DPL: Throw error messages when the oldestPossibleTimeframe is incorrectly decreased

(cherry picked from commit 725befe)

Author: davidrohr

Framework/Core/src/TimesliceIndex.cxx

@@ -171,6 +171,9 @@ TimesliceIndex::OldestInputInfo TimesliceIndex::setOldestPossibleInput(Timeslice
   } else {
     O2_SIGNPOST_EVENT_EMIT(timeslice_index, tid, "setOldestPossibleInput", "No change in oldest possible input");
   }
+  if (mOldestPossibleInput.timeslice.value > result.timeslice.value) {
+    LOG(error) << "DPL internal error - oldestPossibleInput of channel " << channel.value << ": " << getChannelInfo(channel).channel->GetName().c_str() << " decreased from " << mOldestPossibleOutput.timeslice.value << " to " << result.timeslice.value;
+  }
   mOldestPossibleInput = result;
   return mOldestPossibleInput;
 }
@@ -220,6 +223,9 @@ TimesliceIndex::OldestOutputInfo TimesliceIndex::updateOldestPossibleOutput()
                              mOldestPossibleOutput.timeslice.value, result.timeslice.value);
     }
   }
+  if (mOldestPossibleOutput.timeslice.value > result.timeslice.value) {
+    LOG(error) << "DPL internal error - oldestPossibleOutput decreased from " << mOldestPossibleOutput.timeslice.value << " to " << result.timeslice.value;
+  }
   mOldestPossibleOutput = result;
 
   return result;