feat(client): support streaming inserts in Java client

ksqldb-api-client/src/main/java/io/confluent/ksql/api/client/AcksPublisher.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2020 Confluent Inc.
+ *
+ * Licensed under the Confluent Community License (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.confluent.io/confluent-community-license
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OF ANY KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+
+package io.confluent.ksql.api.client;
+
+import org.reactivestreams.Publisher;
+
+/**
+ * A Reactive Streams Publisher that publishes server acknowledgments for rows inserted into
+ * an existing ksqlDB stream via {@link Client#streamInserts(String, Publisher)}.
+ */
+public interface AcksPublisher extends Publisher<InsertAck> {
+
+  /**
+   * Returns whether the {@code AcksPublisher} is complete.
+   *
+   * <p>An {@code AcksPublisher} is complete if the HTTP connection associated with this
+   * {@link Client#streamInserts} request has been ended gracefully. Once complete, the
+   * {@code AcksPublisher} will continue to deliver any remaining rows, then call
+   * {@code onComplete()} on the subscriber, if present.
+   *
+   * @return whether the {@code AcksPublisher} is complete.
+   */
+  boolean isComplete();
+
+  /**
+   * Returns whether the {@code AcksPublisher} is failed.
+   *
+   * <p>An {@code AcksPublisher} is failed if an error is received from the server. Once
+   * failed, {@code onError()} is called on the subscriber, if present, and new calls to
+   * {@code subscribe()} will be rejected.
+   *
+   * @return whether the {@code AcksPublisher} is failed.
+   */
+  boolean isFailed();
+
+}

ksqldb-api-client/src/main/java/io/confluent/ksql/api/client/Client.java

@@ -20,6 +20,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.CompletableFuture;
+import org.reactivestreams.Publisher;
 
 /**
  * A client that connects to a specific ksqlDB server.
@@ -82,6 +83,24 @@ public interface Client {
    */
   CompletableFuture<Void> insertInto(String streamName, KsqlObject row);
 
+  /**
+   * Inserts rows into a ksqlDB stream. Rows to insert are supplied by a
+   * {@code org.reactivestreams.Publisher} and server acknowledgments are exposed similarly.
+   *
+   * <p>The {@code CompletableFuture} will be failed if a non-200 response is received from the
+   * server.
+   *
+   * <p>See {@link InsertsPublisher} for an example publisher that may be passed an argument to
+   * this method.
+   *
+   * @param streamName name of the target stream
+   * @param insertsPublisher the publisher to provide rows to insert
+   * @return a future that completes once the initial server response is received, and contains a
+   *         publisher that publishes server acknowledgments for inserted rows.
+   */
+  CompletableFuture<AcksPublisher>
+      streamInserts(String streamName, Publisher<KsqlObject> insertsPublisher);
+
   /**
    * Terminates a push query with the specified query ID.
    *

ksqldb-api-client/src/main/java/io/confluent/ksql/api/client/InsertAck.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2020 Confluent Inc.
+ *
+ * Licensed under the Confluent Community License (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.confluent.io/confluent-community-license
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OF ANY KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+
+package io.confluent.ksql.api.client;
+
+import org.reactivestreams.Publisher;
+
+/**
+ * An acknowledgment from the ksqlDB server that a row has been successfully inserted into a
+ * ksqlDB stream. See {@link Client#streamInserts(String, Publisher)} for details.
+ */
+public interface InsertAck {
+
+  /**
+   * Returns the corresponding sequence number for this acknowledgment. Sequence numbers start at
+   * zero for each new {@link Client#streamInserts} request.
+   *
+   * @return the sequence number
+   */
+  long seqNum();
+
+}

ksqldb-api-client/src/main/java/io/confluent/ksql/api/client/InsertsPublisher.java

@@ -0,0 +1,198 @@
+/*
+ * Copyright 2020 Confluent Inc.
+ *
+ * Licensed under the Confluent Community License (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.confluent.io/confluent-community-license
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OF ANY KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+
+package io.confluent.ksql.api.client;
+
+import java.util.ArrayDeque;
+import java.util.Objects;
+import java.util.Queue;
+import org.reactivestreams.Publisher;
+import org.reactivestreams.Subscriber;
+import org.reactivestreams.Subscription;
+
+/**
+ * A {@code org.reactivestreams.Publisher} suitable for use with the
+ * {@link Client#streamInserts(String, Publisher)} method. Rows for insertion are passed to the
+ * publisher via the {@link #accept(KsqlObject)} method, and buffered for delivery once the
+ * {@link Client#streamInserts} request is made and the server-side subscriber has been subscribed.
+ */
+public class InsertsPublisher implements Publisher<KsqlObject> {
+
+  /**
+   * The buffer max size indicator value used by the default constructor. See
+   * {@link #InsertsPublisher(int)} for how this value is used.
+   */
+  public static final int DEFAULT_BUFFER_MAX_SIZE = 200;
+
+  private Subscriber<? super KsqlObject> subscriber;
+  private final Queue<KsqlObject> buffer = new ArrayDeque<>();
+  private final int bufferMaxSize;
+  private long demand;
+  private Runnable drainHandler;
+  private volatile boolean cancelled;
+  private boolean complete;
+  private boolean shouldSendComplete;
+  private boolean sentComplete;
+
+  /**
+   * Creates an {@code InsertsPublisher}.
+   */
+  public InsertsPublisher() {
+    this(DEFAULT_BUFFER_MAX_SIZE);
+  }
+
+  /**
+   * Creates an {@code InsertsPublisher}.
+   *
+   * @param bufferMaxSize Indicative max number of elements to store in the buffer. Note that this
+   *                      value is not enforced, but it used to determine what to return from the
+   *                      {@link #accept(KsqlObject)} method so the caller can stop sending more
+   *                      rows and set a drainHandler to be notified when the buffer is cleared
+   */
+  public InsertsPublisher(final int bufferMaxSize) {
+    this.bufferMaxSize = bufferMaxSize;
+  }
+
+  /**
+   * Provides a new row for insertion. The publisher will attempt to deliver it to server endpoint,
+   * once the {@link Client#streamInserts} request has been made. The publisher will buffer the row
+   * internally if it can't deliver it immediately. Note that the row will be buffered even if the
+   * buffer is 'full', i.e., if number of elements is at least {@code bufferMaxSize}, as the
+   * {@code bufferMaxSize} value is not a hard limit. See {@link #InsertsPublisher(int)} for more.
+   *
+   * @param row the row to insert
+   * @return whether the internal buffer is 'full', i.e., if number of elements is at least
+   *         {@code bufferMaxSize}.
+   */
+  public synchronized boolean accept(final KsqlObject row) {
+    if (complete || sentComplete) {
+      throw new IllegalStateException("Cannot call accept after complete is called");
+    }
+    if (!cancelled) {
+      if (demand == 0) {
+        buffer.add(row);
+      } else {
+        doOnNext(row);
+      }
+    }
+    return buffer.size() >= bufferMaxSize;
+  }
+
+  /**
+   * Sets a drain handler on the publisher. The drain handler will be called if after a row is
+   * delivered there are zero elements buffered internally and there is demand from the subscriber
+   * for more elements. Drain handlers may be used in combination with the return value from
+   * {@link #accept(KsqlObject)} to ensure the publisher's buffer does not grow too large.
+   *
+   * <p>Drain handlers are one shot handlers; after a drain handler is called it
+   * will never be called again. Instead, the caller should set a new drain handler for subsequent
+   * use.
+   *
+   * @param handler the drain handler
+   */
+  public synchronized void drainHandler(final Runnable handler) {
+    if (drainHandler != null) {
+      throw new IllegalStateException("drainHandler already set");
+    }
+    this.drainHandler = Objects.requireNonNull(handler);
+  }
+
+  /**
+   * Marks the incoming stream of elements as complete. This means no further rows will be accepted
+   * by the publisher and the {@link Client#streamInserts} connection will be closed once any
+   * buffered rows have been delivered for insertion.
+   */
+  public synchronized void complete() {
+    if (complete) {
+      return;
+    }
+    complete = true;
+    if (buffer.isEmpty() && subscriber != null) {
+      sendComplete();
+    } else {
+      shouldSendComplete = true;
+    }
+  }
+
+  @Override
+  public synchronized void subscribe(final Subscriber<? super KsqlObject> subscriber) {
+    if (this.subscriber != null) {
+      throw new IllegalStateException(
+          "Cannot subscribe a new subscriber: A subscriber is already present.");
+    }
+
+    this.subscriber = subscriber;
+    subscriber.onSubscribe(new Subscription() {
+      @Override
+      public void request(final long l) {
+        doRequest(l);
+      }
+
+      @Override
+      public void cancel() {
+        doCancel();
+      }
+    });
+  }
+
+  private synchronized void doRequest(final long n) {
+    if (n <= 0) {
+      subscriber.onError((new IllegalArgumentException("Amount requested must be > 0")));
+    } else if (demand + n < 1) {
+      // Catch overflow and set to "infinite"
+      demand = Long.MAX_VALUE;
+      maybeSend();
+    } else {
+      demand += n;
+      maybeSend();
+    }
+  }
+
+  private synchronized void doCancel() {
+    cancelled = true;
+    subscriber = null;
+  }
+
+  private void maybeSend() {
+    while (demand > 0 && !buffer.isEmpty()) {
+      final KsqlObject val = buffer.poll();
+      doOnNext(val);
+    }
+
+    if (buffer.isEmpty()) {
+      if (shouldSendComplete) {
+        sendComplete();
+        shouldSendComplete = false;
+      } else if (demand > 0 && drainHandler != null) {
+        drainHandler.run();
+        drainHandler = null;
+      }
+    }
+  }
+
+  private void doOnNext(final KsqlObject row) {
+    subscriber.onNext(row);
+
+    // If demand == Long.MAX_VALUE this means "infinite demand"
+    if (demand != Long.MAX_VALUE) {
+      demand--;
+    }
+  }
+
+  private void sendComplete() {
+    sentComplete = true;
+    subscriber.onComplete();
+  }
+}

ksqldb-api-client/src/main/java/io/confluent/ksql/api/client/impl/AcksPublisherImpl.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2020 Confluent Inc.
+ *
+ * Licensed under the Confluent Community License (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.confluent.io/confluent-community-license
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OF ANY KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+
+package io.confluent.ksql.api.client.impl;
+
+import io.confluent.ksql.api.client.AcksPublisher;
+import io.confluent.ksql.api.client.InsertAck;
+import io.confluent.ksql.reactive.BufferedPublisher;
+import io.vertx.core.Context;
+
+public class AcksPublisherImpl extends BufferedPublisher<InsertAck> implements AcksPublisher {
+
+  public AcksPublisherImpl(final Context context) {
+    super(context);
+  }
+
+  @Override
+  public boolean isComplete() {
+    return super.isComplete();
+  }
+
+  @Override
+  public boolean isFailed() {
+    return super.isFailed();
+  }
+
+  public void handleError(final Exception e) {
+    sendError(e);
+  }
+}