DPL: allow resetting the oldest possible timeframe mechanism (#9895)

* DPL: allow resetting the oldest possible timeframe mechanism

* Update TimesliceIndex.h

* fix clang-format

---------

Co-authored-by: David Rohr <github@jwdt.org>

Author: ktf

Framework/Core/include/Framework/TimesliceIndex.h

@@ -133,6 +133,9 @@ class TimesliceIndex
   OldestOutputInfo updateOldestPossibleOutput();
   [[nodiscard]] InputChannelInfo const& getChannelInfo(ChannelIndex channel) const;
 
+  // Reset the TimesliceIndex to its initial state
+  auto reset() -> void;
+
  private:
   /// @return the oldest slot possible so that we can eventually override it.
   /// This is the timeslices for all the in flight parts.

Framework/Core/src/CommonServices.cxx

@@ -509,6 +509,7 @@ o2::framework::ServiceSpec CommonServices::decongestionSpec()
       decongestion->lastTimeslice = oldestPossibleOutput.timeslice.value; },
     .stop = [](ServiceRegistryRef services, void* service) {
       auto* decongestion = (DecongestionService*)service;
+      services.get<TimesliceIndex>().reset();
       decongestion->nextEnumerationTimeslice = 0;
       decongestion->nextEnumerationTimesliceRewinded = false;
       decongestion->lastTimeslice = 0;

Framework/Core/src/TimesliceIndex.cxx

@@ -205,4 +205,19 @@ InputChannelInfo const& TimesliceIndex::getChannelInfo(ChannelIndex channel) con
   return mChannels[channel.value];
 }
 
+auto TimesliceIndex::reset() -> void
+{
+  mOldestPossibleInput = {
+    .timeslice = {0},
+    /// The actual channel id of the oldest input.
+    .channel = {ChannelIndex::INVALID}};
+  mOldestPossibleOutput = {
+    .timeslice = {0},
+    .channel = {ChannelIndex::INVALID},
+    .slot = {(size_t)-1}};
+  for (auto& channel : mChannels) {
+    channel.oldestForChannel = {0};
+  }
+}
+
 } // namespace o2::framework