EventWatchdogAlg.cpp

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/***********************************************************************************\
* (c) Copyright 2024-2026 CERN for the benefit of the LHCb and ATLAS collaborations *
*                                                                                   *
* This software is distributed under the terms of the Apache version 2 licence,     *
* copied verbatim in the file "LICENSE".                                            *
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#include <Gaudi/Functional/Transformer.h>
#include <Gaudi/Utils/PeriodicAction.h>
#include <GaudiKernel/EventContext.h>
#include <GaudiKernel/IScheduler.h>
#include <GaudiKernel/Memory.h>
#include <TSystem.h>
#include <algorithm>
#include <chrono>
#include <csignal>
#include <format>
#include <mutex>
#include <ranges>
#include <string>
#include <string_view>
#include <utility>
#include <vector>
 
namespace {
  std::string sanitize( std::string_view input ) {
    std::string output{ input };
    std::replace( begin( output ), end( output ), ':', '_' );
    return output;
  }
 
  // mutex to prevent reports from the watchdog to step on each other,
  // for example requiring a stack trace while already producing one
  std::mutex s_watchdogReportMutex;
} // namespace
 
using Gaudi::Utils::PeriodicAction;
 
namespace Gaudi {

  class EventWatchdogAlg : public Gaudi::Functional::Transformer<PeriodicAction( EventContext const& )> {
  public:
    EventWatchdogAlg( const std::string& name, ISvcLocator* pSvcLocator )
        : Transformer( name, pSvcLocator, KeyValue{ "TimerLocation", std::format( ".{}-timer", sanitize( name ) ) } ) {
      // timeout period cannot be smaller than 1
      m_eventTimeout.verifier().setLower( 1 );
    }
 
    PeriodicAction operator()( EventContext const& ctx ) const override {
      using namespace std::chrono_literals;
      // we use a functor because we cannot pass mutable states to a lambda
      struct Action {
        MsgStream          log;
        const bool         doStackTrace;
        const bool         abortOnTimeout;
        const unsigned int timeout;
        const EventContext ctx;
 
        const std::vector<IScheduler*> schedulers;
 
        int counter{ 0 };
 
        const std::chrono::steady_clock::time_point eventStart{ std::chrono::steady_clock::now() };
 
        void operator()() {
          ++counter;
          if ( counter == 1 ) {
            log << MSG::WARNING << std::format( "More than {}s since the beginning of the event ({})", timeout, ctx )
                << endmsg;
          } else {
            log << MSG::WARNING << std::format( "Another {}s passed since last timeout ({})", timeout, ctx ) << endmsg;
          }
          if ( log.level() <= MSG::INFO ) {
            log << MSG::INFO
                << std::format( "Current memory usage is virtual size = {} MB, resident set size = {} MB",
                                System::virtualMemory() / 1024., System::pagedMemory() / 1024. )
                << endmsg;
          }
 
          std::scoped_lock protectReport( s_watchdogReportMutex );
          if ( doStackTrace ) {
            for ( auto scheduler : schedulers ) { scheduler->dumpState(); }
            if ( gSystem ) {
              // TSystem::StackTrace() prints on the standard error, so we do the same
              std::cerr << std::format( "=== Stalled event: current stack trace ({}) ===\n", ctx );
              gSystem->StackTrace();
            }
          }
          if ( abortOnTimeout ) {
            log << MSG::FATAL << std::format( "too much time on a single event ({}): aborting process", ctx ) << endmsg;
            std::raise( SIGQUIT );
          }
        }
 
        ~Action() {
          if ( counter ) {
            const std::chrono::duration<float, std::chrono::seconds::period> duration =
                std::chrono::steady_clock::now() - eventStart;
            log << MSG::INFO << std::format( "An event ({}) took {:.3f}s", ctx, duration.count() ) << endmsg;
          }
        }
      };
 
      std::vector<IScheduler*> schedulers;
      if ( m_stackTrace ) {
        // if we ask for the stack trace we are also interested in the state of the scheduler
        std::ranges::copy( svcLoc()->getServices() |
                               std::views::transform( []( auto svc ) { return Gaudi::Cast<IScheduler>( svc ); } ) |
                               std::views::filter( []( auto* p ) { return p != nullptr; } ),
                           std::back_inserter( schedulers ) );
      }
 
      Action action{ MsgStream{ msgSvc(), "EventWatchdog" }, m_stackTrace, m_abortOnTimeout, m_eventTimeout,
                     // use a partial copy of the context to avoid copying the optional extension
                     EventContext{ ctx.evt(), ctx.slot(), ctx.subSlot() }, std::move( schedulers ) };
      return PeriodicAction( std::move( action ), std::chrono::seconds{ m_eventTimeout } );
    }
 
  private:
    Gaudi::CheckedProperty<unsigned int> m_eventTimeout{ this, "EventTimeout", 600,
                                                         "Number of seconds allowed to process a single event." };
    Gaudi::Property<bool>                m_abortOnTimeout{ this, "AbortOnTimeout", false,
                                            "If set to true, the application is killed when we reach the timeout." };
    Gaudi::Property<bool> m_stackTrace{ this, "StackTrace", false, "Whether to print the stack-trace on timeout." };
  };
  DECLARE_COMPONENT( EventWatchdogAlg )
} // namespace Gaudi