Ichthyostega
577592c66e
as it turns out, "almost" the whole codebase compiles in C++17 mode. with the exception of two metaprogramming-related problems: - our "duck detector" for STL containers does not trigger anymore - the Metafunction to dissect Function sigantures (meta::_Fun) flounders
238 lines
8.2 KiB
C++
238 lines
8.2 KiB
C++
/*
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SUBSYSTEMRUNNER.hpp - helper for controlling execution of several dependent subsystems
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Copyright (C) Lumiera.org
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2008, Hermann Vosseler <Ichthyostega@web.de>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of
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the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/** @file subsystem-runner.hpp
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** Manage execution of the independent [Subsystems](\ref subsys.hpp)
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** of the Lumiera application. The SubsystemRunner is used by
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** lumiera::AppState::init() for actually "performing" the various subsystems,
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** as defined by their [Subsystem descriptors](\ref lumiera::Subsys). Together
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** these parts define the lifecycle protocol.
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**
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** @todo as of 2018, a design rework seems indicated eventually /////////////////////////TICKET #1177
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** @remark While this facility is still pretty much the first implementation draft
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** from 2008, it fulfilled our needs to express simple dependencies and to
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** conduct a controlled shutdown in case of fatal problems. The operations
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** protocol implied by this implementation might be somewhat brittle and
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** creates strong ties to implementation details, like the fine points
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** of thread handling and locking. If we ever consider to build an
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** improved subsystem runner, we should care to include the
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** full set of lifecycle callbacks, similar to a
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** two phase commit in databases.
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**
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** @see SubsystemRunner_test
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**
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*/
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#ifndef LUMIERA_SUBSYSTEMRUNNER_H
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#define LUMIERA_SUBSYSTEMRUNNER_H
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#include "lib/error.hpp"
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#include "lib/util.hpp"
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#include "lib/util-foreach.hpp"
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#include "common/subsys.hpp"
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#include "lib/sync.hpp"
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#include <functional>
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#include <vector>
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#include <string>
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namespace lumiera {
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using std::bind;
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using std::function;
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using std::placeholders::_1;
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using std::vector;
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using std::string;
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using util::cStr;
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using util::isnil;
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using util::and_all;
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using util::for_each;
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using util::removeall;
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using lib::Sync;
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using lib::RecursiveLock_Waitable;
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namespace {
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/** limit waiting for subsystem shutdown in case of
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* an emergency shutdown to max 2 seconds */
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const uint EMERGENCYTIMEOUT = 2000;
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function<bool(Subsys*)>
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isRunning() {
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return bind (&Subsys::isRunning, _1);
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}
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}
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/*************************************************************************//**
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* Implementation helper for managing execution of a collection of subsystems,
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* which may depend on one another and execute in parallel. Properties of the
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* subsystems are available through Subsys object refs, which act as handle.
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* In this context, "Subsystem" is an \em abstraction and doesn't necessarily
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* correspond to a single component, interface or plugin. It may well be a
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* complete layer of the application (e.g. the GUI).
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*
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* ## Protocol of operation
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* The SubsystemRunner is to be configured with a lumiera::Option object first.
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* Then, primary subsystems are \link #maybeRun provided \endlink for eventual
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* startup, which may depend on conditions defined by the subsystem. When
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* a component is actually to be pulled up, all of its prerequisite subsystems
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* shall be started in advance. Problems while starting may result in throwing
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* an exception, which is \em not handled here and aborts the whole operation.
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* On startup, a signal slot is reserved for each subsystem to notify the
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* SubsystemRunner on termination. It is the liability of the subsystems to
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* ensure this signal is activated regardless of what actually causes the
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* termination; failure to do so may deadlock the SubsystemRunner.
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*
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* Usually, the startup process is conducted from one (main) thread, which enters
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* a blocking wait() after starting the subsystems. Awakened by some termination
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* signal from one of the subsystems, termination of any remaining subsystems
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* will be triggered. The #wait() function returns after shutdown of all subsystems,
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* signalling an emergency exit (caused by an exception) with its return value.
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*
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* @todo 2018 this component works well but could be (re)written in a cleaner way
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*
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* @see lumiera::AppState
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* @see lumiera::Subsys
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* @see main.cpp
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*/
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class SubsystemRunner
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: public Sync<RecursiveLock_Waitable>
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{
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Option& opts_;
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volatile bool emergency_;
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vector<Subsys*> running_;
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function<void(Subsys*)> start_,
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stopIt_;
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public:
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SubsystemRunner (Option& opts)
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: opts_(opts)
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, emergency_(false)
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, start_(bind (&SubsystemRunner::triggerStartup, this,_1))
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, stopIt_(bind (&Subsys::triggerShutdown, _1))
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{ }
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void
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maybeRun (Subsys& susy)
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{
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Lock guard (this);
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if (!susy.isRunning() && susy.shouldStart (opts_))
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triggerStartup (&susy);
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}
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void
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shutdownAll ()
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{
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Lock guard (this);
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for_each (running_, stopIt_);
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}
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void
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triggerEmergency (bool cond)
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{
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Lock guard (this);
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if (cond) emergency_= true;
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}
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bool
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wait ()
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{
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Lock wait_blocking(this, &SubsystemRunner::allDead);
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return isEmergencyExit();
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}
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private:
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bool isEmergencyExit () { return emergency_; }
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void
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triggerStartup (Subsys* susy)
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{
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REQUIRE (susy);
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if (susy->isRunning()) return;
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INFO (subsystem, "Triggering startup of subsystem \"%s\"", cStr(*susy));
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for_each (susy->getPrerequisites(), start_);
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bool started = susy->start (opts_, bind (&SubsystemRunner::sigTerm, this, susy, _1));
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if (started)
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{
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if (susy->isRunning())
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running_.push_back (susy); // now responsible for managing the started subsystem
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else
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throw error::Logic("Subsystem "+string(*susy)+" failed to start");
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}
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#if false //////////////////////////////////////////////////////////////////////////////////////////////////TICKET #1138 : sort out C++17 compatibility
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if (not and_all (susy->getPrerequisites(), isRunning() ))
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#endif //////////////////////////////////////////////////////////////////////////////////////////////////TICKET #1138 : sort out C++17 compatibility
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if (true) ////FIXME
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{
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susy->triggerShutdown();
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throw error::State("Unable to start all prerequisites of Subsystem "+string(*susy));
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} }
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void
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sigTerm (Subsys* susy, string* problem) ///< called from subsystem on termination
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{
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REQUIRE (susy);
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Lock sync (this);
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triggerEmergency(!isnil (problem));
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INFO (subsystem, "Subsystem '%s' terminated.", cStr(*susy));
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WARN_IF (!isnil(problem), subsystem, "Irregular shutdown caused by: %s", cStr(*problem));
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ERROR_IF (susy->isRunning(), subsystem, "Subsystem '%s' signals termination, "
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"without resetting running state", cStr(*susy));
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removeall (running_, susy);
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shutdownAll();
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sync.notify();
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}
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bool
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allDead ()
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{
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if (isEmergencyExit())
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{
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Lock sync(this);
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if (!sync.isTimedWait())
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sync.setTimeout(EMERGENCYTIMEOUT);
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}
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return isnil (running_); // end wait if no running subsystem left
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}
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};
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} // namespace lumiera
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#endif
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