Synchronize peer data lookups.

Without this we could broadcast the same data multiple times, due to more than one thread processing the same message from different peers.

src/main/java/org/qortal/controller/arbitrary/ArbitraryDataManager.java

@@ -36,6 +36,7 @@ public class ArbitraryDataManager extends Thread {
 	private static final long ARBITRARY_REQUEST_TIMEOUT = 5 * 1000L; // ms
 
 	private static ArbitraryDataManager instance;
+	private final Object peerDataLock = new Object();
 
 	private boolean buildInProgress = false;
 
@@ -679,6 +680,9 @@ public class ArbitraryDataManager extends Thread {
 
 		boolean containsNewEntry = false;
 
+		// Synchronize peer data lookups to make this process thread safe. Otherwise we could broadcast
+		// the same data multiple times, due to more than one thread processing the same message from different peers
+		synchronized (this.peerDataLock) {
 			try (final Repository repository = RepositoryManager.getRepository()) {
 				for (byte[] signature : signatures) {
 
@@ -703,8 +707,7 @@ public class ArbitraryDataManager extends Thread {
 				if (containsNewEntry) {
 					LOGGER.info("Rebroadcasting arbitrary signature list for peer {}", peerAddress);
 					Network.getInstance().broadcast(broadcastPeer -> arbitrarySignaturesMessage);
-			}
+				} else {
-			else {
 					// Don't re-broadcast as otherwise we could get into a loop
 				}
 
@@ -714,5 +717,6 @@ public class ArbitraryDataManager extends Thread {
 				LOGGER.error(String.format("Repository issue while processing arbitrary transaction signature list from peer %s", peer), e);
 			}
 		}
+	}
 
 }