DPL: earlier forwarding

This anticipates the forwarding to the earliest possible moment, i.e. when
we are about to insert the messages in a slot. This is the earliest moment
we can guarantee messages will be seen only once.

Author: ktf

Framework/Core/src/DataProcessingDevice.cxx

@@ -617,6 +617,20 @@ static auto forwardInputs = [](ServiceRegistryRef registry, TimesliceSlot slot,
   O2_SIGNPOST_END(forwarding, sid, "forwardInputs", "Forwarding done");
 };
 
+static auto cleanEarlyForward = [](ServiceRegistryRef registry, TimesliceSlot slot, std::vector<MessageSet>& currentSetOfInputs,
+                                   TimesliceIndex::OldestOutputInfo oldestTimeslice, bool copy, bool consume = true) {
+  auto& proxy = registry.get<FairMQDeviceProxy>();
+
+  O2_SIGNPOST_ID_GENERATE(sid, forwarding);
+  O2_SIGNPOST_START(forwarding, sid, "forwardInputs", "Cleaning up slot %zu with oldestTimeslice %zu %{public}s%{public}s%{public}s",
+                    slot.index, oldestTimeslice.timeslice.value, copy ? "with copy" : "", copy && consume ? " and " : "", consume ? "with consume" : "");
+  // Always copy them, because we do not want to actually send them.
+  // We merely need the side effect of the consume, if applicable.
+  auto forwardedParts = DataProcessingHelpers::routeForwardedMessageSet(proxy, currentSetOfInputs, true, consume);
+
+  O2_SIGNPOST_END(forwarding, sid, "forwardInputs", "Forwarding done");
+};
+
 extern volatile int region_read_global_dummy_variable;
 volatile int region_read_global_dummy_variable;
 
@@ -1680,6 +1694,51 @@ struct WaitBackpressurePolicy {
   }
 };
 
+auto forwardOnInsertion(ServiceRegistryRef& ref, std::span<fair::mq::MessagePtr>& messages) -> void
+{
+  O2_SIGNPOST_ID_GENERATE(sid, forwarding);
+
+  auto& spec = ref.get<DeviceSpec const>();
+  auto& context = ref.get<DataProcessorContext>();
+  if (!context.canForwardEarly || spec.forwards.empty()) {
+    O2_SIGNPOST_EVENT_EMIT(device, sid, "device", "Early forwardinding not enabled / needed.");
+    return;
+  }
+
+  O2_SIGNPOST_EVENT_EMIT(device, sid, "device", "Early forwardinding before injecting data into relayer.");
+  auto& timesliceIndex = ref.get<TimesliceIndex>();
+  auto oldestTimeslice = timesliceIndex.getOldestPossibleOutput();
+
+  auto& proxy = ref.get<FairMQDeviceProxy>();
+
+  O2_SIGNPOST_START(forwarding, sid, "forwardInputs",
+                    "Starting forwarding for incoming messages with oldestTimeslice %zu with copy",
+                    oldestTimeslice.timeslice.value);
+  std::vector<fair::mq::Parts> forwardedParts(proxy.getNumForwardChannels());
+  DataProcessingHelpers::routeForwardedMessages(proxy, messages, forwardedParts, true, false);
+
+  for (int fi = 0; fi < proxy.getNumForwardChannels(); fi++) {
+    if (forwardedParts[fi].Size() == 0) {
+      continue;
+    }
+    ForwardChannelInfo info = proxy.getForwardChannelInfo(ChannelIndex{fi});
+    auto& parts = forwardedParts[fi];
+    if (info.policy == nullptr) {
+      O2_SIGNPOST_EVENT_EMIT_ERROR(forwarding, sid, "forwardInputs", "Forwarding to %{public}s %d has no policy.", info.name.c_str(), fi);
+      continue;
+    }
+    O2_SIGNPOST_EVENT_EMIT(forwarding, sid, "forwardInputs", "Forwarding to %{public}s %d", info.name.c_str(), fi);
+    info.policy->forward(parts, ChannelIndex{fi}, ref);
+  }
+  auto& asyncQueue = ref.get<AsyncQueue>();
+  auto& decongestion = ref.get<DecongestionService>();
+  O2_SIGNPOST_ID_GENERATE(aid, async_queue);
+  O2_SIGNPOST_EVENT_EMIT(async_queue, aid, "forwardInputs", "Queuing forwarding oldestPossible %zu", oldestTimeslice.timeslice.value);
+  AsyncQueueHelpers::post(asyncQueue, AsyncTask{.timeslice = oldestTimeslice.timeslice, .id = decongestion.oldestPossibleTimesliceTask, .debounce = -1, .callback = decongestionCallbackLate}
+                                        .user<DecongestionContext>({.ref = ref, .oldestTimeslice = oldestTimeslice}));
+  O2_SIGNPOST_END(forwarding, sid, "forwardInputs", "Forwarding done");
+};
+
 /// This is the inner loop of our framework. The actual implementation
 /// is divided in two parts. In the first one we define a set of lambdas
 /// which describe what is actually going to happen, hiding all the state
@@ -1854,12 +1913,13 @@ void DataProcessingDevice::handleData(ServiceRegistryRef ref, InputChannelInfo&
             VariableContextHelpers::getTimeslice(variables);
             forwardInputs(ref, slot, dropped, oldestOutputInfo, false, true);
           };
+
           auto relayed = relayer.relay(parts.At(headerIndex)->GetData(),
                                        &parts.At(headerIndex),
                                        input,
                                        nMessages,
                                        nPayloadsPerHeader,
-                                       nullptr,
+                                       forwardOnInsertion,
                                        onDrop);
           switch (relayed.type) {
             case DataRelayer::RelayChoice::Type::Backpressured:
@@ -2274,9 +2334,16 @@ bool DataProcessingDevice::tryDispatchComputation(ServiceRegistryRef ref, std::v
     bool consumeSomething = action.op == CompletionPolicy::CompletionOp::Consume || action.op == CompletionPolicy::CompletionOp::ConsumeExisting;
 
     if (context.canForwardEarly && hasForwards && consumeSomething) {
-      O2_SIGNPOST_EVENT_EMIT(device, aid, "device", "Early forwainding: %{public}s.", fmt::format("{}", action.op).c_str());
+      // We used to do fowarding here, however we now do it much earlier.
+      // We still need to clean the inputs which were already consumed
+      // via ConsumeExisting and which still have an header to hold the slot.
+      // FIXME: do we? This should really happen when we do the forwarding on
+      // insertion, because otherwise we lose the relevant information on how to
+      // navigate the set of headers. We could actually rely on the messageset index,
+      // is that the right thing to do though?
+      O2_SIGNPOST_EVENT_EMIT(device, aid, "device", "cleaning early forwarding: %{public}s.", fmt::format("{}", action.op).c_str());
       auto& timesliceIndex = ref.get<TimesliceIndex>();
-      forwardInputs(ref, action.slot, currentSetOfInputs, timesliceIndex.getOldestPossibleOutput(), true, action.op == CompletionPolicy::CompletionOp::Consume);
+      cleanEarlyForward(ref, action.slot, currentSetOfInputs, timesliceIndex.getOldestPossibleOutput(), true, action.op == CompletionPolicy::CompletionOp::Consume);
     }
     markInputsAsDone(action.slot);
 

Framework/Core/src/DataRelayer.cxx

@@ -499,6 +499,12 @@ DataRelayer::RelayChoice
     // DataRelayer::relay
     assert(nPayloads > 0);
     size_t saved = 0;
+    // It's guaranteed we will see all these messages only once, so we can
+    // do the forwarding here.
+    auto allMessages = std::span<fair::mq::MessagePtr>(messages, messages + nMessages);
+    if (onInsertion) {
+      onInsertion(services, allMessages);
+    }
     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.
@@ -515,9 +521,6 @@ DataRelayer::RelayChoice
         continue;
       }
       auto span = std::span<fair::mq::MessagePtr>(messages + mi, messages + mi + nPayloads + 1);
-      if (onInsertion) {
-        onInsertion(services, span);
-      }
       target.add([&span](size_t i) -> fair::mq::MessagePtr& { return span[i]; }, nPayloads + 1);
       mi += nPayloads;
       saved += nPayloads;