1 //  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
2 //  This source code is licensed under both the GPLv2 (found in the
3 //  COPYING file in the root directory) and Apache 2.0 License
4 //  (found in the LICENSE.Apache file in the root directory).
5 //
6 // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
7 // Use of this source code is governed by a BSD-style license that can be
8 // found in the LICENSE file. See the AUTHORS file for names of contributors.
9 
10 #pragma once
11 
12 #include "rocksdb/env.h"
13 #include "rocksdb/statistics.h"
14 
15 namespace ROCKSDB_NAMESPACE {
16 
17 class ConcurrentTaskLimiter {
18  public:
~ConcurrentTaskLimiter()19   virtual ~ConcurrentTaskLimiter() {}
20 
21   // Returns a name that identifies this concurrent task limiter.
22   virtual const std::string& GetName() const = 0;
23 
24   // Set max concurrent tasks.
25   // limit = 0 means no new task allowed.
26   // limit < 0 means no limitation.
27   virtual void SetMaxOutstandingTask(int32_t limit) = 0;
28 
29   // Reset to unlimited max concurrent task.
30   virtual void ResetMaxOutstandingTask() = 0;
31 
32   // Returns current outstanding task count.
33   virtual int32_t GetOutstandingTask() const = 0;
34 };
35 
36 // Create a ConcurrentTaskLimiter that can be shared with mulitple CFs
37 // across RocksDB instances to control concurrent tasks.
38 //
39 // @param name: Name of the limiter.
40 // @param limit: max concurrent tasks.
41 //        limit = 0 means no new task allowed.
42 //        limit < 0 means no limitation.
43 extern ConcurrentTaskLimiter* NewConcurrentTaskLimiter(const std::string& name,
44                                                        int32_t limit);
45 
46 }  // namespace ROCKSDB_NAMESPACE
47