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/*
* Copyright (C) 2020 The Android Open Source Project
*
* 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 com.android.volley;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.BlockingQueue;
/**
* Callback to notify the caller when the network request returns. Valid responses can be used by
* all duplicate requests.
*/
class WaitingRequestManager implements Request.NetworkRequestCompleteListener {
/**
* Staging area for requests that already have a duplicate request in flight.
*
* <ul>
* <li>containsKey(cacheKey) indicates that there is a request in flight for the given cache
* key.
* <li>get(cacheKey) returns waiting requests for the given cache key. The in flight request
* is <em>not</em> contained in that list. Is null if no requests are staged.
* </ul>
*/
private final Map<String, List<Request<?>>> mWaitingRequests = new HashMap<>();
private final ResponseDelivery mResponseDelivery;
/**
* RequestQueue that is passed in by the AsyncRequestQueue. This is null when this instance is
* initialized by the {@link CacheDispatcher}
*/
@Nullable private final RequestQueue mRequestQueue;
/**
* CacheDispacter that is passed in by the CacheDispatcher. This is null when this instance is
* initialized by the {@link AsyncRequestQueue}
*/
@Nullable private final CacheDispatcher mCacheDispatcher;
/**
* BlockingQueue that is passed in by the CacheDispatcher. This is null when this instance is
* initialized by the {@link AsyncRequestQueue}
*/
@Nullable private final BlockingQueue<Request<?>> mNetworkQueue;
WaitingRequestManager(@NonNull RequestQueue requestQueue) {
mRequestQueue = requestQueue;
mResponseDelivery = mRequestQueue.getResponseDelivery();
mCacheDispatcher = null;
mNetworkQueue = null;
}
WaitingRequestManager(
@NonNull CacheDispatcher cacheDispatcher,
@NonNull BlockingQueue<Request<?>> networkQueue,
ResponseDelivery responseDelivery) {
mRequestQueue = null;
mResponseDelivery = responseDelivery;
mCacheDispatcher = cacheDispatcher;
mNetworkQueue = networkQueue;
}
/** Request received a valid response that can be used by other waiting requests. */
@Override
public void onResponseReceived(Request<?> request, Response<?> response) {
if (response.cacheEntry == null || response.cacheEntry.isExpired()) {
onNoUsableResponseReceived(request);
return;
}
String cacheKey = request.getCacheKey();
List<Request<?>> waitingRequests;
synchronized (this) {
waitingRequests = mWaitingRequests.remove(cacheKey);
}
if (waitingRequests != null) {
if (VolleyLog.DEBUG) {
VolleyLog.v(
"Releasing %d waiting requests for cacheKey=%s.",
waitingRequests.size(), cacheKey);
}
// Process all queued up requests.
for (Request<?> waiting : waitingRequests) {
mResponseDelivery.postResponse(waiting, response);
}
}
}
/** No valid response received from network, release waiting requests. */
@Override
public synchronized void onNoUsableResponseReceived(Request<?> request) {
String cacheKey = request.getCacheKey();
List<Request<?>> waitingRequests = mWaitingRequests.remove(cacheKey);
if (waitingRequests != null && !waitingRequests.isEmpty()) {
if (VolleyLog.DEBUG) {
VolleyLog.v(
"%d waiting requests for cacheKey=%s; resend to network",
waitingRequests.size(), cacheKey);
}
Request<?> nextInLine = waitingRequests.remove(0);
mWaitingRequests.put(cacheKey, waitingRequests);
nextInLine.setNetworkRequestCompleteListener(this);
// RequestQueue will be non-null if this instance was created in AsyncRequestQueue.
if (mRequestQueue != null) {
// Will send the network request from the RequestQueue.
mRequestQueue.sendRequestOverNetwork(nextInLine);
} else if (mCacheDispatcher != null && mNetworkQueue != null) {
// If we're not using the AsyncRequestQueue, then submit it to the network queue.
try {
mNetworkQueue.put(nextInLine);
} catch (InterruptedException iex) {
VolleyLog.e("Couldn't add request to queue. %s", iex.toString());
// Restore the interrupted status of the calling thread (i.e. NetworkDispatcher)
Thread.currentThread().interrupt();
// Quit the current CacheDispatcher thread.
mCacheDispatcher.quit();
}
}
}
}
/**
* For cacheable requests, if a request for the same cache key is already in flight, add it to a
* queue to wait for that in-flight request to finish.
*
* @return whether the request was queued. If false, we should continue issuing the request over
* the network. If true, we should put the request on hold to be processed when the
* in-flight request finishes.
*/
synchronized boolean maybeAddToWaitingRequests(Request<?> request) {
String cacheKey = request.getCacheKey();
// Insert request into stage if there's already a request with the same cache key
// in flight.
if (mWaitingRequests.containsKey(cacheKey)) {
// There is already a request in flight. Queue up.
List<Request<?>> stagedRequests = mWaitingRequests.get(cacheKey);
if (stagedRequests == null) {
stagedRequests = new ArrayList<>();
}
request.addMarker("waiting-for-response");
stagedRequests.add(request);
mWaitingRequests.put(cacheKey, stagedRequests);
if (VolleyLog.DEBUG) {
VolleyLog.d("Request for cacheKey=%s is in flight, putting on hold.", cacheKey);
}
return true;
} else {
// Insert 'null' queue for this cacheKey, indicating there is now a request in
// flight.
mWaitingRequests.put(cacheKey, null);
request.setNetworkRequestCompleteListener(this);
if (VolleyLog.DEBUG) {
VolleyLog.d("new request, sending to network %s", cacheKey);
}
return false;
}
}
}
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