server_backend.cpp

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/*
Copyright (c) 2025 Giuseppe Roberti.
All rights reserved.
 
Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:
 
1. Redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer.
 
2. Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation and/or
other materials provided with the distribution.
 
3. Neither the name of the copyright holder nor the names of its contributors
may be used to endorse or promote products derived from this software without
specific prior written permission.
 
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "event.h"
#include "fib.h"
 
namespace pars_example::apps
{
 
using namespace event;
using namespace resource;

class server_backend : public app::single<comp::backend>
{
private:
 
  using parent_type = self_type;
  using self = server_backend;

 
  const milli cleanup_timeout{1000};
  const milli rep_recv_timeout{-1};
  const milli rep_send_timeout{1000};

 
  component_type::connect_p connect_p;
  int max_allowed{128}; 
  int max_served{0};    

 
  std::atomic<int> tot_served{0}; 
  app::state_machine<server_state> state = {server_state::creating};
  app::resources<int, pipe_resource> resources;

 
  using parent_type::parent_type;

 
  void startup(int argc, char** argv) override
  {
    enable_source_loc_logging();

    auto ts = state.tx(server_state::creating, server_state::initializing);

    switch (argc)
    {
    case 5:
      max_allowed = std::stoi(argv[4]);
 
      [[fallthrough]];
 
    case 4:
      max_served = std::stoi(argv[3]);
 
      [[fallthrough]];
 
    case 3:
      connect_p.service_cmode = net::cmode_from_string(argv[1]);
 
      connect_p.service_addr = argv[2];
 
      break;
 
    default:
      throw std::invalid_argument("Usage: ./server_backend service_cmode "
                                  "service_addr [max_served [max_allowed]]");
    }

    hfs().on<fired, init>(&self::initialize, this);
 
    hfs().on<fired, shutdown>(&self::terminate, this);
 
    comp().rep().on<received, fib_requested>(&self::fire_compute, this);
 
    comp().rep().on<fired, fib_requested>(&self::compute_answer, this);
 
    comp().rep().on<sent, fib_computed>(&self::recv_next, this);
 
    comp().rep().on<fired, creating_pipe>(&self::accept_pipe, this);
 
    comp().rep().on<fired, pipe_created>(&self::log_new_pipe, this);
 
    comp().rep().on<fired, pipe_removed>(&self::log_rem_pipe, this);
 
    comp().rep().on<fired, network_error>(&self::close_pipe, this);

    ts.commit();
 
    pars::info(SL, "Application Started!");
  }


  void initialize(hf_arg<fired, init> fired)
  {
    auto ts = state.tx(server_state::initializing, server_state::running);
 
    comp().init({.num_ctxs = max_allowed,
                 .rep_opts = {.recv_timeout = rep_recv_timeout.count(),
                              .send_timeout = rep_send_timeout.count()}});
 
    comp().connect(connect_p);
 
    ts.commit();
 
    pars::info(SL, "Fired {}, Application Initialized!", fired.event());
  }

  void accept_pipe(hf_arg<fired, creating_pipe> fired)
  {
    state.ensure(server_state::running);
 
    auto [ev, md] = fired.as_tuple();
 
    auto resources_count = resources.count();
 
    if (resources_count < max_allowed)
    {
      resources.emplace(md.pipe().id(), pipe_state::waiting_work);
 
      pars::info(SL, "{}: Fired {}, Pipe Accepted! [# resources: {} < {}]", md,
                 ev, resources_count, max_allowed);
    }
    else
    {
      md.pipe().close().or_abort();
 
      pars::info(SL, "{}: Fired {}, Pipe Rejected! [# resources: {} >= {}]", md,
                 ev, resources_count, max_allowed);
    }
  }

  void log_new_pipe(hf_arg<fired, pipe_created> fired)
  {
    state.ensure(server_state::running);
 
    auto [ev, md] = fired.as_tuple();
 
    pars::info(SL, "{}: Fired {} [# resources: {}]", md, ev, resources.count());
  }

  void log_rem_pipe(hf_arg<fired, pipe_removed> fired)
  {
    state.ensure(server_state::running);
 
    auto [ev, md] = fired.as_tuple();
 
    pars::info(SL, "{}: Fired {} [# resources: {}]", md, ev, resources.count());
  }

  void fire_compute(hf_arg<received, fib_requested> recv)
  {
    state.ensure(server_state::running);
 
    auto [ev, md] = recv.as_tuple();
 
    auto locked = resources.locked_resource(md.pipe().id());
 
    auto& pipe_resource = locked.resource();

    if (pipe_resource.state.current() == pipe_state::working)
    {
      pars::info(SL, "{}: Received {}, Already Working: Returning ...", md, ev);
 
      return;
    }
 
    auto ts =
      pipe_resource.state.tx(pipe_state::waiting_work, pipe_state::working);
 
    pipe_resource.save_tool(md.tool());
 
    router().queue_fire(ev, md);
 
    ts.commit();
 
    pars::info(SL, "{}: Received {}, Fire {}!", md, ev, ev);
  }

  void compute_answer(hf_arg<fired, fib_requested> fired)
  {
    state.ensure(server_state::running);
 
    auto [ev, md] = fired.as_tuple();
 
    auto p = md.pipe();
 
    auto locked = resources.locked_resource(p.id());
 
    auto& pipe_resource = locked.resource();
 
    auto ts = pipe_resource.state.tx(pipe_state::working, pipe_state::done);

 
    std::size_t fib_n;
 
    try
    {
      fib_n = compute::fib(ev.n, ev.use_fast_fib, md);
    }
    catch (const compute::stop_requested&)
    {
      locked.guard().unlock();
 
      ts.rollback();
 
      resources.delete_resource(p.id());
 
      pars::info(SL, "{}: Fired {}, Stop Requested! [# resources: {}]", md, ev,
                 resources.count());
 
      return;
    }

 
    auto out_ev = fib_computed{ev.work_id, fib_n};
 
    auto& ctx = comp().rep().ctxs().of(pipe_resource.load_tool());
 
    ctx.send(out_ev, p);
 
    ts.commit();
 
    pars::info(SL, "{}: Fired {}, Send {}!", md, ev, out_ev);
  }

  void recv_next(hf_arg<sent, fib_computed> sent)
  {
    state.ensure(server_state::running);
 
    auto [ev, md] = sent.as_tuple();
 
    auto& p = md.pipe();
 
    resources.delete_resource(p.id());
 
    if (++tot_served == max_served)
    {
      auto shutdown_ev = shutdown{};
 
      router().queue_fire(shutdown_ev);
 
      pars::info(SL, "{}: Sent {}, Fire {}! [{} succesfully served]", md, ev,
                 shutdown_ev, max_served);
 
      return;
    }

 
    auto& ctx = comp().rep().ctxs().of(md.tool());
 
    ctx.recv();
 
    pars::info(SL, "{}: Sent {}, Receiving! [# served: {}]", md, ev,
               tot_served.load());
  }

  void close_pipe(hf_arg<fired, network_error> fired)
  {
    state.ensure(server_state::running);
 
    auto [ev, md] = fired.as_tuple();
 
    auto& p = md.pipe();
 
    resources.delete_resource(p.id());
 
    p.close().or_abort();
 
    auto& ctx = comp().rep().ctxs().of(md.tool());
 
    ctx.recv();
 
    auto& [e, dir] = ev;
 
    pars::info(SL, "{}: Fired {} (during {}), Pipe Closed!", md, ev, dir);
  }

  void terminate(hf_arg<fired, shutdown> fired)
  {
    state.ensure(server_state::running);
 
    graceful_terminate();
 
    pars::info(SL, "Fired {}, Graceful Terminated!", fired.event());
 
    std::cout << "SHUTDOWN ..." << std::endl;
  }
};
 
} // namespace pars_example::apps
 
int main(int argc, char** argv)
{
  auto app = ::pars_example::apps::server_backend{};
 
  try
  {
    return app.exec(argc, argv);
  }
  catch (std::exception& e)
  {
    std::cout << std::format("Error: {}", e.what()) << "\n";
 
    return EXIT_FAILURE;
  }
}