aboutsummaryrefslogtreecommitdiffhomepage
path: root/src/cpp/thread_manager/thread_manager.h
blob: d1050f6dede0496593d4810b10d05430d300f9fa (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
/*
 *
 * Copyright 2016, Google Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#ifndef GRPC_INTERNAL_CPP_THREAD_MANAGER_H
#define GRPC_INTERNAL_CPP_THREAD_MANAGER_H

#include <condition_variable>
#include <list>
#include <memory>
#include <mutex>
#include <thread>

#include <grpc++/support/config.h>

namespace grpc {

class ThreadManager {
 public:
  explicit ThreadManager(int min_pollers, int max_pollers);
  virtual ~ThreadManager();

  // Initializes and Starts the Rpc Manager threads
  void Initialize();

  // The return type of PollForWork() function
  enum WorkStatus { WORK_FOUND, SHUTDOWN, TIMEOUT };

  // "Polls" for new work.
  // If the return value is WORK_FOUND:
  //  - The implementaion of PollForWork() MAY set some opaque identifier to
  //    (identify the work item found) via the '*tag' parameter
  //  - The implementaion MUST set the value of 'ok' to 'true' or 'false'. A
  //    value of 'false' indicates some implemenation specific error (that is
  //    neither SHUTDOWN nor TIMEOUT)
  //  - ThreadManager does not interpret the values of 'tag' and 'ok'
  //  - ThreadManager WILL call DoWork() and pass '*tag' and 'ok' as input to
  //    DoWork()
  //
  // If the return value is SHUTDOWN:,
  //  - ThreadManager WILL NOT call DoWork() and terminates the thead
  //
  // If the return value is TIMEOUT:,
  //  - ThreadManager WILL NOT call DoWork()
  //  - ThreadManager MAY terminate the thread depending on the current number
  //    of active poller threads and mix_pollers/max_pollers settings
  //  - Also, the value of timeout is specific to the derived class
  //    implementation
  virtual WorkStatus PollForWork(void** tag, bool* ok) = 0;

  // The implementation of DoWork() is supposed to perform the work found by
  // PollForWork(). The tag and ok parameters are the same as returned by
  // PollForWork()
  //
  // The implementation of DoWork() should also do any setup needed to ensure
  // that the next call to PollForWork() (not necessarily by the current thread)
  // actually finds some work
  virtual void DoWork(void* tag, bool ok) = 0;

  // Mark the ThreadManager as shutdown and begin draining the work. This is a
  // non-blocking call and the caller should call Wait(), a blocking call which
  // returns only once the shutdown is complete
  virtual void Shutdown();

  // Has Shutdown() been called
  bool IsShutdown();

  // A blocking call that returns only after the ThreadManager has shutdown and
  // all the threads have drained all the outstanding work
  virtual void Wait();

 private:
  // Helper wrapper class around std::thread. This takes a ThreadManager object
  // and starts a new std::thread to calls the Run() function.
  //
  // The Run() function calls ThreadManager::MainWorkLoop() function and once
  // that completes, it marks the WorkerThread completed by calling
  // ThreadManager::MarkAsCompleted()
  class WorkerThread {
   public:
    WorkerThread(ThreadManager* thd_mgr);
    ~WorkerThread();

   private:
    // Calls thd_mgr_->MainWorkLoop() and once that completes, calls
    // thd_mgr_>MarkAsCompleted(this) to mark the thread as completed
    void Run();

    ThreadManager* thd_mgr_;
    std::thread thd_;
  };

  // The main funtion in ThreadManager
  void MainWorkLoop();

  void MarkAsCompleted(WorkerThread* thd);
  void CleanupCompletedThreads();

  // Protects shutdown_, num_pollers_ and num_threads_
  // TODO: sreek - Change num_pollers and num_threads_ to atomics
  std::mutex mu_;

  bool shutdown_;
  std::condition_variable shutdown_cv_;

  // Number of threads doing polling
  int num_pollers_;

  // The minimum and maximum number of threads that should be doing polling
  int min_pollers_;
  int max_pollers_;

  // The total number of threads (includes threads includes the threads that are
  // currently polling i.e num_pollers_)
  int num_threads_;

  std::mutex list_mu_;
  std::list<WorkerThread*> completed_threads_;
};

}  // namespace grpc

#endif  // GRPC_INTERNAL_CPP_THREAD_MANAGER_H