Solace Read connector: UnboundedSource and UnboundedReader

sdks/java/io/solace/build.gradle

@@ -32,7 +32,10 @@ dependencies {
     implementation enforcedPlatform(library.java.google_cloud_platform_libraries_bom)
     implementation library.java.vendored_guava_32_1_2_jre
     implementation project(path: ":sdks:java:core", configuration: "shadow")
+    implementation library.java.slf4j_api
     implementation library.java.joda_time
     implementation library.java.solace
     implementation project(":sdks:java:extensions:avro")
+    implementation library.java.avro
+    permitUnusedDeclared library.java.avro
 }

sdks/java/io/solace/src/main/java/org/apache/beam/sdk/io/solace/broker/MessageReceiver.java

@@ -0,0 +1,59 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.beam.sdk.io.solace.broker;
+
+import com.solacesystems.jcsmp.BytesXMLMessage;
+import java.io.IOException;
+
+/**
+ * Interface for receiving messages from a Solace broker.
+ *
+ * <p>Implementations of this interface are responsible for managing the connection to the broker
+ * and for receiving messages from the broker.
+ */
+public interface MessageReceiver {
+  /**
+   * Starts the message receiver.
+   *
+   * <p>This method is called in the {@link
+   * org.apache.beam.sdk.io.solace.read.UnboundedSolaceReader#start()} method.
+   */
+  void start();
+
+  /**
+   * Returns {@literal true} if the message receiver is closed, {@literal false} otherwise.
+   *
+   * <p>A message receiver is closed when it is no longer able to receive messages.
+   */
+  boolean isClosed();
+
+  /**
+   * Receives a message from the broker.
+   *
+   * <p>This method will block until a message is received.
+   */
+  BytesXMLMessage receive() throws IOException;
+
+  /**
+   * Test clients may return {@literal true} to signal that all expected messages have been pulled
+   * and the test may complete. Real clients should always return {@literal false}.
+   */
+  default boolean isEOF() {
+    return false;
+  }
+}

sdks/java/io/solace/src/main/java/org/apache/beam/sdk/io/solace/broker/SempClient.java

@@ -0,0 +1,49 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.beam.sdk.io.solace.broker;
+
+import com.solacesystems.jcsmp.Queue;
+import java.io.IOException;
+import java.io.Serializable;
+
+/**
+ * This interface defines methods for interacting with a Solace message broker using the Solace
+ * Element Management Protocol (SEMP). SEMP provides a way to manage and monitor various aspects of
+ * the broker, including queues and topics.
+ */
+public interface SempClient extends Serializable {
+
+  /**
+   * Determines if the specified queue is non-exclusive. In Solace, non-exclusive queues allow
+   * multiple consumers to receive messages from the queue.
+   */
+  boolean isQueueNonExclusive(String queueName) throws IOException;
+
+  /**
+   * This is only called when a user requests to read data from a topic. This method creates a new
+   * queue on the Solace broker and associates it with the specified topic. This ensures that
+   * messages published to the topic are delivered to the queue, allowing consumers to receive them.
+   */
+  Queue createQueueForTopic(String queueName, String topicName) throws IOException;
+
+  /**
+   * Retrieves the size of the backlog (in bytes) for the specified queue. The backlog represents
+   * the amount of data in messages that are waiting to be delivered to consumers.
+   */
+  long getBacklogBytes(String queueName) throws IOException;
+}

sdks/java/io/solace/src/main/java/org/apache/beam/sdk/io/solace/broker/SempClientFactory.java

@@ -23,4 +23,13 @@
  * This interface serves as a blueprint for creating SempClient objects, which are used to interact
  * with a Solace message broker using the Solace Element Management Protocol (SEMP).
  */
-public interface SempClientFactory extends Serializable {}
+public interface SempClientFactory extends Serializable {
+
+  /**
+   * This method is the core of the factory interface. It defines how to construct and return a
+   * SempClient object. Implementations of this interface will provide the specific logic for
+   * creating a client instance, which might involve connecting to the broker, handling
+   * authentication, and configuring other settings.
+   */
+  SempClient create();
+}

sdks/java/io/solace/src/main/java/org/apache/beam/sdk/io/solace/broker/SessionService.java

@@ -0,0 +1,50 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.beam.sdk.io.solace.broker;
+
+import java.io.Serializable;
+
+/**
+ * The SessionService interface provides a set of methods for managing a session with the Solace
+ * messaging system. It allows for establishing a connection, creating a message-receiver object,
+ * checking if the connection is closed or not, and gracefully closing the session.
+ */
+public interface SessionService extends Serializable {
+
+  /**
+   * Establishes a connection to the service. This could involve providing connection details like
+   * host, port, VPN name, username, and password.
+   */
+  void connect();
+
+  /** Gracefully closes the connection to the service. */
+  void close();
+
+  /**
+   * Checks whether the connection to the service is currently closed. This method is called when an
+   * `UnboundedSolaceReader` is starting to read messages - a session will be created if this
+   * returns true.
+   */
+  boolean isClosed();
+
+  /**
+   * Creates a MessageReceiver object for receiving messages from Solace. Typically, this object is
+   * created from the session instance.
+   */
+  MessageReceiver createReceiver();
+}

sdks/java/io/solace/src/main/java/org/apache/beam/sdk/io/solace/broker/SessionServiceFactory.java

@@ -23,4 +23,11 @@
  * This abstract class serves as a blueprint for creating `SessionService` objects. It introduces a
  * queue property and mandates the implementation of a create() method in concrete subclasses.
  */
-public abstract class SessionServiceFactory implements Serializable {}
+public abstract class SessionServiceFactory implements Serializable {
+
+  /**
+   * This is the core method that subclasses must implement. It defines how to construct and return
+   * a SessionService object.
+   */
+  public abstract SessionService create();
+}

sdks/java/io/solace/src/main/java/org/apache/beam/sdk/io/solace/read/SolaceCheckpointMark.java

@@ -23,17 +23,21 @@
 import java.util.List;
 import java.util.Objects;
 import java.util.concurrent.atomic.AtomicBoolean;
+import org.apache.beam.sdk.annotations.Internal;
 import org.apache.beam.sdk.coders.DefaultCoder;
 import org.apache.beam.sdk.extensions.avro.coders.AvroCoder;
 import org.apache.beam.sdk.io.UnboundedSource;
+import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.annotations.VisibleForTesting;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
 /**
  * Checkpoint for an unbounded Solace source. Consists of the Solace messages waiting to be
  * acknowledged.
  */
 @DefaultCoder(AvroCoder.class)
-class SolaceCheckpointMark implements UnboundedSource.CheckpointMark {
+@Internal
+@VisibleForTesting
+public class SolaceCheckpointMark implements UnboundedSource.CheckpointMark {
   private transient AtomicBoolean activeReader;
   // BytesXMLMessage is not serializable so if a job restarts from the checkpoint, we cannot retry
   // these messages here. We relay on Solace's retry mechanism.