feat: end to end wiring for per message nack

src/main/java/io/numaproj/numaflow/batchmapper/Message.java

@@ -1,14 +1,17 @@
 package io.numaproj.numaflow.batchmapper;
 
+import io.numaproj.numaflow.shared.NackOptions;
 import lombok.Getter;
 
 /** Message is used to wrap the data returned by Mapper. */
 @Getter
 public class Message {
   private static final String[] DROP_TAGS = {"U+005C__DROP__"};
+  private static final String[] NACK_TAGS = {"U+005C__NACK__"};
   private final String[] keys;
   private final byte[] value;
   private final String[] tags;
+  private final NackOptions nackOptions;
 
   /**
    * used to create Message with value, keys and tags(used for conditional forwarding)
@@ -18,10 +21,15 @@ public class Message {
    * @param tags message tags which will be used for conditional forwarding
    */
   public Message(byte[] value, String[] keys, String[] tags) {
+    this(value, keys, tags, (NackOptions) null);
+  }
+
+  private Message(byte[] value, String[] keys, String[] tags, NackOptions nackOptions) {
     // defensive copy - once the Message is created, the caller should not be able to modify it.
     this.keys = keys == null ? null : keys.clone();
     this.value = value == null ? null : value.clone();
     this.tags = tags == null ? null : tags.clone();
+    this.nackOptions = nackOptions;
   }
 
   /**
@@ -51,4 +59,14 @@ public Message(byte[] value, String[] keys) {
   public static Message toDrop() {
     return new Message(new byte[0], null, DROP_TAGS);
   }
+
+  /**
+   * creates a Message that negatively acknowledges the input message, requesting redelivery.
+   *
+   * @param nackOptions optional redelivery options (may be null)
+   * @return the Message which will be nacked
+   */
+  public static Message toNack(NackOptions nackOptions) {
+    return new Message(new byte[0], null, NACK_TAGS, nackOptions);
+  }
 }

src/main/java/io/numaproj/numaflow/batchmapper/Service.java

@@ -137,18 +137,15 @@ private void buildAndStreamResponse(
             responses.getItems().forEach(message -> {
                 List<MapOuterClass.MapResponse.Result> mapResponseResult = new ArrayList<>();
                 message.getItems().forEach(res -> {
-                    mapResponseResult.add(
-                            MapOuterClass.MapResponse.Result
-                                    .newBuilder()
-                                    .setValue(res.getValue()
-                                            == null ? ByteString.EMPTY : ByteString.copyFrom(
-                                            res.getValue()))
-                                    .addAllKeys(res.getKeys()
-                                            == null ? new ArrayList<>() : Arrays.asList(res.getKeys()))
-                                    .addAllTags(res.getTags()
-                                            == null ? new ArrayList<>() : Arrays.asList(res.getTags()))
-                                    .build()
-                    );
+                    MapOuterClass.MapResponse.Result.Builder resultBuilder = MapOuterClass.MapResponse.Result
+                            .newBuilder()
+                            .setValue(res.getValue() == null ? ByteString.EMPTY : ByteString.copyFrom(res.getValue()))
+                            .addAllKeys(res.getKeys() == null ? new ArrayList<>() : Arrays.asList(res.getKeys()))
+                            .addAllTags(res.getTags() == null ? new ArrayList<>() : Arrays.asList(res.getTags()));
+                    if (res.getNackOptions() != null) {
+                        resultBuilder.setNackOptions(res.getNackOptions().toProto());
+                    }
+                    mapResponseResult.add(resultBuilder.build());
                 });
                 MapOuterClass.MapResponse singleRequestResponse = MapOuterClass.MapResponse
                         .newBuilder()

src/main/java/io/numaproj/numaflow/mapper/MapperActor.java

@@ -87,16 +87,19 @@ private MapOuterClass.MapResponse buildResponse(MessageList messageList, String
                 .newBuilder();
 
         messageList.getMessages().forEach(message -> {
-            responseBuilder.addResults(MapOuterClass.MapResponse.Result.newBuilder()
+            MapOuterClass.MapResponse.Result.Builder resultBuilder = MapOuterClass.MapResponse.Result.newBuilder()
                     .setValue(message.getValue() == null ? ByteString.EMPTY : ByteString.copyFrom(
                             message.getValue()))
                     .addAllKeys(message.getKeys()
                             == null ? new ArrayList<>() : Arrays.asList(message.getKeys()))
                     .addAllTags(message.getTags()
                             == null ? new ArrayList<>() : Arrays.asList(message.getTags()))
                     .setMetadata(message.getUserMetadata()
-                            == null ? MetadataOuterClass.Metadata.getDefaultInstance() : message.getUserMetadata().toProto())
-                    .build());
+                            == null ? MetadataOuterClass.Metadata.getDefaultInstance() : message.getUserMetadata().toProto());
+            if (message.getNackOptions() != null) {
+                resultBuilder.setNackOptions(message.getNackOptions().toProto());
+            }
+            responseBuilder.addResults(resultBuilder.build());
         });
         return responseBuilder.setId(ID).build();
     }

src/main/java/io/numaproj/numaflow/mapper/Message.java

@@ -1,5 +1,6 @@
 package io.numaproj.numaflow.mapper;
 
+import io.numaproj.numaflow.shared.NackOptions;
 import io.numaproj.numaflow.shared.UserMetadata;
 import lombok.Getter;
 
@@ -11,10 +12,12 @@
 @Getter
 public class Message {
   private static final String[] DROP_TAGS = {"U+005C__DROP__"};
+  private static final String[] NACK_TAGS = {"U+005C__NACK__"};
   private final String[] keys;
   private final byte[] value;
   private final String[] tags;
   private final UserMetadata userMetadata;
+  private final NackOptions nackOptions;
 
   /**
    * used to create Message with value, keys, tags(used for conditional forwarding) and userMetadata
@@ -25,12 +28,17 @@ public class Message {
    * @param userMetadata user metadata, this is used to pass user defined metadata to the next vertex
    */
   public Message(byte[] value, String[] keys, String[] tags, UserMetadata userMetadata) {
+    this(value, keys, tags, userMetadata, null);
+  }
+
+  private Message(byte[] value, String[] keys, String[] tags, UserMetadata userMetadata, NackOptions nackOptions) {
     // defensive copy - once the Message is created, the caller should not be able to modify it.
     this.keys = keys == null ? null : keys.clone();
     this.value = value == null ? null : value.clone();
     this.tags = tags == null ? null : tags.clone();
     // Copy the data using copy constructor to prevent mutation
     this.userMetadata = userMetadata == null ? null : new UserMetadata(userMetadata);
+    this.nackOptions = nackOptions;
   }
 
   /**
@@ -71,4 +79,14 @@ public Message(byte[] value, String[] keys, String[] tags) {
   public static Message toDrop() {
     return new Message(new byte[0], null, DROP_TAGS, null);
   }
+
+  /**
+   * creates a Message that negatively acknowledges the input message, requesting redelivery.
+   *
+   * @param nackOptions optional redelivery options (may be null)
+   * @return the Message which will be nacked
+   */
+  public static Message toNack(NackOptions nackOptions) {
+    return new Message(new byte[0], null, NACK_TAGS, null, nackOptions);
+  }
 }

src/main/java/io/numaproj/numaflow/mapstreamer/Message.java

@@ -1,14 +1,17 @@
 package io.numaproj.numaflow.mapstreamer;
 
+import io.numaproj.numaflow.shared.NackOptions;
 import lombok.Getter;
 
 /** Message is used to wrap the data returned by MapStreamer. */
 @Getter
 public class Message {
   private static final String[] DROP_TAGS = {"U+005C__DROP__"};
+  private static final String[] NACK_TAGS = {"U+005C__NACK__"};
   private final String[] keys;
   private final byte[] value;
   private final String[] tags;
+  private final NackOptions nackOptions;
 
   /**
    * used to create Message with value, keys and tags(used for conditional forwarding)
@@ -18,10 +21,15 @@ public class Message {
    * @param tags message tags which will be used for conditional forwarding
    */
   public Message(byte[] value, String[] keys, String[] tags) {
+    this(value, keys, tags, (NackOptions) null);
+  }
+
+  private Message(byte[] value, String[] keys, String[] tags, NackOptions nackOptions) {
     // defensive copy - once the Message is created, the caller should not be able to modify it.
     this.keys = keys == null ? null : keys.clone();
     this.value = value == null ? null : value.clone();
     this.tags = tags == null ? null : tags.clone();
+    this.nackOptions = nackOptions;
   }
 
   /**
@@ -51,4 +59,14 @@ public Message(byte[] value, String[] keys) {
   public static Message toDrop() {
     return new Message(new byte[0], null, DROP_TAGS);
   }
+
+  /**
+   * creates a Message that negatively acknowledges the input message, requesting redelivery.
+   *
+   * @param nackOptions optional redelivery options (may be null)
+   * @return the Message which will be nacked
+   */
+  public static Message toNack(NackOptions nackOptions) {
+    return new Message(new byte[0], null, NACK_TAGS, nackOptions);
+  }
 }

src/main/java/io/numaproj/numaflow/mapstreamer/OutputObserverImpl.java

@@ -29,17 +29,17 @@ public void send(Message message) {
         if (message == null) {
             return;
         }
+        MapOuterClass.MapResponse.Result.Builder resultBuilder = MapOuterClass.MapResponse.Result.newBuilder()
+                .setValue(message.getValue() == null ? ByteString.EMPTY : ByteString.copyFrom(message.getValue()))
+                .addAllKeys(message.getKeys() == null ? new ArrayList<>() : Arrays.asList(message.getKeys()))
+                .addAllTags(message.getTags() == null ? new ArrayList<>() : Arrays.asList(message.getTags()));
+        if (message.getNackOptions() != null) {
+            resultBuilder.setNackOptions(message.getNackOptions().toProto());
+        }
         MapOuterClass.MapResponse response = MapOuterClass.MapResponse.newBuilder()
                 .setId(requestID)
-                .addResults(MapOuterClass.MapResponse.Result.newBuilder()
-                        .setValue(
-                                message.getValue() == null ? ByteString.EMPTY : ByteString.copyFrom(
-                                        message.getValue()))
-                        .addAllKeys(message.getKeys()
-                                == null ? new ArrayList<>() : Arrays.asList(message.getKeys()))
-                        .addAllTags(message.getTags()
-                                == null ? new ArrayList<>() : Arrays.asList(message.getTags()))
-                        .build()).build();
+                .addResults(resultBuilder.build())
+                .build();
         supervisorActor.tell(response, ActorRef.noSender());
     }
 

src/main/java/io/numaproj/numaflow/shared/NackOptions.java

@@ -0,0 +1,53 @@
+package io.numaproj.numaflow.shared;
+
+import lombok.Builder;
+import lombok.Getter;
+
+/**
+ * NackOptions carries per-message redelivery options for a negative acknowledgement (nack).
+ * All fields are optional; a null value means unset.
+ */
+@Getter
+@Builder(builderMethodName = "newBuilder")
+public class NackOptions {
+    /** redelivery delay in milliseconds. */
+    private final Long delay;
+    /** maximum number of redelivery attempts. */
+    private final Integer maxDeliveries;
+    /** human-readable reason for the nack. */
+    private final String reason;
+
+    /** Converts to the outgoing proto type, setting only the fields that are present. */
+    public common.NackOptionsOuterClass.NackOptions toProto() {
+        common.NackOptionsOuterClass.NackOptions.Builder b =
+                common.NackOptionsOuterClass.NackOptions.newBuilder();
+        if (delay != null) {
+            b.setDelay(delay);
+        }
+        if (maxDeliveries != null) {
+            b.setMaxDeliveries(maxDeliveries);
+        }
+        if (reason != null) {
+            b.setReason(reason);
+        }
+        return b.build();
+    }
+
+    /** Converts from the incoming proto type. Returns null for null input. */
+    public static NackOptions fromProto(common.NackOptionsOuterClass.NackOptions p) {
+        if (p == null) {
+            return null;
+        }
+        NackOptionsBuilder b = NackOptions.newBuilder();
+        if (p.hasDelay()) {
+            b.delay(p.getDelay());
+        }
+        if (p.hasMaxDeliveries()) {
+            b.maxDeliveries(p.getMaxDeliveries());
+        }
+        if (p.hasReason()) {
+            b.reason(p.getReason());
+        }
+        return b.build();
+    }
+}

src/main/java/io/numaproj/numaflow/sinker/Response.java

@@ -1,5 +1,6 @@
 package io.numaproj.numaflow.sinker;
 
+import io.numaproj.numaflow.shared.NackOptions;
 import lombok.AccessLevel;
 import lombok.AllArgsConstructor;
 import lombok.Getter;
@@ -20,6 +21,8 @@ public class Response {
   private final byte[] serveResponse;
   private final Boolean onSuccess;
   private final Message onSuccessMessage;
+  private final Boolean nack;
+  private final NackOptions nackOptions;
 
     /**
    * Static method to create response for successful message processing.
@@ -28,7 +31,7 @@ public class Response {
    * @return Response object with success status
    */
   public static Response responseOK(String id) {
-    return new Response(id, true, null, false, false, null, false, null);
+    return new Response(id, true, null, false, false, null, false, null, false, null);
   }
 
   /**
@@ -39,7 +42,7 @@ public static Response responseOK(String id) {
    * @return Response object with failure status and error message
    */
   public static Response responseFailure(String id, String errMsg) {
-    return new Response(id, false, errMsg, false, false, null, false, null);
+    return new Response(id, false, errMsg, false, false, null, false, null, false, null);
   }
 
   /**
@@ -50,7 +53,7 @@ public static Response responseFailure(String id, String errMsg) {
    * @return Response object with fallback status
    */
   public static Response responseFallback(String id) {
-    return new Response(id, false, null, true, false, null, false, null);
+    return new Response(id, false, null, true, false, null, false, null, false, null);
   }
 
   /**
@@ -63,7 +66,7 @@ public static Response responseFallback(String id) {
    * @return Response object with serve status and serve response
    */
   public static Response responseServe(String id, byte[] serveResponse) {
-    return new Response(id, false, null, false, true, serveResponse, false, null);
+    return new Response(id, false, null, false, true, serveResponse, false, null, false, null);
   }
 
   /**
@@ -76,6 +79,18 @@ public static Response responseServe(String id, byte[] serveResponse) {
    * @return Response object with onSuccess status and onSuccess message
    */
   public static Response responseOnSuccess(String id, Message onSuccessMessage) {
-      return new Response(id, false, null, false, false, null, true, onSuccessMessage);
+      return new Response(id, false, null, false, false, null, true, onSuccessMessage, false, null);
+  }
+
+  /**
+   * Static method to create a nack response, indicating the message should be negatively
+   * acknowledged and redelivered. nackOptions may be null.
+   *
+   * @param id id of the message
+   * @param nackOptions optional redelivery options
+   * @return Response object with nack status
+   */
+  public static Response responseNack(String id, NackOptions nackOptions) {
+    return new Response(id, false, null, false, false, null, false, null, true, nackOptions);
   }
 }

src/main/java/io/numaproj/numaflow/sinker/Service.java

@@ -161,6 +161,14 @@ private SinkOuterClass.SinkResponse.Result buildResult(Response response) {
                     .setStatus(SinkOuterClass.Status.ON_SUCCESS)
                     .setOnSuccessMsg(Message.toProto(response.getOnSuccessMessage()))
                     .build();
+        } else if (response.getNack() != null && response.getNack()) {
+            SinkOuterClass.SinkResponse.Result.Builder b = SinkOuterClass.SinkResponse.Result.newBuilder()
+                    .setId(response.getId() == null ? "" : response.getId())
+                    .setStatus(SinkOuterClass.Status.NACK);
+            if (response.getNackOptions() != null) {
+                b.setNackOptions(response.getNackOptions().toProto());
+            }
+            return b.build();
         } else {
             // FIXME: Return error when error message is not set?
             return SinkOuterClass.SinkResponse.Result.newBuilder()

src/main/java/io/numaproj/numaflow/sourcer/NackRequest.java

@@ -1,5 +1,6 @@
 package io.numaproj.numaflow.sourcer;
 
+import io.numaproj.numaflow.shared.NackOptions;
 
 import java.util.List;
 
@@ -11,4 +12,9 @@ public interface NackRequest {
      * @return the list of offsets to be negatively acknowledged.
      */
     List<Offset> getOffsets();
+
+    /**
+     * @return the redelivery options for this nack, or null if none were provided.
+     */
+    NackOptions getNackOptions();
 }