Support file observer on/off toggling (#509)

* #508 Support toggling file observer on or off.

* #508 Remove unused variable.

* #508 Remove superfluous value reference collections.

* #508 Ensure value writer is present.

* Fix typo

* Add panic message

* find_variables_of_type() is obsolete. Consolidate usage of find_variables().

* Add concurrency support to file observer.

* Review follow-up

include/cse/model.hpp

@@ -331,13 +331,6 @@ struct model_description
 /// Getter for returning a variable description.
 const variable_description find_variable(const model_description& description, const std::string& variable_name);
 
-/// Getter for returning a variable description.
-const variable_description find_variable(const model_description& description, variable_type type, value_reference reference);
-
-/// Getter for returning all variable descriptions of the given datatype.
-const std::vector<variable_description> find_variables_of_type(const model_description& description, variable_type type);
-
-
 /// Possible outcomes of a subsimulator time step
 enum class step_result
 {

include/cse/observer/file_observer.hpp

@@ -10,6 +10,7 @@
 #include <boost/filesystem/path.hpp>
 #include <boost/property_tree/ptree.hpp>
 
+#include <atomic>
 #include <memory>
 #include <unordered_map>
 
@@ -19,15 +20,49 @@ namespace cse
 
 
 /**
- * An observer implementation, for saving observed variable values to file in the preferred format (csv or binary).
+ * An observer implementation, for saving observed variable values to file in csv format.
+ *
+ * Recording may be toggled on or off mid simulation. This functionality is thread safe.
  */
 class file_observer : public observer
 {
 public:
+    /**
+     * Creates an observer which logs all variable values to file in csv format.
+     *
+     * \param logDir the directory where log files will be created.
+     */
     file_observer(const boost::filesystem::path& logDir);
 
+    /**
+     * Creates an observer which logs selected variable values to file in csv format.
+     *
+     * \param logDir the directory where log files will be created.
+     * \param configPath the path to an xml file containing the logging configuration.
+     */
     file_observer(const boost::filesystem::path& logDir, const boost::filesystem::path& configPath);
 
+    /**
+     * Returns whether the observer is currently recording values.
+     *
+     * This method can safely be called from different threads.
+     */
+    bool is_recording();
+
+    /**
+     * Starts recording values. Throws an exception if the observer is already recording.
+     *
+     * This method can safely be called from different threads.
+     */
+    void start_recording();
+
+    /**
+     * Stops recording values. Throws an exception if the observer is not recording.
+     *
+     * This method can safely be called from different threads.
+     */
+    void stop_recording();
+
     void simulator_added(simulator_index, observable*, time_point) override;
 
     void simulator_removed(simulator_index, time_point) override;
@@ -56,22 +91,23 @@ class file_observer : public observer
     ~file_observer() override;
 
 private:
-    void parse_config(const std::string& simulatorName);
+    struct simulator_logging_config
+    {
+        std::vector<variable_description> variables;
+        size_t decimationFactor;
+    };
+
+    simulator_logging_config parse_config(const std::string& simulatorName);
 
     class slave_value_writer;
     std::unordered_map<simulator_index, std::unique_ptr<slave_value_writer>> valueWriters_;
     std::unordered_map<simulator_index, observable*> simulators_;
-    std::vector<variable_description> loggableRealVariables_;
-    std::vector<variable_description> loggableIntVariables_;
-    std::vector<variable_description> loggableBoolVariables_;
-    std::vector<variable_description> loggableStringVariables_;
     boost::property_tree::ptree ptree_;
     boost::filesystem::path configPath_;
     boost::filesystem::path logDir_;
-    boost::filesystem::path logPath_;
     bool logFromConfig_ = false;
-    size_t decimationFactor_;
     size_t defaultDecimationFactor_ = 1;
+    std::atomic<bool> recording_ = true;
 };
 
 

src/cpp/model.cpp

@@ -14,16 +14,4 @@ const variable_description find_variable(const model_description& description, c
     throw std::invalid_argument("Can't find variable descriptor with name " + variable_name + " for model with name " + description.name);
 }
 
-const std::vector<variable_description> find_variables_of_type(const model_description& description, variable_type type)
-{
-    std::vector<variable_description> vars;
-
-    for (const auto& variable : description.variables) {
-        if (variable.type == type) {
-            vars.push_back(variable);
-        }
-    }
-    return vars;
-}
-
 } // namespace cse