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