[improve] Change PersistentMessageFinder's fields modifier to reuse in plugins (#24308)

Author: dao-jun

pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentMessageFinder.java

@@ -39,17 +39,17 @@
  * given a timestamp find the first message (position) (published) at or before the timestamp.
  */
 public class PersistentMessageFinder implements AsyncCallbacks.FindEntryCallback {
-    private final ManagedCursor cursor;
-    private final String subName;
-    private final int ledgerCloseTimestampMaxClockSkewMillis;
-    private final String topicName;
-    private long timestamp = 0;
+    protected final ManagedCursor cursor;
+    protected final String subName;
+    protected final int ledgerCloseTimestampMaxClockSkewMillis;
+    protected final String topicName;
+    protected long timestamp = 0;
 
-    private static final int FALSE = 0;
-    private static final int TRUE = 1;
+    protected static final int FALSE = 0;
+    protected static final int TRUE = 1;
     @SuppressWarnings("unused")
-    private volatile int messageFindInProgress = FALSE;
-    private static final AtomicIntegerFieldUpdater<PersistentMessageFinder> messageFindInProgressUpdater =
+    protected volatile int messageFindInProgress = FALSE;
+    protected static final AtomicIntegerFieldUpdater<PersistentMessageFinder> MESSAGE_FIND_IN_PROGRESS =
             AtomicIntegerFieldUpdater
                     .newUpdater(PersistentMessageFinder.class, "messageFindInProgress");
 
@@ -61,7 +61,7 @@ public PersistentMessageFinder(String topicName, ManagedCursor cursor, int ledge
     }
 
     public void findMessages(final long timestamp, AsyncCallbacks.FindEntryCallback callback) {
-        if (messageFindInProgressUpdater.compareAndSet(this, FALSE, TRUE)) {
+        if (MESSAGE_FIND_IN_PROGRESS.compareAndSet(this, FALSE, TRUE)) {
             this.timestamp = timestamp;
             if (log.isDebugEnabled()) {
                 log.debug("[{}] Starting message position find at timestamp {}", subName, timestamp);