io.axoniq.axonserver.connector.impl.SynchronizedRequestStream Maven / Gradle / Ivy

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Connector module providing infrastructure components that connect to AxonServer.

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/*
 * Copyright (c) 2021. 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.grpc.stub.ClientCallStreamObserver;

import java.util.concurrent.atomic.AtomicBoolean;

/**
 * Lock-based synchronized implementation of a {@link ClientCallStreamObserver}. Acts as a wrapper of another {@code
 * ClientCallStreamObserver}, to which all of operations will be delegated, adding synchronization logic to {@link
 * #onNext(Object)}, {@link #onCompleted()} and {@link #onError(Throwable)}.
 *
 * @param  the type of value returned by this stream
 */
public class SynchronizedRequestStream extends ClientCallStreamObserver {

    private final ClientCallStreamObserver delegate;
    private final AtomicBoolean lock = new AtomicBoolean(false);
    private final AtomicBoolean halfClosed = new AtomicBoolean(false);

    /**
     * Instantiate a {@link SynchronizedRequestStream}, delegating all operations to the given {@code requestStream}
     *
     * @param requestStream the {@link ClientCallStreamObserver} to delegate method invocations to
     */
    public SynchronizedRequestStream(ClientCallStreamObserver requestStream) {
        delegate = requestStream;
    }

    @Override
    public void cancel(String message, Throwable cause) {
        halfClosed.set(true);
        delegate.cancel(message, cause);
    }

    @Override
    public boolean isReady() {
        return delegate.isReady();
    }

    @Override
    public void setOnReadyHandler(Runnable onReadyHandler) {
        delegate.setOnReadyHandler(onReadyHandler);
    }

    @Override
    public void disableAutoInboundFlowControl() {
        delegate.disableAutoInboundFlowControl();
    }

    @Override
    public void request(int count) {
        delegate.request(count);
    }

    @Override
    public void setMessageCompression(boolean enable) {
        delegate.setMessageCompression(enable);
    }

    @Override
    public void onNext(T value) {
        inLock(() -> delegate.onNext(value));
    }

    @Override
    public void disableAutoRequestWithInitial(int request) {
        delegate.disableAutoRequestWithInitial(request);
    }

    @Override
    public void onError(Throwable t) {
        inLock(() -> {
            delegate.onError(t);
            halfClosed.set(true);
        });
    }

    @Override
    public void onCompleted() {
        inLock(() -> {
            delegate.onCompleted();
            halfClosed.set(true);
        });
    }

    private void inLock(Runnable action) {
        while (!lock.compareAndSet(false, true)) {
            Thread.yield();
        }
        try {
            if (!halfClosed.get()) {
                action.run();
            }
        } finally {
            lock.set(false);
        }
    }
}