Log error message for unexpected exception only (#7414)

* Log error message if not runtime exception only

* Add todo

shardingsphere-proxy/shardingsphere-proxy-frontend/shardingsphere-proxy-frontend-core/src/main/java/org/apache/shardingsphere/proxy/frontend/command/CommandExecutorTask.java

@@ -74,10 +74,12 @@ public final class CommandExecutorTask implements Runnable {
             // CHECKSTYLE:OFF
         } catch (final Exception ex) {
             // CHECKSTYLE:ON
-            log.error("Exception occur: ", ex);
             context.writeAndFlush(databaseProtocolFrontendEngine.getCommandExecuteEngine().getErrorPacket(ex));
             Optional<DatabasePacket<?>> databasePacket = databaseProtocolFrontendEngine.getCommandExecuteEngine().getOtherPacket();
             databasePacket.ifPresent(context::writeAndFlush);
+            if (!isExpectedException(ex)) {
+                log.error("Exception occur: ", ex);
+            }
         } finally {
             if (isNeedFlush) {
                 context.flush();
@@ -86,6 +88,11 @@ public final class CommandExecutorTask implements Runnable {
         }
     }
     
+    // TODO finish expected exception
+    private boolean isExpectedException(final Exception ex) {
+        return ex instanceof RuntimeException;
+    }
+    
     private boolean executeCommand(final ChannelHandlerContext context, final PacketPayload payload, final BackendConnection backendConnection) throws SQLException {
         CommandExecuteEngine commandExecuteEngine = databaseProtocolFrontendEngine.getCommandExecuteEngine();
         CommandPacketType type = commandExecuteEngine.getCommandPacketType(payload);