public void CountDown()
{
MockRepository mr = Mocks;
int latchSize = 5;
CountDownLatch startLatch = new CountDownLatch(0);
CountDownLatch latch = new CountDownLatch(latchSize);
IShard shard = mr.DynamicMock <IShard>();
IExitStrategy <object> strat = mr.CreateMock <IExitStrategy <object> >();
ICallable <object> anotherCallable = mr.DynamicMock <ICallable <object> >();
IShardOperation <object> operation = mr.DynamicMock <IShardOperation <object> >();
//Expectations and results
Expect.Call(strat.AddResult(null, shard)).Return(false);
Expect.Call(strat.AddResult(null, shard)).Return(false);
Expect.Call(strat.AddResult(null, shard)).Return(true);
Expect.Call(strat.AddResult(null, shard)).Return(true);
SetupResult.For(shard.ShardIds).Return(new HashedSet <ShardId>(new ShardId[] { (new ShardId(0)) }));
mr.ReplayAll();
IList <StartAwareFutureTask <object> > futureTasks = new List <StartAwareFutureTask <object> >();
ParallelShardOperationCallable <object> callable = new ParallelShardOperationCallable <object>(
startLatch,
latch,
strat,
operation,
shard,
futureTasks);
callable.Call();
// addResult returns false so latch is only decremented by 1
Assert.AreEqual(latchSize - 1, latch.Count);
// addResult returns false so latch is only decremented by 1
callable.Call();
Assert.AreEqual(latchSize - 2, latch.Count);
StartAwareFutureTask <object> ft = new StartAwareFutureTask_CancelReturnFalse(anotherCallable, 0);
futureTasks.Add(ft);
callable.Call();
// cancelling the 1 task returns false, so latch is only decremented by 1
Assert.AreEqual(latchSize - 3, latch.Count);
ft = new StartAwareFutureTask_CancelReturnTrue(anotherCallable, 0);
futureTasks.Add(ft);
callable.Call();
// 1 decrement for myself and 1 for the task that returned true when cancelled
Assert.AreEqual(latchSize - 5, latch.Count);
}
/// <summary>
/// Computes a result, or throws an exception if unable to do so.
/// </summary>
/// <returns></returns>
public T Call()
{
try
{
WaitForStartSignal();
log.DebugFormat("Starting execution of {0} against shard {1}", operation.OperationName, shard);
///If addResult() returns true it means there is no more work to be
///performed. Cancel all the outstanding tasks.
if (exitStrategy.AddResult(operation.Execute(shard), shard))
{
log.DebugFormat("Short-circuiting execution of {0} on other threads after execution against shard {1}",
operation.OperationName, shard);
//It's ok to cancel ourselves because StartAwareFutureTask.cancel()
//will return false if a task has already started executing, and we're
//already executing.
log.DebugFormat("Checking {0} future tasks to see if they need to be cancelled.", futureTasks.Count);
foreach (StartAwareFutureTask <T> ft in futureTasks)
{
log.DebugFormat("Preparing to cancel future task %d.", ft.Id);
//If a task was successfully cancelled that means it had not yet
//started running. Since the task won't run, the task won't be
// able to decrement the CountDownLatch. We need to decrement
//it on behalf of the cancelled task.
if (ft.Cancel(INTERRUPT_IF_RUNNING))
{
log.Debug("Task cancel returned true, decrementing counter on its behalf.");
doneSignal.CountDown();
}
else
{
log.Debug("Task cancel returned false, not decrementing counter on its behalf.");
}
}
}
else
{
log.DebugFormat("No need to short-cirtcuit execution of {0} on other threads after execution against shard {1}",
operation.OperationName, shard);
}
}
finally
{
// counter must get decremented no matter what
log.DebugFormat("Decrementing counter for operation {0} on shard {1}", operation.OperationName, shard);
doneSignal.CountDown();
}
return(default(T));
}
public T Apply <T>(IEnumerable <IShard> shards, IShardOperation <T> operation, IExitStrategy <T> exitStrategy)
{
foreach (var shard in GetNextOrderingOfShards(shards))
{
var shardOperation = operation.Prepare(shard);
var result = shardOperation();
if (result != null && exitStrategy.AddResult(result, shard))
{
Log.Debug("Short-circuiting operation {0} after execution against shard {1}", operation.OperationName, shard);
break;
}
}
return(exitStrategy.CompileResults());
}
public T Apply <T>(IList <IShard> shards, IShardOperation <T> operation, IExitStrategy <T> exitStrategy,
IExitOperationsCollector exitOperationsCollector)
{
foreach (IShard shard in GetNextOrderingOfShards(shards))
{
if (exitStrategy.AddResult(operation.Execute(shard), shard))
{
log.DebugFormat("Short-circuiting operation {0} after execution against shard {1}",
operation.OperationName, shard);
break;
}
}
return(exitStrategy.CompileResults(exitOperationsCollector));
}
public async Task <T> ApplyAsync <T>(IEnumerable <IShard> shards, IAsyncShardOperation <T> operation, IExitStrategy <T> exitStrategy, CancellationToken cancellationToken)
{
foreach (var shard in GetNextOrderingOfShards(shards))
{
var shardOperation = operation.PrepareAsync(shard);
var result = await shardOperation(cancellationToken);
if (result != null && exitStrategy.AddResult(result, shard))
{
Log.Debug("Short-circuiting operation {0} after execution against shard {1}", operation.OperationName, shard);
break;
}
}
return(exitStrategy.CompileResults());
}
private void ExecuteForShard(object state)
{
var s = (IShard)state;
try
{
Func <T> shardOperation;
// Perform thread-safe preparation of the operation for a single shard.
lock (this)
{
// Prevent execution if parallel operation has already been cancelled.
if (_isCancelled)
{
if (--_activeCount <= 0)
{
Monitor.Pulse(this);
}
return;
}
shardOperation = _operation.Prepare(s);
}
// Perform operation execution on multiple shards in parallel.
var result = shardOperation();
// Perform thread-safe aggregation of operation results.
lock (this)
{
// Only add result if operation still has not been cancelled and result is not null.
if (!_isCancelled && !Equals(result, null))
{
_isCancelled = _exitStrategy.AddResult(result, s);
}
if (--_activeCount <= 0)
{
Monitor.Pulse(this);
}
}
}
catch (Exception e)
{
lock (this)
{
if (!_isCancelled)
{
_exception = e;
_isCancelled = true;
}
if (--_activeCount <= 0)
{
Monitor.Pulse(this);
}
}
Log.DebugFormat("Failed parallel operation '{0}' on shard '{1:X}'.",
_operation.OperationName, s.ShardIds.First());
}
}
