More robust CScheduler unit test

On a busy or slow system, the CScheduler unit test could fail because it
assumed all threads would be done after a couple of milliseconds.

Replace the hard-coded sleep with CScheduler stop() method that
will cleanly exit the servicing threads when all tasks are completely
finished.

src/scheduler.cpp

@@ -8,7 +8,7 @@
 #include <boost/bind.hpp>
 #include <utility>
 
-CScheduler::CScheduler() : nThreadsServicingQueue(0)
+CScheduler::CScheduler() : nThreadsServicingQueue(0), stopRequested(false), stopWhenEmpty(false)
 {
 }
 
@@ -29,32 +29,37 @@ void CScheduler::serviceQueue()
 {
     boost::unique_lock<boost::mutex> lock(newTaskMutex);
     ++nThreadsServicingQueue;
+    stopRequested = false;
+    stopWhenEmpty = false;
 
     // newTaskMutex is locked throughout this loop EXCEPT
     // when the thread is waiting or when the user's function
     // is called.
-    while (1) {
+    while (!shouldStop()) {
         try {
-            while (taskQueue.empty()) {
+            while (!shouldStop() && taskQueue.empty()) {
                 // Wait until there is something to do.
                 newTaskScheduled.wait(lock);
             }
+
             // Wait until either there is a new task, or until
             // the time of the first item on the queue:
 
 // wait_until needs boost 1.50 or later; older versions have timed_wait:
 #if BOOST_VERSION < 105000
-            while (!taskQueue.empty() && newTaskScheduled.timed_wait(lock, toPosixTime(taskQueue.begin()->first))) {
+            while (!shouldStop() && !taskQueue.empty() &&
+                   newTaskScheduled.timed_wait(lock, toPosixTime(taskQueue.begin()->first))) {
                 // Keep waiting until timeout
             }
 #else
-            while (!taskQueue.empty() && newTaskScheduled.wait_until(lock, taskQueue.begin()->first) != boost::cv_status::timeout) {
+            while (!shouldStop() && !taskQueue.empty() &&
+                   newTaskScheduled.wait_until(lock, taskQueue.begin()->first) != boost::cv_status::timeout) {
                 // Keep waiting until timeout
             }
 #endif
             // If there are multiple threads, the queue can empty while we're waiting (another
             // thread may service the task we were waiting on).
-            if (taskQueue.empty())
+            if (shouldStop() || taskQueue.empty())
                 continue;
 
             Function f = taskQueue.begin()->second;
@@ -70,6 +75,19 @@ void CScheduler::serviceQueue()
             throw;
         }
     }
+    --nThreadsServicingQueue;
+}
+
+void CScheduler::stop(bool drain)
+{
+    {
+        boost::unique_lock<boost::mutex> lock(newTaskMutex);
+        if (drain)
+            stopWhenEmpty = true;
+        else
+            stopRequested = true;
+    }
+    newTaskScheduled.notify_all();
 }
 
 void CScheduler::schedule(CScheduler::Function f, boost::chrono::system_clock::time_point t)
@@ -96,3 +114,15 @@ void CScheduler::scheduleEvery(CScheduler::Function f, int64_t deltaSeconds)
 {
     scheduleFromNow(boost::bind(&Repeat, this, f, deltaSeconds), deltaSeconds);
 }
+
+size_t CScheduler::getQueueInfo(boost::chrono::system_clock::time_point &first,
+                             boost::chrono::system_clock::time_point &last) const
+{
+    boost::unique_lock<boost::mutex> lock(newTaskMutex);
+    size_t result = taskQueue.size();
+    if (!taskQueue.empty()) {
+        first = taskQueue.begin()->first;
+        last = taskQueue.rbegin()->first;
+    }
+    return result;
+}

src/scheduler.h

@@ -60,11 +60,24 @@ public:
     // and interrupted using boost::interrupt_thread
     void serviceQueue();
 
+    // Tell any threads running serviceQueue to stop as soon as they're
+    // done servicing whatever task they're currently servicing (drain=false)
+    // or when there is no work left to be done (drain=true)
+    void stop(bool drain=false);
+
+    // Returns number of tasks waiting to be serviced,
+    // and first and last task times
+    size_t getQueueInfo(boost::chrono::system_clock::time_point &first,
+                        boost::chrono::system_clock::time_point &last) const;
+
 private:
     std::multimap<boost::chrono::system_clock::time_point, Function> taskQueue;
     boost::condition_variable newTaskScheduled;
-    boost::mutex newTaskMutex;
+    mutable boost::mutex newTaskMutex;
     int nThreadsServicingQueue;
+    bool stopRequested;
+    bool stopWhenEmpty;
+    bool shouldStop() { return stopRequested || (stopWhenEmpty && taskQueue.empty()); }
 };
 
 #endif

src/test/scheduler_tests.cpp

@@ -42,6 +42,8 @@ static void MicroSleep(uint64_t n)
 
 BOOST_AUTO_TEST_CASE(manythreads)
 {
+    seed_insecure_rand(false);
+
     // Stress test: hundreds of microsecond-scheduled tasks,
     // serviced by 10 threads.
     //
@@ -54,10 +56,6 @@ BOOST_AUTO_TEST_CASE(manythreads)
     // counters should sum to the number of initial tasks performed.
     CScheduler microTasks;
 
-    boost::thread_group microThreads;
-    for (int i = 0; i < 5; i++)
-        microThreads.create_thread(boost::bind(&CScheduler::serviceQueue, &microTasks));
-
     boost::mutex counterMutex[10];
     int counter[10] = { 0 };
     boost::random::mt19937 rng(insecure_rand());
@@ -67,6 +65,9 @@ BOOST_AUTO_TEST_CASE(manythreads)
 
     boost::chrono::system_clock::time_point start = boost::chrono::system_clock::now();
     boost::chrono::system_clock::time_point now = start;
+    boost::chrono::system_clock::time_point first, last;
+    size_t nTasks = microTasks.getQueueInfo(first, last);
+    BOOST_CHECK(nTasks == 0);
 
     for (int i = 0; i < 100; i++) {
         boost::chrono::system_clock::time_point t = now + boost::chrono::microseconds(randomMsec(rng));
@@ -77,9 +78,19 @@ BOOST_AUTO_TEST_CASE(manythreads)
                                              randomDelta(rng), tReschedule);
         microTasks.schedule(f, t);
     }
+    nTasks = microTasks.getQueueInfo(first, last);
+    BOOST_CHECK(nTasks == 100);
+    BOOST_CHECK(first < last);
+    BOOST_CHECK(last > now);
+
+    // As soon as these are created they will start running and servicing the queue
+    boost::thread_group microThreads;
+    for (int i = 0; i < 5; i++)
+        microThreads.create_thread(boost::bind(&CScheduler::serviceQueue, &microTasks));
 
     MicroSleep(600);
     now = boost::chrono::system_clock::now();
+
     // More threads and more tasks:
     for (int i = 0; i < 5; i++)
         microThreads.create_thread(boost::bind(&CScheduler::serviceQueue, &microTasks));
@@ -93,11 +104,9 @@ BOOST_AUTO_TEST_CASE(manythreads)
         microTasks.schedule(f, t);
     }
 
-    // All 2,000 tasks should be finished within 2 milliseconds. Sleep a bit longer.
-    MicroSleep(2100);
-
-    microThreads.interrupt_all();
-    microThreads.join_all();
+    // Drain the task queue then exit threads
+    microTasks.stop(true);
+    microThreads.join_all(); // ... wait until all the threads are done
 
     int counterSum = 0;
     for (int i = 0; i < 10; i++) {