DPL: add o2-dpl-null-sink workflow

This workflow can be configured to terminate any other workflow by providing
the appropriate --inputs option.

Author: ktf

Framework/Core/CMakeLists.txt

@@ -198,6 +198,11 @@ foreach(t
               PUBLIC_LINK_LIBRARIES O2::Framework)
 endforeach()
 
+o2_add_executable(dpl-null-sink
+                  SOURCES src/o2NullSink.cxx
+                  PUBLIC_LINK_LIBRARIES O2::Framework
+                 )
+
 o2_add_executable(dpl-run
                   SOURCES src/dplRun.cxx
                   PUBLIC_LINK_LIBRARIES O2::Framework

Framework/Core/src/o2NullSink.cxx

@@ -0,0 +1,53 @@
+// Copyright CERN and copyright holders of ALICE O2. This software is
+// distributed under the terms of the GNU General Public License v3 (GPL
+// Version 3), copied verbatim in the file "COPYING".
+//
+// See http://alice-o2.web.cern.ch/license for full licensing information.
+//
+// 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/ConfigContext.h"
+#include "Framework/ControlService.h"
+#include "Framework/DataProcessorSpec.h"
+#include "Framework/DataSpecUtils.h"
+#include "Framework/Logger.h"
+#include "Framework/ParallelContext.h"
+#include "Framework/DataDescriptorQueryBuilder.h"
+
+#include <chrono>
+#include <thread>
+#include <vector>
+
+/// A DataProcessor which terminates a provided set of
+/// inputs.
+using namespace o2::framework;
+
+void customize(std::vector<ConfigParamSpec>& options)
+{
+  options.push_back(o2::framework::ConfigParamSpec{"inputs", VariantType::String, "", {"inputs for the dataprocessor"}});
+};
+
+#include "Framework/runDataProcessing.h"
+
+// This is a simple consumer / producer workflow where both are
+// stateful, i.e. they have context which comes from their initialization.
+WorkflowSpec defineDataProcessing(ConfigContext const& context)
+{
+  WorkflowSpec workflow;
+  // This is an example of how we can parallelize by subSpec.
+  // templatedProducer will be instanciated 32 times and the lambda function
+  // passed to the parallel statement will be applied to each one of the
+  // instances in order to modify it. Parallel will also make sure the name of
+  // the instance is amended from "some-producer" to "some-producer-<index>".
+  auto inputsDesc = context.options().get<std::string>("inputs");
+  auto inputs = DataDescriptorQueryBuilder::parse(inputsDesc.c_str());
+
+  workflow.push_back(DataProcessorSpec{
+    "null",
+    inputs,
+    {},
+    AlgorithmSpec{[](ProcessingContext& ctx) {}}});
+
+  return workflow;
+}