From c7e79030dddbff465e4237cff9e5b5afc0957e39 Mon Sep 17 00:00:00 2001
From: Norman Feske <norman.feske@genode-labs.com>
Date: Sat, 29 Jun 2019 18:56:31 +0200
Subject: [PATCH] sculpt: limit rate of depot queries

The triggering of a new depot query can happen more than once per
activation of the sculpt manager if multiple conditions call for updated
information about the depot. When this happens, the depot-query
component produces intermediate results, which are not consumed by the
sculpt manager. By deferring depot queries for a few milliseconds, we
avoid such intermediate queries, relieving the workload of the
depot-query component at system boot time.

Issue #3436
---
 repos/gems/src/app/sculpt_manager/main.cc | 29 ++++++++++++++++++-----
 1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/repos/gems/src/app/sculpt_manager/main.cc b/repos/gems/src/app/sculpt_manager/main.cc
index 5494d316f..65dae97bf 100644
--- a/repos/gems/src/app/sculpt_manager/main.cc
+++ b/repos/gems/src/app/sculpt_manager/main.cc
@@ -18,6 +18,7 @@
 #include <os/reporter.h>
 #include <nitpicker_session/connection.h>
 #include <vm_session/vm_session.h>
+#include <timer_session/connection.h>
 
 /* included from depot_deploy tool */
 #include <children.h>
@@ -213,14 +214,15 @@ struct Sculpt::Main : Input_event_handler,
 		return _query_version;
 	}
 
-	/**
-	 * Depot_query interface
-	 */
-	void trigger_depot_query() override
-	{
-		_query_version.value++;
+	Timer::Connection _timer { _env };
 
+	Timer::One_shot_timeout<Main> _deferred_depot_query_handler {
+		_timer, *this, &Main::_handle_deferred_depot_query };
+
+	void _handle_deferred_depot_query(Duration)
+	{
 		if (_deploy._arch.valid()) {
+			_query_version.value++;
 			_depot_query_reporter.generate([&] (Xml_generator &xml) {
 				xml.attribute("arch",    _deploy._arch);
 				xml.attribute("version", _query_version.value);
@@ -233,6 +235,21 @@ struct Sculpt::Main : Input_event_handler,
 		}
 	}
 
+	/**
+	 * Depot_query interface
+	 */
+	void trigger_depot_query() override
+	{
+		/*
+		 * Defer the submission of the query for a few milliseconds because
+		 * 'trigger_depot_query' may be consecutively called several times
+		 * while evaluating different conditions. Without deferring, the depot
+		 * query component would produce intermediate results that take time
+		 * but are ultimately discarded.
+		 */
+		_deferred_depot_query_handler.schedule(Microseconds{5000});
+	}
+
 
 	/*********************
 	 ** Blueprint query **