Implement curl connection throttling (CurlConcurrentConnections)

indra/llmessage/aicurl.h

@@ -99,7 +99,7 @@ struct TransferInfo {
 void initCurl(void (*)(void) = NULL);
 
 // Called once at start of application (from LLAppViewer::initThreads), starts AICurlThread.
-void startCurlThread(void);
+void startCurlThread(U32 CurlConcurrentConnections);
 
 // Called once at end of application (from newview/llappviewer.cpp by main thread),
 // with purpose to stop curl threads, free curl resources and deinitialize curl.

indra/llmessage/aicurlthread.cpp

@@ -1440,18 +1440,27 @@ CURLMsg const* MultiHandle::info_read(int* msgs_in_queue) const
   return ret;
 }
 
-CURLMcode MultiHandle::add_easy_request(AICurlEasyRequest const& easy_request)
+static U32 curl_concurrent_connections = 8;						// Initialized on start up by startCurlThread().
+
+void MultiHandle::add_easy_request(AICurlEasyRequest const& easy_request)
 {
-  std::pair<addedEasyRequests_type::iterator, bool> res = mAddedEasyRequests.insert(easy_request);
-  llassert(res.second);							// May not have been added before.
-  CURLMcode ret;
+  if (mAddedEasyRequests.size() < curl_concurrent_connections)	// Not throttled?
   {
-	AICurlEasyRequest_wat curl_easy_request_w(*easy_request);
-	ret = curl_easy_request_w->add_handle_to_multi(curl_easy_request_w, mMultiHandle);
+	CURLMcode ret;
+	{
+	  AICurlEasyRequest_wat curl_easy_request_w(*easy_request);
+	  ret = curl_easy_request_w->add_handle_to_multi(curl_easy_request_w, mMultiHandle);
+	}
+	if (ret == CURLM_OK)
+	{
+	  mHandleAddedOrRemoved = true;
+	  std::pair<addedEasyRequests_type::iterator, bool> res = mAddedEasyRequests.insert(easy_request);
+	  llassert(res.second);							// May not have been added before.
+	  Dout(dc::curl, "MultiHandle::add_easy_request: Added AICurlEasyRequest " << (void*)easy_request.get() << "; now processing " << mAddedEasyRequests.size() << " easy handles.");
+	  return;
+	}
   }
-  mHandleAddedOrRemoved = true;
-  Dout(dc::curl, "MultiHandle::add_easy_request: Added AICurlEasyRequest " << (void*)easy_request.get() << "; now processing " << mAddedEasyRequests.size() << " easy handles.");
-  return ret;
+  mQueuedRequests.push_back(easy_request);
 }
 
 CURLMcode MultiHandle::remove_easy_request(AICurlEasyRequest const& easy_request, bool as_per_command)
@@ -1470,6 +1479,14 @@ CURLMcode MultiHandle::remove_easy_request(AICurlEasyRequest const& easy_request
   mAddedEasyRequests.erase(iter);
   mHandleAddedOrRemoved = true;
   Dout(dc::curl, "MultiHandle::remove_easy_request: Removed AICurlEasyRequest " << (void*)easy_request.get() << "; now processing " << mAddedEasyRequests.size() << " easy handles.");
+
+  // Attempt to add a queued request, if any.
+  if (!mQueuedRequests.empty())
+  {
+	add_easy_request(mQueuedRequests.front());
+	mQueuedRequests.pop_front();
+  }
+
   return res;
 }
 
@@ -1697,11 +1714,12 @@ void AICurlEasyRequest::removeRequest(void)
 
 namespace AICurlInterface {
 
-void startCurlThread(void)
+void startCurlThread(U32 CurlConcurrentConnections)
 {
   using namespace AICurlPrivate::curlthread;
 
   llassert(is_main_thread());
+  curl_concurrent_connections = CurlConcurrentConnections;	// Debug Setting.
   AICurlThread::sInstance = new AICurlThread;
   AICurlThread::sInstance->start();
 }

indra/llmessage/aicurlthread.h

@@ -33,6 +33,7 @@
 
 #include "aicurl.h"
 #include <vector>
+#include <deque>
 
 #undef AICurlPrivate
 
@@ -59,7 +60,7 @@ class MultiHandle : public CurlMultiHandle
 	~MultiHandle();
 
 	// Add/remove an easy handle to/from a multi session.
-	CURLMcode add_easy_request(AICurlEasyRequest const& easy_request);
+	void add_easy_request(AICurlEasyRequest const& easy_request);
 	CURLMcode remove_easy_request(AICurlEasyRequest const& easy_request, bool as_per_command = false);
 
 	// Reads/writes available data from a particular socket (non-blocking).
@@ -100,6 +101,10 @@ class MultiHandle : public CurlMultiHandle
 
 	PollSet* mReadPollSet;
 	PollSet* mWritePollSet;
+
+  private:
+	// Temporary throttling hack.
+	std::deque<AICurlEasyRequest> mQueuedRequests;	// Waiting (throttled) requests.
 };
 
 } // namespace curlthread

indra/newview/app_settings/settings.xml

@@ -4205,6 +4205,17 @@
       <key>Value</key>
       <integer>0</integer>
     </map>
+    <key>CurlConcurrentConnections</key>
+    <map>
+      <key>Comment</key>
+      <string>Maximum number of simultaneous curl connections (requires restart)</string>
+      <key>Persist</key>
+      <integer>1</integer>
+      <key>Type</key>
+      <string>U32</string>
+      <key>Value</key>
+      <integer>16</integer>
+    </map>
     <key>CurlMaximumNumberOfHandles</key>
     <map>
       <key>Comment</key>

indra/newview/llappviewer.cpp

@@ -1817,7 +1817,7 @@ bool LLAppViewer::initThreads()
 		LLWatchdog::getInstance()->init(watchdog_killer_callback);
 	}
 
-	AICurlInterface::startCurlThread();
+	AICurlInterface::startCurlThread(gSavedSettings.getU32("CurlConcurrentConnections"));
 
 	LLImage::initClass();