Use the same lock for the scanner and site replication healing (#15985)

cmd/shared-lock.go

@@ -0,0 +1,86 @@
+// Copyright (c) 2015-2022 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package cmd
+
+import (
+	"context"
+	"time"
+)
+
+var sharedLockTimeout = newDynamicTimeoutWithOpts(dynamicTimeoutOpts{
+	timeout:       30 * time.Second,
+	minimum:       10 * time.Second,
+	retryInterval: time.Minute,
+})
+
+type sharedLock struct {
+	lockContext chan LockContext
+}
+
+func (ld sharedLock) backgroundRoutine(ctx context.Context, objAPI ObjectLayer, lockName string) {
+	for {
+		locker := objAPI.NewNSLock(minioMetaBucket, lockName)
+		lkctx, err := locker.GetLock(ctx, sharedLockTimeout)
+		if err != nil {
+			continue
+		}
+
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case <-lkctx.Context().Done():
+				// The context of the lock is canceled, this can happen
+				// if one lock lost quorum due to cluster instability
+				// in that case, try to lock again.
+				break
+			case ld.lockContext <- lkctx:
+				// Send the lock context to anyone asking for it
+			}
+		}
+	}
+}
+
+func mergeContext(ctx1, ctx2 context.Context) (context.Context, context.CancelFunc) {
+	ctx, cancel := context.WithCancel(context.Background())
+	go func() {
+		select {
+		case <-ctx1.Done():
+		case <-ctx2.Done():
+		}
+
+		cancel()
+	}()
+	return ctx, cancel
+}
+
+func (ld sharedLock) GetLock(ctx context.Context) (context.Context, context.CancelFunc) {
+	select {
+	case l := <-ld.lockContext:
+		return mergeContext(l.Context(), ctx)
+	}
+}
+
+func newSharedLock(ctx context.Context, objAPI ObjectLayer, lockName string) *sharedLock {
+	l := &sharedLock{
+		lockContext: make(chan LockContext),
+	}
+	go l.backgroundRoutine(ctx, objAPI, lockName)
+
+	return l
+}