add number of cache reads received in custom payload to the trace

Author: Karolina

driver-core/src/main/java/com/datastax/driver/core/RequestHandler.java

@@ -1199,6 +1199,7 @@ private void setFinalResult(Connection connection, Message.Response response) {
           }
         }
         parentTracingInfo.setReplicas(replicasBuilder.toString());
+        parentTracingInfo.setCacheCounter(buf.getInt());
       }
 
       parentTracingInfo.tracingFinished();

driver-core/src/main/java/com/datastax/driver/core/tracing/NoopTracingInfoFactory.java

@@ -78,6 +78,9 @@ public void setTable(String table) {}
     @Override
     public void setReplicas(String replicas) {}
 
+    @Override
+    public void setCacheCounter(int cacheCounter) {}
+
     @Override
     public void recordException(Exception exception) {}
 

driver-core/src/main/java/com/datastax/driver/core/tracing/TracingInfo.java

@@ -162,6 +162,13 @@ enum StatusCode {
    */
   void setReplicas(String replicas);
 
+  /**
+   * Adds provided cache reads counter to the trace.
+   *
+   * @param cacheCounter the counter to be set.
+   */
+  void setCacheCounter(int cacheCounter);
+
   /**
    * Records in the trace that the provided exception occured.
    *

driver-core/src/test/java/com/datastax/driver/core/tracing/TestTracingInfo.java

@@ -51,6 +51,7 @@ public class TestTracingInfo implements TracingInfo {
   private String partitionKey;
   private String table;
   private String replicas;
+  private Integer cacheCounter;
 
   public TestTracingInfo(PrecisionLevel precision) {
     this.precision = precision;
@@ -159,6 +160,11 @@ public void setReplicas(String replicas) {
     this.replicas = replicas;
   }
 
+  @Override
+  public void setCacheCounter(int cacheCounter) {
+    this.cacheCounter = cacheCounter;
+  }
+
   @Override
   public void recordException(Exception exception) {
     if (this.exceptions == null) {
@@ -267,6 +273,10 @@ public String getReplicas() {
     return replicas;
   }
 
+  public Integer getCacheCounter() {
+    return cacheCounter;
+  }
+
   public StatusCode getStatusCode() {
     return statusCode;
   }

driver-opentelemetry/src/main/java/com/datastax/driver/opentelemetry/OpenTelemetryTracingInfo.java

@@ -184,6 +184,12 @@ public void setReplicas(String replicas) {
     span.setAttribute("db.scylla.replicas", replicas);
   }
 
+  @Override
+  public void setCacheCounter(int cacheCounter) {
+    assertStarted();
+    span.setAttribute("db.scylla.cache_counter", cacheCounter);
+  }
+
   private io.opentelemetry.api.trace.StatusCode mapStatusCode(StatusCode code) {
     switch (code) {
       case OK: