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
17package com.android.volley;
18
19import android.annotation.TargetApi;
20import android.net.TrafficStats;
21import android.os.Build;
22import android.os.Process;
23import android.os.SystemClock;
24
25import java.util.concurrent.BlockingQueue;
26
27/**
28 * Provides a thread for performing network dispatch from a queue of requests.
29 *
30 * Requests added to the specified queue are processed from the network via a
31 * specified {@link Network} interface. Responses are committed to cache, if
32 * eligible, using a specified {@link Cache} interface. Valid responses and
33 * errors are posted back to the caller via a {@link ResponseDelivery}.
34 */
35public class NetworkDispatcher extends Thread {
36    /** The queue of requests to service. */
37    private final BlockingQueue<Request<?>> mQueue;
38    /** The network interface for processing requests. */
39    private final Network mNetwork;
40    /** The cache to write to. */
41    private final Cache mCache;
42    /** For posting responses and errors. */
43    private final ResponseDelivery mDelivery;
44    /** Used for telling us to die. */
45    private volatile boolean mQuit = false;
46
47    /**
48     * Creates a new network dispatcher thread.  You must call {@link #start()}
49     * in order to begin processing.
50     *
51     * @param queue Queue of incoming requests for triage
52     * @param network Network interface to use for performing requests
53     * @param cache Cache interface to use for writing responses to cache
54     * @param delivery Delivery interface to use for posting responses
55     */
56    public NetworkDispatcher(BlockingQueue<Request<?>> queue,
57            Network network, Cache cache,
58            ResponseDelivery delivery) {
59        mQueue = queue;
60        mNetwork = network;
61        mCache = cache;
62        mDelivery = delivery;
63    }
64
65    /**
66     * Forces this dispatcher to quit immediately.  If any requests are still in
67     * the queue, they are not guaranteed to be processed.
68     */
69    public void quit() {
70        mQuit = true;
71        interrupt();
72    }
73
74    @TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
75    private void addTrafficStatsTag(Request<?> request) {
76        // Tag the request (if API >= 14)
77        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
78            TrafficStats.setThreadStatsTag(request.getTrafficStatsTag());
79        }
80    }
81
82    @Override
83    public void run() {
84        Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);
85        while (true) {
86            long startTimeMs = SystemClock.elapsedRealtime();
87            Request<?> request;
88            try {
89                // Take a request from the queue.
90                request = mQueue.take();
91            } catch (InterruptedException e) {
92                // We may have been interrupted because it was time to quit.
93                if (mQuit) {
94                    return;
95                }
96                continue;
97            }
98
99            try {
100                request.addMarker("network-queue-take");
101
102                // If the request was cancelled already, do not perform the
103                // network request.
104                if (request.isCanceled()) {
105                    request.finish("network-discard-cancelled");
106                    continue;
107                }
108
109                addTrafficStatsTag(request);
110
111                // Perform the network request.
112                NetworkResponse networkResponse = mNetwork.performRequest(request);
113                request.addMarker("network-http-complete");
114
115                // If the server returned 304 AND we delivered a response already,
116                // we're done -- don't deliver a second identical response.
117                if (networkResponse.notModified && request.hasHadResponseDelivered()) {
118                    request.finish("not-modified");
119                    continue;
120                }
121
122                // Parse the response here on the worker thread.
123                Response<?> response = request.parseNetworkResponse(networkResponse);
124                request.addMarker("network-parse-complete");
125
126                // Write to cache if applicable.
127                // TODO: Only update cache metadata instead of entire record for 304s.
128                if (request.shouldCache() && response.cacheEntry != null) {
129                    mCache.put(request.getCacheKey(), response.cacheEntry);
130                    request.addMarker("network-cache-written");
131                }
132
133                // Post the response back.
134                request.markDelivered();
135                mDelivery.postResponse(request, response);
136            } catch (VolleyError volleyError) {
137                volleyError.setNetworkTimeMs(SystemClock.elapsedRealtime() - startTimeMs);
138                parseAndDeliverNetworkError(request, volleyError);
139            } catch (Exception e) {
140                VolleyLog.e(e, "Unhandled exception %s", e.toString());
141                VolleyError volleyError = new VolleyError(e);
142                volleyError.setNetworkTimeMs(SystemClock.elapsedRealtime() - startTimeMs);
143                mDelivery.postError(request, volleyError);
144            }
145        }
146    }
147
148    private void parseAndDeliverNetworkError(Request<?> request, VolleyError error) {
149        error = request.parseNetworkError(error);
150        mDelivery.postError(request, error);
151    }
152}
153