Adds method to wait for Dapr sidecar.

examples/src/main/java/io/dapr/examples/state/README.md

@@ -43,6 +43,10 @@ public class StateClient {
   ///...
   public static void main(String[] args) throws Exception {
       try (DaprClient client = new DaprClientBuilder().build()) {
+        System.out.println("Waiting for Dapr sidecar ...");
+        client.waitForSidecar(10000).block();
+        System.out.println("Dapr sidecar is ready.");
+
         String message = args.length == 0 ? " " : args[0];
 
         MyClass myClass = new MyClass();
@@ -102,7 +106,8 @@ public class StateClient {
 ```
 The code uses the `DaprClient` created by the `DaprClientBuilder`. Notice that this builder uses default settings. Internally, it is using `DefaultObjectSerializer` for two properties: `objectSerializer` is for Dapr's sent and received objects, and `stateSerializer` is for objects to be persisted. 
 
-This example performs multiple operations: 
+This example performs multiple operations:
+* `client.waitForSidecar(...)` for waiting until Dapr sidecar is ready.
 * `client.saveState(...)` for persisting an instance of `MyClass`.
 * `client.getState(...)` operation in order to retrieve back the persisted state using the same key. 
 * `client.executeStateTransaction(...)` operation in order to update existing state and add new state. 

examples/src/main/java/io/dapr/examples/state/StateClient.java

@@ -46,6 +46,10 @@ public String toString() {
    */
   public static void main(String[] args) throws Exception {
     try (DaprClient client = new DaprClientBuilder().build()) {
+      System.out.println("Waiting for Dapr sidecar ...");
+      client.waitForSidecar(10000).block();
+      System.out.println("Dapr sidecar is ready.");
+
       String message = args.length == 0 ? " " : args[0];
 
       MyClass myClass = new MyClass();

sdk/src/main/java/io/dapr/client/DaprClient.java

@@ -32,6 +32,13 @@
  */
 public interface DaprClient extends AutoCloseable {
 
+  /**
+   * Waits for the sidecar, giving up after timeout.
+   * @param timeoutInMilliseconds Timeout in milliseconds to wait for sidecar.
+   * @return a Mono plan of type Void.
+   */
+  Mono<Void> waitForSidecar(int timeoutInMilliseconds);
+
   /**
    * Publish an event.
    *

sdk/src/main/java/io/dapr/client/DaprClientGrpc.java

@@ -26,6 +26,7 @@
 import io.dapr.config.Properties;
 import io.dapr.exceptions.DaprException;
 import io.dapr.serializer.DaprObjectSerializer;
+import io.dapr.utils.NetworkUtils;
 import io.dapr.utils.TypeRef;
 import io.dapr.v1.CommonProtos;
 import io.dapr.v1.DaprGrpc;
@@ -131,6 +132,20 @@ private CommonProtos.StateOptions.StateConcurrency getGrpcStateConcurrency(State
     }
   }
 
+  /**
+   * {@inheritDoc}
+   */
+  @Override
+  public Mono<Void> waitForSidecar(int timeoutInMilliseconds) {
+    return Mono.fromRunnable(() -> {
+      try {
+        NetworkUtils.waitForSocket(Properties.SIDECAR_IP.get(), Properties.GRPC_PORT.get(), timeoutInMilliseconds);
+      } catch (InterruptedException e) {
+        throw new RuntimeException(e);
+      }
+    });
+  }
+
   /**
    * {@inheritDoc}
    */

sdk/src/main/java/io/dapr/client/DaprClientHttp.java

@@ -26,6 +26,7 @@
 import io.dapr.exceptions.DaprException;
 import io.dapr.serializer.DaprObjectSerializer;
 import io.dapr.serializer.DefaultObjectSerializer;
+import io.dapr.utils.NetworkUtils;
 import io.dapr.utils.TypeRef;
 import io.opentelemetry.context.Context;
 import reactor.core.publisher.Mono;
@@ -101,6 +102,20 @@ public class DaprClientHttp extends AbstractDaprClient {
     this(client, new DefaultObjectSerializer(), new DefaultObjectSerializer());
   }
 
+  /**
+   * {@inheritDoc}
+   */
+  @Override
+  public Mono<Void> waitForSidecar(int timeoutInMilliseconds) {
+    return Mono.fromRunnable(() -> {
+      try {
+        NetworkUtils.waitForSocket(Properties.SIDECAR_IP.get(), Properties.HTTP_PORT.get(), timeoutInMilliseconds);
+      } catch (InterruptedException e) {
+        throw new RuntimeException(e);
+      }
+    });
+  }
+
   /**
    * {@inheritDoc}
    */

sdk/src/main/java/io/dapr/utils/NetworkUtils.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) Microsoft Corporation.
+ * Licensed under the MIT License.
+ */
+
+package io.dapr.utils;
+
+import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.net.Socket;
+
+/**
+ * Utility methods for network, internal to Dapr SDK.
+ */
+public final class NetworkUtils {
+
+  private NetworkUtils() {
+  }
+
+  /**
+   * Tries to connect to a socket, retrying every 1 second.
+   * @param host Host to connect to.
+   * @param port Port to connect to.
+   * @param timeoutInMilliseconds Timeout in milliseconds to give up trying.
+   * @throws InterruptedException If retry is interrupted.
+   */
+  public static void waitForSocket(String host, int port, int timeoutInMilliseconds) throws InterruptedException {
+    long started = System.currentTimeMillis();
+    Retry.callWithRetry(() -> {
+      try {
+        try (Socket socket = new Socket()) {
+          // timeout cannot be negative.
+          // zero timeout means infinite, so 1 is the practical minimum.
+          int remainingTimeout = (int) Math.max(1, timeoutInMilliseconds - (System.currentTimeMillis() - started));
+          socket.connect(new InetSocketAddress(host, port), remainingTimeout);
+        }
+      } catch (IOException e) {
+        throw new RuntimeException(e);
+      }
+    }, timeoutInMilliseconds);
+  }
+}

sdk/src/main/java/io/dapr/utils/Retry.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) Microsoft Corporation.
+ * Licensed under the MIT License.
+ */
+
+package io.dapr.utils;
+
+class Retry {
+
+  private static final long RETRY_WAIT_MILLISECONDS = 1000;
+
+  private Retry() {
+  }
+
+  static void callWithRetry(Runnable function, long retryTimeoutMilliseconds) throws InterruptedException {
+    long started = System.currentTimeMillis();
+    while (true) {
+      Throwable exception;
+      try {
+        function.run();
+        return;
+      } catch (Exception e) {
+        exception = e;
+      } catch (AssertionError e) {
+        exception = e;
+      }
+
+      long elapsed = System.currentTimeMillis() - started;
+      if (elapsed >= retryTimeoutMilliseconds) {
+        if (exception instanceof RuntimeException) {
+          throw (RuntimeException)exception;
+        }
+
+        throw new RuntimeException(exception);
+      }
+
+      long remaining = retryTimeoutMilliseconds - elapsed;
+      Thread.sleep(Math.min(remaining, RETRY_WAIT_MILLISECONDS));
+    }
+  }
+}

sdk/src/test/java/io/dapr/client/DaprClientGrpcTest.java

@@ -23,6 +23,7 @@
 import io.dapr.client.domain.State;
 import io.dapr.client.domain.StateOptions;
 import io.dapr.client.domain.TransactionalStateOperation;
+import io.dapr.config.Properties;
 import io.dapr.serializer.DaprObjectSerializer;
 import io.dapr.serializer.DefaultObjectSerializer;
 import io.dapr.utils.TypeRef;
@@ -40,6 +41,8 @@
 
 import java.io.Closeable;
 import java.io.IOException;
+import java.net.ServerSocket;
+import java.net.Socket;
 import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 import java.util.Collections;
@@ -51,7 +54,9 @@
 import static com.google.common.util.concurrent.Futures.addCallback;
 import static com.google.common.util.concurrent.MoreExecutors.directExecutor;
 import static io.dapr.utils.TestUtils.assertThrowsDaprException;
+import static io.dapr.utils.TestUtils.findFreePort;
 import static org.junit.Assert.*;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.argThat;
 import static org.mockito.Mockito.doNothing;
@@ -89,6 +94,30 @@ public void tearDown() throws Exception {
     verifyNoMoreInteractions(closeable);
   }
 
+  @Test
+  public void waitForSidecarTimeout() throws Exception {
+    int port = findFreePort();
+    System.setProperty(Properties.GRPC_PORT.getName(), Integer.toString(port));
+    assertThrows(RuntimeException.class, () -> adapter.waitForSidecar(1).block());
+  }
+
+  @Test
+  public void waitForSidecarTimeoutOK() throws Exception {
+    try (ServerSocket serverSocket = new ServerSocket(0)) {
+      final int port = serverSocket.getLocalPort();
+      System.setProperty(Properties.GRPC_PORT.getName(), Integer.toString(port));
+      Thread t = new Thread(() -> {
+        try {
+          try (Socket socket = serverSocket.accept()) {
+          }
+        } catch (IOException e) {
+        }
+      });
+      t.start();
+      adapter.waitForSidecar(10000).block();
+    }
+  }
+
   @Test
   public void publishEventExceptionThrownTest() {
     when(client.publishEvent(any(DaprProtos.PublishEventRequest.class)))

sdk/src/test/java/io/dapr/client/DaprClientHttpTest.java

@@ -6,8 +6,8 @@
 
 import com.fasterxml.jackson.core.JsonParseException;
 import io.dapr.client.domain.DeleteStateRequestBuilder;
-import io.dapr.client.domain.GetStateRequestBuilder;
 import io.dapr.client.domain.GetBulkStateRequestBuilder;
+import io.dapr.client.domain.GetStateRequestBuilder;
 import io.dapr.client.domain.HttpExtension;
 import io.dapr.client.domain.Response;
 import io.dapr.client.domain.State;
@@ -26,6 +26,8 @@
 import reactor.core.publisher.Mono;
 
 import java.io.IOException;
+import java.net.ServerSocket;
+import java.net.Socket;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Base64;
@@ -35,10 +37,8 @@
 import java.util.Map;
 
 import static io.dapr.utils.TestUtils.assertThrowsDaprException;
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertNotNull;
-import static org.junit.Assert.assertNull;
-import static org.junit.Assert.assertTrue;
+import static io.dapr.utils.TestUtils.findFreePort;
+import static org.junit.Assert.*;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.mockito.Mockito.mock;
 
@@ -65,6 +65,34 @@ public void setUp() {
     okHttpClient = new OkHttpClient.Builder().addInterceptor(mockInterceptor).build();
   }
 
+  @Test
+  public void waitForSidecarTimeout() throws Exception {
+    int port = findFreePort();
+    System.setProperty(Properties.HTTP_PORT.getName(), Integer.toString(port));
+    daprHttp = new DaprHttp(Properties.SIDECAR_IP.get(), port, okHttpClient);
+    DaprClientHttp daprClientHttp = new DaprClientHttp(daprHttp);
+    assertThrows(RuntimeException.class, () -> daprClientHttp.waitForSidecar(1).block());
+  }
+
+  @Test
+  public void waitForSidecarTimeoutOK() throws Exception {
+    try (ServerSocket serverSocket = new ServerSocket(0)) {
+      final int port = serverSocket.getLocalPort();
+      System.setProperty(Properties.HTTP_PORT.getName(), Integer.toString(port));
+      Thread t = new Thread(() -> {
+        try {
+            try (Socket socket = serverSocket.accept()) {
+            }
+        } catch (IOException e) {
+        }
+      });
+      t.start();
+      daprHttp = new DaprHttp(Properties.SIDECAR_IP.get(), port, okHttpClient);
+      DaprClientHttp daprClientHttp = new DaprClientHttp(daprHttp);
+      daprClientHttp.waitForSidecar(10000).block();
+    }
+  }
+
   @Test
   public void publishEventInvokation() {
     mockInterceptor.addRule()

sdk/src/test/java/io/dapr/utils/TestUtils.java

@@ -9,6 +9,11 @@
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.function.Executable;
 
+import java.io.IOException;
+import java.net.ServerSocket;
+import java.util.HashSet;
+import java.util.Set;
+
 public final class TestUtils {
 
   private TestUtils() {}
@@ -46,4 +51,11 @@ public static <T extends Throwable> void assertThrowsDaprException(
     Assertions.assertEquals(expectedErrorCode, daprException.getErrorCode());
     Assertions.assertEquals(expectedErrorMessage, daprException.getMessage());
   }
+
+  public static int findFreePort() throws IOException {
+    try (ServerSocket socket = new ServerSocket(0)) {
+      socket.setReuseAddress(true);
+      return socket.getLocalPort();
+    }
+  }
 }