stats: const-ify variables and arguments

We cannot convert `DEFAULT_STATSD*` to `std::string_view`s as they're
being used as default arguments and `GetArgs` expects `std::string`s

Author: kwvg

src/statsd_client.cpp

@@ -61,8 +61,8 @@ bool StatsdClient::ShouldSend(float sample_rate)
     return sample_rate > std::uniform_real_distribution<float>(0.f, 1.f)(insecure_rand);
 }
 
-StatsdClient::StatsdClient(const std::string& host, const std::string& nodename, uint16_t port, const std::string& ns,
-                           bool enabled)
+StatsdClient::StatsdClient(const std::string& host, const std::string& nodename, const uint16_t port,
+                           const std::string& ns, const bool enabled)
     : m_port{port}, m_host{host}, m_nodename{nodename}, m_ns{ns}
 {
     if (!enabled) {
@@ -106,37 +106,37 @@ void StatsdClient::cleanup(std::string& key)
     }
 }
 
-bool StatsdClient::dec(const std::string& key, float sample_rate)
+bool StatsdClient::dec(const std::string& key, const float sample_rate)
 {
     return count(key, -1, sample_rate);
 }
 
-bool StatsdClient::inc(const std::string& key, float sample_rate)
+bool StatsdClient::inc(const std::string& key, const float sample_rate)
 {
     return count(key, 1, sample_rate);
 }
 
-bool StatsdClient::count(const std::string& key, uint32_t value, float sample_rate)
+bool StatsdClient::count(const std::string& key, const uint32_t value, const float sample_rate)
 {
     return send(key, value, "c", sample_rate);
 }
 
-bool StatsdClient::gauge(const std::string& key, uint32_t value, float sample_rate)
+bool StatsdClient::gauge(const std::string& key, const uint32_t value, const float sample_rate)
 {
     return send(key, value, "g", sample_rate);
 }
 
-bool StatsdClient::gaugeDouble(const std::string& key, double value, float sample_rate)
+bool StatsdClient::gaugeDouble(const std::string& key, const double value, const float sample_rate)
 {
     return sendDouble(key, value, "g", sample_rate);
 }
 
-bool StatsdClient::timing(const std::string& key, uint32_t ms, float sample_rate)
+bool StatsdClient::timing(const std::string& key, const uint32_t ms, const float sample_rate)
 {
     return send(key, ms, "ms", sample_rate);
 }
 
-bool StatsdClient::send(std::string key, uint32_t value, const std::string& type, float sample_rate)
+bool StatsdClient::send(std::string key, const uint32_t value, const std::string& type, const float sample_rate)
 {
     if (!m_sock) {
         return false;
@@ -161,7 +161,7 @@ bool StatsdClient::send(std::string key, uint32_t value, const std::string& type
     return send(buf);
 }
 
-bool StatsdClient::sendDouble(std::string key, double value, const std::string& type, float sample_rate)
+bool StatsdClient::sendDouble(std::string key, const double value, const std::string& type, const float sample_rate)
 {
     if (!m_sock) {
         return false;

src/statsd_client.h

@@ -13,36 +13,36 @@
 #include <string>
 #include <memory>
 
-static const bool DEFAULT_STATSD_ENABLE = false;
-static const uint16_t DEFAULT_STATSD_PORT = 8125;
-static const std::string DEFAULT_STATSD_HOST = "127.0.0.1";
-static const std::string DEFAULT_STATSD_HOSTNAME = "";
-static const std::string DEFAULT_STATSD_NAMESPACE = "";
+static constexpr bool DEFAULT_STATSD_ENABLE{false};
+static constexpr uint16_t DEFAULT_STATSD_PORT{8125};
+static const std::string DEFAULT_STATSD_HOST{"127.0.0.1"};
+static const std::string DEFAULT_STATSD_HOSTNAME{""};
+static const std::string DEFAULT_STATSD_NAMESPACE{""};
 
 // schedule periodic measurements, in seconds: default - 1 minute, min - 5 sec, max - 1h.
-static const int DEFAULT_STATSD_PERIOD = 60;
-static const int MIN_STATSD_PERIOD = 5;
-static const int MAX_STATSD_PERIOD = 60 * 60;
+static constexpr int DEFAULT_STATSD_PERIOD{60};
+static constexpr int MIN_STATSD_PERIOD{5};
+static constexpr int MAX_STATSD_PERIOD{60*60};
 
 namespace statsd {
 class StatsdClient {
     public:
-        explicit StatsdClient(const std::string& host, const std::string& nodename, uint16_t port, const std::string& ns,
-                              bool enabled);
+        explicit StatsdClient(const std::string& host, const std::string& nodename, const uint16_t port,
+                              const std::string& ns, const bool enabled);
 
     public:
-        bool inc(const std::string& key, float sample_rate = 1.f);
-        bool dec(const std::string& key, float sample_rate = 1.f);
-        bool count(const std::string& key, uint32_t value, float sample_rate = 1.f);
-        bool gauge(const std::string& key, uint32_t value, float sample_rate = 1.f);
-        bool gaugeDouble(const std::string& key, double value, float sample_rate = 1.f);
-        bool timing(const std::string& key, uint32_t ms, float sample_rate = 1.f);
+        bool inc(const std::string& key, const float sample_rate = 1.f);
+        bool dec(const std::string& key, const float sample_rate = 1.f);
+        bool count(const std::string& key, const uint32_t value, const float sample_rate = 1.f);
+        bool gauge(const std::string& key, const uint32_t value, const float sample_rate = 1.f);
+        bool gaugeDouble(const std::string& key, const double value, const float sample_rate = 1.f);
+        bool timing(const std::string& key, const uint32_t ms, const float sample_rate = 1.f);
 
         /* (Low Level Api) manually send a message
          * type = "c", "g" or "ms"
          */
-        bool send(std::string key, uint32_t value, const std::string& type, float sample_rate);
-        bool sendDouble(std::string key, double value, const std::string& type, float sample_rate);
+        bool send(std::string key, const uint32_t value, const std::string& type, const float sample_rate);
+        bool sendDouble(std::string key, const double value, const std::string& type, const float sample_rate);
 
     private:
         /**