send serialized cache counter to the client in custom payload

Author: Karolina Drabik

tracing/trace_state.cc

@@ -359,4 +359,10 @@ void opentelemetry_state::serialize_replicas(bytes& serialized) const {
 void opentelemetry_state::serialize_statement_type(bytes& serialized) const {
     serialized += bytes{reinterpret_cast<const signed char*>(_statement_type.c_str()), _statement_type.length()};
 }
+
+void opentelemetry_state::serialize_cache_counter(bytes& serialized) const {
+    const auto counter = htonl(_cache_counter);
+    const auto *counter_ptr = reinterpret_cast<const int8_t*>(&counter);
+    serialized += bytes{counter_ptr, sizeof(counter)};
+}
 }

tracing/trace_state.hh

@@ -521,6 +521,7 @@ private:
 
     void serialize_replicas(bytes& serialized) const;
     void serialize_statement_type(bytes& serialized) const;
+    void serialize_cache_counter(bytes& serialized) const;
 
 public:
     opentelemetry_state() = default;
@@ -538,6 +539,7 @@ public:
         bytes serialized{};
 
         serialize_replicas(serialized);
+        serialize_cache_counter(serialized);
         serialize_statement_type(serialized);
 
         return serialized;