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/*
* Copyright 2017 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
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package com.google.api.gax.longrunning;
import com.google.api.core.ApiFuture;
import com.google.api.gax.retrying.RetryingFuture;
import java.util.concurrent.ExecutionException;
/**
* An ApiFuture which tracks polling of a service. The polling is done periodically, based on the
* {@link com.google.api.gax.retrying.TimedRetryAlgorithm}.
*
* Implementations are expected to be thread-safe.
*/
public interface OperationFuture extends ApiFuture {
/**
* Returns the value of the name of the operation from the initial operation object returned from
* the initial call to start the operation. Blocks if the initial call to start the operation
* hasn't returned yet.
*/
String getName() throws InterruptedException, ExecutionException;
/**
* Returns the {@link OperationSnapshot} future of the initial request which started this {@code
* OperationFuture}.
*/
ApiFuture getInitialFuture();
/** Returns the {@link RetryingFuture} which continues to poll {@link OperationSnapshot}. */
RetryingFuture getPollingFuture();
/**
* Peeks at the metadata of the operation tracked by this {@link OperationFuture}. If the initial
* future hasn't completed yet this method returns {@code null}, otherwise it returns the latest
* metadata returned from the server (i.e. either initial call metadata or the metadata received
* from the latest completed poll iteration).
*
* If not {@code null}, the returned result is guaranteed to be an already completed future, so
* {@link ApiFuture#isDone()} will always be {@code true} and {@link ApiFuture#get()} will always
* be non-blocking.
*
*
Note, some APIs may return {@code null} in metadata response message. In such cases this
* method may return a non-null future whose {@code get()} method will return {@code null}. This
* behavior is API specific an should be considered a valid case, which indicates that the recent
* poll request has completed, but no specific metadata was provided by the server (i.e. most
* probably providing metadata for an intermediate result is not supported by the server).
*
*
This method should be used to check operation progress without blocking current thread.
* Since this method returns metadata from the latest completed poll, it is potentially slightly
* stale compared to the most recent data. To get the most recent data and/or get notified when
* the current scheduled poll request completes use the {@link #getMetadata()} method instead.
*
*
If this operation future is completed, this method always returns the metadata from the last
* poll request (which completed the operation future).
*
*
If this operation future failed, this method may (depending on the failure type) return a
* non-failing future, representing the metadata from the last poll request (which failed the
* operation future).
*
*
If this operation future was cancelled, this method returns a canceled metatata future as
* well.
*
*
In general this method behaves similarly to {@link RetryingFuture#peekAttemptResult()}.
*/
ApiFuture peekMetadata();
/**
* Gets the metadata of the operation tracked by this {@link OperationFuture}. This method returns
* the current poll metadata result (or the initial call metadata if it hasn't completed yet). The
* returned future completes once the current scheduled poll request (or the initial request if it
* hasn't completed yet) is executed and response is received from the server. The time when the
* polling request is executed is determined by the underlying polling algorithm.
*
* Adding direct executor (same thread) callbacks to the future returned by this method is
* strongly not recommended, since the future is resolved under retrying future's internal lock
* and may affect the operation polling process. Adding separate thread callbacks is ok.
*
*
Note, some APIs may return {@code null} in metadata response message. In such cases this
* method may return a non-null future whose {@code get()} method will return {@code null}. This
* behavior is API specific an should be considered a valid case, which indicates that the recent
* poll request has completed, but no specific metadata was provided by the server. (i.e. most
* probably providing metadata for an intermediate result is not supported by the server).
*
*
In most cases this method returns a future which is not completed yet, so calling {@link
* ApiFuture#get()} is a potentially blocking operation. To get metadata without blocking the
* current thread use the {@link #peekMetadata()} method instead.
*
*
If this operation future is completed, this method always returns the metadata from the last
* poll request (which completed the operation future).
*
*
If this operation future failed, this method may (depending on the failure type) return a
* non-failing future, representing the metadata from the last poll request (which failed the
* operation future).
*
*
If this operation future was cancelled, this method returns a canceled metatata future as
* well.
*
*
In general this method behaves similarly to {@link RetryingFuture#getAttemptResult()}.
*/
ApiFuture getMetadata();
}