[QC-471] Do not create a Dispatcher if there are no policies (#4758)

knopers8 · web-flow · commit 6f47deb41cd2 · 2020-11-10T13:21:46.000+01:00
diff --git a/Utilities/DataSampling/README.md b/Utilities/DataSampling/README.md
@@ -61,6 +61,7 @@ std::vector<DataProcessorSpec> defineDataProcessing(ConfigContext &ctx)
 ```
 
 Sampled data can be subscribed to by adding `InputSpecs` provided by `std::vector<InputSpec> DataSampling::InputSpecsForPolicy(const std::string& policiesSource, const std::string& policyName)` to a chosen data processor. Then, they can be accessed by the bindings specified in the configuration file. Dispatcher adds a `DataSamplingHeader` to the header stack, which contains statistics like total number of evaluated/accepted messages for a given Policy or the sampling time since epoch.
+If no sampling policies are specified, Dispatcher will not be spawned.
 
 The [o2-datasampling-pod-and-root](https://github.com/AliceO2Group/AliceO2/blob/dev/Utilities/DataSampling/test/dataSamplingPodAndRoot.cxx) workflow can serve as a usage example.
 
diff --git a/Utilities/DataSampling/include/DataSampling/Dispatcher.h b/Utilities/DataSampling/include/DataSampling/Dispatcher.h
@@ -52,6 +52,8 @@ class Dispatcher : public framework::Task
 
   /// \brief Register a Data Sampling Policy
   void registerPolicy(std::unique_ptr<DataSamplingPolicy>&&);
+  /// \brief Returns the number of registered policies.
+  size_t numberOfPolicies();
 
   const std::string& getName();
   /// \brief Assembles InputSpecs of all registered policies in a single vector, removing overlapping entries.
diff --git a/Utilities/DataSampling/src/DataSampling.cxx b/Utilities/DataSampling/src/DataSampling.cxx
@@ -75,7 +75,7 @@ void DataSampling::DoGenerateInfrastructure(Dispatcher& dispatcher, WorkflowSpec
     }
   }
 
-  if (dispatcher.getInputSpecs().size() > 0) {
+  if (dispatcher.numberOfPolicies() > 0) {
     DataProcessorSpec spec;
     spec.name = dispatcher.getName();
     spec.inputs = dispatcher.getInputSpecs();
diff --git a/Utilities/DataSampling/src/Dispatcher.cxx b/Utilities/DataSampling/src/Dispatcher.cxx
@@ -258,5 +258,9 @@ framework::Options Dispatcher::getOptions()
 
   return options;
 }
+size_t Dispatcher::numberOfPolicies()
+{
+  return mPolicies.size();
+}
 
 } // namespace o2::utilities

Original file line number	Diff line number	Diff line change
`@@ -75,7 +75,7 @@ void DataSampling::DoGenerateInfrastructure(Dispatcher& dispatcher, WorkflowSpec`
`75`	`75`	`}`
`76`	`76`	`}`
`77`	`77`
`78`		`- if (dispatcher.getInputSpecs().size() > 0) {`
	`78`	`+ if (dispatcher.numberOfPolicies() > 0) {`
`79`	`79`	`DataProcessorSpec spec;`
`80`	`80`	`spec.name = dispatcher.getName();`
`81`	`81`	`spec.inputs = dispatcher.getInputSpecs();`
Original file line number	Diff line number	Diff line change
`@@ -258,5 +258,9 @@ framework::Options Dispatcher::getOptions()`
`258`	`258`
`259`	`259`	`return options;`
`260`	`260`	`}`
	`261`	`+size_t Dispatcher::numberOfPolicies()`
	`262`	`+{`
	`263`	`+ return mPolicies.size();`
	`264`	`+}`
`261`	`265`
`262`	`266`	`} // namespace o2::utilities`