Synchronized LatestATStates, to make rebuildLatestAtStates() thread safe.

src/main/java/org/qortal/repository/hsqldb/HSQLDBATRepository.java

@@ -604,6 +604,11 @@ public class HSQLDBATRepository implements ATRepository {
 
 	@Override
 	public void rebuildLatestAtStates() throws DataException {
+		// latestATStatesLock is to prevent concurrent updates on LatestATStates
+		// that could result in one process using a partial or empty dataset
+		// because it was in the process of being rebuilt by another thread
+		synchronized (this.repository.latestATStatesLock) {
+
 			// Rebuild cache of latest AT states that we can't trim
 			String deleteSql = "DELETE FROM LatestATStates";
 			try {
@@ -628,6 +633,7 @@ public class HSQLDBATRepository implements ATRepository {
 				throw new DataException("Unable to populate temporary latest AT states cache in repository", e);
 			}
 		}
+	}
 
 
 	@Override
@@ -666,6 +672,11 @@ public class HSQLDBATRepository implements ATRepository {
 		if (minHeight >= maxHeight)
 			return 0;
 
+		// latestATStatesLock is to prevent concurrent updates on LatestATStates
+		// that could result in one process using a partial or empty dataset
+		// because it was in the process of being rebuilt by another thread
+		synchronized (this.repository.latestATStatesLock) {
+
 			// We're often called so no need to trim all states in one go.
 			// Limit updates to reduce CPU and memory load.
 			String sql = "DELETE FROM ATStatesData "
@@ -684,6 +695,7 @@ public class HSQLDBATRepository implements ATRepository {
 				throw new DataException("Unable to trim AT states in repository", e);
 			}
 		}
+	}
 
 
 	@Override
@@ -719,9 +731,14 @@ public class HSQLDBATRepository implements ATRepository {
 
 	@Override
 	public int pruneAtStates(int minHeight, int maxHeight) throws DataException {
+		// latestATStatesLock is to prevent concurrent updates on LatestATStates
+		// that could result in one process using a partial or empty dataset
+		// because it was in the process of being rebuilt by another thread
+		synchronized (this.repository.latestATStatesLock) {
+
 			int deletedCount = 0;
 
-		for (int height=minHeight; height<maxHeight; height++) {
+			for (int height = minHeight; height < maxHeight; height++) {
 
 				// Give up if we're stopping
 				if (Controller.isStopping()) {
@@ -771,6 +788,7 @@ public class HSQLDBATRepository implements ATRepository {
 
 			return deletedCount;
 		}
+	}
 
 
 	@Override

src/main/java/org/qortal/repository/hsqldb/HSQLDBRepository.java

@@ -69,6 +69,7 @@ public class HSQLDBRepository implements Repository {
 	protected final Map<String, PreparedStatement> preparedStatementCache = new HashMap<>();
 	// We want the same object corresponding to the actual DB
 	protected final Object trimHeightsLock = RepositoryManager.getRepositoryFactory();
+	protected final Object latestATStatesLock = RepositoryManager.getRepositoryFactory();
 
 	private final ATRepository atRepository = new HSQLDBATRepository(this);
 	private final AccountRepository accountRepository = new HSQLDBAccountRepository(this);