/v1/events: don't lock I/O thread

lib/remote/eventqueue.cpp

@@ -2,8 +2,10 @@
 
 #include "remote/eventqueue.hpp"
 #include "remote/filterutility.hpp"
+#include "base/io-engine.hpp"
 #include "base/singleton.hpp"
 #include "base/logger.hpp"
+#include <boost/asio/spawn.hpp>
 
 using namespace icinga;
 
@@ -100,6 +102,26 @@ Dictionary::Ptr EventQueue::WaitForEvent(void *client, double timeout)
 	}
 }
 
+Dictionary::Ptr EventQueue::WaitForEvent(void *client, boost::asio::yield_context yc)
+{
+	for (;;) {
+		{
+			boost::mutex::scoped_lock lock(m_Mutex);
+
+			auto it = m_Events.find(client);
+			ASSERT(it != m_Events.end());
+
+			if (!it->second.empty()) {
+				Dictionary::Ptr result = *it->second.begin();
+				it->second.pop_front();
+				return result;
+			}
+		}
+
+		IoBoundWorkSlot dontLockTheIoThreadWhileWaiting (yc);
+	}
+}
+
 std::vector<EventQueue::Ptr> EventQueue::GetQueuesForType(const String& type)
 {
 	EventQueueRegistry::ItemMap queues = EventQueueRegistry::GetInstance()->GetItems();

lib/remote/eventqueue.hpp

@@ -6,6 +6,7 @@
 #include "remote/httphandler.hpp"
 #include "base/object.hpp"
 #include "config/expression.hpp"
+#include <boost/asio/spawn.hpp>
 #include <boost/thread/mutex.hpp>
 #include <boost/thread/condition_variable.hpp>
 #include <set>
@@ -31,6 +32,7 @@ public:
 	void SetFilter(std::unique_ptr<Expression> filter);
 
 	Dictionary::Ptr WaitForEvent(void *client, double timeout = 5);
+	Dictionary::Ptr WaitForEvent(void *client, boost::asio::yield_context yc);
 
 	static std::vector<EventQueue::Ptr> GetQueuesForType(const String& type);
 	static void UnregisterIfUnused(const String& name, const EventQueue::Ptr& queue);

lib/remote/eventshandler.cpp

@@ -6,6 +6,7 @@
 #include "config/configcompiler.hpp"
 #include "config/expression.hpp"
 #include "base/defer.hpp"
+#include "base/io-engine.hpp"
 #include "base/objectlock.hpp"
 #include "base/json.hpp"
 #include <boost/asio/buffer.hpp>
@@ -91,23 +92,24 @@ bool EventsHandler::HandleRequest(
 	response.result(http::status::ok);
 	response.set(http::field::content_type, "application/json");
 
+	{
+		IoBoundWorkSlot dontLockTheIoThreadWhileWriting (yc);
+
 		http::async_write(stream, response, yc);
 		stream.async_flush(yc);
+	}
 
 	asio::const_buffer newLine ("\n", 1);
 
 	for (;;) {
-		Dictionary::Ptr result = queue->WaitForEvent(&request);
+		String body = JsonEncode(queue->WaitForEvent(&request, yc));
-
-		if (!result)
-			continue;
-
-		String body = JsonEncode(result);
 
 		boost::algorithm::replace_all(body, "\n", "");
 
 		asio::const_buffer payload (body.CStr(), body.GetLength());
 
+		IoBoundWorkSlot dontLockTheIoThreadWhileWriting (yc);
+
 		stream.async_write_some(payload, yc);
 		stream.async_write_some(newLine, yc);
 		stream.async_flush(yc);