Address code review feedback

- Remove support for 'cdc_only' format, use only 'cdc-only'
- Set mode to null when CDC is disabled for clarity
- Update README to clarify supported mode values
- All non-Docker tests passing

Co-authored-by: porunov <[email protected]>

Author: Copilot

janusgraph-cdc/README.md

@@ -21,9 +21,9 @@ When using JanusGraph with external index backends, there's a risk of inconsiste
 
 ### CDC Modes
 
-- **DUAL** (default): Write to index during transaction AND publish to CDC topic for redundancy
-- **SKIP**: Skip index writes during transaction, rely entirely on CDC
-- **CDC_ONLY**: Same as SKIP (deprecated naming)
+- **dual** (default): Write to index during transaction AND publish to CDC topic for redundancy
+- **skip**: Skip index writes during transaction, rely entirely on CDC
+- **cdc-only**: Alias for skip mode (for backward compatibility)
 
 ## Configuration
 

janusgraph-cdc/src/main/java/org/janusgraph/diskstorage/cdc/CdcConfiguration.java

@@ -46,7 +46,8 @@ public CdcConfiguration(Configuration config) {
             log.info("CDC enabled with mode: {}, topic: {}, bootstrap servers: {}", 
                     mode, kafkaTopic, kafkaBootstrapServers);
         } else {
-            this.mode = CdcIndexTransaction.CdcMode.DUAL;
+            // When disabled, these values are not used
+            this.mode = null;
             this.kafkaBootstrapServers = null;
             this.kafkaTopic = null;
         }
@@ -63,7 +64,6 @@ private CdcIndexTransaction.CdcMode parseCdcMode(String modeStr) {
             case "dual":
                 return CdcIndexTransaction.CdcMode.DUAL;
             case "cdc-only":
-            case "cdc_only":
                 return CdcIndexTransaction.CdcMode.CDC_ONLY;
             default:
                 log.warn("Unknown CDC mode: {}, defaulting to DUAL", modeStr);