1/*
2 * Copyright (C) 2015 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.messaging.util;
18
19import android.content.Intent;
20import android.os.AsyncTask;
21import android.os.Debug;
22import android.os.SystemClock;
23
24import com.android.messaging.Factory;
25import com.android.messaging.util.Assert.RunsOnAnyThread;
26
27/**
28 * Wrapper class which provides explicit API for:
29 * <ol>
30 *   <li>Threading policy choice - Users of this class should use the explicit API instead of
31 *       {@link #execute} which uses different threading policy on different OS versions.
32 *   <li>Enforce creation on main thread as required by AsyncTask
33 *   <li>Enforce that the background task does not take longer than expected.
34 * </ol>
35 */
36public abstract class SafeAsyncTask<Params, Progress, Result>
37        extends AsyncTask<Params, Progress, Result> {
38    private static final long DEFAULT_MAX_EXECUTION_TIME_MILLIS = 10 * 1000; // 10 seconds
39
40    /** This is strongly discouraged as it can block other AsyncTasks indefinitely. */
41    public static final long UNBOUNDED_TIME = Long.MAX_VALUE;
42
43    private static final String WAKELOCK_ID = "bugle_safe_async_task_wakelock";
44    protected static final int WAKELOCK_OP = 1000;
45    private static WakeLockHelper sWakeLock = new WakeLockHelper(WAKELOCK_ID);
46
47    private final long mMaxExecutionTimeMillis;
48    private final boolean mCancelExecutionOnTimeout;
49    private boolean mThreadPoolRequested;
50
51    public SafeAsyncTask() {
52        this(DEFAULT_MAX_EXECUTION_TIME_MILLIS, false);
53    }
54
55    public SafeAsyncTask(final long maxTimeMillis) {
56        this(maxTimeMillis, false);
57    }
58
59    /**
60     * @param maxTimeMillis maximum expected time for the background operation. This is just
61     *        a diagnostic tool to catch unexpectedly long operations. If an operation does take
62     *        longer than expected, it is fine to increase this argument. If the value is larger
63     *        than a minute, you should consider using a dedicated thread so as not to interfere
64     *        with other AsyncTasks.
65     *
66     *        <p>Use {@link #UNBOUNDED_TIME} if you do not know the maximum expected time. This
67     *        is strongly discouraged as it can block other AsyncTasks indefinitely.
68     *
69     * @param cancelExecutionOnTimeout whether to attempt to cancel the task execution on timeout.
70     *        If this is set, at execution timeout we will call cancel(), so doInBackgroundTimed()
71     *        should periodically check if the task is to be cancelled and finish promptly if
72     *        possible, and handle the cancel event in onCancelled(). Also, at the end of execution
73     *        we will not crash the execution if it went over limit since we explicitly canceled it.
74     */
75    public SafeAsyncTask(final long maxTimeMillis, final boolean cancelExecutionOnTimeout) {
76        Assert.isMainThread(); // AsyncTask has to be created on the main thread
77        mMaxExecutionTimeMillis = maxTimeMillis;
78        mCancelExecutionOnTimeout = cancelExecutionOnTimeout;
79    }
80
81    public final SafeAsyncTask<Params, Progress, Result> executeOnThreadPool(
82            final Params... params) {
83        Assert.isMainThread(); // AsyncTask requires this
84        mThreadPoolRequested = true;
85        executeOnExecutor(THREAD_POOL_EXECUTOR, params);
86        return this;
87    }
88
89    protected abstract Result doInBackgroundTimed(final Params... params);
90
91    @Override
92    protected final Result doInBackground(final Params... params) {
93        // This enforces that executeOnThreadPool was called, not execute. Ideally, we would
94        // make execute throw an exception, but since it is final, we cannot override it.
95        Assert.isTrue(mThreadPoolRequested);
96
97        if (mCancelExecutionOnTimeout) {
98            ThreadUtil.getMainThreadHandler().postDelayed(new Runnable() {
99                @Override
100                public void run() {
101                    if (getStatus() == Status.RUNNING) {
102                        // Cancel the task if it's still running.
103                        LogUtil.w(LogUtil.BUGLE_TAG, String.format("%s timed out and is canceled",
104                                this));
105                        cancel(true /* mayInterruptIfRunning */);
106                    }
107                }
108            }, mMaxExecutionTimeMillis);
109        }
110
111        final long startTime = SystemClock.elapsedRealtime();
112        try {
113            return doInBackgroundTimed(params);
114        } finally {
115            final long executionTime = SystemClock.elapsedRealtime() - startTime;
116            if (executionTime > mMaxExecutionTimeMillis) {
117                LogUtil.w(LogUtil.BUGLE_TAG, String.format("%s took %dms", this, executionTime));
118                // Don't crash if debugger is attached or if we are asked to cancel on timeout.
119                if (!Debug.isDebuggerConnected() && !mCancelExecutionOnTimeout) {
120                    Assert.fail(this + " took too long");
121                }
122            }
123        }
124
125    }
126
127    @Override
128    protected void onPostExecute(final Result result) {
129        // No need to use AsyncTask at all if there is no onPostExecute
130        Assert.fail("Use SafeAsyncTask.executeOnThreadPool");
131    }
132
133    /**
134     * This provides a way for people to run async tasks but without onPostExecute.
135     * This can be called on any thread.
136     *
137     * Run code in a thread using AsyncTask's thread pool.
138     *
139     * To enable wakelock during the execution, see {@link #executeOnThreadPool(Runnable, boolean)}
140     *
141     * @param runnable The Runnable to execute asynchronously
142     */
143    @RunsOnAnyThread
144    public static void executeOnThreadPool(final Runnable runnable) {
145        executeOnThreadPool(runnable, false);
146    }
147
148    /**
149     * This provides a way for people to run async tasks but without onPostExecute.
150     * This can be called on any thread.
151     *
152     * Run code in a thread using AsyncTask's thread pool.
153     *
154     * @param runnable The Runnable to execute asynchronously
155     * @param withWakeLock when set, a wake lock will be held for the duration of the runnable
156     *        execution
157     */
158    public static void executeOnThreadPool(final Runnable runnable, final boolean withWakeLock) {
159        if (withWakeLock) {
160            final Intent intent = new Intent();
161            sWakeLock.acquire(Factory.get().getApplicationContext(), intent, WAKELOCK_OP);
162            THREAD_POOL_EXECUTOR.execute(new Runnable() {
163                @Override
164                public void run() {
165                    try {
166                        runnable.run();
167                    } finally {
168                        sWakeLock.release(intent, WAKELOCK_OP);
169                    }
170                }
171            });
172        } else {
173            THREAD_POOL_EXECUTOR.execute(runnable);
174        }
175    }
176}
177