Source:
public long restore(DataTree dt, Map<Long, Integer> sessions, PlayBackListener listener) throws IOException { long deserializeResult = snapLog.deserialize(dt, sessions); FileTxnLog txnLog = new FileTxnLog(dataDir); boolean suspectEmptyDB; File initFile = new File(dataDir.getParent(), "initialize"); if (initFile.exists()) { if (!initFile.delete()) { throw new IOException("Unable to delete initialization file " + initFile.toString()); } suspectEmptyDB = false; } else { suspectEmptyDB = !autoCreateDB; } if (-1L == deserializeResult) { if (txnLog.getLastLoggedZxid() != -1) { throw new IOException( "No snapshot found, but there are log entries. " + "Something is broken!"); } if (suspectEmptyDB) { LOG.warn("Unexpected empty data tree, setting zxid to -1"); dt.lastProcessedZxid = -1L; return -1L; } else { save(dt, (ConcurrentHashMap<Long, Integer>)sessions); return 0L; } } TxnIterator itr = txnLog.read(dt.lastProcessedZxid+1); long highestZxid = dt.lastProcessedZxid; TxnHeader hdr; try { while (true) { hdr = itr.getHeader(); if (hdr == null) { return dt.lastProcessedZxid; } if (hdr.getZxid() < highestZxid && highestZxid != 0) { LOG.error("{}(higestZxid) > {}(next log) for type {}", new Object[] { highestZxid, hdr.getZxid(), hdr.getType() }); } else { highestZxid = hdr.getZxid(); } try { processTransaction(hdr,dt,sessions, itr.getTxn()); } catch(KeeperException.NoNodeException e) { throw new IOException("Failed to process transaction type: " + hdr.getType() + " error: " + e.getMessage(), e); } listener.onTxnLoaded(hdr, itr.getTxn()); if (!itr.next()) break; } } finally { if (itr != null) { itr.close(); } } return highestZxid; }

Target:
public long restore(DataTree dt, Map<Long, Integer> sessions, PlayBackListener listener) throws IOException { long deserializeResult = snapLog.deserialize(dt, sessions); FileTxnLog txnLog = new FileTxnLog(dataDir); boolean trustEmptyDB; File initFile = new File(dataDir.getParent(), "initialize"); if (Files.deleteIfExists(initFile.toPath())) { LOG.info("Initialize file found, an empty database will not block voting participation"); trustEmptyDB = true; } else { trustEmptyDB = autoCreateDB; } if (-1L == deserializeResult) { if (txnLog.getLastLoggedZxid() != -1) { throw new IOException( "No snapshot found, but there are log entries. " + "Something is broken!"); } if (trustEmptyDB) { save(dt, (ConcurrentHashMap<Long, Integer>)sessions); return 0L; } else { LOG.warn("Unexpected empty data tree, setting zxid to -1"); dt.lastProcessedZxid = -1L; return -1L; } } TxnIterator itr = txnLog.read(dt.lastProcessedZxid+1); long highestZxid = dt.lastProcessedZxid; TxnHeader hdr; try { while (true) { hdr = itr.getHeader(); if (hdr == null) { return dt.lastProcessedZxid; } if (hdr.getZxid() < highestZxid && highestZxid != 0) { LOG.error("{}(higestZxid) > {}(next log) for type {}", new Object[] { highestZxid, hdr.getZxid(), hdr.getType() }); } else { highestZxid = hdr.getZxid(); } try { processTransaction(hdr,dt,sessions, itr.getTxn()); } catch(KeeperException.NoNodeException e) { throw new IOException("Failed to process transaction type: " + hdr.getType() + " error: " + e.getMessage(), e); } listener.onTxnLoaded(hdr, itr.getTxn()); if (!itr.next()) break; } } finally { if (itr != null) { itr.close(); } } return highestZxid; }