DataRelayer.cxx

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// Copyright 2019-2020 CERN and copyright holders of ALICE O2.
// See https://alice-o2.web.cern.ch/copyright for details of the copyright holders.
// All rights not expressly granted are reserved.
//
// This software is distributed under the terms of the GNU General Public
// License v3 (GPL Version 3), copied verbatim in the file "COPYING".
//
// In applying this license CERN does not waive the privileges and immunities
// granted to it by virtue of its status as an Intergovernmental Organization
// or submit itself to any jurisdiction.
#include "Framework/DeviceState.h"
#include "Framework/RootSerializationSupport.h"
#include "Framework/DataRelayer.h"
#include "Framework/DataProcessingStats.h"
#include "Framework/DriverConfig.h"
 
#include "Framework/CompilerBuiltins.h"
#include "Framework/DataDescriptorMatcher.h"
#include "Framework/DataSpecUtils.h"
#include "Framework/DataProcessingHeader.h"
#include "Framework/DataProcessingContext.h"
#include "Framework/DataRef.h"
#include "Framework/InputRecord.h"
#include "Framework/InputSpan.h"
#include "Framework/CompletionPolicy.h"
#include "Framework/Logger.h"
#include "Framework/PartRef.h"
#include "Framework/TimesliceIndex.h"
#include "Framework/RoutingIndices.h"
#include "Framework/VariableContextHelpers.h"
#include "Framework/FairMQDeviceProxy.h"
#include "DataProcessingStatus.h"
#include "DataRelayerHelpers.h"
#include "InputRouteHelpers.h"
#include "Framework/LifetimeHelpers.h"
#include "Framework/CommonServices.h"
#include "Framework/DataProcessingStates.h"
#include "Framework/DataTakingContext.h"
#include "Framework/DefaultsHelpers.h"
 
#include "Headers/DataHeaderHelpers.h"
#include "Framework/Formatters.h"
 
#include <Monitoring/Metric.h>
#include <Monitoring/Monitoring.h>
 
#include <fairlogger/Logger.h>
#include <fairmq/Channel.h>
#include <functional>
#include <fairmq/shmem/Message.h>
#include <fmt/format.h>
#include <fmt/ostream.h>
#include <span>
#include <string>
 
using namespace o2::framework::data_matcher;
using DataHeader = o2::header::DataHeader;
using DataProcessingHeader = o2::framework::DataProcessingHeader;
using Verbosity = o2::monitoring::Verbosity;
 
O2_DECLARE_DYNAMIC_LOG(data_relayer);
// Stream which keeps track of the calibration lifetime logic
O2_DECLARE_DYNAMIC_LOG(calibration);
 
namespace o2::framework
{
 
constexpr int INVALID_INPUT = -1;
 
DataRelayer::DataRelayer(const CompletionPolicy& policy,
                         std::vector<InputRoute> const& routes,
                         TimesliceIndex& index,
                         ServiceRegistryRef services)
  : mContext{services},
    mTimesliceIndex{index},
    mCompletionPolicy{policy},
    mDistinctRoutesIndex{DataRelayerHelpers::createDistinctRouteIndex(routes)},
    mInputMatchers{DataRelayerHelpers::createInputMatchers(routes)},
    mMaxLanes{InputRouteHelpers::maxLanes(routes)}
{
  std::scoped_lock<O2_LOCKABLE(std::recursive_mutex)> lock(mMutex);
 
  if (policy.configureRelayer == nullptr) {
    static int pipelineLength = DefaultsHelpers::pipelineLength();
    setPipelineLength(pipelineLength);
  } else {
    policy.configureRelayer(*this);
  }
 
  // The queries are all the same, so we only have width 1
  auto numInputTypes = mDistinctRoutesIndex.size();
  auto& states = services.get<DataProcessingStates>();
  std::string queries = "";
  for (short i = 0; i < numInputTypes; ++i) {
    char buffer[128];
    assert(mDistinctRoutesIndex[i] < routes.size());
    mInputs.push_back(routes[mDistinctRoutesIndex[i]].matcher);
    auto& matcher = routes[mDistinctRoutesIndex[i]].matcher;
    DataSpecUtils::describe(buffer, 127, matcher);
    queries += std::string_view(buffer, strlen(buffer));
    queries += ";";
  }
  auto stateId = (short)ProcessingStateId::DATA_QUERIES;
  states.registerState({.name = "data_queries", .stateId = stateId, .sendInitialValue = true, .defaultEnabled = true});
  states.updateState(DataProcessingStates::CommandSpec{.id = stateId, .size = (int)queries.size(), .data = queries.data()});
  states.processCommandQueue();
}
 
TimesliceId DataRelayer::getTimesliceForSlot(TimesliceSlot slot)
{
  std::scoped_lock<O2_LOCKABLE(std::recursive_mutex)> lock(mMutex);
  auto& variables = mTimesliceIndex.getVariablesForSlot(slot);
  return VariableContextHelpers::getTimeslice(variables);
}
 
DataRelayer::ActivityStats DataRelayer::processDanglingInputs(std::vector<ExpirationHandler> const& expirationHandlers,
                                                              ServiceRegistryRef services, bool createNew)
{
  LOGP(debug, "DataRelayer::processDanglingInputs");
  std::scoped_lock<O2_LOCKABLE(std::recursive_mutex)> lock(mMutex);
  auto& deviceProxy = services.get<FairMQDeviceProxy>();
 
  ActivityStats activity;
  if (expirationHandlers.empty()) {
    LOGP(debug, "DataRelayer::processDanglingInputs: No expiration handlers");
    return activity;
  }
  // Create any slot for the time based fields
  std::vector<TimesliceSlot> slotsCreatedByHandlers;
  if (createNew) {
    LOGP(debug, "Creating new slot");
    for (auto& handler : expirationHandlers) {
      LOGP(debug, "handler.creator for {}", handler.name);
      auto channelIndex = deviceProxy.getInputChannelIndex(handler.routeIndex);
      slotsCreatedByHandlers.push_back(handler.creator(services, channelIndex));
    }
  }
  // Count how many slots are not invalid
  auto validSlots = 0;
  for (auto slot : slotsCreatedByHandlers) {
    if (slot.index == TimesliceSlot::INVALID) {
      continue;
    }
    validSlots++;
  }
  if (validSlots > 0) {
    activity.newSlots++;
    LOGP(debug, "DataRelayer::processDanglingInputs: {} slots created by handler", validSlots);
  } else {
    LOGP(debug, "DataRelayer::processDanglingInputs: no slots created by handler");
  }
  // Outer loop, we process all the records because the fact that the record
  // expires is independent from having received data for it.
  int headerPresent = 0;
  int payloadPresent = 0;
  int noCheckers = 0;
  int badSlot = 0;
  int checkerDenied = 0;
  for (size_t ti = 0; ti < mTimesliceIndex.size(); ++ti) {
    TimesliceSlot slot{ti};
    if (mTimesliceIndex.isValid(slot) == false) {
      continue;
    }
    assert(mDistinctRoutesIndex.empty() == false);
    auto& variables = mTimesliceIndex.getVariablesForSlot(slot);
    auto timestamp = VariableContextHelpers::getTimeslice(variables);
    // We iterate on all the hanlders checking if they need to be expired.
    for (size_t ei = 0; ei < expirationHandlers.size(); ++ei) {
      auto& expirator = expirationHandlers[ei];
      // We check that no data is already there for the given cell
      // it is enough to check the first element
      auto& part = mCache[ti * mDistinctRoutesIndex.size() + expirator.routeIndex.value];
      if (part.size() > 0 && part.header(0) != nullptr) {
        headerPresent++;
        continue;
      }
      if (part.size() > 0 && part.payload(0) != nullptr) {
        payloadPresent++;
        continue;
      }
      // We check that the cell can actually be expired.
      if (!expirator.checker) {
        noCheckers++;
        continue;
      }
      if (slotsCreatedByHandlers[ei] != slot) {
        badSlot++;
        continue;
      }
 
      auto getPartialRecord = [&cache = mCache, numInputTypes = mDistinctRoutesIndex.size()](int li) -> std::span<MessageSet const> {
        auto offset = li * numInputTypes;
        assert(cache.size() >= offset + numInputTypes);
        auto const start = cache.data() + offset;
        auto const end = cache.data() + offset + numInputTypes;
        return {start, end};
      };
 
      auto partial = getPartialRecord(ti);
      // TODO: get the data ref from message model
      auto getter = [&partial](size_t idx, size_t part) {
        if (partial[idx].size() > 0 && partial[idx].header(part).get()) {
          auto header = partial[idx].header(part).get();
          auto payload = partial[idx].payload(part).get();
          return DataRef{nullptr,
                         reinterpret_cast<const char*>(header->GetData()),
                         reinterpret_cast<char const*>(payload ? payload->GetData() : nullptr),
                         payload ? payload->GetSize() : 0};
        }
        return DataRef{};
      };
      auto nPartsGetter = [&partial](size_t idx) {
        return partial[idx].size();
      };
      auto refCountGetter = [&partial](size_t idx) -> int {
        auto& header = static_cast<const fair::mq::shmem::Message&>(*partial[idx].header(0));
        return header.GetRefCount();
      };
      InputSpan span{getter, nPartsGetter, refCountGetter, static_cast<size_t>(partial.size())};
      // Setup the input span
 
      if (expirator.checker(services, timestamp.value, span) == false) {
        checkerDenied++;
        continue;
      }
 
      assert(ti * mDistinctRoutesIndex.size() + expirator.routeIndex.value < mCache.size());
      assert(expirator.handler);
      PartRef newRef;
      expirator.handler(services, newRef, variables);
      part.reset(std::move(newRef));
      activity.expiredSlots++;
 
      mTimesliceIndex.markAsDirty(slot, true);
      assert(part.header(0) != nullptr);
      assert(part.payload(0) != nullptr);
    }
  }
  LOGP(debug, "DataRelayer::processDanglingInputs headerPresent:{}, payloadPresent:{}, noCheckers:{}, badSlot:{}, checkerDenied:{}",
       headerPresent, payloadPresent, noCheckers, badSlot, checkerDenied);
  return activity;
}
 
size_t matchToContext(void const* data,
                      std::vector<DataDescriptorMatcher> const& matchers,
                      std::vector<size_t> const& index,
                      VariableContext& context)
{
  for (size_t ri = 0, re = index.size(); ri < re; ++ri) {
    auto& matcher = matchers[index[ri]];
 
    if (matcher.match(reinterpret_cast<char const*>(data), context)) {
      context.commit();
      return ri;
    }
    context.discard();
  }
  return INVALID_INPUT;
}
 
void sendVariableContextMetrics(VariableContext& context, TimesliceSlot slot, DataProcessingStates& states)
{
  static const std::string nullstring{"null"};
 
  context.publish([](VariableContext const& variables, TimesliceSlot slot, void* context) {
    auto& states = *static_cast<DataProcessingStates*>(context);
    static std::string state = "";
    state.clear();
    for (size_t i = 0; i < MAX_MATCHING_VARIABLE; ++i) {
      auto var = variables.get(i);
      if (auto pval = std::get_if<uint64_t>(&var)) {
        state += std::to_string(*pval);
      } else if (auto pval = std::get_if<uint32_t>(&var)) {
        state += std::to_string(*pval);
      } else if (auto pval2 = std::get_if<std::string>(&var)) {
        state += *pval2;
      } else {
      }
      state += ";";
    }
    states.updateState({.id = short((int)ProcessingStateId::CONTEXT_VARIABLES_BASE + slot.index),
                        .size = (int)state.size(),
                        .data = state.data()});
  },
                  &states, slot);
}
 
void DataRelayer::setOldestPossibleInput(TimesliceId proposed, ChannelIndex channel)
{
  auto newOldest = mTimesliceIndex.setOldestPossibleInput(proposed, channel);
  LOGP(debug, "DataRelayer::setOldestPossibleInput {} from channel {}", newOldest.timeslice.value, newOldest.channel.value);
  static bool dontDrop = getenv("DPL_DONT_DROP_OLD_TIMESLICE") && atoi(getenv("DPL_DONT_DROP_OLD_TIMESLICE"));
  if (dontDrop) {
    return;
  }
  for (size_t si = 0; si < mCache.size() / mInputs.size(); ++si) {
    auto& variables = mTimesliceIndex.getVariablesForSlot({si});
    auto timestamp = VariableContextHelpers::getTimeslice(variables);
    auto valid = mTimesliceIndex.validateSlot({si}, newOldest.timeslice);
    if (valid) {
      if (mTimesliceIndex.isValid({si})) {
        LOGP(debug, "Keeping slot {} because data has timestamp {} while oldest possible timestamp is {}", si, timestamp.value, newOldest.timeslice.value);
      }
      continue;
    }
    mPruneOps.push_back(PruneOp{si});
    bool didDrop = false;
    for (size_t mi = 0; mi < mInputs.size(); ++mi) {
      auto& input = mInputs[mi];
      auto& element = mCache[si * mInputs.size() + mi];
      if (element.size() != 0) {
        if (input.lifetime != Lifetime::Condition && mCompletionPolicy.name != "internal-dpl-injected-dummy-sink") {
          didDrop = true;
          auto& state = mContext.get<DeviceState>();
          if (state.transitionHandling != TransitionHandlingState::NoTransition && DefaultsHelpers::onlineDeploymentMode()) {
            LOGP(warning, "Stop transition requested. Dropping incomplete {} Lifetime::{} data in slot {} with timestamp {} < {} as it will never be completed.", DataSpecUtils::describe(input), input.lifetime, si, timestamp.value, newOldest.timeslice.value);
          } else {
            LOGP(error, "Dropping incomplete {} Lifetime::{} data in slot {} with timestamp {} < {} as it can never be completed.", DataSpecUtils::describe(input), input.lifetime, si, timestamp.value, newOldest.timeslice.value);
          }
        } else {
          LOGP(debug,
               "Silently dropping data {} in pipeline slot {} because it has timeslice {} < {} after receiving data from channel {}."
               "Because Lifetime::Timeframe data not there and not expected (e.g. due to sampling) we drop non sampled, non timeframe data (e.g. Conditions).",
               DataSpecUtils::describe(input), si, timestamp.value, newOldest.timeslice.value,
               mTimesliceIndex.getChannelInfo(channel).channel->GetName());
        }
      }
    }
    // We did drop some data. Let's print what was missing.
    if (didDrop) {
      for (size_t mi = 0; mi < mInputs.size(); ++mi) {
        auto& input = mInputs[mi];
        if (input.lifetime == Lifetime::Timer) {
          continue;
        }
        auto& element = mCache[si * mInputs.size() + mi];
        if (element.size() == 0) {
          auto& state = mContext.get<DeviceState>();
          if (state.transitionHandling != TransitionHandlingState::NoTransition && DefaultsHelpers::onlineDeploymentMode()) {
            if (state.allowedProcessing == DeviceState::CalibrationOnly) {
              O2_SIGNPOST_ID_GENERATE(cid, calibration);
              O2_SIGNPOST_EVENT_EMIT(calibration, cid, "expected_missing_data", "Expected missing %{public}s (lifetime:%d) while dropping non-calibration data in slot %zu with timestamp %zu < %zu.",
                                     DataSpecUtils::describe(input).c_str(), (int)input.lifetime, si, timestamp.value, newOldest.timeslice.value);
            } else {
              LOGP(info, "Missing {} (lifetime:{}) while dropping incomplete data in slot {} with timestamp {} < {}.", DataSpecUtils::describe(input), input.lifetime, si, timestamp.value, newOldest.timeslice.value);
            }
          } else {
            if (state.allowedProcessing == DeviceState::CalibrationOnly) {
              O2_SIGNPOST_ID_GENERATE(cid, calibration);
              O2_SIGNPOST_EVENT_EMIT_INFO(calibration, cid, "expected_missing_data", "Not processing in calibration mode: missing %s (lifetime:%d) while dropping incomplete data in slot %zu with timestamp %zu < %zu.",
                                          DataSpecUtils::describe(input).c_str(), (int)input.lifetime, si, timestamp.value, newOldest.timeslice.value);
            } else {
              LOGP(error, "Missing {} (lifetime:{}) while dropping incomplete data in slot {} with timestamp {} < {}.", DataSpecUtils::describe(input), input.lifetime, si, timestamp.value, newOldest.timeslice.value);
            }
          }
        }
      }
    }
  }
}
 
TimesliceIndex::OldestOutputInfo DataRelayer::getOldestPossibleOutput() const
{
  return mTimesliceIndex.getOldestPossibleOutput();
}
 
void DataRelayer::prunePending(OnDropCallback onDrop)
{
  for (auto& op : mPruneOps) {
    this->pruneCache(op.slot, onDrop);
  }
  mPruneOps.clear();
}
 
void DataRelayer::pruneCache(TimesliceSlot slot, OnDropCallback onDrop)
{
  // We need to prune the cache from the old stuff, if any. Otherwise we
  // simply store the payload in the cache and we mark relevant bit in the
  // hence the first if.
  auto pruneCache = [&onDrop,
                     &cache = mCache,
                     &cachedStateMetrics = mCachedStateMetrics,
                     numInputTypes = mDistinctRoutesIndex.size(),
                     &index = mTimesliceIndex,
                     ref = mContext](TimesliceSlot slot) {
    if (onDrop) {
      auto oldestPossibleTimeslice = index.getOldestPossibleOutput();
      // State of the computation
      std::vector<MessageSet> dropped(numInputTypes);
      for (size_t ai = 0, ae = numInputTypes; ai != ae; ++ai) {
        auto cacheId = slot.index * numInputTypes + ai;
        cachedStateMetrics[cacheId] = CacheEntryStatus::RUNNING;
        // TODO: in the original implementation of the cache, there have been only two messages per entry,
        // check if the 2 above corresponds to the number of messages.
        if (cache[cacheId].size() > 0) {
          dropped[ai] = std::move(cache[cacheId]);
        }
      }
      bool anyDropped = std::any_of(dropped.begin(), dropped.end(), [](auto& m) { return m.size(); });
      if (anyDropped) {
        O2_SIGNPOST_ID_GENERATE(aid, data_relayer);
        O2_SIGNPOST_EVENT_EMIT(data_relayer, aid, "pruneCache", "Dropping stuff from slot %zu with timeslice %zu", slot.index, oldestPossibleTimeslice.timeslice.value);
        onDrop(slot, dropped, oldestPossibleTimeslice);
      }
    }
    assert(cache.empty() == false);
    assert(index.size() * numInputTypes == cache.size());
    // Prune old stuff from the cache, hopefully deleting it...
    // We set the current slot to the timeslice value, so that old stuff
    // will be ignored.
    assert(numInputTypes * slot.index < cache.size());
    for (size_t ai = slot.index * numInputTypes, ae = ai + numInputTypes; ai != ae; ++ai) {
      cache[ai].clear();
      cachedStateMetrics[ai] = CacheEntryStatus::EMPTY;
    }
  };
 
  pruneCache(slot);
}
 
bool isCalibrationData(std::unique_ptr<fair::mq::Message>& first)
{
  auto* dph = o2::header::get<DataProcessingHeader*>(first->GetData());
  return static_cast<o2::header::BaseHeader const&>(*dph).flagsDerivedHeader & DataProcessingHeader::KEEP_AT_EOS_FLAG;
}
 
DataRelayer::RelayChoice
  DataRelayer::relay(void const* rawHeader,
                     std::unique_ptr<fair::mq::Message>* messages,
                     InputInfo const& info,
                     size_t nMessages,
                     size_t nPayloads,
                     std::function<void(TimesliceSlot, std::vector<MessageSet>&, TimesliceIndex::OldestOutputInfo)> onDrop)
{
  std::scoped_lock<O2_LOCKABLE(std::recursive_mutex)> lock(mMutex);
  DataProcessingHeader const* dph = o2::header::get<DataProcessingHeader*>(rawHeader);
  // IMPLEMENTATION DETAILS
  //
  // This returns true if a given slot is available for the current number of lanes
  auto isSlotInLane = [currentLane = dph->startTime, maxLanes = mMaxLanes](TimesliceSlot slot) {
    return (slot.index % maxLanes) == (currentLane % maxLanes);
  };
  // This returns the identifier for the given input. We use a separate
  // function because while it's trivial now, the actual matchmaking will
  // become more complicated when we will start supporting ranges.
  auto getInputTimeslice = [&matchers = mInputMatchers,
                            &distinctRoutes = mDistinctRoutesIndex,
                            &rawHeader,
                            &index = mTimesliceIndex](VariableContext& context)
    -> std::tuple<int, TimesliceId> {
    auto input = matchToContext(rawHeader, matchers, distinctRoutes, context);
 
    if (input == INVALID_INPUT) {
      return {
        INVALID_INPUT,
        TimesliceId{TimesliceId::INVALID},
      };
    }
    if (auto pval = std::get_if<uint64_t>(&context.get(0))) {
      TimesliceId timeslice{*pval};
      return {input, timeslice};
    }
    // If we get here it means we need to push something out of the cache.
    return {
      INVALID_INPUT,
      TimesliceId{TimesliceId::INVALID},
    };
  };
 
  // Actually save the header / payload in the slot
  auto saveInSlot = [&cachedStateMetrics = mCachedStateMetrics,
                     &messages,
                     &nMessages,
                     &nPayloads,
                     &cache = mCache,
                     &services = mContext,
                     numInputTypes = mDistinctRoutesIndex.size()](TimesliceId timeslice, int input, TimesliceSlot slot, InputInfo const& info) -> size_t {
    O2_SIGNPOST_ID_GENERATE(aid, data_relayer);
    O2_SIGNPOST_EVENT_EMIT(data_relayer, aid, "saveInSlot", "saving %{public}s@%zu in slot %zu from %{public}s",
                           fmt::format("{:x}", *o2::header::get<DataHeader*>(messages[0]->GetData())).c_str(),
                           timeslice.value, slot.index,
                           info.index.value == ChannelIndex::INVALID ? "invalid" : services.get<FairMQDeviceProxy>().getInputChannel(info.index)->GetName().c_str());
    auto cacheIdx = numInputTypes * slot.index + input;
    MessageSet& target = cache[cacheIdx];
    cachedStateMetrics[cacheIdx] = CacheEntryStatus::PENDING;
    // TODO: make sure that multiple parts can only be added within the same call of
    // DataRelayer::relay
    assert(nPayloads > 0);
    size_t saved = 0;
    for (size_t mi = 0; mi < nMessages; ++mi) {
      assert(mi + nPayloads < nMessages);
      // We are in calibration mode and the data does not have the calibration bit set.
      // We do not store it.
      if (services.get<DeviceState>().allowedProcessing == DeviceState::ProcessingType::CalibrationOnly && !isCalibrationData(messages[mi])) {
        O2_SIGNPOST_ID_FROM_POINTER(cid, calibration, &services.get<DataProcessorContext>());
        O2_SIGNPOST_EVENT_EMIT(calibration, cid, "calibration",
                               "Dropping incoming %zu messages because they are data processing.", nPayloads);
        // Actually dropping messages.
        for (size_t i = mi; i < mi + nPayloads + 1; i++) {
          auto discard = std::move(messages[i]);
        }
        mi += nPayloads;
        continue;
      }
      target.add([&messages, &mi](size_t i) -> fair::mq::MessagePtr& { return messages[mi + i]; }, nPayloads + 1);
      mi += nPayloads;
      saved += nPayloads;
    }
    return saved;
  };
 
  auto updateStatistics = [ref = mContext](TimesliceIndex::ActionTaken action) {
    auto& stats = ref.get<DataProcessingStats>();
 
    // Update statistics for what happened
    switch (action) {
      case TimesliceIndex::ActionTaken::DropObsolete:
        stats.updateStats({static_cast<short>(ProcessingStatsId::DROPPED_INCOMING_MESSAGES), DataProcessingStats::Op::Add, (int)1});
        break;
      case TimesliceIndex::ActionTaken::DropInvalid:
        stats.updateStats({static_cast<short>(ProcessingStatsId::MALFORMED_INPUTS), DataProcessingStats::Op::Add, (int)1});
        stats.updateStats({static_cast<short>(ProcessingStatsId::DROPPED_COMPUTATIONS), DataProcessingStats::Op::Add, (int)1});
        break;
      case TimesliceIndex::ActionTaken::ReplaceUnused:
        stats.updateStats({static_cast<short>(ProcessingStatsId::RELAYED_MESSAGES), DataProcessingStats::Op::Add, (int)1});
        break;
      case TimesliceIndex::ActionTaken::ReplaceObsolete:
        stats.updateStats({static_cast<short>(ProcessingStatsId::MALFORMED_INPUTS), DataProcessingStats::Op::Add, (int)1});
        stats.updateStats({static_cast<short>(ProcessingStatsId::DROPPED_COMPUTATIONS), DataProcessingStats::Op::Add, (int)1});
        break;
      case TimesliceIndex::ActionTaken::Wait:
        break;
    }
  };
 
  // OUTER LOOP
  //
  // This is the actual outer loop processing input as part of a given
  // timeslice. All the other implementation details are hidden by the lambdas
  auto input = INVALID_INPUT;
  auto timeslice = TimesliceId{TimesliceId::INVALID};
  auto slot = TimesliceSlot{TimesliceSlot::INVALID};
  auto& index = mTimesliceIndex;
 
  bool needsCleaning = false;
  // First look for matching slots which already have some
  // partial match.
  for (size_t ci = 0; ci < index.size(); ++ci) {
    slot = TimesliceSlot{ci};
    if (!isSlotInLane(slot)) {
      continue;
    }
    if (index.isValid(slot) == false) {
      continue;
    }
    std::tie(input, timeslice) = getInputTimeslice(index.getVariablesForSlot(slot));
    if (input != INVALID_INPUT) {
      break;
    }
  }
 
  // If we did not find anything, look for slots which
  // are invalid.
  if (input == INVALID_INPUT) {
    for (size_t ci = 0; ci < index.size(); ++ci) {
      slot = TimesliceSlot{ci};
      if (index.isValid(slot) == true) {
        continue;
      }
      if (!isSlotInLane(slot)) {
        continue;
      }
      std::tie(input, timeslice) = getInputTimeslice(index.getVariablesForSlot(slot));
      if (input != INVALID_INPUT) {
        needsCleaning = true;
        break;
      }
    }
  }
 
  auto& stats = mContext.get<DataProcessingStats>();
  if (input != INVALID_INPUT && TimesliceId::isValid(timeslice) && TimesliceSlot::isValid(slot)) {
    if (needsCleaning) {
      this->pruneCache(slot, onDrop);
      mPruneOps.erase(std::remove_if(mPruneOps.begin(), mPruneOps.end(), [slot](const auto& x) { return x.slot == slot; }), mPruneOps.end());
    }
    size_t saved = saveInSlot(timeslice, input, slot, info);
    if (saved == 0) {
      return RelayChoice{.type = RelayChoice::Type::Dropped, .timeslice = timeslice};
    }
    index.publishSlot(slot);
    index.markAsDirty(slot, true);
    stats.updateStats({static_cast<short>(ProcessingStatsId::RELAYED_MESSAGES), DataProcessingStats::Op::Add, (int)1});
    return RelayChoice{.type = RelayChoice::Type::WillRelay, .timeslice = timeslice};
  }
 
  VariableContext pristineContext;
  std::tie(input, timeslice) = getInputTimeslice(pristineContext);
 
  auto DataHeaderInfo = [&rawHeader]() {
    std::string error;
    // extract header from message model
    const auto* dh = o2::header::get<o2::header::DataHeader*>(rawHeader);
    if (dh) {
      error += fmt::format("{}/{}/{}", dh->dataOrigin, dh->dataDescription, dh->subSpecification);
    } else {
      error += "invalid header";
    }
    return error;
  };
 
  if (input == INVALID_INPUT) {
    LOG(error) << "Could not match incoming data to any input route: " << DataHeaderInfo();
    stats.updateStats({static_cast<short>(ProcessingStatsId::MALFORMED_INPUTS), DataProcessingStats::Op::Add, (int)1});
    stats.updateStats({static_cast<short>(ProcessingStatsId::DROPPED_INCOMING_MESSAGES), DataProcessingStats::Op::Add, (int)1});
    for (size_t pi = 0; pi < nMessages; ++pi) {
      messages[pi].reset(nullptr);
    }
    return RelayChoice{.type = RelayChoice::Type::Invalid, .timeslice = timeslice};
  }
 
  if (TimesliceId::isValid(timeslice) == false) {
    LOG(error) << "Could not determine the timeslice for input: " << DataHeaderInfo();
    stats.updateStats({static_cast<short>(ProcessingStatsId::MALFORMED_INPUTS), DataProcessingStats::Op::Add, (int)1});
    stats.updateStats({static_cast<short>(ProcessingStatsId::DROPPED_INCOMING_MESSAGES), DataProcessingStats::Op::Add, (int)1});
    for (size_t pi = 0; pi < nMessages; ++pi) {
      messages[pi].reset(nullptr);
    }
    return RelayChoice{.type = RelayChoice::Type::Invalid, .timeslice = timeslice};
  }
 
  O2_SIGNPOST_ID_GENERATE(aid, data_relayer);
  TimesliceIndex::ActionTaken action;
  std::tie(action, slot) = index.replaceLRUWith(pristineContext, timeslice);
  uint64_t const* debugTimestamp = std::get_if<uint64_t>(&pristineContext.get(0));
  if (action != TimesliceIndex::ActionTaken::Wait) {
    O2_SIGNPOST_EVENT_EMIT(data_relayer, aid, "saveInSlot",
                           "Slot %zu updated with %zu using action %d, %" PRIu64, slot.index, timeslice.value, (int)action, *debugTimestamp);
  }
 
  updateStatistics(action);
 
  switch (action) {
    case TimesliceIndex::ActionTaken::Wait:
      return RelayChoice{.type = RelayChoice::Type::Backpressured, .timeslice = timeslice};
    case TimesliceIndex::ActionTaken::DropObsolete:
      static std::atomic<size_t> obsoleteCount = 0;
      static std::atomic<size_t> mult = 1;
      if ((obsoleteCount++ % (1 * mult)) == 0) {
        LOGP(warning, "Over {} incoming messages are already obsolete, not relaying.", obsoleteCount.load());
        if (obsoleteCount > mult * 10) {
          mult = mult * 10;
        }
      }
      return RelayChoice{.type = RelayChoice::Type::Dropped, .timeslice = timeslice};
    case TimesliceIndex::ActionTaken::DropInvalid:
      LOG(warning) << "Incoming data is invalid, not relaying.";
      stats.updateStats({static_cast<short>(ProcessingStatsId::MALFORMED_INPUTS), DataProcessingStats::Op::Add, (int)1});
      stats.updateStats({static_cast<short>(ProcessingStatsId::DROPPED_INCOMING_MESSAGES), DataProcessingStats::Op::Add, (int)1});
      for (size_t pi = 0; pi < nMessages; ++pi) {
        messages[pi].reset(nullptr);
      }
      return RelayChoice{.type = RelayChoice::Type::Invalid, .timeslice = timeslice};
    case TimesliceIndex::ActionTaken::ReplaceUnused:
    case TimesliceIndex::ActionTaken::ReplaceObsolete:
      // At this point the variables match the new input but the
      // cache still holds the old data, so we prune it.
      this->pruneCache(slot, onDrop);
      mPruneOps.erase(std::remove_if(mPruneOps.begin(), mPruneOps.end(), [slot](const auto& x) { return x.slot == slot; }), mPruneOps.end());
      size_t saved = saveInSlot(timeslice, input, slot, info);
      if (saved == 0) {
        return RelayChoice{.type = RelayChoice::Type::Dropped, .timeslice = timeslice};
      }
      index.publishSlot(slot);
      index.markAsDirty(slot, true);
      return RelayChoice{.type = RelayChoice::Type::WillRelay, .timeslice = timeslice};
  }
  O2_BUILTIN_UNREACHABLE();
}
 
void DataRelayer::getReadyToProcess(std::vector<DataRelayer::RecordAction>& completed)
{
  LOGP(debug, "DataRelayer::getReadyToProcess");
  std::scoped_lock<O2_LOCKABLE(std::recursive_mutex)> lock(mMutex);
 
  // THE STATE
  const auto& cache = mCache;
  const auto numInputTypes = mDistinctRoutesIndex.size();
  //
  // THE IMPLEMENTATION DETAILS
  //
  // We use this to bail out early from the check as soon as we find something
  // which we know is not complete.
  auto getPartialRecord = [&cache, &numInputTypes](int li) -> std::span<MessageSet const> {
    auto offset = li * numInputTypes;
    assert(cache.size() >= offset + numInputTypes);
    auto const start = cache.data() + offset;
    auto const end = cache.data() + offset + numInputTypes;
    return {start, end};
  };
 
  // These two are trivial, but in principle the whole loop could be parallelised
  // or vectorised so "completed" could be a thread local variable which needs
  // merging at the end.
  auto updateCompletionResults = [&completed](TimesliceSlot li, uint64_t const* timeslice, CompletionPolicy::CompletionOp op) {
    if (timeslice) {
      LOGP(debug, "Doing action {} for slot {} (timeslice: {})", (int)op, li.index, *timeslice);
      completed.emplace_back(RecordAction{li, {*timeslice}, op});
    } else {
      LOGP(debug, "No timeslice associated with slot ", li.index);
    }
  };
 
  // THE OUTER LOOP
  //
  // To determine if a line is complete, we iterate on all the arguments
  // and check if they are ready. We do it this way, because in the end
  // the number of inputs is going to be small and having a more complex
  // structure will probably result in a larger footprint in any case.
  // Also notice that ai == inputsNumber only when we reach the end of the
  // iteration, that means we have found all the required bits.
  //
  // Notice that the only time numInputTypes is 0 is when we are a dummy
  // device created as a source for timers / conditions.
  if (numInputTypes == 0) {
    LOGP(debug, "numInputTypes == 0, returning.");
    return;
  }
  size_t cacheLines = cache.size() / numInputTypes;
  assert(cacheLines * numInputTypes == cache.size());
  int countConsume = 0;
  int countConsumeExisting = 0;
  int countProcess = 0;
  int countDiscard = 0;
  int countWait = 0;
  int notDirty = 0;
 
  for (int li = cacheLines - 1; li >= 0; --li) {
    TimesliceSlot slot{(size_t)li};
    // We only check the cachelines which have been updated by an incoming
    // message.
    if (mTimesliceIndex.isDirty(slot) == false) {
      notDirty++;
      continue;
    }
    if (!mCompletionPolicy.callbackFull) {
      throw runtime_error_f("Completion police %s has no callback set", mCompletionPolicy.name.c_str());
    }
    auto partial = getPartialRecord(li);
    // TODO: get the data ref from message model
    auto getter = [&partial](size_t idx, size_t part) {
      if (partial[idx].size() > 0 && partial[idx].header(part).get()) {
        auto header = partial[idx].header(part).get();
        auto payload = partial[idx].payload(part).get();
        return DataRef{nullptr,
                       reinterpret_cast<const char*>(header->GetData()),
                       reinterpret_cast<char const*>(payload ? payload->GetData() : nullptr),
                       payload ? payload->GetSize() : 0};
      }
      return DataRef{};
    };
    auto nPartsGetter = [&partial](size_t idx) {
      return partial[idx].size();
    };
    auto refCountGetter = [&partial](size_t idx) -> int {
      auto& header = static_cast<const fair::mq::shmem::Message&>(*partial[idx].header(0));
      return header.GetRefCount();
    };
    InputSpan span{getter, nPartsGetter, refCountGetter, static_cast<size_t>(partial.size())};
    CompletionPolicy::CompletionOp action = mCompletionPolicy.callbackFull(span, mInputs, mContext);
 
    auto& variables = mTimesliceIndex.getVariablesForSlot(slot);
    auto timeslice = std::get_if<uint64_t>(&variables.get(0));
    switch (action) {
      case CompletionPolicy::CompletionOp::Consume:
        countConsume++;
        updateCompletionResults(slot, timeslice, action);
        mTimesliceIndex.markAsDirty(slot, false);
        break;
      case CompletionPolicy::CompletionOp::ConsumeAndRescan:
        // This is just like Consume, but we also mark all slots as dirty
        countConsume++;
        action = CompletionPolicy::CompletionOp::Consume;
        updateCompletionResults(slot, timeslice, action);
        mTimesliceIndex.rescan();
        break;
      case CompletionPolicy::CompletionOp::ConsumeExisting:
        countConsumeExisting++;
        updateCompletionResults(slot, timeslice, action);
        mTimesliceIndex.markAsDirty(slot, false);
        break;
      case CompletionPolicy::CompletionOp::Process:
        countProcess++;
        updateCompletionResults(slot, timeslice, action);
        mTimesliceIndex.markAsDirty(slot, false);
        break;
      case CompletionPolicy::CompletionOp::Discard:
        countDiscard++;
        updateCompletionResults(slot, timeslice, action);
        mTimesliceIndex.markAsDirty(slot, false);
        break;
      case CompletionPolicy::CompletionOp::Retry:
        countWait++;
        mTimesliceIndex.markAsDirty(slot, true);
        action = CompletionPolicy::CompletionOp::Wait;
        break;
      case CompletionPolicy::CompletionOp::Wait:
        countWait++;
        mTimesliceIndex.markAsDirty(slot, false);
        break;
    }
  }
  mTimesliceIndex.updateOldestPossibleOutput(false);
  LOGP(debug, "DataRelayer::getReadyToProcess results notDirty:{}, consume:{}, consumeExisting:{}, process:{}, discard:{}, wait:{}",
       notDirty, countConsume, countConsumeExisting, countProcess,
       countDiscard, countWait);
}
 
void DataRelayer::updateCacheStatus(TimesliceSlot slot, CacheEntryStatus oldStatus, CacheEntryStatus newStatus)
{
  std::scoped_lock<O2_LOCKABLE(std::recursive_mutex)> lock(mMutex);
  const auto numInputTypes = mDistinctRoutesIndex.size();
 
  auto markInputDone = [&cachedStateMetrics = mCachedStateMetrics,
                        &numInputTypes](TimesliceSlot s, size_t arg, CacheEntryStatus oldStatus, CacheEntryStatus newStatus) {
    auto cacheId = s.index * numInputTypes + arg;
    if (cachedStateMetrics[cacheId] == oldStatus) {
      cachedStateMetrics[cacheId] = newStatus;
    }
  };
 
  for (size_t ai = 0, ae = numInputTypes; ai != ae; ++ai) {
    markInputDone(slot, ai, oldStatus, newStatus);
  }
}
 
std::vector<o2::framework::MessageSet> DataRelayer::consumeAllInputsForTimeslice(TimesliceSlot slot)
{
  std::scoped_lock<O2_LOCKABLE(std::recursive_mutex)> lock(mMutex);
 
  const auto numInputTypes = mDistinctRoutesIndex.size();
  // State of the computation
  std::vector<MessageSet> messages(numInputTypes);
  auto& cache = mCache;
  auto& index = mTimesliceIndex;
 
  // Nothing to see here, this is just to make the outer loop more understandable.
  auto jumpToCacheEntryAssociatedWith = [](TimesliceSlot) {
    return;
  };
 
  // We move ownership so that the cache can be reused once the computation is
  // finished. We mark the given cache slot invalid, so that it can be reused
  // This means we can still handle old messages if there is still space in the
  // cache where to put them.
  auto moveHeaderPayloadToOutput = [&messages,
                                    &cachedStateMetrics = mCachedStateMetrics,
                                    &cache, &index, &numInputTypes](TimesliceSlot s, size_t arg) {
    auto cacheId = s.index * numInputTypes + arg;
    cachedStateMetrics[cacheId] = CacheEntryStatus::RUNNING;
    // TODO: in the original implementation of the cache, there have been only two messages per entry,
    // check if the 2 above corresponds to the number of messages.
    if (cache[cacheId].size() > 0) {
      messages[arg] = std::move(cache[cacheId]);
    }
    index.markAsInvalid(s);
  };
 
  // An invalid set of arguments is a set of arguments associated to an invalid
  // timeslice, so I can simply do that. I keep the assertion there because in principle
  // we should have dispatched the timeslice already!
  // FIXME: what happens when we have enough timeslices to hit the invalid one?
  auto invalidateCacheFor = [&numInputTypes, &index, &cache](TimesliceSlot s) {
    for (size_t ai = s.index * numInputTypes, ae = ai + numInputTypes; ai != ae; ++ai) {
      assert(std::accumulate(cache[ai].messages.begin(), cache[ai].messages.end(), true, [](bool result, auto const& element) { return result && element.get() == nullptr; }));
      cache[ai].clear();
    }
    index.markAsInvalid(s);
  };
 
  // Outer loop here.
  jumpToCacheEntryAssociatedWith(slot);
  for (size_t ai = 0, ae = numInputTypes; ai != ae; ++ai) {
    moveHeaderPayloadToOutput(slot, ai);
  }
  invalidateCacheFor(slot);
 
  return messages;
}
 
std::vector<o2::framework::MessageSet> DataRelayer::consumeExistingInputsForTimeslice(TimesliceSlot slot)
{
  std::scoped_lock<O2_LOCKABLE(std::recursive_mutex)> lock(mMutex);
 
  const auto numInputTypes = mDistinctRoutesIndex.size();
  // State of the computation
  std::vector<MessageSet> messages(numInputTypes);
  auto& cache = mCache;
  auto& index = mTimesliceIndex;
 
  // Nothing to see here, this is just to make the outer loop more understandable.
  auto jumpToCacheEntryAssociatedWith = [](TimesliceSlot) {
    return;
  };
 
  // We move ownership so that the cache can be reused once the computation is
  // finished. We mark the given cache slot invalid, so that it can be reused
  // This means we can still handle old messages if there is still space in the
  // cache where to put them.
  auto copyHeaderPayloadToOutput = [&messages,
                                    &cachedStateMetrics = mCachedStateMetrics,
                                    &cache, &index, &numInputTypes](TimesliceSlot s, size_t arg) {
    auto cacheId = s.index * numInputTypes + arg;
    cachedStateMetrics[cacheId] = CacheEntryStatus::RUNNING;
    // TODO: in the original implementation of the cache, there have been only two messages per entry,
    // check if the 2 above corresponds to the number of messages.
    for (size_t pi = 0; pi < cache[cacheId].size(); pi++) {
      auto& header = cache[cacheId].header(pi);
      auto&& newHeader = header->GetTransport()->CreateMessage();
      newHeader->Copy(*header);
      messages[arg].add(PartRef{std::move(newHeader), std::move(cache[cacheId].payload(pi))});
    }
  };
 
  // Outer loop here.
  jumpToCacheEntryAssociatedWith(slot);
  for (size_t ai = 0, ae = numInputTypes; ai != ae; ++ai) {
    copyHeaderPayloadToOutput(slot, ai);
  }
 
  return std::move(messages);
}
 
void DataRelayer::clear()
{
  std::scoped_lock<O2_LOCKABLE(std::recursive_mutex)> lock(mMutex);
 
  for (auto& cache : mCache) {
    cache.clear();
  }
  for (size_t s = 0; s < mTimesliceIndex.size(); ++s) {
    mTimesliceIndex.markAsInvalid(TimesliceSlot{s});
  }
}
 
size_t
  DataRelayer::getParallelTimeslices() const
{
  return mCache.size() / mDistinctRoutesIndex.size();
}
 
void DataRelayer::setPipelineLength(size_t s)
{
  std::scoped_lock<O2_LOCKABLE(std::recursive_mutex)> lock(mMutex);
 
  mTimesliceIndex.resize(s);
  mVariableContextes.resize(s);
  publishMetrics();
}
 
void DataRelayer::publishMetrics()
{
  std::scoped_lock<O2_LOCKABLE(std::recursive_mutex)> lock(mMutex);
 
  auto numInputTypes = mDistinctRoutesIndex.size();
  // FIXME: many of the DataRelayer function rely on allocated cache, so its
  // maybe misleading to have the allocation in a function primarily for
  // metrics publishing, do better in setPipelineLength?
  mCache.resize(numInputTypes * mTimesliceIndex.size());
  auto& states = mContext.get<DataProcessingStates>();
 
  mCachedStateMetrics.resize(mCache.size());
 
  // There is maximum 16 variables available. We keep them row-wise so that
  // that we can take mod 16 of the index to understand which variable we
  // are talking about.
  for (size_t i = 0; i < mVariableContextes.size(); ++i) {
    states.registerState(DataProcessingStates::StateSpec{
      .name = fmt::format("matcher_variables/{}", i),
      .stateId = static_cast<short>((short)(ProcessingStateId::CONTEXT_VARIABLES_BASE) + i),
      .minPublishInterval = 500, // if we publish too often we flood the GUI and we are not able to read it in any case
      .sendInitialValue = true,
      .defaultEnabled = mContext.get<DriverConfig const>().driverHasGUI,
    });
  }
 
  for (int ci = 0; ci < mTimesliceIndex.size(); ci++) {
    states.registerState(DataProcessingStates::StateSpec{
      .name = fmt::format("data_relayer/{}", ci),
      .stateId = static_cast<short>((short)(ProcessingStateId::DATA_RELAYER_BASE) + (short)ci),
      .minPublishInterval = 800, // if we publish too often we flood the GUI and we are not able to read it in any case
      .sendInitialValue = true,
      .defaultEnabled = mContext.get<DriverConfig const>().driverHasGUI,
    });
  }
}
 
uint32_t DataRelayer::getFirstTFOrbitForSlot(TimesliceSlot slot)
{
  std::scoped_lock<O2_LOCKABLE(std::recursive_mutex)> lock(mMutex);
  return VariableContextHelpers::getFirstTFOrbit(mTimesliceIndex.getVariablesForSlot(slot));
}
 
uint32_t DataRelayer::getFirstTFCounterForSlot(TimesliceSlot slot)
{
  std::scoped_lock<O2_LOCKABLE(std::recursive_mutex)> lock(mMutex);
  return VariableContextHelpers::getFirstTFCounter(mTimesliceIndex.getVariablesForSlot(slot));
}
 
uint32_t DataRelayer::getRunNumberForSlot(TimesliceSlot slot)
{
  std::scoped_lock<O2_LOCKABLE(std::recursive_mutex)> lock(mMutex);
  return VariableContextHelpers::getRunNumber(mTimesliceIndex.getVariablesForSlot(slot));
}
 
uint64_t DataRelayer::getCreationTimeForSlot(TimesliceSlot slot)
{
  std::scoped_lock<O2_LOCKABLE(std::recursive_mutex)> lock(mMutex);
  return VariableContextHelpers::getCreationTime(mTimesliceIndex.getVariablesForSlot(slot));
}
 
void DataRelayer::sendContextState()
{
  if (!mContext.get<DriverConfig const>().driverHasGUI) {
    return;
  }
  std::scoped_lock<O2_LOCKABLE(std::recursive_mutex)> lock(mMutex);
  auto& states = mContext.get<DataProcessingStates>();
  for (size_t ci = 0; ci < mTimesliceIndex.size(); ++ci) {
    auto slot = TimesliceSlot{ci};
    sendVariableContextMetrics(mTimesliceIndex.getPublishedVariablesForSlot(slot), slot,
                               states);
  }
  char relayerSlotState[1024];
  // The number of timeslices is encoded in each state
  // We serialise the state of a Timeslot in a given state.
  int written = snprintf(relayerSlotState, 1024, "%d ", (int)mTimesliceIndex.size());
  char* buffer = relayerSlotState + written;
  for (size_t ci = 0; ci < mTimesliceIndex.size(); ++ci) {
    for (size_t si = 0; si < mDistinctRoutesIndex.size(); ++si) {
      int index = ci * mDistinctRoutesIndex.size() + si;
      int value = static_cast<int>(mCachedStateMetrics[index]);
      buffer[si] = value + '0';
      // Anything which is done is actually already empty,
      // so after we report it we mark it as such.
      if (mCachedStateMetrics[index] == CacheEntryStatus::DONE) {
        mCachedStateMetrics[index] = CacheEntryStatus::EMPTY;
      }
    }
    buffer[mDistinctRoutesIndex.size()] = '\0';
    auto size = (int)(buffer - relayerSlotState + mDistinctRoutesIndex.size());
    states.updateState({.id = short((int)ProcessingStateId::DATA_RELAYER_BASE + ci), .size = size, .data = relayerSlotState});
  }
}
 
} // namespace o2::framework