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Batcher.java
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Batcher.java
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/*
* Copyright 2019 Google LLC
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google LLC nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package com.google.api.gax.batching;
import com.google.api.core.ApiFuture;
import com.google.api.core.BetaApi;
import com.google.api.core.InternalExtensionOnly;
import com.google.api.gax.rpc.ApiCallContext;
/**
* Represents a batching context where individual elements will be accumulated and flushed in a
* large batch request at some point in the future. The buffered elements can be flushed manually or
* when triggered by an internal threshold. This is intended to be used for high throughput
* scenarios at the cost of latency.
*
* <p>Batcher instances are not thread safe. To use across different threads, create a new Batcher
* instance per thread.
*
* @param <ElementT> The type of each individual element to be batched.
* @param <ElementResultT> The type of the result for each individual element.
*/
@BetaApi("The surface for batching is not stable yet and may change in the future.")
@InternalExtensionOnly
public interface Batcher<ElementT, ElementResultT> extends AutoCloseable {
/** {@link ApiCallContext.Key} for tracking batch total throttled time */
ApiCallContext.Key<Long> THROTTLED_TIME_KEY = ApiCallContext.Key.create("total_throttled_time");
/**
* Queues the passed in element to be sent at some point in the future.
*
* <p>The element will be sent as part of a larger batch request at some point in the future. The
* returned {@link ApiFuture} will be resolved once the result for the element has been extracted
* from the batch response.
*
* <p>Note: Cancelling returned result simply marks the future cancelled, It would not stop the
* batch request.
*/
ApiFuture<ElementResultT> add(ElementT entry);
/**
* Synchronously sends any pending elements as a batch and waits for all outstanding batches to be
* complete.
*/
void flush() throws InterruptedException;
/**
* Sends accumulated elements asynchronously for batching.
*
* <p>Note: This method can be invoked concurrently unlike {@link #add} and {@link #close}, which
* can only be called from a single user thread. Please take caution to avoid race condition.
*/
void sendOutstanding();
/**
* Closes this Batcher by preventing new elements from being added, and then flushing the existing
* elements.
*/
@Override
void close() throws InterruptedException;
/**
* Closes this Batcher by preventing new elements from being added, and then sending outstanding
* elements. The returned future will be resolved when the last element completes
*/
ApiFuture<Void> closeAsync();
}