io.axoniq.axonserver.connector.query.SubscriptionQueryResult Maven / Gradle / Ivy

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Connector module providing infrastructure components that connect to AxonServer.

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/*
 * Copyright (c) 2020. 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.query;

import io.axoniq.axonserver.connector.ResultStream;
import io.axoniq.axonserver.grpc.query.QueryResponse;
import io.axoniq.axonserver.grpc.query.QueryUpdate;

import java.util.concurrent.CompletableFuture;

/**
 * Interface describing the results of a subscription query. This type of query consists of an initial response,
 * representing the state of a projection at the start of the query, and a stream of updates which represent the updates
 * to the model since the query started.
 */
public interface SubscriptionQueryResult {

    /**
     * Returns a CompletableFuture that completes when the initial result of the query is available. If an error
     * occurred while querying, the CompletableFuture completes exceptionally.
     * 
     * Invoking this method will send a request for the initial result, if that hasn't been requested before. Subsequent
     * invocations of this method will return the same CompletableFuture instance.
     *
     * @return a CompletableFuture that completes with the initial result of the subscription query
     */
    CompletableFuture initialResult();

    /**
     * Returns the stream of updates to the queried projection. The stream can be read in a blocking and non-blocking
     * fashion, as desired by downstream processes.
     * 
     * Multiple invocation of this method will return the same stream instance.
     *
     * @return a stream of updates
     */
    ResultStream updates();
}