prefer to handle cache RPC requests synchronously (#428)

* only handle RPC requests in a worker thread if we have an upstream. we may as well handle the request inline on the http_io thread if we're only dealing with local data since the response times should be pretty consistent in that case
* http.sys: don't create async worker thread pool until it's needed (typically only if we have an upstream)

1 files changed, 17 insertions, 4 deletions

diff --git a/src/zenserver/cache/httpstructuredcache.cpp b/src/zenserver/cache/httpstructuredcache.cpp
index 11ac81dcb..4a2fdd96b 100644
--- a/src/zenserver/cache/httpstructuredcache.cpp
+++ b/src/zenserver/cache/httpstructuredcache.cpp
@@ -1729,6 +1729,9 @@ void
 HttpStructuredCacheService::HandleRpcRequest(HttpServerRequest& Request)
 {
 	ZEN_TRACE_CPU("z$::Http::HandleRpcRequest");
+
+	const bool HasUpstream = m_UpstreamCache.IsActive();
+
 	switch (Request.RequestVerb())
 	{
 		case HttpVerb::kPost:
@@ -1745,7 +1748,7 @@ HttpStructuredCacheService::HandleRpcRequest(HttpServerRequest& Request)
 					return Request.WriteResponse(HttpResponseCode::BadRequest);
 				}
 
-				Request.WriteResponseAsync(
+				auto HandleRpc =
 					[this, RequestContext, Body = Request.ReadPayload(), ContentType, AcceptType](HttpServerRequest& AsyncRequest) mutable {
 						ZEN_TRACE_CPU("z$::Http::HandleRpcRequest::WriteResponseAsync");
 						std::uint64_t RequestIndex =
@@ -1764,9 +1767,9 @@ HttpStructuredCacheService::HandleRpcRequest(HttpServerRequest& Request)
 																	   RpcResult);
 						if (!IsHttpSuccessCode(ResultCode))
 						{
-							AsyncRequest.WriteResponse(ResultCode);
-							return;
+							return AsyncRequest.WriteResponse(ResultCode);
 						}
+
 						if (AcceptMagic == kCbPkgMagic)
 						{
 							void*		TargetProcessHandle = nullptr;
@@ -1804,9 +1807,19 @@ HttpStructuredCacheService::HandleRpcRequest(HttpServerRequest& Request)
 													   HttpContentType::kCbPackage,
 													   IoBuffer(IoBuffer::Wrap, MemStream.GetData(), MemStream.GetSize()));
 						}
-					});
+					};
+
+				if (HasUpstream)
+				{
+					Request.WriteResponseAsync(std::move(HandleRpc));
+				}
+				else
+				{
+					HandleRpc(Request);
+				}
 			}
 			break;
+
 		default:
 			m_CacheStats.BadRequestCount++;
 			Request.WriteResponse(HttpResponseCode::BadRequest);