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

@@ -1202,6 +1202,7 @@ private void setFinalResult(Connection connection, Message.Response response) {
           }
         }
         parentTracingInfo.setReplicas(replicasBuilder.toString());
+        parentTracingInfo.setCacheReadCount(buf.getInt());
       }
 
       parentTracingInfo.tracingFinished();

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

@@ -81,6 +81,9 @@ public void setOperationType(String operationType) {}
     @Override
     public void setReplicas(String replicas) {}
 
+    @Override
+    public void setCacheReadCount(int cacheReadCount) {}
+
     @Override
     public void recordException(Exception exception) {}
 

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

@@ -169,6 +169,13 @@ enum StatusCode {
    */
   void setReplicas(String replicas);
 
+  /**
+   * Adds provided cache reads counter to the trace.
+   *
+   * @param cacheReadCount the counter to be set.
+   */
+  void setCacheReadCount(int cacheReadCount);
+
   /**
    * Records in the trace that the provided exception occured.
    *

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

@@ -52,6 +52,7 @@ public class TestTracingInfo implements TracingInfo {
   private String table;
   private String operationType;
   private String replicas;
+  private Integer cacheReadCount;
 
   public TestTracingInfo(PrecisionLevel precision) {
     this.precision = precision;
@@ -165,6 +166,11 @@ public void setReplicas(String replicas) {
     this.replicas = replicas;
   }
 
+  @Override
+  public void setCacheReadCount(int cacheReadCount) {
+    this.cacheReadCount = cacheReadCount;
+  }
+
   @Override
   public void recordException(Exception exception) {
     if (this.exceptions == null) {
@@ -277,6 +283,10 @@ public String getReplicas() {
     return replicas;
   }
 
+  public Integer getcacheReadCount() {
+    return cacheReadCount;
+  }
+
   public StatusCode getStatusCode() {
     return statusCode;
   }

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

@@ -190,6 +190,12 @@ public void setReplicas(String replicas) {
     span.setAttribute("db.scylla.replicas", replicas);
   }
 
+  @Override
+  public void setCacheReadCount(int cacheReadCount) {
+    assertStarted();
+    span.setAttribute("db.scylla.cache_read_count", cacheReadCount);
+  }
+
   private io.opentelemetry.api.trace.StatusCode mapStatusCode(StatusCode code) {
     switch (code) {
       case OK: