Reduce memory allocation in StdCout backend (#96)

Author: awegrzyn

include/Monitoring/Metric.h

@@ -61,6 +61,9 @@ class Metric
     /// \return	metric name
     std::string getName() const;
 
+    /// Const name getter
+    const std::string& getConstName() const;
+
     /// Timestamp getter
     /// \return 	metric timestamp
     std::chrono::time_point<std::chrono::system_clock> getTimestamp() const;
@@ -86,6 +89,9 @@ class Metric
     /// return          timestamp as std::chrono::system_clock
     static auto getCurrentTimestamp() -> decltype(std::chrono::system_clock::now());
 
+    /// Tagset vector size getter
+    std::size_t tagSize() const;
+
   protected:
     /// Metric value
     boost::variant< int, std::string, double, uint64_t > mValue;

src/Backends/StdOut.cxx

@@ -56,27 +56,29 @@ void StdOut::sendMultiple(std::string measurement, std::vector<Metric>&& metrics
     if (!metricTags.empty()) {
       metricTags = "," + metricTags;
     }
-    mStream <<  "[METRIC] " << measurement << "/" << metric.getName() << "," << metric.getType() << " "
+    mStream <<  "[METRIC] " << measurement << "/" << metric.getConstName() << "," << metric.getType() << " "
       << metric.getValue() << " " << convertTimestamp(metric.getTimestamp()) << " " << tagString
       << metricTags << "\n";
   }
 }
 
 void StdOut::send(const Metric& metric)
 {
-  std::string metricTags{};
-  for (const auto& tag : metric.getTags()) {
-    if (!metricTags.empty()) {
-      metricTags += ",";
+  if (metric.tagSize() == 0) {
+    mStream << "[METRIC] " << metric.getConstName() << "," << metric.getType() << " " << metric.getValue()
+      << " " << convertTimestamp(metric.getTimestamp()) << " " << tagString << "\n";
+  } else {
+    std::string metricTags{};
+    for (const auto& tag : metric.getTags()) {
+      metricTags += "," + tag.name + "=" + tag.value;
     }
-    metricTags += tag.name + "=" + tag.value;
-  }
-  if (!metricTags.empty()) {
-    metricTags = "," + metricTags;
+    if (tagString.empty()) {
+      metricTags.erase(0, 1);
+    }
+
+    mStream << "[METRIC] " << metric.getConstName() << "," << metric.getType() << " " << metric.getValue()
+      << " " << convertTimestamp(metric.getTimestamp()) << " " << tagString << metricTags << "\n";
   }
-  mStream << "[METRIC] " << metric.getName() << "," << metric.getType() << " " << metric.getValue()
-    << " " << convertTimestamp(metric.getTimestamp()) << " " << tagString << metricTags
-    << "\n";
 }
 
 } // namespace backends

src/Metric.cxx

@@ -30,6 +30,16 @@ std::string Metric::getName() const
   return mName;
 }
 
+const std::string& Metric::getConstName() const
+{
+  return mName;
+}
+
+std::size_t Metric::tagSize() const
+{
+  return tagSet.size();
+}
+
 Metric::Metric(int value, const std::string& name, std::chrono::time_point<std::chrono::system_clock> timestamp) :
   mValue(value), mName(name), mTimestamp(timestamp)
 {}