Add addGlobalTag (#55)

Author: awegrzyn

README.md

@@ -185,6 +185,13 @@ The module can calculate derived metrics. To do so, use `addDerivedMetric(std::s
 
 Derived metrics are generated each time as new value is passed to the module. Their names are suffixed with derived mode name.
 
+### Global tags
+Glabal tags are tags that are added to each metric. The following tags are set to global by library itself:
+- `hostname`
+- `name` - process name
+
+You can add your own global tag by calling `addGlobalTag(std::string name, std::string value)`.
+
 ### Monitoring process
 Currently process monitoring is supported only on Linux. To enable it use:
 ```cpp

include/Monitoring/Monitoring.h

@@ -87,6 +87,11 @@ class Monitoring
     /// Enables metric buffering
     /// \param size 		buffer size
     void enableBuffering(const unsigned int size = 20);
+
+    /// Adds global tag
+    /// \param name 		tag name
+    /// \param value 		tag value
+    void addGlobalTag(std::string name, std::string value);
   private:
     /// Derived metrics handler
     /// \see class DerivedMetrics

src/Monitoring.cxx

@@ -90,6 +90,13 @@ void Monitoring::stopAndSendTimer(std::string name) {
   }
 }
 
+void Monitoring::addGlobalTag(std::string name, std::string value)
+{
+  for (auto& backend: mBackends) {
+    backend->addGlobalTag(name, value);
+  }
+}
+
 void Monitoring::addBackend(std::unique_ptr<Backend> backend) {
    ProcessDetails processDetails{};
    backend->addGlobalTag("hostname", processDetails.getHostname());

test/testMonitoring.cxx

@@ -22,6 +22,8 @@ BOOST_AUTO_TEST_CASE(createMonitoring)
   std::string stringMetric("monitoringString");
   double doubleMetric = static_cast <double> (rand()) / static_cast <double> (RAND_MAX);
 
+  monitoring->addGlobalTag("device", "sampleDevice");
+
   monitoring->send({intMetric, "myCrazyMetricI"});
   monitoring->send({stringMetric, "myCrazyMetricS"});
   monitoring->send({doubleMetric, "myCrazyMetricD"});