Fixing oversight of missing synchronized on long version of recalibrate (#9480)

* Fixing oversight of missing synchronized on long version of recalibrate

* Adding spotbugs suppression

The racy updates of cache stat fields is deliberate -- and that's the cause of the inconsistent sync-ing

* spotless

* Removing leftover SIZE variable

Author: dougqh

dd-trace-core/src/main/java/datadog/trace/common/writer/ddagent/GenerationalUtf8Cache.java

@@ -2,6 +2,7 @@
 
 import datadog.communication.serialization.EncodingCache;
 import datadog.trace.common.writer.ddagent.SimpleUtf8Cache.CacheEntry;
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import java.nio.charset.StandardCharsets;
 
 /**
@@ -63,6 +64,10 @@
  * calling ValueUtf8Cache#reclibrate will adjust promotion thresholds to
  * provide better cache utilization.
  */
+@SuppressFBWarnings(
+    value = "IS2_INCONSISTENT_SYNC",
+    justification =
+        "stat updates are deliberately racy - sync is only used to prevent simultaneous bulk updates")
 public final class GenerationalUtf8Cache implements EncodingCache {
   static final int MAX_EDEN_CAPACITY = 512;
   static final int MAX_TENURED_CAPACITY = 1024;
@@ -156,7 +161,7 @@ public synchronized void recalibrate() {
    *
    * <p>While still racy this method is synchronized to avoid simultaneous recalibrations
    */
-  public void recalibrate(long accessTimeMs) {
+  public synchronized void recalibrate(long accessTimeMs) {
     this.accessTimeMs = accessTimeMs;
 
     recalibrate(this.edenEntries);

dd-trace-core/src/main/java/datadog/trace/common/writer/ddagent/SimpleUtf8Cache.java

@@ -47,8 +47,6 @@ public final class SimpleUtf8Cache implements EncodingCache {
 
   private static final int MAX_PROBES = 4;
 
-  private final int SIZE = 64;
-
   private final int[] markers;
   private final CacheEntry[] entries;