feat: introduce handshake to client and gRPC server

pom.xml

@@ -103,6 +103,13 @@
             <scope>test</scope>
         </dependency>
 
+        <!-- jackson-databind for converting POJOs to JSON and back -->
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+            <version>2.14.2</version>
+        </dependency>
+
     </dependencies>
 
     <dependencyManagement>

src/main/java/io/numaproj/numaflow/common/GRPCServerConfig.java

@@ -1,6 +1,7 @@
 package io.numaproj.numaflow.common;
 
-import io.numaproj.numaflow.function.Function;
+import io.numaproj.numaflow.function.FunctionConstants;
+import io.numaproj.numaflow.info.ServerInfoConstants;
 import lombok.AllArgsConstructor;
 import lombok.Getter;
 import lombok.Setter;
@@ -11,12 +12,11 @@
 public class GRPCServerConfig {
     private String socketPath;
     private int maxMessageSize;
+    private String infoFilePath;
 
-    public GRPCServerConfig(int maxMessageSize) {
-        this(Function.SOCKET_PATH, maxMessageSize);
-    }
-
-    public GRPCServerConfig(String socketPath) {
-        this(socketPath, Function.DEFAULT_MESSAGE_SIZE);
+    public GRPCServerConfig() {
+        this.socketPath = FunctionConstants.DEFAULT_SOCKET_PATH;
+        this.maxMessageSize = FunctionConstants.DEFAULT_MESSAGE_SIZE;
+        this.infoFilePath = ServerInfoConstants.DEFAULT_SERVER_INFO_FILE_PATH;
     }
 }

src/main/java/io/numaproj/numaflow/function/Function.java → src/main/java/io/numaproj/numaflow/function/FunctionConstants.java

@@ -3,8 +3,8 @@
 import io.grpc.Context;
 import io.grpc.Metadata;
 
-public class Function {
-    public static final String SOCKET_PATH = "/var/run/numaflow/function.sock";
+public class FunctionConstants {
+    public static final String DEFAULT_SOCKET_PATH = "/var/run/numaflow/function.sock";
 
     public static final int DEFAULT_MESSAGE_SIZE = 1024 * 1024 * 4;
 
@@ -19,18 +19,17 @@ public class Function {
     public static final String DELIMITTER = ":";
 
     public static final Metadata.Key<String> DATUM_METADATA_WIN_START = Metadata.Key.of(
-            Function.WIN_START_KEY,
+            FunctionConstants.WIN_START_KEY,
             Metadata.ASCII_STRING_MARSHALLER);
 
     public static final Metadata.Key<String> DATUM_METADATA_WIN_END = Metadata.Key.of(
-            Function.WIN_END_KEY,
+            FunctionConstants.WIN_END_KEY,
             Metadata.ASCII_STRING_MARSHALLER);
-
     public static final Context.Key<String> WINDOW_START_TIME = Context.keyWithDefault(
-            Function.WIN_START_KEY,
+            FunctionConstants.WIN_START_KEY,
             "");
 
     public static final Context.Key<String> WINDOW_END_TIME = Context.keyWithDefault(
-            Function.WIN_END_KEY,
+            FunctionConstants.WIN_END_KEY,
             "");
 }

src/main/java/io/numaproj/numaflow/function/FunctionServer.java

@@ -1,5 +1,6 @@
 package io.numaproj.numaflow.function;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
 import io.grpc.Context;
 import io.grpc.Contexts;
 import io.grpc.Metadata;
@@ -17,12 +18,17 @@
 import io.numaproj.numaflow.function.mapt.MapTHandler;
 import io.numaproj.numaflow.function.reduce.ReduceHandler;
 import io.numaproj.numaflow.function.reduce.ReducerFactory;
+import io.numaproj.numaflow.info.Language;
+import io.numaproj.numaflow.info.Protocol;
+import io.numaproj.numaflow.info.ServerInfo;
+import io.numaproj.numaflow.info.ServerInfoAccessor;
+import io.numaproj.numaflow.info.ServerInfoAccessorImpl;
 import lombok.extern.slf4j.Slf4j;
 
-import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
+import java.util.HashMap;
 import java.util.concurrent.TimeUnit;
 
 @Slf4j
@@ -31,10 +37,11 @@ public class FunctionServer {
     private final GRPCServerConfig grpcServerConfig;
     private final ServerBuilder<?> serverBuilder;
     private final FunctionService functionService = new FunctionService();
+    private final ServerInfoAccessor serverInfoAccessor = new ServerInfoAccessorImpl(new ObjectMapper());
     private Server server;
 
     public FunctionServer() {
-        this(new GRPCServerConfig(Function.SOCKET_PATH, Function.DEFAULT_MESSAGE_SIZE));
+        this(new GRPCServerConfig());
     }
 
     /**
@@ -78,17 +85,26 @@ public FunctionServer registerReducerFactory(ReducerFactory<? extends ReduceHand
     /**
      * Start serving requests.
      */
-    public void start() throws IOException {
+    public void start() throws Exception {
+        String socketPath = grpcServerConfig.getSocketPath();
+        String infoFilePath = grpcServerConfig.getInfoFilePath();
         // cleanup socket path if it exists (unit test builder doesn't use one)
-        if (grpcServerConfig.getSocketPath() != null) {
-            Path path = Paths.get(grpcServerConfig.getSocketPath());
+        if (socketPath != null) {
+            Path path = Paths.get(socketPath);
             Files.deleteIfExists(path);
             if (Files.exists(path)) {
-                log.error("Failed to clean up socket path \"" + grpcServerConfig.getSocketPath()
-                        + "\". Exiting");
+                log.error("Failed to clean up socket path {}. Exiting", socketPath);
             }
         }
 
+        // write server info to file
+        ServerInfo serverInfo = new ServerInfo(
+                Protocol.UDS_PROTOCOL,
+                Language.JAVA,
+                serverInfoAccessor.getSDKVersion(),
+                new HashMap<>());
+        serverInfoAccessor.write(serverInfo, infoFilePath);
+
         // build server
         ServerInterceptor interceptor = new ServerInterceptor() {
             @Override
@@ -99,10 +115,10 @@ public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(
 
                 final var context =
                         Context.current().withValues(
-                                Function.WINDOW_START_TIME,
-                                headers.get(Function.DATUM_METADATA_WIN_START),
-                                Function.WINDOW_END_TIME,
-                                headers.get(Function.DATUM_METADATA_WIN_END));
+                                FunctionConstants.WINDOW_START_TIME,
+                                headers.get(FunctionConstants.DATUM_METADATA_WIN_START),
+                                FunctionConstants.WINDOW_END_TIME,
+                                headers.get(FunctionConstants.DATUM_METADATA_WIN_END));
                 return Contexts.interceptCall(context, call, headers, next);
             }
         };

src/main/java/io/numaproj/numaflow/function/FunctionService.java

@@ -28,7 +28,7 @@
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
 
-import static io.numaproj.numaflow.function.Function.EOF;
+import static io.numaproj.numaflow.function.FunctionConstants.EOF;
 import static io.numaproj.numaflow.function.v1.UserDefinedFunctionGrpc.getMapFnMethod;
 import static io.numaproj.numaflow.function.v1.UserDefinedFunctionGrpc.getReduceFnMethod;
 
@@ -145,8 +145,8 @@ public StreamObserver<Udfunction.DatumRequest> reduceFn(final StreamObserver<Udf
         }
 
         // get window start and end time from gPRC metadata
-        String winSt = Function.WINDOW_START_TIME.get();
-        String winEt = Function.WINDOW_END_TIME.get();
+        String winSt = FunctionConstants.WINDOW_START_TIME.get();
+        String winEt = FunctionConstants.WINDOW_END_TIME.get();
 
         // convert the start and end time to Instant
         Instant startTime = Instant.ofEpochMilli(Long.parseLong(winSt));
@@ -220,9 +220,9 @@ private Udfunction.DatumResponseList buildDatumListResponse(MessageList messageL
                     .setValue(message.getValue() == null ? ByteString.EMPTY : ByteString.copyFrom(
                             message.getValue()))
                     .addAllKeys(message.getKeys()
-                            == null ? new ArrayList<>() : List.of(message.getKeys()))
+                            == null ? new ArrayList<>():List.of(message.getKeys()))
                     .addAllTags(message.getTags()
-                            == null ? new ArrayList<>() : List.of(message.getTags()))
+                            == null ? new ArrayList<>():List.of(message.getTags()))
                     .build());
         });
         return datumListBuilder.build();

src/main/java/io/numaproj/numaflow/function/reduce/ReduceSupervisorActor.java

@@ -9,7 +9,7 @@
 import akka.japi.pf.ReceiveBuilder;
 import com.google.common.base.Preconditions;
 import io.grpc.stub.StreamObserver;
-import io.numaproj.numaflow.function.Function;
+import io.numaproj.numaflow.function.FunctionConstants;
 import io.numaproj.numaflow.function.FunctionService;
 import io.numaproj.numaflow.function.HandlerDatum;
 import io.numaproj.numaflow.function.HandlerDatumMetadata;
@@ -77,7 +77,7 @@ public SupervisorStrategy supervisorStrategy() {
     @Override
     public void postStop() {
         log.debug("post stop of supervisor executed - {}", getSelf().toString());
-        shutdownActor.tell(Function.SUCCESS, ActorRef.noSender());
+        shutdownActor.tell(FunctionConstants.SUCCESS, ActorRef.noSender());
     }
 
     @Override
@@ -97,7 +97,7 @@ public Receive createReceive() {
      */
     private void invokeActors(Udfunction.DatumRequest datumRequest) {
         String[] keys = datumRequest.getKeysList().toArray(new String[0]);
-        String keyStr = String.join(Function.DELIMITTER, keys);
+        String keyStr = String.join(FunctionConstants.DELIMITTER, keys);
         if (!actorsMap.containsKey(keyStr)) {
             ReduceHandler reduceHandler = reducerFactory.createReducer();
             ActorRef actorRef = getContext()
@@ -125,7 +125,7 @@ private void responseListener(ActorResponse actorResponse) {
          */
 
         responseObserver.onNext(actorResponse.getDatumList());
-        actorsMap.remove(String.join(Function.DELIMITTER, actorResponse.getKeys()));
+        actorsMap.remove(String.join(FunctionConstants.DELIMITTER, actorResponse.getKeys()));
         if (actorsMap.isEmpty()) {
             responseObserver.onCompleted();
             getContext().getSystem().stop(getSelf());

src/main/java/io/numaproj/numaflow/info/Language.java

@@ -0,0 +1,24 @@
+package io.numaproj.numaflow.info;
+
+import com.fasterxml.jackson.annotation.JsonValue;
+
+/**
+ * Please exercise cautions when updating the values below because the exact same values are defined in other Numaflow SDKs
+ * to form a contract between server and clients.
+ */
+public enum Language {
+    GO("go"),
+    PYTHON("python"),
+    JAVA("java");
+
+    private final String name;
+
+    Language(String name) {
+        this.name = name;
+    }
+
+    @JsonValue
+    public String getName() {
+        return name;
+    }
+}

src/main/java/io/numaproj/numaflow/info/Protocol.java

@@ -0,0 +1,23 @@
+package io.numaproj.numaflow.info;
+
+import com.fasterxml.jackson.annotation.JsonValue;
+
+/**
+ * Please exercise cautions when updating the values below because the exact same values are defined in other Numaflow SDKs
+ * to form a contract between server and clients.
+ */
+public enum Protocol {
+    UDS_PROTOCOL("uds"),
+    TCP_PROTOCOL("tcp");
+
+    private final String name;
+
+    Protocol(String name) {
+        this.name = name;
+    }
+
+    @JsonValue
+    public String getName() {
+        return name;
+    }
+}

src/main/java/io/numaproj/numaflow/info/ServerInfo.java

@@ -0,0 +1,31 @@
+package io.numaproj.numaflow.info;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.Setter;
+
+import java.util.Map;
+
+/**
+ * Server Information to be used by client to determine:
+ * - protocol: what is right protocol to use (UDS or TCP)
+ * - language: what is language used by the server
+ * - version: what is the numaflow sdk version used by the server
+ * - metadata: other information
+ */
+@Getter
+@Setter
+@NoArgsConstructor
+@AllArgsConstructor
+public class ServerInfo {
+    @JsonProperty("protocol")
+    private Protocol protocol;
+    @JsonProperty("language")
+    private Language language;
+    @JsonProperty("version")
+    private String version;
+    @JsonProperty("metadata")
+    private Map<String, String> metadata;
+}

src/main/java/io/numaproj/numaflow/info/ServerInfoAccessor.java

@@ -0,0 +1,32 @@
+package io.numaproj.numaflow.info;
+
+public interface ServerInfoAccessor {
+    /**
+     * Get runtime Java SDK version.
+     */
+    String getSDKVersion();
+
+    /**
+     * Delete filePath if it exists.
+     * Write serverInfo to filePath in Json format.
+     * Append {@link ServerInfoConstants#EOF} as a new line to indicate end of file.
+     *
+     * @param serverInfo server information POJO
+     * @param filePath file path to write to
+     *
+     * @throws Exception any exceptions are thrown to the caller.
+     */
+    void write(ServerInfo serverInfo, String filePath) throws Exception;
+
+    /**
+     * Read from filePath to retrieve server information POJO.
+     * This API is only used for unit tests.
+     *
+     * @param filePath file path to read from
+     *
+     * @return server information POJO
+     *
+     * @throws Exception any exceptions are thrown to the caller.
+     */
+    ServerInfo read(String filePath) throws Exception;
+}