Jean-Baptiste Queru | d56b88a | 2012-11-07 07:48:57 -0800 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2011 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package com.android.volley; |
| 18 | |
Jean-Baptiste Queru | 6772bce | 2012-11-07 07:51:33 -0800 | [diff] [blame^] | 19 | import android.os.Process; |
| 20 | |
Jean-Baptiste Queru | d56b88a | 2012-11-07 07:48:57 -0800 | [diff] [blame] | 21 | import java.util.concurrent.BlockingQueue; |
| 22 | |
| 23 | /** |
| 24 | * Provides a thread for performing cache triage on a queue of requests. |
| 25 | * |
| 26 | * Requests added to the specified cache queue are resolved from cache. |
| 27 | * Any deliverable response is posted back to the caller via a |
| 28 | * {@link ResponseDelivery}. Cache misses and responses that require |
| 29 | * refresh are enqueued on the specified network queue for processing |
| 30 | * by a {@link NetworkDispatcher}. |
| 31 | */ |
| 32 | @SuppressWarnings("rawtypes") |
| 33 | public class CacheDispatcher extends Thread { |
| 34 | |
| 35 | private static final boolean DEBUG = VolleyLog.DEBUG; |
| 36 | |
| 37 | /** The queue of requests coming in for triage. */ |
| 38 | private final BlockingQueue<Request> mCacheQueue; |
| 39 | |
| 40 | /** The queue of requests going out to the network. */ |
| 41 | private final BlockingQueue<Request> mNetworkQueue; |
| 42 | |
| 43 | /** The cache to read from. */ |
| 44 | private final Cache mCache; |
| 45 | |
| 46 | /** For posting responses. */ |
| 47 | private final ResponseDelivery mDelivery; |
| 48 | |
| 49 | /** Used for telling us to die. */ |
| 50 | private volatile boolean mQuit = false; |
| 51 | |
| 52 | /** |
| 53 | * Creates a new cache triage dispatcher thread. You must call {@link #start()} |
| 54 | * in order to begin processing. |
| 55 | * |
| 56 | * @param cacheQueue Queue of incoming requests for triage |
| 57 | * @param networkQueue Queue to post requests that require network to |
| 58 | * @param cache Cache interface to use for resolution |
| 59 | * @param delivery Delivery interface to use for posting responses |
| 60 | */ |
| 61 | public CacheDispatcher( |
| 62 | BlockingQueue<Request> cacheQueue, BlockingQueue<Request> networkQueue, |
| 63 | Cache cache, ResponseDelivery delivery) { |
| 64 | mCacheQueue = cacheQueue; |
| 65 | mNetworkQueue = networkQueue; |
| 66 | mCache = cache; |
| 67 | mDelivery = delivery; |
| 68 | } |
| 69 | |
| 70 | /** |
| 71 | * Forces this dispatcher to quit immediately. If any requests are still in |
| 72 | * the queue, they are not guaranteed to be processed. |
| 73 | */ |
| 74 | public void quit() { |
| 75 | mQuit = true; |
| 76 | interrupt(); |
| 77 | } |
| 78 | |
| 79 | @Override |
| 80 | public void run() { |
| 81 | if (DEBUG) VolleyLog.v("start new dispatcher"); |
Jean-Baptiste Queru | 6772bce | 2012-11-07 07:51:33 -0800 | [diff] [blame^] | 82 | Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND); |
Jean-Baptiste Queru | d56b88a | 2012-11-07 07:48:57 -0800 | [diff] [blame] | 83 | |
| 84 | // Make a blocking call to initialize the cache. |
| 85 | mCache.initialize(); |
| 86 | |
| 87 | while (true) { |
| 88 | try { |
| 89 | // Get a request from the cache triage queue, blocking until |
| 90 | // at least one is available. |
| 91 | final Request request = mCacheQueue.take(); |
| 92 | request.addMarker("cache-queue-take"); |
| 93 | |
| 94 | // If the request has been canceled, don't bother dispatching it. |
| 95 | if (request.isCanceled()) { |
| 96 | request.finish("cache-discard-canceled"); |
| 97 | continue; |
| 98 | } |
| 99 | |
| 100 | // Attempt to retrieve this item from cache. |
| 101 | Cache.Entry entry = mCache.get(request.getCacheKey()); |
| 102 | if (entry == null) { |
| 103 | request.addMarker("cache-miss"); |
| 104 | // Cache miss; send off to the network dispatcher. |
| 105 | mNetworkQueue.put(request); |
| 106 | continue; |
| 107 | } |
| 108 | |
| 109 | // If it is completely expired, just send it to the network. |
| 110 | if (entry.isExpired()) { |
| 111 | request.addMarker("cache-hit-expired"); |
| 112 | request.setCacheEntry(entry); |
| 113 | mNetworkQueue.put(request); |
| 114 | continue; |
| 115 | } |
| 116 | |
| 117 | // We have a cache hit; parse its data for delivery back to the request. |
| 118 | request.addMarker("cache-hit"); |
| 119 | Response<?> response = request.parseNetworkResponse( |
| 120 | new NetworkResponse(entry.data)); |
| 121 | request.addMarker("cache-hit-parsed"); |
| 122 | |
| 123 | if (!entry.refreshNeeded()) { |
| 124 | // Completely unexpired cache hit. Just deliver the response. |
| 125 | mDelivery.postResponse(request, response); |
| 126 | } else { |
| 127 | // Soft-expired cache hit. We can deliver the cached response, |
| 128 | // but we need to also send the request to the network for |
| 129 | // refreshing. |
| 130 | request.addMarker("cache-hit-refresh-needed"); |
| 131 | request.setCacheEntry(entry); |
| 132 | |
| 133 | // Mark the response as intermediate. |
| 134 | response.intermediate = true; |
| 135 | |
| 136 | // Post the intermediate response back to the user and have |
| 137 | // the delivery then forward the request along to the network. |
| 138 | mDelivery.postResponse(request, response, new Runnable() { |
| 139 | @Override |
| 140 | public void run() { |
| 141 | try { |
| 142 | mNetworkQueue.put(request); |
| 143 | } catch (InterruptedException e) { |
| 144 | // Not much we can do about this. |
| 145 | } |
| 146 | } |
| 147 | }); |
| 148 | } |
| 149 | |
| 150 | } catch (InterruptedException e) { |
| 151 | // We may have been interrupted because it was time to quit. |
| 152 | if (mQuit) { |
| 153 | return; |
| 154 | } |
| 155 | continue; |
| 156 | } |
| 157 | } |
| 158 | } |
| 159 | } |