storj.io/minio@v0.0.0-20230509071714-0cbc90f649b1/pkg/dsync/dsync-server_test.go (about)

     1  /*
     2   * Minio Cloud Storage, (C) 2016 Minio, Inc.
     3   *
     4   * Licensed under the Apache License, Version 2.0 (the "License");
     5   * you may not use this file except in compliance with the License.
     6   * You may obtain a copy of the License at
     7   *
     8   *     http://www.apache.org/licenses/LICENSE-2.0
     9   *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   * See the License for the specific language governing permissions and
    14   * limitations under the License.
    15   */
    16  
    17  package dsync_test
    18  
    19  import (
    20  	"fmt"
    21  	"sync"
    22  
    23  	. "storj.io/minio/pkg/dsync"
    24  )
    25  
    26  const WriteLock = -1
    27  
    28  type lockServer struct {
    29  	mutex sync.Mutex
    30  	// Map of locks, with negative value indicating (exclusive) write lock
    31  	// and positive values indicating number of read locks
    32  	lockMap map[string]int64
    33  
    34  	// Refresh returns lock not found if set to true
    35  	lockNotFound bool
    36  }
    37  
    38  func (l *lockServer) setRefreshReply(refreshed bool) {
    39  	l.mutex.Lock()
    40  	defer l.mutex.Unlock()
    41  	l.lockNotFound = !refreshed
    42  }
    43  
    44  func (l *lockServer) Lock(args *LockArgs, reply *bool) error {
    45  	l.mutex.Lock()
    46  	defer l.mutex.Unlock()
    47  	if _, *reply = l.lockMap[args.Resources[0]]; !*reply {
    48  		l.lockMap[args.Resources[0]] = WriteLock // No locks held on the given name, so claim write lock
    49  	}
    50  	*reply = !*reply // Negate *reply to return true when lock is granted or false otherwise
    51  	return nil
    52  }
    53  
    54  func (l *lockServer) Unlock(args *LockArgs, reply *bool) error {
    55  	l.mutex.Lock()
    56  	defer l.mutex.Unlock()
    57  	var locksHeld int64
    58  	if locksHeld, *reply = l.lockMap[args.Resources[0]]; !*reply { // No lock is held on the given name
    59  		return fmt.Errorf("Unlock attempted on an unlocked entity: %s", args.Resources[0])
    60  	}
    61  	if *reply = locksHeld == WriteLock; !*reply { // Unless it is a write lock
    62  		return fmt.Errorf("Unlock attempted on a read locked entity: %s (%d read locks active)", args.Resources[0], locksHeld)
    63  	}
    64  	delete(l.lockMap, args.Resources[0]) // Remove the write lock
    65  	return nil
    66  }
    67  
    68  const ReadLock = 1
    69  
    70  func (l *lockServer) RLock(args *LockArgs, reply *bool) error {
    71  	l.mutex.Lock()
    72  	defer l.mutex.Unlock()
    73  	var locksHeld int64
    74  	if locksHeld, *reply = l.lockMap[args.Resources[0]]; !*reply {
    75  		l.lockMap[args.Resources[0]] = ReadLock // No locks held on the given name, so claim (first) read lock
    76  		*reply = true
    77  	} else {
    78  		if *reply = locksHeld != WriteLock; *reply { // Unless there is a write lock
    79  			l.lockMap[args.Resources[0]] = locksHeld + ReadLock // Grant another read lock
    80  		}
    81  	}
    82  	return nil
    83  }
    84  
    85  func (l *lockServer) RUnlock(args *LockArgs, reply *bool) error {
    86  	l.mutex.Lock()
    87  	defer l.mutex.Unlock()
    88  	var locksHeld int64
    89  	if locksHeld, *reply = l.lockMap[args.Resources[0]]; !*reply { // No lock is held on the given name
    90  		return fmt.Errorf("RUnlock attempted on an unlocked entity: %s", args.Resources[0])
    91  	}
    92  	if *reply = locksHeld != WriteLock; !*reply { // A write-lock is held, cannot release a read lock
    93  		return fmt.Errorf("RUnlock attempted on a write locked entity: %s", args.Resources[0])
    94  	}
    95  	if locksHeld > ReadLock {
    96  		l.lockMap[args.Resources[0]] = locksHeld - ReadLock // Remove one of the read locks held
    97  	} else {
    98  		delete(l.lockMap, args.Resources[0]) // Remove the (last) read lock
    99  	}
   100  	return nil
   101  }
   102  
   103  func (l *lockServer) Refresh(args *LockArgs, reply *bool) error {
   104  	l.mutex.Lock()
   105  	defer l.mutex.Unlock()
   106  	*reply = !l.lockNotFound
   107  	return nil
   108  }
   109  
   110  func (l *lockServer) ForceUnlock(args *LockArgs, reply *bool) error {
   111  	l.mutex.Lock()
   112  	defer l.mutex.Unlock()
   113  	if len(args.UID) != 0 {
   114  		return fmt.Errorf("ForceUnlock called with non-empty UID: %s", args.UID)
   115  	}
   116  	delete(l.lockMap, args.Resources[0]) // Remove the lock (irrespective of write or read lock)
   117  	*reply = true
   118  	return nil
   119  }