From f880d3b19ee98dfb2f09843401aeb2a30389cac1 Mon Sep 17 00:00:00 2001
From: "Alexander A. Klimov" <alexander.klimov@icinga.com>
Date: Wed, 7 Feb 2024 10:53:03 +0100
Subject: [PATCH] HttpServerConnection#StartStreaming(): release CpuBoundWork

so that /v1/events doesn't have to use IoBoundWorkSlot. IoBoundWorkSlot#~IoBoundWorkSlot() will wait for a free semaphore slot which will be almost immediately released by CpuBoundWork#~CpuBoundWork(). Just releasing the already aquired slot in HttpServerConnection#StartStreaming() is more efficient.
---
 lib/remote/eventshandler.cpp        | 2 --
 lib/remote/httpserverconnection.cpp | 9 +++++++--
 lib/remote/httpserverconnection.hpp | 2 ++
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/lib/remote/eventshandler.cpp b/lib/remote/eventshandler.cpp
index bdda71461..20a331a8b 100644
--- a/lib/remote/eventshandler.cpp
+++ b/lib/remote/eventshandler.cpp
@@ -105,8 +105,6 @@ bool EventsHandler::HandleRequest(
 	response.result(http::status::ok);
 	response.set(http::field::content_type, "application/json");
 
-	IoBoundWorkSlot dontLockTheIoThread (yc);
-
 	http::async_write(stream, response, yc);
 	stream.async_flush(yc);
 
diff --git a/lib/remote/httpserverconnection.cpp b/lib/remote/httpserverconnection.cpp
index bb5831f4a..ed14fb30a 100644
--- a/lib/remote/httpserverconnection.cpp
+++ b/lib/remote/httpserverconnection.cpp
@@ -12,7 +12,6 @@
 #include "base/configtype.hpp"
 #include "base/defer.hpp"
 #include "base/exception.hpp"
-#include "base/io-engine.hpp"
 #include "base/logger.hpp"
 #include "base/objectlock.hpp"
 #include "base/timer.hpp"
@@ -119,6 +118,9 @@ void HttpServerConnection::StartStreaming()
 
 	m_HasStartedStreaming = true;
 
+	VERIFY(m_HandlingRequest);
+	m_HandlingRequest->Done();
+
 	HttpServerConnection::Ptr keepAlive (this);
 
 	IoEngine::SpawnCoroutine(m_IoStrand, [this, keepAlive](asio::yield_context yc) {
@@ -432,6 +434,7 @@ bool ProcessRequest(
 	ApiUser::Ptr& authenticatedUser,
 	boost::beast::http::response<boost::beast::http::string_body>& response,
 	HttpServerConnection& server,
+	CpuBoundWork*& m_HandlingRequest,
 	bool& hasStartedStreaming,
 	boost::asio::yield_context& yc
 )
@@ -440,6 +443,8 @@ bool ProcessRequest(
 
 	try {
 		CpuBoundWork handlingRequest (yc);
+		Defer resetHandlingRequest ([&m_HandlingRequest] { m_HandlingRequest = nullptr; });
+		m_HandlingRequest = &handlingRequest;
 
 		HttpHandler::ProcessRequest(stream, authenticatedUser, request, response, yc, server);
 	} catch (const std::exception& ex) {
@@ -553,7 +558,7 @@ void HttpServerConnection::ProcessMessages(boost::asio::yield_context yc)
 
 			m_Seen = std::numeric_limits<decltype(m_Seen)>::max();
 
-			if (!ProcessRequest(*m_Stream, request, authenticatedUser, response, *this, m_HasStartedStreaming, yc)) {
+			if (!ProcessRequest(*m_Stream, request, authenticatedUser, response, *this, m_HandlingRequest, m_HasStartedStreaming, yc)) {
 				break;
 			}
 
diff --git a/lib/remote/httpserverconnection.hpp b/lib/remote/httpserverconnection.hpp
index 63f99e19c..8826705e0 100644
--- a/lib/remote/httpserverconnection.hpp
+++ b/lib/remote/httpserverconnection.hpp
@@ -4,6 +4,7 @@
 #define HTTPSERVERCONNECTION_H
 
 #include "remote/apiuser.hpp"
+#include "base/io-engine.hpp"
 #include "base/string.hpp"
 #include "base/tlsstream.hpp"
 #include <memory>
@@ -40,6 +41,7 @@ private:
 	boost::asio::io_context::strand m_IoStrand;
 	bool m_ShuttingDown;
 	bool m_HasStartedStreaming;
+	CpuBoundWork* m_HandlingRequest = nullptr;
 	boost::asio::deadline_timer m_CheckLivenessTimer;
 
 	HttpServerConnection(const String& identity, bool authenticated, const Shared<AsioTlsStream>::Ptr& stream, boost::asio::io_context& io);