use safeTimestamp (#48)

logproxy-client/src/main/java/com/oceanbase/clogproxy/client/config/ObReaderConfig.java

@@ -137,7 +137,12 @@ public class ObReaderConfig extends AbstractConnectionConfig {
     @Override
     public void updateCheckpoint(String checkpoint) {
         try {
-            startTimestamp.set(Long.parseLong(checkpoint));
+            long timestamp = Long.parseLong(checkpoint);
+            if (timestamp < 0) {
+                throw new IllegalArgumentException(
+                        "update checkpoint with invalid value: " + checkpoint);
+            }
+            startTimestamp.set(timestamp);
         } catch (NumberFormatException e) {
             // do nothing
         }

logproxy-client/src/main/java/com/oceanbase/clogproxy/client/connection/ClientHandler.java

@@ -331,10 +331,14 @@ public class ClientHandler extends ChannelInboundHandlerAdapter {
                 throw new LogProxyClientException(ErrorCode.E_PARSE, e);
             }
 
+            if (logger.isTraceEnabled()) {
+                logger.trace("Log message: {}", logMessage);
+            }
+
             while (true) {
                 try {
                     recordQueue.put(new StreamContext.TransferPacket(logMessage));
-                    stream.setCheckpointString(logMessage.getTimestamp());
+                    stream.setCheckpointString(logMessage.getSafeTimestamp());
                     break;
                 } catch (InterruptedException e) {
                     // do nothing