feat: implement sdk for session reduce

examples/pom.xml

@@ -151,6 +151,23 @@
                             </to>
                         </configuration>
                     </execution>
+                    <execution>
+                        <id>session-reduce-count</id>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>dockerBuild</goal>
+                        </goals>
+                        <configuration>
+                            <container>
+                                <mainClass>
+                                    io.numaproj.numaflow.examples.reducesession.counter.CountFactory
+                                </mainClass>
+                            </container>
+                            <to>
+                                <image>numaflow-java-examples/session-reduce-count</image>
+                            </to>
+                        </configuration>
+                    </execution>
                 </executions>
             </plugin>
         </plugins>

examples/src/main/java/io/numaproj/numaflow/examples/reducesession/counter/CountFactory.java

@@ -0,0 +1,23 @@
+package io.numaproj.numaflow.examples.reducesession.counter;
+
+import io.numaproj.numaflow.sessionreducer.Server;
+import io.numaproj.numaflow.sessionreducer.model.SessionReducerFactory;
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * CountFactory extends SessionReducerFactory to support creating instances of SumFunction.
+ * It also provides a main function to start a server for handling the session reduce stream.
+ */
+@Slf4j
+public class CountFactory extends SessionReducerFactory<CountFunction> {
+
+    public static void main(String[] args) throws Exception {
+        log.info("count udf was invoked");
+        new Server(new CountFactory()).start();
+    }
+
+    @Override
+    public CountFunction createSessionReducer() {
+        return new CountFunction();
+    }
+}

examples/src/main/java/io/numaproj/numaflow/examples/reducesession/counter/CountFunction.java

@@ -0,0 +1,48 @@
+package io.numaproj.numaflow.examples.reducesession.counter;
+
+import io.numaproj.numaflow.sessionreducer.model.Datum;
+import io.numaproj.numaflow.sessionreducer.model.Message;
+import io.numaproj.numaflow.sessionreducer.model.SessionReducer;
+import lombok.extern.slf4j.Slf4j;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * CountFunction is a simple session reducer which counts the number of events in a session.
+ */
+@Slf4j
+public class CountFunction extends SessionReducer {
+
+    private final AtomicInteger count = new AtomicInteger(0);
+
+    @Override
+    public void processMessage(
+            String[] keys,
+            Datum datum,
+            io.numaproj.numaflow.sessionreducer.model.OutputStreamObserver outputStreamObserver) {
+        this.count.incrementAndGet();
+    }
+
+    @Override
+    public void handleEndOfStream(
+            String[] keys,
+            io.numaproj.numaflow.sessionreducer.model.OutputStreamObserver outputStreamObserver) {
+        outputStreamObserver.send(new Message(String.valueOf(this.count.get()).getBytes()));
+    }
+
+    @Override
+    public byte[] accumulator() {
+        return String.valueOf(this.count.get()).getBytes();
+    }
+
+    @Override
+    public void mergeAccumulator(byte[] accumulator) {
+        int value = 0;
+        try {
+            value = Integer.parseInt(new String(accumulator));
+        } catch (NumberFormatException e) {
+            log.info("error while parsing integer - {}", e.getMessage());
+        }
+        this.count.addAndGet(value);
+    }
+}

examples/src/main/java/io/numaproj/numaflow/examples/reducestreamer/sum/SumFunction.java

@@ -1,5 +1,6 @@
 package io.numaproj.numaflow.examples.reducestreamer.sum;
 
+import io.numaproj.numaflow.reducestreamer.model.Datum;
 import io.numaproj.numaflow.reducestreamer.model.Message;
 import io.numaproj.numaflow.reducestreamer.model.Metadata;
 import io.numaproj.numaflow.reducestreamer.model.OutputStreamObserver;
@@ -19,9 +20,9 @@ public class SumFunction extends ReduceStreamer {
     @Override
     public void processMessage(
             String[] keys,
-            io.numaproj.numaflow.reducestreamer.model.Datum datum,
+            Datum datum,
             OutputStreamObserver outputStreamObserver,
-            io.numaproj.numaflow.reducestreamer.model.Metadata md) {
+            Metadata md) {
         try {
             sum += Integer.parseInt(new String(datum.getValue()));
         } catch (NumberFormatException e) {

pom.xml

@@ -296,6 +296,7 @@
                         <exclude>io.numaproj.numaflow.mapstream.v1</exclude>
                         <exclude>io.numaproj.numaflow.map.v1</exclude>
                         <exclude>io.numaproj.numaflow.reduce.v1</exclude>
+                        <exclude>io.numaproj.numaflow.sessionreduce.v1</exclude>
                         <exclude>io.numaproj.numaflow.sourcetransformer.v1</exclude>
                         <exclude>io.numaproj.numaflow.sink.v1</exclude>
                         <exclude>io.numaproj.numaflow.sideinput.v1</exclude>
@@ -337,6 +338,7 @@
                                 <exclude>io/numaproj/numaflow/examples/*</exclude>
                                 <exclude>io/numaproj/numaflow/mapstream/v1/*</exclude>
                                 <exclude>io/numaproj/numaflow/reduce/v1/*</exclude>
+                                <exclude>io/numaproj/numaflow/sessionreduce/v1/*</exclude>
                                 <exclude>io/numaproj/numaflow/map/v1/*</exclude>
                                 <exclude>io/numaproj/numaflow/sourcetransformer/v1/*</exclude>
                                 <exclude>io/numaproj/numaflow/sink/v1/*</exclude>

src/main/java/io/numaproj/numaflow/reducestreamer/OutputActor.java

@@ -10,7 +10,7 @@
 /**
  * Output actor is a wrapper around the gRPC output stream.
  * It ensures synchronized calls to the responseObserver onNext() and invokes onComplete at the end of the stream.
- * ALL reduce responses are sent to the response stream actor before getting forwarded to the output gRPC stream.
+ * ALL reduce responses are sent to the output actor before getting forwarded to the output gRPC stream.
  * <p>
  * More details about gRPC StreamObserver concurrency: https://grpc.github.io/grpc-java/javadoc/io/grpc/stub/StreamObserver.html
  */

src/main/java/io/numaproj/numaflow/reducestreamer/OutputStreamObserverImpl.java

@@ -16,11 +16,11 @@
 @AllArgsConstructor
 class OutputStreamObserverImpl implements OutputStreamObserver {
     private final Metadata md;
-    private final ActorRef responseStreamActor;
+    private final ActorRef outputActor;
 
     @Override
     public void send(Message message) {
-        this.responseStreamActor.tell(buildResponse(message), ActorRef.noSender());
+        this.outputActor.tell(buildResponse(message), ActorRef.noSender());
     }
 
     private ActorResponse buildResponse(Message message) {

src/main/java/io/numaproj/numaflow/reducestreamer/ReduceStreamerActor.java

@@ -27,13 +27,13 @@ class ReduceStreamerActor extends AbstractActor {
     private OutputStreamObserver outputStream;
 
     public static Props props(
-            String[] keys, Metadata md, ReduceStreamer groupBy, ActorRef responseStreamActor) {
+            String[] keys, Metadata md, ReduceStreamer groupBy, ActorRef outputActor) {
         return Props.create(
                 ReduceStreamerActor.class,
                 keys,
                 md,
                 groupBy,
-                new OutputStreamObserverImpl(md, responseStreamActor));
+                new OutputStreamObserverImpl(md, outputActor));
     }
 
     @Override

src/main/java/io/numaproj/numaflow/reducestreamer/SupervisorActor.java

@@ -29,31 +29,31 @@ class SupervisorActor extends AbstractActor {
     private final ReduceStreamerFactory<? extends ReduceStreamer> reduceStreamerFactory;
     private final Metadata md;
     private final ActorRef shutdownActor;
-    private final ActorRef responseStreamActor;
+    private final ActorRef outputActor;
     private final Map<String, ActorRef> actorsMap = new HashMap<>();
 
     public SupervisorActor(
             ReduceStreamerFactory<? extends ReduceStreamer> reduceStreamerFactory,
             Metadata md,
             ActorRef shutdownActor,
-            ActorRef responseStreamActor) {
+            ActorRef outputActor) {
         this.reduceStreamerFactory = reduceStreamerFactory;
         this.md = md;
         this.shutdownActor = shutdownActor;
-        this.responseStreamActor = responseStreamActor;
+        this.outputActor = outputActor;
     }
 
     public static Props props(
             ReduceStreamerFactory<? extends ReduceStreamer> reduceStreamerFactory,
             Metadata md,
             ActorRef shutdownActor,
-            ActorRef responseStreamActor) {
+            ActorRef outputActor) {
         return Props.create(
                 SupervisorActor.class,
                 reduceStreamerFactory,
                 md,
                 shutdownActor,
-                responseStreamActor);
+                outputActor);
     }
 
     // if there is an uncaught exception stop in the supervisor actor, send a signal to shut down
@@ -101,7 +101,7 @@ private void invokeActor(ActorRequest actorRequest) {
                             keys,
                             this.md,
                             reduceStreamerHandler,
-                            this.responseStreamActor));
+                            this.outputActor));
             actorsMap.put(uniqueId, actorRef);
         }
         HandlerDatum handlerDatum = constructHandlerDatum(actorRequest.getRequest().getPayload());
@@ -122,9 +122,9 @@ private void handleActorResponse(ActorResponse actorResponse) {
         if (actorsMap.isEmpty()) {
             // since the actors map is empty, this particular actor response is the last response to forward to output gRPC stream.
             actorResponse.setLast(true);
-            this.responseStreamActor.tell(actorResponse, getSelf());
+            this.outputActor.tell(actorResponse, getSelf());
         } else {
-            this.responseStreamActor.tell(actorResponse, getSelf());
+            this.outputActor.tell(actorResponse, getSelf());
         }
     }
 

src/main/java/io/numaproj/numaflow/sessionreducer/ActorRequest.java

@@ -0,0 +1,61 @@
+package io.numaproj.numaflow.sessionreducer;
+
+import io.numaproj.numaflow.sessionreduce.v1.Sessionreduce;
+import lombok.Builder;
+import lombok.Getter;
+
+/**
+ * ActorRequest is used by the supervisor actor to distribute session reduce operations to
+ * individual session reducer actors. One actor request is sent to only one session reducer actor.
+ */
+@Getter
+class ActorRequest {
+    private final ActorRequestType type;
+    // the window of the target session the actor request is sent to
+    private final Sessionreduce.KeyedWindow keyedWindow;
+    // the new keyed window the target session is to be expanded to
+    // it is specified only when the actor request is an EXPAND
+    private final Sessionreduce.KeyedWindow newKeyedWindow;
+    // the payload of the request
+    private final Sessionreduce.SessionReduceRequest.Payload payload;
+    // the id of the merge task this request belongs to, it's equal to the unique id of the merged window,
+    // it is specified only when the actor request is a GET_ACCUMULATOR
+    private final String mergeTaskId;
+
+    @Builder
+    private ActorRequest(
+            ActorRequestType type,
+            Sessionreduce.KeyedWindow keyedWindow,
+            Sessionreduce.KeyedWindow newKeyedWindow,
+            Sessionreduce.SessionReduceRequest.Payload payload,
+            String mergeTaskId
+    ) {
+        this.type = type;
+        this.keyedWindow = keyedWindow;
+        this.newKeyedWindow = newKeyedWindow;
+        this.payload = payload;
+        this.mergeTaskId = mergeTaskId;
+    }
+
+    static class ActorRequestBuilder {
+        ActorRequest build() {
+            if (newKeyedWindow != null && type != ActorRequestType.EXPAND) {
+                throw new IllegalStateException(
+                        "attribute newKeyedWindow can only be set when the request is an EXPAND.");
+            }
+            if (newKeyedWindow == null && type == ActorRequestType.EXPAND) {
+                throw new IllegalStateException(
+                        "attribute newKeyedWindow must be set when the request is an EXPAND.");
+            }
+            if (mergeTaskId != null && type != ActorRequestType.GET_ACCUMULATOR) {
+                throw new IllegalStateException(
+                        "attribute mergeTaskId can only be set when the request is a GET_ACCUMULATOR.");
+            }
+            if (mergeTaskId == null && type == ActorRequestType.GET_ACCUMULATOR) {
+                throw new IllegalStateException(
+                        "attribute mergeTaskId must be set when the request is a GET_ACCUMULATOR.");
+            }
+            return new ActorRequest(type, keyedWindow, newKeyedWindow, payload, mergeTaskId);
+        }
+    }
+}

src/main/java/io/numaproj/numaflow/sessionreducer/ActorRequestType.java

@@ -0,0 +1,17 @@
+package io.numaproj.numaflow.sessionreducer;
+
+/**
+ * ActorRequestType represents the purpose of an ActorRequest.
+ */
+public enum ActorRequestType {
+    // open a brand-new session window
+    OPEN,
+    // append a message to an existing session window
+    APPEND,
+    // close a session window
+    CLOSE,
+    // expand a session window
+    EXPAND,
+    // ask a to-be-merged session window for it's accumulator
+    GET_ACCUMULATOR,
+}

src/main/java/io/numaproj/numaflow/sessionreducer/ActorResponse.java

@@ -0,0 +1,52 @@
+package io.numaproj.numaflow.sessionreducer;
+
+import io.numaproj.numaflow.sessionreduce.v1.Sessionreduce;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.Setter;
+
+/**
+ * The actor response holds the session reduce response from a particular session window.
+ */
+@Getter
+@Setter
+class ActorResponse {
+    Sessionreduce.SessionReduceResponse response;
+    // The isLast attribute indicates whether the response is globally the last one to be sent to
+    // the output gRPC stream, if set to true, it means the response is the very last response among
+    // all windows. When output actor receives an isLast response, it sends the response to and immediately
+    // closes the output stream.
+    boolean isLast;
+    // The accumulator attribute holds the accumulator of the session.
+    byte[] accumulator;
+    // The mergeTaskId attribute holds the id of the merged window that this session is to be merged into.
+    String mergeTaskId;
+
+    @Builder
+    private ActorResponse(
+            Sessionreduce.SessionReduceResponse response,
+            boolean isLast,
+            byte[] accumulator,
+            String mergeTaskId
+    ) {
+        this.response = response;
+        this.isLast = isLast;
+        this.accumulator = accumulator;
+        this.mergeTaskId = mergeTaskId;
+    }
+
+    static class ActorResponseBuilder {
+        ActorResponse build() {
+            if ((accumulator != null && mergeTaskId == null) || (accumulator == null
+                    && mergeTaskId != null)) {
+                throw new IllegalStateException(
+                        "attributes accumulator and mergeTaskId should be either both null or both non-null.");
+            }
+            return new ActorResponse(response, isLast, accumulator, mergeTaskId);
+        }
+    }
+
+    boolean isEOFResponse() {
+        return this.accumulator == null && this.mergeTaskId == null;
+    }
+}

src/main/java/io/numaproj/numaflow/sessionreducer/Constants.java

@@ -0,0 +1,15 @@
+package io.numaproj.numaflow.sessionreducer;
+
+class Constants {
+    public static final int DEFAULT_MESSAGE_SIZE = 1024 * 1024 * 64;
+
+    public static final String DEFAULT_SOCKET_PATH = "/var/run/numaflow/sessionreduce.sock";
+
+    public static final String DEFAULT_SERVER_INFO_FILE_PATH = "/var/run/numaflow/sessionreducer-server-info";
+
+    public static final String EOF = "EOF";
+
+    public static final String SUCCESS = "SUCCESS";
+
+    public static final String DELIMITER = ":";
+}