock.accessLockTime.Add(LockDuration).After(time.Now())
+}
+
+func (locks *AdminLocks) isValidToken(lockName string, ts time.Time, token int64) bool {
+	locks.RLock()
+	defer locks.RUnlock()
+	adminLock, found := locks.locks[lockName]
+	if !found {
+		return false
+	}
+	return adminLock.accessLockTime.Equal(ts) && adminLock.accessSecret == token
+}
+
+func (locks *AdminLocks) generateToken(lockName string, clientName string) (ts time.Time, token int64) {
+	locks.Lock()
+	defer locks.Unlock()
+	lock := &AdminLock{
+		accessSecret:   rand.Int63(),
+		accessLockTime: time.Now(),
+		lastClient:     clientName,
+	}
+	locks.locks[lockName] = lock
+	return lock.accessLockTime, lock.accessSecret
+}
+
+func (locks *AdminLocks) deleteLock(lockName string) {
+	locks.Lock()
+	defer locks.Unlock()
+	delete(locks.locks, lockName)
+}
+
+func (ms *MasterServer) LeaseAdminToken(ctx context.Context, req *master_pb.LeaseAdminTokenRequest) (*master_pb.LeaseAdminTokenResponse, error) {
+	resp := &master_pb.LeaseAdminTokenResponse{}
+
+	if lastClient, isLocked := ms.adminLocks.isLocked(req.LockName); isLocked {
+		glog.V(4).Infof("LeaseAdminToken %v", lastClient)
+		if req.PreviousToken != 0 && ms.adminLocks.isValidToken(req.LockName, time.Unix(0, req.PreviousLockTime), req.PreviousToken) {
+			// for renew
+			ts, token := ms.adminLocks.generateToken(req.LockName, req.ClientName)
+			resp.Token, resp.LockTsNs = token, ts.UnixNano()
+			return resp, nil
+		}
+		// refuse since still locked
+		return resp, fmt.Errorf("already locked by " + lastClient)
+	}
+	// for fresh lease request
+	ts, token := ms.adminLocks.generateToken(req.LockName, req.ClientName)
+	resp.Token, resp.LockTsNs = token, ts.UnixNano()
+	return resp, nil
+}
+
+func (ms *MasterServer) ReleaseAdminToken(ctx context.Context, req *master_pb.ReleaseAdminTokenRequest) (*master_pb.ReleaseAdminTokenResponse, error) {
+	resp := &master_pb.ReleaseAdminTokenResponse{}
+	if ms.adminLocks.isValidToken(req.LockName, time.Unix(0, req.PreviousLockTime), req.PreviousToken) {
+		ms.adminLocks.deleteLock(req.LockName)
+	}
+	return resp, nil
+}