private void DeactivateActiveRequest(
SafeCurlMultiHandle multiHandle, EasyRequest easy,
IntPtr gcHandlePtr, CancellationTokenRegistration cancellationRegistration)
{
// Remove the operation from the multi handle so we can shut down the multi handle cleanly
CURLMcode removeResult = Interop.Http.MultiRemoveHandle(multiHandle, easy._easyHandle);
Debug.Assert(removeResult == CURLMcode.CURLM_OK, "Failed to remove easy handle"); // ignore cleanup errors in release
// Release the associated GCHandle so that it's not kept alive forever
if (gcHandlePtr != IntPtr.Zero)
{
try
{
GCHandle.FromIntPtr(gcHandlePtr).Free();
_activeOperations.Remove(gcHandlePtr);
}
catch (InvalidOperationException)
{
Debug.Fail("Couldn't get/free the GCHandle for an active operation while shutting down due to failure");
}
}
// Undo cancellation registration
cancellationRegistration.Dispose();
}
private void ActivateNewRequest(SafeCurlMultiHandle multiHandle, EasyRequest easy)
{
Debug.Assert(easy != null, "We should never get a null request");
Debug.Assert(easy._associatedMultiAgent == null, "New requests should not be associated with an agent yet");
// If cancellation has been requested, complete the request proactively
if (easy._cancellationToken.IsCancellationRequested)
{
easy.FailRequest(new OperationCanceledException(easy._cancellationToken));
easy.Cleanup(); // no active processing remains, so cleanup
return;
}
// Otherwise, configure it. Most of the configuration was already done when the EasyRequest
// was created, but there's additional configuration we need to do specific to this
// multi agent, specifically telling the easy request about its own GCHandle and setting
// up callbacks for data processing. Once it's configured, add it to the multi handle.
GCHandle gcHandle = GCHandle.Alloc(easy);
IntPtr gcHandlePtr = GCHandle.ToIntPtr(gcHandle);
try
{
easy._associatedMultiAgent = this;
easy.SetCurlOption(CURLoption.CURLOPT_PRIVATE, gcHandlePtr);
easy.SetCurlCallbacks(gcHandlePtr, s_receiveHeadersCallback, s_sendCallback, s_seekCallback, s_receiveBodyCallback);
ThrowIfCURLMError(Interop.Http.MultiAddHandle(multiHandle, easy._easyHandle));
}
catch (Exception exc)
{
gcHandle.Free();
easy.FailRequest(exc);
easy.Cleanup(); // no active processing remains, so cleanup
return;
}
// And if cancellation can be requested, hook up a cancellation callback.
// This callback will put the easy request back into the queue, which will
// ensure that a wake-up request has been issued. When we pull
// the easy request out of the request queue, we'll see that it's already
// associated with this agent, meaning that it's a cancellation request,
// and we'll deal with it appropriately.
var cancellationReg = default(CancellationTokenRegistration);
if (easy._cancellationToken.CanBeCanceled)
{
cancellationReg = easy._cancellationToken.Register(s =>
{
var state = (Tuple<MultiAgent, EasyRequest>)s;
state.Item1.Queue(new IncomingRequest { Easy = state.Item2, Type = IncomingRequestType.Cancel });
}, Tuple.Create<MultiAgent, EasyRequest>(this, easy));
}
// Finally, add it to our map.
_activeOperations.Add(
gcHandlePtr,
new ActiveRequest { Easy = easy, CancellationRegistration = cancellationReg });
}
private void FindAndFailActiveRequest(SafeCurlMultiHandle multiHandle, EasyRequest easy, Exception error)
{
VerboseTrace("Error: " + error.Message, easy: easy);
IntPtr gcHandlePtr;
ActiveRequest activeRequest;
if (FindActiveRequest(easy, out gcHandlePtr, out activeRequest))
{
DeactivateActiveRequest(multiHandle, easy, gcHandlePtr, activeRequest.CancellationRegistration);
easy.FailRequest(error);
easy.Cleanup(); // no active processing remains, so we can cleanup
}
else
{
Debug.Assert(easy.Task.IsCompleted, "We should only not be able to find the request if it failed or we started to send back the response.");
}
}
private void HandleIncomingRequest(SafeCurlMultiHandle multiHandle, IncomingRequest request)
{
Debug.Assert(!Monitor.IsEntered(_incomingRequests), "Incoming requests lock should only be held while accessing the queue");
VerboseTrace("Type: " + request.Type, easy: request.Easy);
EasyRequest easy = request.Easy;
switch (request.Type)
{
case IncomingRequestType.New:
ActivateNewRequest(multiHandle, easy);
break;
case IncomingRequestType.Cancel:
Debug.Assert(easy._associatedMultiAgent == this, "Should only cancel associated easy requests");
Debug.Assert(easy._cancellationToken.IsCancellationRequested, "Cancellation should have been requested");
FindAndFailActiveRequest(multiHandle, easy, new OperationCanceledException(easy._cancellationToken));
break;
case IncomingRequestType.Unpause:
Debug.Assert(easy._associatedMultiAgent == this, "Should only unpause associated easy requests");
if (!easy._easyHandle.IsClosed)
{
IntPtr gcHandlePtr;
ActiveRequest ar;
Debug.Assert(FindActiveRequest(easy, out gcHandlePtr, out ar), "Couldn't find active request for unpause");
CURLcode unpauseResult = Interop.Http.EasyUnpause(easy._easyHandle);
try
{
ThrowIfCURLEError(unpauseResult);
}
catch (Exception exc)
{
FindAndFailActiveRequest(multiHandle, easy, exc);
}
}
break;
default:
Debug.Fail("Invalid request type: " + request.Type);
break;
}
}
/// <summary>Creates and configures a new multi handle.</summary>
private SafeCurlMultiHandle CreateAndConfigureMultiHandle()
{
// Create the new handle
SafeCurlMultiHandle multiHandle = Interop.Http.MultiCreate();
if (multiHandle.IsInvalid)
{
throw CreateHttpRequestException();
}
// In support of HTTP/2, enable HTTP/2 connections to be multiplexed if possible.
// We must only do this if the version of libcurl being used supports HTTP/2 multiplexing.
// Due to a change in a libcurl signature, if we try to make this call on an older libcurl,
// we'll end up accidentally and unconditionally enabling HTTP 1.1 pipelining.
if (s_supportsHttp2Multiplexing)
{
ThrowIfCURLMError(Interop.Http.MultiSetOptionLong(multiHandle,
Interop.Http.CURLMoption.CURLMOPT_PIPELINING,
(long)Interop.Http.CurlPipe.CURLPIPE_MULTIPLEX));
}
return multiHandle;
}
private void HandleIncomingRequest(SafeCurlMultiHandle multiHandle, IncomingRequest request)
{
Debug.Assert(!Monitor.IsEntered(_incomingRequests), "Incoming requests lock should only be held while accessing the queue");
VerboseTrace("Type: " + request.Type, easy: request.Easy);
EasyRequest easy = request.Easy;
switch (request.Type)
{
case IncomingRequestType.New:
ActivateNewRequest(multiHandle, easy);
break;
case IncomingRequestType.Cancel:
Debug.Assert(easy._associatedMultiAgent == this, "Should only cancel associated easy requests");
Debug.Assert(easy._cancellationToken.IsCancellationRequested, "Cancellation should have been requested");
FindAndFailActiveRequest(multiHandle, easy, new OperationCanceledException(easy._cancellationToken));
break;
case IncomingRequestType.Unpause:
Debug.Assert(easy._associatedMultiAgent == this, "Should only unpause associated easy requests");
if (!easy._easyHandle.IsClosed)
{
IntPtr gcHandlePtr;
ActiveRequest ar;
Debug.Assert(FindActiveRequest(easy, out gcHandlePtr, out ar), "Couldn't find active request for unpause");
CURLcode unpauseResult = Interop.Http.EasyUnpause(easy._easyHandle);
try
{
ThrowIfCURLEError(unpauseResult);
}
catch (Exception exc)
{
FindAndFailActiveRequest(multiHandle, easy, exc);
}
}
break;
default:
Debug.Fail("Invalid request type: " + request.Type);
break;
}
}
private void WorkerLoop()
{
Debug.Assert(!Monitor.IsEntered(_incomingRequests), "No locks should be held while invoking Process");
Debug.Assert(_runningWorker != null && _runningWorker.Id == Task.CurrentId, "This is the worker, so it must be running");
Debug.Assert(_wakeupRequestedPipeFd != null && !_wakeupRequestedPipeFd.IsInvalid, "Should have a valid pipe for wake ups");
// Create the multi handle to use for this round of processing. This one handle will be used
// to service all easy requests currently available and all those that come in while
// we're processing other requests. Once the work quiesces and there are no more requests
// to process, this multi handle will be released as the worker goes away. The next
// time a request arrives and a new worker is spun up, a new multi handle will be created.
SafeCurlMultiHandle multiHandle = CreateAndConfigureMultiHandle();
// Clear our active operations table. This should already be clear, either because
// all previous operations completed without unexpected exception, or in the case of an
// unexpected exception we should have cleaned up gracefully anyway. But just in case...
Debug.Assert(_activeOperations.Count == 0, "We shouldn't have any active operations when starting processing.");
_activeOperations.Clear();
bool endingSuccessfully = false;
try
{
// Continue processing as long as there are any active operations
while (true)
{
// First handle any requests in the incoming requests queue.
while (true)
{
IncomingRequest request;
lock (_incomingRequests)
{
if (_incomingRequests.Count == 0) break;
request = _incomingRequests.Dequeue();
}
HandleIncomingRequest(multiHandle, request);
}
// If we have no active operations, we're done.
if (_activeOperations.Count == 0)
{
endingSuccessfully = true;
return;
}
// We have one or more active operations. Run any work that needs to be run.
ThrowIfCURLMError(Interop.Http.MultiPerform(multiHandle));
// Complete and remove any requests that have finished being processed.
CURLMSG message;
IntPtr easyHandle;
CURLcode result;
while (Interop.Http.MultiInfoRead(multiHandle, out message, out easyHandle, out result))
{
Debug.Assert(message == CURLMSG.CURLMSG_DONE, "CURLMSG_DONE is supposed to be the only message type");
if (message == CURLMSG.CURLMSG_DONE)
{
IntPtr gcHandlePtr;
CURLcode getInfoResult = Interop.Http.EasyGetInfoPointer(easyHandle, CURLINFO.CURLINFO_PRIVATE, out gcHandlePtr);
Debug.Assert(getInfoResult == CURLcode.CURLE_OK, "Failed to get info on a completing easy handle");
if (getInfoResult == CURLcode.CURLE_OK)
{
ActiveRequest completedOperation;
bool gotActiveOp = _activeOperations.TryGetValue(gcHandlePtr, out completedOperation);
Debug.Assert(gotActiveOp, "Expected to find GCHandle ptr in active operations table");
if (gotActiveOp)
{
DeactivateActiveRequest(multiHandle, completedOperation.Easy, gcHandlePtr, completedOperation.CancellationRegistration);
FinishRequest(completedOperation.Easy, result);
}
}
}
}
// Wait for more things to do.
bool isWakeupRequestedPipeActive;
bool isTimeout;
ThrowIfCURLMError(Interop.Http.MultiWait(multiHandle, _wakeupRequestedPipeFd, out isWakeupRequestedPipeActive, out isTimeout));
if (isWakeupRequestedPipeActive)
{
// We woke up (at least in part) because a wake-up was requested.
// Read the data out of the pipe to clear it.
Debug.Assert(!isTimeout, "should not have timed out if isExtraFileDescriptorActive");
VerboseTrace("curl_multi_wait wake-up notification");
ReadFromWakeupPipeWhenKnownToContainData();
}
VerboseTraceIf(isTimeout, "curl_multi_wait timeout");
// PERF NOTE: curl_multi_wait uses poll (assuming it's available), which is O(N) in terms of the number of fds
// being waited on. If this ends up being a scalability bottleneck, we can look into using the curl_multi_socket_*
// APIs, which would let us switch to using epoll by being notified when sockets file descriptors are added or
// removed and configuring the epoll context with EPOLL_CTL_ADD/DEL, which at the expense of a lot of additional
// complexity would let us turn the O(N) operation into an O(1) operation. The additional complexity would come
// not only in the form of additional callbacks and managing the socket collection, but also in the form of timer
// management, which is necessary when using the curl_multi_socket_* APIs and which we avoid by using just
// curl_multi_wait/perform.
}
}
finally
{
// If we got an unexpected exception, something very bad happened. We may have some
// operations that we initiated but that weren't completed. Make sure to clean up any
// such operations, failing them and releasing their resources.
if (_activeOperations.Count > 0)
{
Debug.Assert(!endingSuccessfully, "We should only have remaining operations if we got an unexpected exception");
foreach (KeyValuePair<IntPtr, ActiveRequest> pair in _activeOperations)
{
ActiveRequest failingOperation = pair.Value;
IntPtr failingOperationGcHandle = pair.Key;
DeactivateActiveRequest(multiHandle, failingOperation.Easy, failingOperationGcHandle, failingOperation.CancellationRegistration);
// Complete the operation's task and clean up any of its resources
failingOperation.Easy.FailRequest(CreateHttpRequestException());
failingOperation.Easy.Cleanup(); // no active processing remains, so cleanup
}
// Clear the table.
_activeOperations.Clear();
}
// Finally, dispose of the multi handle.
multiHandle.Dispose();
}
}
