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/* Copyright (c) 2021-2025. The SimGrid Team. All rights reserved. */
/* This program is free software; you can redistribute it and/or modify it
* under the terms of the license (GNU LGPL) which comes with this package. */
/* This examples shows how to survive to host failure exceptions that occur when an host is turned off.
*
* The actors do not get notified when the host on which they run is turned off: they are just terminated
* in this case, and their ``on_exit()`` callback gets executed.
*
* For remote executions on failing hosts however, any blocking operation such as ``exec`` or ``wait`` will
* raise an exception that you can catch and react to, as illustrated in this example.
*/
#include <simgrid/s4u.hpp>
#include "simgrid/kernel/ProfileBuilder.hpp"
XBT_LOG_NEW_DEFAULT_CATEGORY(s4u_exec_failure, "Messages specific for this s4u example");
namespace sg4 = simgrid::s4u;
static void dispatcher(std::vector<sg4::Host*> const& hosts)
{
std::vector<sg4::ExecPtr> pending_execs;
for (auto* host: hosts) {
XBT_INFO("Initiating asynchronous exec on %s", host->get_cname());
// Computing 20 flops on an host which speed is 1f takes 20 seconds (when it does not fail)
auto exec = sg4::this_actor::exec_init(20)->set_host(host);
pending_execs.push_back(exec);
exec->start();
}
XBT_INFO("---------------------------------");
XBT_INFO("Wait on the first exec, which host is turned off at t=10 by the another actor.");
try {
pending_execs[0]->wait();
xbt_assert("This wait was not supposed to succeed.");
} catch (const simgrid::HostFailureException&) {
XBT_INFO("Dispatcher has experienced a host failure exception, so it knows that something went wrong.");
}
XBT_INFO("State of each exec:");
for (auto const& exec : pending_execs)
XBT_INFO(" Exec on %s has state: %s", exec->get_host()->get_cname(), exec->get_state_str());
XBT_INFO("---------------------------------");
XBT_INFO("Wait on the second exec, which host is turned off at t=12 by the state profile.");
try {
pending_execs[1]->wait();
xbt_assert("This wait was not supposed to succeed.");
} catch (const simgrid::HostFailureException&) {
XBT_INFO("Dispatcher has experienced a host failure exception, so it knows that something went wrong.");
}
XBT_INFO("State of each exec:");
for (auto const& exec : pending_execs)
XBT_INFO(" Exec on %s has state: %s", exec->get_host()->get_cname(), exec->get_state_str());
XBT_INFO("---------------------------------");
XBT_INFO("Wait on the third exec, which should succeed.");
try {
pending_execs[2]->wait();
XBT_INFO("No exception occured.");
} catch (const simgrid::HostFailureException&) {
xbt_assert("This wait was not supposed to fail.");
}
XBT_INFO("State of each exec:");
for (auto const& exec : pending_execs)
XBT_INFO(" Exec on %s has state: %s", exec->get_host()->get_cname(), exec->get_state_str());
}
static void host_killer(sg4::Host* to_kill)
{
sg4::this_actor::sleep_for(10.0);
XBT_INFO("HostKiller turns off the host '%s'.", to_kill->get_cname());
to_kill->turn_off();
}
int main(int argc, char** argv)
{
sg4::Engine engine(&argc, argv);
auto* zone = engine.get_netzone_root();
std::vector<sg4::Host*> hosts;
for (const auto* name : {"Host1", "Host2", "Host3"}) {
auto* host = zone->add_host(name, "1f");
hosts.push_back(host);
}
/* Attaching a state profile (ie a list of events changing the on/off state of the resource) to host3.
* The syntax of the profile (second parameter) is a list of: "date state\n"
* The R"( )" thing is the C++ way of writing multiline strings, including literals \n.
* You'd have the same behavior by using "12 0\n20 1\n" instead.
* So here, the link is turned off at t=12 and back on at t=20.
* The last parameter is the period of that profile, meaning that it loops after 30 seconds.
*/
hosts[1]->set_state_profile(simgrid::kernel::profile::ProfileBuilder::from_string("profile name", R"(
12 0
20 1
)", 30));
zone->seal();
hosts[2]->add_actor("Dispatcher", dispatcher, hosts);
hosts[2]->add_actor("HostKiller", host_killer, hosts[0]);
engine.run();
return 0;
}
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