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// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.
package com.azure.storage.blob.changefeed;
import com.azure.core.util.Context;
import com.azure.core.util.FluxUtil;
import com.azure.core.util.logging.ClientLogger;
import com.azure.core.util.paging.ContinuablePage;
import com.azure.core.util.paging.ContinuablePagedFlux;
import com.azure.storage.blob.changefeed.implementation.models.BlobChangefeedEventWrapper;
import com.azure.storage.blob.changefeed.implementation.models.ChangefeedCursor;
import com.azure.storage.blob.changefeed.models.BlobChangefeedEvent;
import com.azure.storage.common.implementation.StorageImplUtils;
import reactor.core.CoreSubscriber;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
import java.time.OffsetDateTime;
import java.util.List;
/**
* Implementation of {@link ContinuablePagedFlux} for Changefeed where the continuation token type is {@link String},
* the element type is {@link BlobChangefeedEvent}, and the page type is {@link BlobChangefeedPagedResponse}.
*/
public final class BlobChangefeedPagedFlux
extends ContinuablePagedFlux {
private static final ClientLogger LOGGER = new ClientLogger(BlobChangefeedPagedFlux.class);
private final Changefeed changefeed;
private static final Integer DEFAULT_PAGE_SIZE = 5000;
private Context context;
/**
* Creates an instance of {@link BlobChangefeedPagedFlux}.
*/
BlobChangefeedPagedFlux(ChangefeedFactory changefeedFactory, OffsetDateTime startTime, OffsetDateTime endTime) {
StorageImplUtils.assertNotNull("changefeedFactory", changefeedFactory);
this.changefeed = changefeedFactory.getChangefeed(startTime, endTime);
}
/**
* Creates an instance of {@link BlobChangefeedPagedFlux}.
*/
BlobChangefeedPagedFlux(ChangefeedFactory changefeedFactory, String cursor) {
StorageImplUtils.assertNotNull("changefeedFactory", changefeedFactory);
this.changefeed = changefeedFactory.getChangefeed(cursor);
}
/**
* Package-private method used only by "BlobChangeFeedPagedIterable" to set context
*/
BlobChangefeedPagedFlux setSubscriberContext(Context context) {
this.context = context;
return this;
}
@Override
public Flux byPage() {
return byPage(null, DEFAULT_PAGE_SIZE);
}
/**
* Unsupported. To resume with the continuation token, call {@link BlobChangefeedAsyncClient#getEvents(String)} or
* {@link BlobChangefeedClient#getEvents(String)}.
* @param continuationToken Unsupported.
* @return Unsupported.
* @throws UnsupportedOperationException if a continuation token is specified.
*/
@Override
public Flux byPage(String continuationToken) {
return byPage(continuationToken, DEFAULT_PAGE_SIZE);
}
@Override
public Flux byPage(int preferredPageSize) {
return byPage(null, preferredPageSize);
}
/**
* Gets a {@link Flux} of {@link ContinuablePage} beginning at the page identified by the Changefeed
* requesting each page to contain the number of elements equal to the preferred page size.
*
* The service may or may not honor the preferred page size therefore the client MUST be prepared to handle
* pages with different page sizes.
*
* @param continuationToken Unsupported. To resume with the continuation token, call
* {@link BlobChangefeedAsyncClient#getEvents(String)} or {@link BlobChangefeedClient#getEvents(String)}.
* @param preferredPageSize The preferred page size.
* @return A {@link Flux} of {@link ContinuablePage}.
* @throws UnsupportedOperationException if a continuation token is specified.
*/
@Override
public Flux byPage(String continuationToken, int preferredPageSize) {
if (continuationToken != null) {
return FluxUtil.pagedFluxError(LOGGER, new UnsupportedOperationException(
"continuationToken not " + "supported. Use client.getEvents(String) to pass in a cursor."));
}
if (preferredPageSize <= 0) {
return FluxUtil.pagedFluxError(LOGGER,
new IllegalArgumentException("preferredPageSize > 0 required but " + "provided: " + preferredPageSize));
}
preferredPageSize = Integer.min(preferredPageSize, DEFAULT_PAGE_SIZE);
return changefeed.getEvents()
/* Window the events to the page size. This takes the Flux and
transforms it into a Flux>, where the internal Fluxes can have at most
preferredPageSize elements. */
.window(preferredPageSize)
/* Convert the BlobChangefeedEventWrappers into BlobChangefeedEvents, and bundle them up with the last
element's cursor. */
.concatMap(eventWrappers -> {
/* 1. cache the Flux to turn it into a HotFlux so we can subscribe to it multiple times. */
Flux cachedEventWrappers = eventWrappers.cache();
/* 2. Get the last element in the flux and grab it's cursor. This will be the continuationToken
returned to the user if they want to get the next page. */
Mono c = cachedEventWrappers.last().map(BlobChangefeedEventWrapper::getCursor);
/* 3. Map all the BlobChangefeedEventWrapper to just the BlobChangefeedEvents, and turn them into
a list. */
Mono> e
= cachedEventWrappers.map(BlobChangefeedEventWrapper::getEvent).collectList();
/* Zip them together into a tuple to construct a BlobChangefeedPagedResponse. */
return Mono.zip(e, c);
})
/* Construct the BlobChangefeedPagedResponse. */
.map(tuple2 -> new BlobChangefeedPagedResponse(tuple2.getT1(), tuple2.getT2()))
.contextWrite(FluxUtil.toReactorContext(this.context));
}
@Override
public void subscribe(CoreSubscriber coreSubscriber) {
changefeed.getEvents().map(BlobChangefeedEventWrapper::getEvent).subscribe(coreSubscriber);
}
}