Android example source code file (DeviceMonitor.java)

This example Android source code file (DeviceMonitor.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, base, couldn't, devicemonitor, file, fileinputstream, interruptedexception, interval, io, ioexception, max_files, outputstream, paths, sample_count, string, suppresswarnings, util, utilities, utils

The DeviceMonitor.java Android example source code

/*
 * Copyright (C) 2008 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.server.am;

import android.util.Slog;

import java.io.*;
import java.util.Arrays;

/**
 * Monitors device resources periodically for some period of time. Useful for
 * tracking down performance problems.
 */
class DeviceMonitor {

    private static final String LOG_TAG = DeviceMonitor.class.getName();

    /** Number of samples to take. */
    private static final int SAMPLE_COUNT = 10;

    /** Time to wait in ms between samples. */
    private static final int INTERVAL = 1000;

    /** Time to wait in ms between samples. */
    private static final int MAX_FILES = 30;

    private final byte[] buffer = new byte[1024];

    /** Is the monitor currently running? */
    private boolean running = false;

    private DeviceMonitor() {
        new Thread() {
            public void run() {
                monitor();
            }
        }.start();
    }

    /**
     * Loops continuously. Pauses until someone tells us to start monitoring.
     */
    @SuppressWarnings("InfiniteLoopStatement")
    private void monitor() {
        while (true) {
            waitForStart();

            purge();

            for (int i = 0; i < SAMPLE_COUNT; i++) {
                try {
                    dump();
                } catch (IOException e) {
                    Slog.w(LOG_TAG, "Dump failed.", e);
                }
                pause();
            }

            stop();
        }
    }

    private static final File PROC = new File("/proc");
    private static final File BASE = new File("/data/anr/");
    static {
        if (!BASE.isDirectory() && !BASE.mkdirs()) {
            throw new AssertionError("Couldn't create " + BASE + ".");
        }
    }

    private static final File[] PATHS = {
        new File(PROC, "zoneinfo"),
        new File(PROC, "interrupts"),
        new File(PROC, "meminfo"),
        new File(PROC, "slabinfo"),
    };


    /**
     * Deletes old files.
     */
    private void purge() {
        File[] files = BASE.listFiles();
        int count = files.length - MAX_FILES;
        if (count > 0) {
            Arrays.sort(files);
            for (int i = 0; i < count; i++) {
                if (!files[i].delete()) {
                    Slog.w(LOG_TAG, "Couldn't delete " + files[i] + ".");
                }
            }
        }
    }

    /**
     * Dumps the current device stats to a new file.
     */
    private void dump() throws IOException {
        OutputStream out = new FileOutputStream(
                new File(BASE, String.valueOf(System.currentTimeMillis())));
        try {
            // Copy /proc/*/stat
            for (File processDirectory : PROC.listFiles()) {
                if (isProcessDirectory(processDirectory)) {
                    dump(new File(processDirectory, "stat"), out);
                }
            }

            // Copy other files.
            for (File file : PATHS) {
                dump(file, out);
            }
        } finally {
            closeQuietly(out);
        }
    }

    /**
     * Returns true if the given file represents a process directory.
     */
    private static boolean isProcessDirectory(File file) {
        try {
            Integer.parseInt(file.getName());
            return file.isDirectory();
        } catch (NumberFormatException e) {
            return false;
        }
    }

    /**
     * Copies from a file to an output stream.
     */
    private void dump(File from, OutputStream out) throws IOException {
        writeHeader(from, out);
        
        FileInputStream in = null;
        try {
            in = new FileInputStream(from);
            int count;
            while ((count = in.read(buffer)) != -1) {
                out.write(buffer, 0, count);
            }
        } finally {
            closeQuietly(in);
        }
    }

    /**
     * Writes a header for the given file.
     */
    private static void writeHeader(File file, OutputStream out)
            throws IOException {
        String header = "*** " + file.toString() + "\n";
        out.write(header.getBytes());
    }

    /**
     * Closes the given resource. Logs exceptions.
     * @param closeable
     */
    private static void closeQuietly(Closeable closeable) {
        try {
            if (closeable != null) {
                closeable.close();
            }
        } catch (IOException e) {
            Slog.w(LOG_TAG, e);
        }
    }

    /**
     * Pauses momentarily before we start the next dump.
     */
    private void pause() {
        try {
            Thread.sleep(INTERVAL);
        } catch (InterruptedException e) { /* ignore */ }
    }

    /**
     * Stops dumping.
     */
    private synchronized void stop() {
        running = false;        
    }

    /**
     * Waits until someone starts us.
     */
    private synchronized void waitForStart() {
        while (!running) {
            try {
                wait();
            } catch (InterruptedException e) { /* ignore */ }
        }
    }

    /**
     * Instructs the monitoring to start if it hasn't already.
     */
    private synchronized void startMonitoring() {
        if (!running) {
            running = true;
            notifyAll();
        }
    }

    private static DeviceMonitor instance = new DeviceMonitor();

    /**
     * Starts monitoring if it hasn't started already.
     */
    static void start() {
        instance.startMonitoring();
    }
}