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 #include "JExecutionEngine.h"
 #include <JANA/Utils/JApplicationInspector.h>
 #include <JANA/JVersion.h>
 
 #if JANA2_HAVE_PERFETTO
 #include <JANA/Services/JPerfettoService.h>
 #endif
 
 #include <chrono>
 #include <cstddef>
 #include <cstdio>
 #include <ctime>
 #include <exception>
 #include <mutex>
 #include <csignal>
 #include <ostream>
 #include <sstream>
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <unistd.h>
 
 thread_local int jana2_worker_id = -1;
 thread_local JBacktrace* jana2_worker_backtrace = nullptr;
 
 void JExecutionEngine::Init() {
     auto params = GetApplication()->GetJParameterManager();
 
     params->SetDefaultParameter("jana:timeout", m_timeout_s, 
         "Max time (in seconds) JANA will wait for a thread to update its heartbeat before hard-exiting. 0 to disable timeout completely.");
 
     params->SetDefaultParameter("jana:warmup_timeout", m_warmup_timeout_s, 
         "Max time (in seconds) JANA will wait for 'initial' events to complete before hard-exiting.");
 
     params->SetDefaultParameter("jana:backoff_interval", m_backoff_ms, 
         "Max time (in seconds) JANA will wait for 'initial' events to complete before hard-exiting.");
 
     params->SetDefaultParameter("jana:show_ticker", m_show_ticker, "Controls whether the ticker is visible");
 
     params->SetDefaultParameter("jana:ticker_interval", m_ticker_ms, "Controls the ticker interval (in ms)");
 
     auto p = params->SetDefaultParameter("jana:status_fname", m_path_to_named_pipe,
         "Filename of named pipe for retrieving instantaneous status info");
 
     size_t pid = getpid();
     mkfifo(m_path_to_named_pipe.c_str(), 0666);
 
     LOG_WARN(GetLogger()) << "To pause processing and inspect, press Ctrl-C." << LOG_END;
     LOG_WARN(GetLogger()) << "For a clean shutdown, press Ctrl-C twice." << LOG_END;
     LOG_WARN(GetLogger()) << "For a hard shutdown, press Ctrl-C three times." << LOG_END;
 
     if (p->IsDefault()) {
         LOG_WARN(GetLogger()) << "For worker status information, press Ctrl-Z, or run `jana-status " << pid << "`" << LOG_END;
     }
     else {
         LOG_WARN(GetLogger()) << "For worker status information, press Ctrl-Z, or run `jana-status " << pid << " " << m_path_to_named_pipe << "`" << LOG_END;
     }
 
 
     // Not sure how I feel about putting this here yet, but I think it will at least work in both cases it needs to.
     // The reason this works is because JTopologyBuilder::create_topology() has already been called before 
     // JApplication::ProvideService<JExecutionEngine>().
     for (JArrow* arrow : m_topology->GetArrows()) {
 
         arrow->Initialize();
 
         m_arrow_states.emplace_back();
         auto& arrow_state = m_arrow_states.back();
         arrow_state.is_source = arrow->IsSource();
         arrow_state.is_sink = arrow->IsSink();
         arrow_state.is_parallel = arrow->IsParallel();
         arrow_state.next_input = arrow->GetNextPortIndex();
     }
 }
 
 void JExecutionEngine::RequestInspector() {
     std::unique_lock<std::mutex> lock(m_mutex);
     m_interrupt_status = InterruptStatus::InspectRequested;
 }
 
 void JExecutionEngine::RunTopology() {
     std::unique_lock<std::mutex> lock(m_mutex);
 
     if (m_runstatus == RunStatus::Failed) {
         throw JException("Cannot switch topology runstatus to Running because it is already Failed");
     }
     if (m_runstatus == RunStatus::Finished) {
         throw JException("Cannot switch topology runstatus to Running because it is already Finished");
     }
     if (m_arrow_states.size() == 0) {
         throw JException("Cannot execute an empty topology! Hint: Have you provided an event source?");
     }
 
     // Set start time and event count
     m_time_at_start = clock_t::now();
     m_event_count_at_start = m_event_count_at_finish;
 
     // Reactivate topology
     for (auto& arrow: m_arrow_states) {
         if (arrow.status == ArrowState::Status::Paused) {
             arrow.status = ArrowState::Status::Running;
         }
     }
 
     m_runstatus = RunStatus::Running;
 
     lock.unlock();
     m_condvar.notify_one();
 }
 
 void JExecutionEngine::ScaleWorkers(size_t nthreads) {
     // We both create and destroy the pool of workers here. They all sleep until they 
     // receive work from the scheduler, which won't happen until the runstatus <- {Running, 
     // Pausing, Draining} and there is a task ready to execute. This way worker creation/destruction
     // is decoupled from topology execution.
 
     // If we scale to zero, no workers will run. This is useful for testing, and also for using
     // an external thread team, should the need arise.
 
     std::unique_lock<std::mutex> lock(m_mutex);
 
     if (nthreads != 0 && m_arrow_states.size() == 0) {
         // We check that (nthreads != 0) because this gets called at shutdown even if the topology wasn't run
         // Remember, we want JApplication::Initialize() to succeed and JMain to shut down cleanly even when the topology is empty
         throw JException("Cannot execute an empty topology! Hint: Have you provided an event source?");
     }
 
     auto prev_nthreads = m_worker_states.size();
 
     if (prev_nthreads < nthreads) {
         // We are launching additional worker threads
         LOG_DEBUG(GetLogger()) << "Scaling up to " << nthreads << " worker threads" << LOG_END;
         auto mapping = m_topology->GetProcessorMapping();
         for (size_t worker_id=prev_nthreads; worker_id < nthreads; ++worker_id) {
             auto worker = std::make_unique<WorkerState>();
             worker->worker_id = worker_id;
             worker->is_stop_requested = false;
             worker->cpu_id = mapping.get_cpu_id(worker_id);
             worker->location_id = mapping.get_loc_id(worker_id);
             worker->thread = new std::thread(&JExecutionEngine::RunWorker, this, Worker{worker_id, &worker->backtrace});
             LOG_DEBUG(GetLogger()) << "Launching worker thread " << worker_id << " on cpu=" << worker->cpu_id << ", location=" << worker->location_id << LOG_END;
             m_worker_states.push_back(std::move(worker));
 
             bool pin_to_cpu = (mapping.get_affinity() != JProcessorMapping::AffinityStrategy::None);
             if (pin_to_cpu) {
                 JCpuInfo::PinThreadToCpu(worker->thread, worker->cpu_id);
             }
         }
     }
 
     else if (prev_nthreads > nthreads) {
         // We are destroying existing worker threads
         LOG_DEBUG(GetLogger()) << "Scaling down to " << nthreads << " worker threads" << LOG_END;
 
         // Signal to threads that they need to terminate.
         for (int worker_id=prev_nthreads-1; worker_id >= (int)nthreads; --worker_id) {
             LOG_DEBUG(GetLogger()) << "Stopping worker " << worker_id << LOG_END;
             m_worker_states[worker_id]->is_stop_requested = true;
         }
         m_condvar.notify_all(); // Wake up all threads so that they can exit the condvar wait loop
         lock.unlock();
 
         // We join all (eligible) threads _outside_ of the mutex
         for (int worker_id=prev_nthreads-1; worker_id >= (int) nthreads; --worker_id) {
             if (m_worker_states[worker_id]->thread != nullptr) {
                 if (m_worker_states[worker_id]->is_timed_out) {
                     // Thread has timed out. Rather than non-cooperatively killing it,
                     // we relinquish ownership of it but remember that it was ours once and
                     // is still out there, somewhere, biding its time
                     m_worker_states[worker_id]->thread->detach();
                     LOG_DEBUG(GetLogger()) << "Detached worker " << worker_id << LOG_END;
                 }
                 else {
                     LOG_DEBUG(GetLogger()) << "Joining worker " << worker_id << LOG_END;
                     m_worker_states[worker_id]->thread->join();
                     LOG_DEBUG(GetLogger()) << "Joined worker " << worker_id << LOG_END;
                 }
             }
             else {
                 LOG_DEBUG(GetLogger()) << "Skipping worker " << worker_id << LOG_END;
             }
         }
 
         lock.lock();
         // We retake the mutex so we can safely modify m_worker_states
         for (int worker_id=prev_nthreads-1; worker_id >= (int)nthreads; --worker_id) {
             if (m_worker_states.back()->thread != nullptr) {
                 delete m_worker_states.back()->thread;
             }
             m_worker_states.pop_back();
         }
     }
 }
 
 void JExecutionEngine::PauseTopology() {
     std::unique_lock<std::mutex> lock(m_mutex);
     if (m_runstatus != RunStatus::Running) return;
     m_runstatus = RunStatus::Pausing;
     for (auto& arrow: m_arrow_states) {
         if (arrow.status == ArrowState::Status::Running) {
             arrow.status = ArrowState::Status::Paused;
         }
     }
     LOG_WARN(GetLogger()) << "Requested pause" << LOG_END;
     lock.unlock();
     m_condvar.notify_all();
 }
 
 void JExecutionEngine::DrainTopology() {
     std::unique_lock<std::mutex> lock(m_mutex);
     if (m_runstatus != RunStatus::Running) return;
     m_runstatus = RunStatus::Draining;
     for (auto& arrow: m_arrow_states) {
         if (arrow.is_source) {
             if (arrow.status == ArrowState::Status::Running) {
                 arrow.status = ArrowState::Status::Paused;
             }
         }
     }
     LOG_WARN(GetLogger()) << "Requested drain" << LOG_END;
     lock.unlock();
     m_condvar.notify_all();
 }
 
 void JExecutionEngine::RunSupervisor() {
 
     if (m_interrupt_status == InterruptStatus::NoInterruptsUnsupervised) {
         m_interrupt_status = InterruptStatus::NoInterruptsSupervised;
     }
     size_t last_event_count = 0;
     clock_t::time_point last_measurement_time = clock_t::now();
 
     Perf perf;
     while (true) {
 
         if (m_enable_timeout && m_timeout_s > 0) {
             CheckTimeout();
         }
 
         if (m_print_worker_report_requested) {
             PrintWorkerReport(false);
             m_print_worker_report_requested = false;
         }
 
         if (m_send_worker_report_requested) {
             PrintWorkerReport(true);
             m_send_worker_report_requested = false;
         }
 
         perf = GetPerf();
         if ((perf.runstatus == RunStatus::Paused && m_interrupt_status != InterruptStatus::InspectRequested) || 
             perf.runstatus == RunStatus::Finished || 
             perf.runstatus == RunStatus::Failed) {
             break;
         }
 
         if (m_interrupt_status == InterruptStatus::InspectRequested) {
             if (perf.runstatus == RunStatus::Paused) {
                 LOG_INFO(GetLogger()) << "Entering inspector" << LOG_END;
                 m_enable_timeout = false;
                 m_interrupt_status = InterruptStatus::InspectInProgress;
                 InspectApplication(GetApplication());
                 m_interrupt_status = InterruptStatus::NoInterruptsSupervised;
 
                 // Jump back to the top of the loop so that we have fresh event count data
                 last_measurement_time = clock_t::now();
                 last_event_count = 0;
                 continue; 
             }
             else if (perf.runstatus == RunStatus::Running) {
                 PauseTopology();
             }
         }
         else if (m_interrupt_status == InterruptStatus::PauseAndQuit) {
             PauseTopology();
         }
 
         if (m_show_ticker) {
             auto next_measurement_time = clock_t::now();
             auto last_measurement_duration_ms = std::chrono::duration_cast<std::chrono::milliseconds>(next_measurement_time - last_measurement_time).count();
             float latest_throughput_hz = (last_measurement_duration_ms == 0) ? 0 : (perf.event_count - last_event_count) * 1000.0 / last_measurement_duration_ms;
             last_measurement_time = next_measurement_time;
             last_event_count = perf.event_count;
 
             // Print rates
             LOG_INFO(m_logger) << "Status: " << perf.event_count << " events processed at "
                             << JTypeInfo::to_string_with_si_prefix(latest_throughput_hz) << "Hz ("
                             << JTypeInfo::to_string_with_si_prefix(perf.throughput_hz) << "Hz avg)" << LOG_END;
         }
 
         std::this_thread::sleep_for(std::chrono::milliseconds(m_ticker_ms));
     }
     LOG_INFO(GetLogger()) << "Processing paused." << LOG_END;
 
     if (perf.runstatus == RunStatus::Failed) {
         HandleFailures();
     }
 
     PrintFinalReport();
 }
 
 bool JExecutionEngine::CheckTimeout() {
     std::unique_lock<std::mutex> lock(m_mutex);
     auto now = clock_t::now();
     bool timeout_detected = false;
     for (auto& worker: m_worker_states) {
         auto timeout_s = (worker->is_event_warmed_up) ? m_timeout_s : m_warmup_timeout_s;
         auto duration_s = std::chrono::duration_cast<std::chrono::seconds>(now - worker->last_checkout_time).count();
         if (duration_s > timeout_s && worker->last_arrow_id != static_cast<uint64_t>(-1)) {
             worker->is_timed_out = true;
             timeout_detected = true;
             m_runstatus = RunStatus::Failed;
         }
     }
     return timeout_detected;
 }
 
 void JExecutionEngine::HandleFailures() {
 
     std::unique_lock<std::mutex> lock(m_mutex);
 
     // First, we log all of the failures we've found
     for (auto& worker: m_worker_states) {
         if (worker->is_timed_out) {
             std::string arrow_name = (worker->last_arrow_id == static_cast<uint64_t>(-1)) ? "(none)" : m_topology->GetArrows()[worker->last_arrow_id]->GetName();
             LOG_FATAL(GetLogger()) << "Timeout in worker thread " << worker->worker_id << " while executing " << arrow_name << " on event #" << worker->last_event_nr << LOG_END;
             pthread_kill(worker->thread->native_handle(), SIGUSR2);
             LOG_INFO(GetLogger()) << "Worker thread signalled; waiting for backtrace capture." << LOG_END;
             worker->backtrace.WaitForCapture();
         }
         if (worker->stored_exception != nullptr) {
             std::string arrow_name = (worker->last_arrow_id == static_cast<uint64_t>(-1)) ? "(none)" : m_topology->GetArrows()[worker->last_arrow_id]->GetName();
             LOG_FATAL(GetLogger()) << "Exception in worker thread " << worker->worker_id << " while executing " << arrow_name << " on event #" << worker->last_event_nr << LOG_END;
         }
     }
 
     // Now we throw each of these exceptions in order, in case the caller is going to attempt to catch them.
     // In reality all callers are going to print everything they can about the exception and exit.
     for (auto& worker: m_worker_states) {
         if (worker->stored_exception != nullptr) {
             GetApplication()->SetExitCode((int) JApplication::ExitCode::UnhandledException);
             std::rethrow_exception(worker->stored_exception);
         }
         if (worker->is_timed_out) {
             GetApplication()->SetExitCode((int) JApplication::ExitCode::Timeout);
             auto ex = JException("Timeout in worker thread");
             ex.backtrace = worker->backtrace;
             throw ex;
         }
     }
 }
 
 void JExecutionEngine::FinishTopology() {
     std::unique_lock<std::mutex> lock(m_mutex);
     assert(m_runstatus == RunStatus::Paused);
 
     LOG_DEBUG(GetLogger()) << "Finishing processing..." << LOG_END;
     for (auto* arrow : m_topology->GetArrows()) {
         arrow->Finalize();
     }
     for (auto* pool: m_topology->GetPools()) {
         pool->Finalize();
     }
     m_runstatus = RunStatus::Finished;
     LOG_INFO(GetLogger()) << "Finished processing." << LOG_END;
 }
 
 JExecutionEngine::RunStatus JExecutionEngine::GetRunStatus() {
     std::unique_lock<std::mutex> lock(m_mutex);
     return m_runstatus;
 }
 
 JExecutionEngine::Perf JExecutionEngine::GetPerf() {
     std::unique_lock<std::mutex> lock(m_mutex);
     Perf result;
     if (m_runstatus == RunStatus::Paused || m_runstatus == RunStatus::Failed) {
         result.event_count = m_event_count_at_finish - m_event_count_at_start;
         result.uptime_ms = std::chrono::duration_cast<std::chrono::milliseconds>(m_time_at_finish - m_time_at_start).count();
     }
     else {
         // Obtain current event count
         size_t current_event_count = 0;
         for (auto& state : m_arrow_states) {
             if (state.is_sink) {
                 current_event_count += state.events_processed;
             }
         }
         result.event_count = current_event_count - m_event_count_at_start;
         result.uptime_ms = std::chrono::duration_cast<std::chrono::milliseconds>(clock_t::now() - m_time_at_start).count();
     }
     result.runstatus = m_runstatus;
     result.thread_count = m_worker_states.size();
     result.throughput_hz = (result.uptime_ms == 0) ? 0 : (result.event_count * 1000.0) / result.uptime_ms;
     result.event_level = JEventLevel::PhysicsEvent;
     return result;
 }
 
 JExecutionEngine::Worker JExecutionEngine::RegisterWorker() {
     std::unique_lock<std::mutex> lock(m_mutex);
     auto mapping = m_topology->GetProcessorMapping();
     auto worker_id = m_worker_states.size();
     auto worker = std::make_unique<WorkerState>();
     worker->worker_id = worker_id;
     worker->is_stop_requested = false;
     worker->cpu_id = mapping.get_cpu_id(worker_id);
     worker->location_id = mapping.get_loc_id(worker_id);
     worker->thread = nullptr;
     m_worker_states.push_back(std::move(worker));
 
     bool pin_to_cpu = (mapping.get_affinity() != JProcessorMapping::AffinityStrategy::None);
     if (pin_to_cpu) {
         JCpuInfo::PinThreadToCpu(worker->thread, worker->cpu_id);
     }
     return {worker_id, &worker->backtrace};
 
 }
 
 
 void JExecutionEngine::RunWorker(Worker worker) {
 
     LOG_DEBUG(GetLogger()) << "Launched worker thread " << worker.worker_id << LOG_END;
     jana2_worker_id = worker.worker_id;
     jana2_worker_backtrace = worker.backtrace;
 #if JANA2_HAVE_PERFETTO
     JPerfettoService::RegisterCurrentThread(worker.worker_id);
 #endif
     try {
         Task task;
         while (true) {
             ExchangeTask(task, worker.worker_id);
             if (task.arrow == nullptr) break; // Exit as soon as ExchangeTask() stops blocking
             {
 #if JANA2_HAVE_PERFETTO
                 TRACE_EVENT("jana", perfetto::DynamicString{task.arrow->GetName()},
                     "worker_id", (uint64_t)worker.worker_id);
 #endif
                 task.arrow->Fire(task.input_event, task.outputs, task.output_count, task.status);
             }
         }
         LOG_DEBUG(GetLogger()) << "Stopped worker thread " << worker.worker_id << LOG_END;
     }
     catch(JException& ex) {
         LOG_ERROR(GetLogger()) << "Exception on worker thread " << worker.worker_id << ": " << ex.GetMessage();
         std::unique_lock<std::mutex> lock(m_mutex);
         m_runstatus = RunStatus::Failed;
         m_worker_states.at(worker.worker_id)->stored_exception = std::current_exception();
     }
     catch (...) {
         LOG_ERROR(GetLogger()) << "Exception on worker thread " << worker.worker_id << LOG_END;
         std::unique_lock<std::mutex> lock(m_mutex);
         m_runstatus = RunStatus::Failed;
         m_worker_states.at(worker.worker_id)->stored_exception = std::current_exception();
     }
 }
 
 
 void JExecutionEngine::ExchangeTask(Task& task, size_t worker_id, bool nonblocking) {
 
     auto checkin_time = std::chrono::steady_clock::now();
     // It's important to start measuring this _before_ acquiring the lock because acquiring the lock
     // may be a big part of the scheduler overhead
 
     std::unique_lock<std::mutex> lock(m_mutex);
     
     auto& worker = *m_worker_states.at(worker_id);
 
     if (task.arrow != nullptr) {
         CheckinCompletedTask_Unsafe(task, worker, checkin_time);
     }
 
     if (worker.is_stop_requested) {
         return;
     }
 
     FindNextReadyTask_Unsafe(task, worker);
 
     if (nonblocking) { return; }
     auto idle_time_start = clock_t::now();
     m_total_scheduler_duration += (idle_time_start - checkin_time);
 
     while (task.arrow == nullptr && !worker.is_stop_requested) {
         m_condvar.wait(lock);
         FindNextReadyTask_Unsafe(task, worker);
     }
     worker.last_checkout_time = clock_t::now();
 
     if (task.input_event != nullptr) {
         worker.last_event_nr = task.input_event->GetEventNumber();
     }
     else {
         worker.last_event_nr = 0;
     }
     m_total_idle_duration += (worker.last_checkout_time - idle_time_start);
 
     // Notify one worker, who will notify the next, etc, as long as FindNextReadyTaskUnsafe() succeeds.
     // After FindNextReadyTaskUnsafe fails, all threads block until the next returning worker reactivates the
     // notification chain.
     if (task.arrow != nullptr && task.arrow->IsParallel()) {
         m_condvar.notify_one();
     }
 }
 
 
 void JExecutionEngine::CheckinCompletedTask_Unsafe(Task& task, WorkerState& worker, clock_t::time_point checkin_time) {
 
     auto processing_duration = checkin_time - worker.last_checkout_time;
 
     ArrowState& arrow_state = m_arrow_states.at(worker.last_arrow_id);
 
     arrow_state.active_tasks -= 1;
     arrow_state.total_processing_duration += processing_duration;
 
     for (size_t output=0; output<task.output_count; ++output) {
         if (!task.arrow->GetPort(task.outputs[output].second).GetSkipFinishEvent()) {
             arrow_state.events_processed++;
         }
     }
 
     // Put each output in its correct queue or pool
     task.arrow->Push(task.outputs, task.output_count, worker.location_id);
 
     if (task.status == JArrow::FireResult::Finished) {
         // If this is an eventsource self-terminating (the only thing that returns Status::Finished right now) it will
         // have already called DoClose(). I'm tempted to always call DoClose() as part of JExecutionEngine::Finish() instead, however.
 
         // Mark arrow as finished
         arrow_state.status = ArrowState::Status::Finished;
 
         // Check if this switches the topology to Draining()
         if (m_runstatus == RunStatus::Running) {
             bool draining = true;
             for (auto& arrow: m_arrow_states) {
                 if (arrow.is_source && arrow.status == ArrowState::Status::Running) {
                     draining = false;
                 }
             }
             if (draining) {
                 m_runstatus = RunStatus::Draining;
             }
         }
     }
     worker.last_arrow_id = -1;
     worker.last_event_nr = 0;
 
     task.arrow = nullptr;
     task.input_event = nullptr;
     task.output_count = 0;
     task.status = JArrow::FireResult::NotRunYet;
 };
 
 
 void JExecutionEngine::FindNextReadyTask_Unsafe(Task& task, WorkerState& worker) {
 
     if (m_runstatus == RunStatus::Running || m_runstatus == RunStatus::Draining) {
         // We only pick up a new task if the topology is running or draining.
 
         // Each call to FindNextReadyTask_Unsafe() starts with a different m_next_arrow_id to ensure balanced arrow assignments
         size_t arrow_count = m_arrow_states.size();
         m_next_arrow_id += 1;
         m_next_arrow_id %= arrow_count;
 
         for (size_t i=m_next_arrow_id; i<(m_next_arrow_id+arrow_count); ++i) {
             size_t arrow_id = i % arrow_count;
 
             auto& state = m_arrow_states[arrow_id];
             if (!state.is_parallel && (state.active_tasks != 0)) {
                 // We've found a sequential arrow that is already active. Nothing we can do here.
                 LOG_TRACE(GetLogger()) << "Scheduler: Arrow with id " << arrow_id << " is unready: Sequential and already active." << LOG_END;
                 continue;
             }
 
             if (state.status != ArrowState::Status::Running) {
                 LOG_TRACE(GetLogger()) << "Scheduler: Arrow with id " << arrow_id << " is unready: Arrow is either paused or finished." << LOG_END;
                 continue;
             }
             // TODO: Support next_visit_time so that we don't hammer blocked event sources
 
             // See if we can obtain an input event (this is silly)
             JArrow* arrow = m_topology->GetArrows()[arrow_id];
             // TODO: consider setting state.next_input, retrieving via Fire()
             auto port = arrow->GetNextPortIndex();
             JEvent* event = (port == -1) ? nullptr : arrow->Pull(port, worker.location_id);
             if (event != nullptr || port == -1) {
                 LOG_TRACE(GetLogger()) << "Scheduler: Found next ready arrow with id " << arrow_id << LOG_END;
                 // We've found a task that is ready!
                 state.active_tasks += 1;
 
                 task.arrow = arrow;
                 task.input_port = port;
                 task.input_event = event;
                 task.output_count = 0;
                 task.status = JArrow::FireResult::NotRunYet;
 
                 worker.last_arrow_id = arrow_id;
                 if (event != nullptr) {
                     worker.is_event_warmed_up = event->IsWarmedUp();
                     worker.last_event_nr = event->GetEventNumber();
                 }
                 else {
                     worker.is_event_warmed_up = true; // Use shorter timeout
                     worker.last_event_nr = 0;
                 }
                 return;
             }
             else {
                 LOG_TRACE(GetLogger()) << "Scheduler: Arrow with id " << arrow_id << " is unready: Input event is needed but not on queue yet." << LOG_END;
             }
         }
     }
 
     // Because we reached this point, we know that there aren't any tasks ready,
     // so we check whether more are potentially coming. If not, we can pause the topology.
     // Note that our worker threads will still wait at ExchangeTask() until they get
     // shut down separately during Scale().
     
     if (m_runstatus == RunStatus::Pausing || m_runstatus == RunStatus::Draining) {
         // We want to avoid scenarios such as where the topology already Finished but then gets reset to Paused
         // This also leaves a cleaner narrative in the logs. 
 
         bool any_active_source_found = false;
         bool any_active_task_found = false;
         
         LOG_DEBUG(GetLogger()) << "Scheduler: No tasks ready" << LOG_END;
 
         for (size_t arrow_id = 0; arrow_id < m_arrow_states.size(); ++arrow_id) {
             auto& state = m_arrow_states[arrow_id];
             any_active_source_found |= (state.status == ArrowState::Status::Running && state.is_source);
             any_active_task_found |= (state.active_tasks != 0);
             // A source might have been deactivated by RequestPause, Ctrl-C, etc, and might be inactive even though it still has active tasks
         }
 
         if (!any_active_source_found && !any_active_task_found) {
             // Pause the topology
             m_time_at_finish = clock_t::now();
             m_event_count_at_finish = 0;
             for (auto& arrow_state : m_arrow_states) {
                 if (arrow_state.is_sink) {
                     m_event_count_at_finish += arrow_state.events_processed;
                 }
             }
             LOG_DEBUG(GetLogger()) << "Scheduler: Processing paused" << LOG_END;
             m_runstatus = RunStatus::Paused;
             // I think this is the ONLY site where the topology gets paused. Verify this?
         }
     }
 
     worker.last_arrow_id = -1;
 
     task.arrow = nullptr;
     task.input_port = -1;
     task.input_event = nullptr;
     task.output_count = 0;
     task.status = JArrow::FireResult::NotRunYet;
 }
 
 
 void JExecutionEngine::PrintFinalReport() {
 
     std::unique_lock<std::mutex> lock(m_mutex);
     auto event_count = m_event_count_at_finish - m_event_count_at_start;
     auto uptime_ms = std::chrono::duration_cast<std::chrono::milliseconds>(m_time_at_finish - m_time_at_start).count();
     auto thread_count = m_worker_states.size();
     auto throughput_hz = (event_count * 1000.0) / uptime_ms;
 
     LOG_INFO(GetLogger()) << "Detailed report:" << LOG_END;
     LOG_INFO(GetLogger()) << LOG_END;
     LOG_INFO(GetLogger()) << "  Avg throughput [Hz]:         " << std::setprecision(3) << throughput_hz << LOG_END;
     LOG_INFO(GetLogger()) << "  Completed events [count]:    " << event_count << LOG_END;
     LOG_INFO(GetLogger()) << "  Total uptime [s]:            " << std::setprecision(4) << uptime_ms/1000.0 << LOG_END;
     LOG_INFO(GetLogger()) << "  Thread team size [count]:    " << thread_count << LOG_END;
     LOG_INFO(GetLogger()) << LOG_END;
     LOG_INFO(GetLogger()) << "  Arrow-level metrics:" << LOG_END;
     LOG_INFO(GetLogger()) << LOG_END;
 
     size_t total_useful_ms = 0;
 
     for (size_t arrow_id=0; arrow_id < m_arrow_states.size(); ++arrow_id) {
         auto* arrow = m_topology->GetArrows()[arrow_id];
         auto& arrow_state = m_arrow_states[arrow_id];
         auto useful_ms = std::chrono::duration_cast<std::chrono::milliseconds>(arrow_state.total_processing_duration).count();
         total_useful_ms += useful_ms;
         auto avg_latency = useful_ms*1.0/arrow_state.events_processed;
         auto throughput_bottleneck = 1000.0 / avg_latency;
         if (arrow->IsParallel()) {
             throughput_bottleneck *= thread_count;
         }
 
         LOG_INFO(GetLogger()) << "  - Arrow name:                 " << arrow->GetName() << LOG_END;
         LOG_INFO(GetLogger()) << "    Parallel:                   " << arrow->IsParallel() << LOG_END;
         LOG_INFO(GetLogger()) << "    Events completed:           " << arrow_state.events_processed << LOG_END;
         LOG_INFO(GetLogger()) << "    Avg latency [ms/event]:     " << avg_latency << LOG_END;
         LOG_INFO(GetLogger()) << "    Throughput bottleneck [Hz]: " << throughput_bottleneck << LOG_END;
         LOG_INFO(GetLogger()) << LOG_END;
     }
 
     auto total_scheduler_ms = std::chrono::duration_cast<std::chrono::milliseconds>(m_total_scheduler_duration).count();
     auto total_idle_ms = std::chrono::duration_cast<std::chrono::milliseconds>(m_total_idle_duration).count();
 
     LOG_INFO(GetLogger()) << "  Total useful time [s]:     " << std::setprecision(6) << total_useful_ms/1000.0 << LOG_END;
     LOG_INFO(GetLogger()) << "  Total scheduler time [s]:  " << std::setprecision(6) << total_scheduler_ms/1000.0 << LOG_END;
     LOG_INFO(GetLogger()) << "  Total idle time [s]:       " << std::setprecision(6) << total_idle_ms/1000.0 << LOG_END;
 
     LOG_INFO(GetLogger()) << LOG_END;
 
     LOG_INFO(GetLogger()) << "Final report: " << event_count << " events processed at "
                           << JTypeInfo::to_string_with_si_prefix(throughput_hz) << "Hz" << LOG_END;
 
 }
 
 void JExecutionEngine::SetTickerEnabled(bool show_ticker) {
     m_show_ticker = show_ticker;
 }
 
 bool JExecutionEngine::IsTickerEnabled() const {
     return m_show_ticker;
 }
 
 void JExecutionEngine::SetTimeoutEnabled(bool timeout_enabled) {
     m_enable_timeout = timeout_enabled;
 }
 
 bool JExecutionEngine::IsTimeoutEnabled() const {
     return m_enable_timeout;
 }
 
 JArrow::FireResult JExecutionEngine::Fire(size_t arrow_id, size_t location_id) {
 
     std::unique_lock<std::mutex> lock(m_mutex);
     if (arrow_id >= m_topology->GetArrows().size()) {
         LOG_WARN(GetLogger()) << "Firing unsuccessful: No arrow exists with id=" << arrow_id << LOG_END;
         return JArrow::FireResult::NotRunYet;
     }
     JArrow* arrow = m_topology->GetArrows()[arrow_id];
     LOG_WARN(GetLogger()) << "Attempting to fire arrow with name=" << arrow->GetName() 
                           << ", index=" << arrow_id << ", location=" << location_id << LOG_END;
 
     ArrowState& arrow_state = m_arrow_states[arrow_id];
     if (arrow_state.status == ArrowState::Status::Finished) {
         LOG_WARN(GetLogger()) << "Firing unsuccessful: Arrow status is Finished." << arrow_id << LOG_END;
         return JArrow::FireResult::Finished;
     }
     if (!arrow_state.is_parallel && arrow_state.active_tasks != 0) {
         LOG_WARN(GetLogger()) << "Firing unsuccessful: Arrow is sequential and already has an active task." << arrow_id << LOG_END;
         return JArrow::FireResult::NotRunYet;
     }
     arrow_state.active_tasks += 1;
 
     auto port = arrow->GetNextPortIndex();
     JEvent* event = nullptr;
     if (port != -1) {
         event = arrow->Pull(port, location_id);
         if (event == nullptr) {
             LOG_WARN(GetLogger()) << "Firing unsuccessful: Arrow needs an input event from port " << port << ", but the queue or pool is empty." << LOG_END;
             arrow_state.active_tasks -= 1;
             return JArrow::FireResult::NotRunYet;
         }
         else {
             LOG_WARN(GetLogger()) << "Input event #" << event->GetEventNumber() << " from port " << port << LOG_END;
         }
     }
     else {
         LOG_WARN(GetLogger()) << "No input events" << LOG_END;
     }
     lock.unlock();
 
     size_t output_count;
     JArrow::OutputData outputs;
     JArrow::FireResult result = JArrow::FireResult::NotRunYet;
 
     LOG_WARN(GetLogger()) << "Firing arrow" << LOG_END;
     arrow->Fire(event, outputs, output_count, result);
     LOG_WARN(GetLogger()) << "Fired arrow with result " << ToString(result) << LOG_END;
     if (output_count == 0) {
         LOG_WARN(GetLogger()) << "No output events" << LOG_END;
     }
     else {
         for (size_t i=0; i<output_count; ++i) {
             LOG_WARN(GetLogger()) << "Output event #" << outputs.at(i).first->GetEventNumber() << " on port " << outputs.at(i).second << LOG_END;
         }
     }
 
     lock.lock();
     arrow->Push(outputs, output_count, location_id);
     arrow_state.active_tasks -= 1;
     lock.unlock();
     return result;
 }
 
 
 void JExecutionEngine::HandleSIGINT() {
     InterruptStatus status = m_interrupt_status;
     std::cout << std::endl;
     switch (status) {
         case InterruptStatus::NoInterruptsSupervised: m_interrupt_status = InterruptStatus::InspectRequested; break;
         case InterruptStatus::InspectRequested: m_interrupt_status = InterruptStatus::PauseAndQuit; break;
         case InterruptStatus::NoInterruptsUnsupervised:
         case InterruptStatus::PauseAndQuit:
         case InterruptStatus::InspectInProgress: 
             _exit(-2);
     }
 }
 
 void JExecutionEngine::HandleSIGUSR1() {
     m_send_worker_report_requested = true;
 }
 
 void JExecutionEngine::HandleSIGUSR2() {
     if (jana2_worker_backtrace != nullptr) {
         jana2_worker_backtrace->Capture(3);
     }
 }
 
 void JExecutionEngine::HandleSIGTSTP() {
     std::cout << std::endl;
     m_print_worker_report_requested = true;
 }
 
 void JExecutionEngine::PrintWorkerReport(bool send_to_pipe) {
 
     std::unique_lock<std::mutex> lock(m_mutex);
     LOG_INFO(GetLogger()) << "Generating worker report. It may take some time to retrieve each symbol's debug information." << LOG_END;
     for (auto& worker: m_worker_states) {
         worker->backtrace.Reset();
         pthread_kill(worker->thread->native_handle(), SIGUSR2);
     }
     for (auto& worker: m_worker_states) {
         worker->backtrace.WaitForCapture();
     }
     std::ostringstream oss;
     oss << "Worker report" << std::endl;
     for (auto& worker: m_worker_states) {
         oss << "------------------------------" << std::endl 
             << "  Worker:        " << worker->worker_id << std::endl
             << "  Current arrow: " << worker->last_arrow_id << std::endl
             << "  Current event: " << worker->last_event_nr << std::endl
             << "  Backtrace:" << std::endl << std::endl
             << worker->backtrace.ToString();
     }
     auto s = oss.str();
     LOG_WARN(GetLogger()) << s << LOG_END;
 
     if (send_to_pipe) {
 
         int fd = open(m_path_to_named_pipe.c_str(), O_WRONLY);
         if (fd >= 0) {
             write(fd, s.c_str(), s.length()+1);
             close(fd);
         }
         else {
             LOG_ERROR(GetLogger()) << "Unable to open named pipe '" << m_path_to_named_pipe << "' for writing. \n"
             << "  You can use a different named pipe for status info by setting the parameter `jana:status_fname`.\n"
             << "  The status report will still show up in the log." << LOG_END;
         }
     }
 }
 
 
 std::string ToString(JExecutionEngine::RunStatus runstatus) {
     switch(runstatus) {
         case JExecutionEngine::RunStatus::Running: return "Running";
         case JExecutionEngine::RunStatus::Paused: return "Paused";
         case JExecutionEngine::RunStatus::Failed: return "Failed";
         case JExecutionEngine::RunStatus::Pausing: return "Pausing";
         case JExecutionEngine::RunStatus::Draining: return "Draining";
         case JExecutionEngine::RunStatus::Finished: return "Finished";
         default: return "CorruptedRunStatus";
     }
 }
 

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