Streaming query support

src/main/java/io/axoniq/axonserver/connector/FlowControl.java

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+/*
+ * Copyright (c) 2020-2022. AxonIQ
+ *
+ * Licensed 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 io.axoniq.axonserver.connector;
+
+/**
+ * Controls the flow of the messages via communication channel. Implementations should send messages only when
+ * requested. Once the cancellation is invoked, implementations should stop sending messages.
+ *
+ * @author Milan Savic
+ * @author Stefan Dragisic
+ * @author Allard Buijze
+ * @since 4.6.0
+ */
+public interface FlowControl {
+
+    /**
+     * Requests the {@code requested} amount of responses to be sent.
+     *
+     * @param requested number of responses to be sent
+     */
+    void request(long requested);
+
+    /**
+     * Cancels response sending.
+     */
+    void cancel();
+}

src/main/java/io/axoniq/axonserver/connector/impl/BufferingReplyChannel.java

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+/*
+ * Copyright (c) 2020-2022. AxonIQ
+ *
+ * Licensed 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 io.axoniq.axonserver.connector.impl;
+
+import io.axoniq.axonserver.connector.ErrorCategory;
+import io.axoniq.axonserver.connector.ReplyChannel;
+import io.axoniq.axonserver.grpc.ErrorMessage;
+
+/**
+ * A {@link ReplyChannel} implementation that uses a given {@link CloseableBuffer buffer} to buffer send, complete and
+ * complete-with-error. {@code ACK}s and {@code NACK}s are delegated via {@code delegate ReplyChannel}.
+ *
+ * @param <T> the type of messages this {@link ReplyChannel} deals with
+ * @author Milan Savic
+ * @author Stefan Dragisic
+ * @author Allard Buijze
+ * @since 4.6.0
+ */
+public class BufferingReplyChannel<T> implements ReplyChannel<T> {
+
+    private final ReplyChannel<T> delegate;
+    private final CloseableBuffer<T> buffer;
+
+    /**
+     * Instantiates this {@link BufferingReplyChannel} with given {@code delegate} and {@code buffer}.
+     *
+     * @param delegate used to delegate {@code ack}s and {@code nack}s
+     * @param buffer   used to buffer sends, completes and completes with error
+     */
+    public BufferingReplyChannel(ReplyChannel<T> delegate, CloseableBuffer<T> buffer) {
+        this.delegate = delegate;
+        this.buffer = buffer;
+    }
+
+    @Override
+    public void send(T outboundMessage) {
+        buffer.put(outboundMessage);
+    }
+
+    @Override
+    public void sendAck() {
+        delegate.sendAck();
+    }
+
+    @Override
+    public void sendNack(ErrorMessage errorMessage) {
+        delegate.sendNack(errorMessage);
+    }
+
+    @Override
+    public void complete() {
+        buffer.close();
+    }
+
+    @Override
+    public void completeWithError(ErrorMessage errorMessage) {
+        buffer.closeExceptionally(errorMessage);
+    }
+
+    @Override
+    public void completeWithError(ErrorCategory errorCategory, String message) {
+        ErrorMessage error = ErrorMessage.newBuilder()
+                                         .setErrorCode(errorCategory.errorCode())
+                                         .setMessage(message)
+                                         .build();
+        buffer.closeExceptionally(error);
+    }
+}

src/main/java/io/axoniq/axonserver/connector/impl/CloseAwareReplyChannel.java

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+/*
+ * Copyright (c) 2020-2022. AxonIQ
+ *
+ * Licensed 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 io.axoniq.axonserver.connector.impl;
+
+import io.axoniq.axonserver.connector.ErrorCategory;
+import io.axoniq.axonserver.connector.ReplyChannel;
+import io.axoniq.axonserver.grpc.ErrorMessage;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * A {@link ReplyChannel} implementation that will trigger a given {@link Runnable action} when it is closed.
+ *
+ * @param <T> the type of messages flowing through this {@link ReplyChannel}
+ * @author Milan Savic
+ * @author Stefan Dragisic
+ * @author Allard Buijze
+ * @since 4.6.0
+ */
+public class CloseAwareReplyChannel<T> implements ReplyChannel<T> {
+
+    private final ReplyChannel<T> delegate;
+    private final Runnable onClose;
+    private final AtomicBoolean closed = new AtomicBoolean();
+
+    /**
+     * Instantiates this {@link ReplyChannel} with given {@code delegate}.
+     *
+     * @param delegate the delegate
+     */
+    public CloseAwareReplyChannel(ReplyChannel<T> delegate) {
+        this(delegate, () -> {
+        });
+    }
+
+    /**
+     * Instantiates this {@link ReplyChannel} with given {@code delegate} and {@code onClose} {@link Runnable} execution
+     * to be executed once the channel is closed.
+     *
+     * @param delegate the delegate
+     * @param onClose  to be executed when channel is closed
+     */
+    public CloseAwareReplyChannel(ReplyChannel<T> delegate, Runnable onClose) {
+        this.delegate = delegate;
+        this.onClose = () -> {
+            closed.set(true);
+            onClose.run();
+        };
+    }
+
+    @Override
+    public void send(T outboundMessage) {
+        delegate.send(outboundMessage);
+    }
+
+    @Override
+    public void sendLast(T outboundMessage) {
+        delegate.sendLast(outboundMessage);
+        onClose.run();
+    }
+
+    @Override
+    public void sendAck() {
+        delegate.sendAck();
+    }
+
+    @Override
+    public void sendNack() {
+        delegate.sendNack();
+    }
+
+    @Override
+    public void sendNack(ErrorMessage errorMessage) {
+        delegate.sendNack(errorMessage);
+    }
+
+    @Override
+    public void complete() {
+        delegate.complete();
+        onClose.run();
+    }
+
+    @Override
+    public void completeWithError(ErrorMessage errorMessage) {
+        delegate.completeWithError(errorMessage);
+        onClose.run();
+    }
+
+    @Override
+    public void completeWithError(ErrorCategory errorCategory, String message) {
+        delegate.completeWithError(errorCategory, message);
+        onClose.run();
+    }
+
+    /**
+     * Indicates whether this {@link ReplyChannel} is closed.
+     *
+     * @return {@code true} if closed, {@code false} otherwise
+     */
+    public boolean isClosed() {
+        return closed.get();
+    }
+}

src/main/java/io/axoniq/axonserver/connector/impl/CloseableBuffer.java

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+/*
+ * Copyright (c) 2020-2022. AxonIQ
+ *
+ * Licensed 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 io.axoniq.axonserver.connector.impl;
+
+import io.axoniq.axonserver.grpc.ErrorMessage;
+
+/**
+ * A {@link CloseableReadonlyBuffer buffer} that can be closed by the producing side.
+ *
+ * @param <T> the type of messages in this buffer
+ * @author Milan Savic
+ * @author Stefan Dragisic
+ * @author Allard Buijze
+ * @since 4.6.0
+ */
+public interface CloseableBuffer<T> extends CloseableReadonlyBuffer<T> {
+
+    /**
+     * Puts a message in this buffer.
+     *
+     * @param message the message to be put in this buffer
+     */
+    void put(T message);
+
+    /**
+     * Closes this buffer from the producing side.
+     */
+    void close();
+
+    /**
+     * Closes this buffer exceptionally from the producing side.
+     *
+     * @param errorMessage an error indicating why this buffer is closed
+     */
+    void closeExceptionally(ErrorMessage errorMessage);
+}

src/main/java/io/axoniq/axonserver/connector/impl/CloseableReadonlyBuffer.java

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+/*
+ * Copyright (c) 2020-2022. AxonIQ
+ *
+ * Licensed 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 io.axoniq.axonserver.connector.impl;
+
+import io.axoniq.axonserver.grpc.ErrorMessage;
+
+import java.util.Optional;
+
+/**
+ * A readonly buffer that can be closed from the producing side.
+ *
+ * @param <T> the type of messages in this buffer
+ * @author Milan Savic
+ * @author Stefan Dragisic
+ * @author Allard Buijze
+ * @since 4.6.0
+ */
+public interface CloseableReadonlyBuffer<T> {
+
+    /**
+     * Polls the message from this buffer. If the returned {@link Optional} is empty, that doesn't mean that this buffer
+     * stays empty forever. The {@link #closed()} method should be consolidated to validate this.
+     *
+     * @return an {@link Optional} with polled message
+     */
+    Optional<T> poll();
+
+    /**
+     * Indicates whether there are messages in the buffer. If this returns {@code false}, that doesn't mean that this
+     * buffer stays empty forever. The {@link #closed()} method should be consolidated to validate this.
+     *
+     * @return {@code true} if buffer is empty, {@code false} otherwise
+     */
+    boolean isEmpty();
+
+    /**
+     * Returns the overall capacity of this buffer.
+     *
+     * @return the overall capacity of this buffer
+     */
+    int capacity();
+
+    /**
+     * Registers an action to be triggered when there is a new message added to the buffer, or the buffer is closed, or
+     * the buffer is closed with an error. The action can check {@link #poll()}, {@link #closed()}, and {@link #error()}
+     * to validate this.
+     *
+     * @param onAvailable to be invoked when there are changes in this buffer
+     */
+    void onAvailable(Runnable onAvailable);
+
+    /**
+     * Indicates whether the buffer is closed by the producing side.
+     *
+     * @return {@code true} if closed, {@code false} otherwise
+     */
+    boolean closed();
+
+    /**
+     * Returns an error from this buffer, if any.
+     *
+     * @return an {@link Optional} of an error, if any
+     */
+    Optional<ErrorMessage> error();
+}