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VolleyのDiskBasedCacheのパフォーマンスの問題

私の Photo Collage アプリfor Android私は画像の読み込みにVolleyを使用しています。再起動を防ぐために、50 mbストレージでDiskBasedCache(volleyに付属)を使用しています-同じ画像を複数回ダウンロードする。

前回チェックしたとき、DiskBasedCacheには約1000のキャッシュエントリが含まれていました。

アプリが起動すると、VolleyがmCache.initialize()を呼び出し、Galaxy S4で約10秒(!)を費やして次のことを行います。

  1. キャッシュフォルダー内のすべてのファイルを一覧表示する
  2. すべてのファイルを開き、ヘッダーセクションを読みます。

起動時に1000以上のファイルを読み取ることは、キャッシュインデックスをロードするための非常に効率的な方法ではないことがわかりました。 :-)

Volley/toolbox/DiskBasedCache.Javaから:

@Override
public synchronized void initialize() {
    if (!mRootDirectory.exists()) {
        if (!mRootDirectory.mkdirs()) {
            VolleyLog.e("Unable to create cache dir %s", mRootDirectory.getAbsolutePath());
        }
        return;
    }

    File[] files = mRootDirectory.listFiles();
    if (files == null) {
        return;
    }
    for (File file : files) {
        FileInputStream fis = null;
        try {
            fis = new FileInputStream(file);
            CacheHeader entry = CacheHeader.readHeader(fis);
            entry.size = file.length();
            putEntry(entry.key, entry);
        } catch (IOException e) {
            if (file != null) {
               file.delete();
            }
        } finally {
            try {
                if (fis != null) {
                    fis.close();
                }
            } catch (IOException ignored) { }
        }
    }
}

高速でスケーラブルなソリューションを探しています。おそらく、代替のDiskBasedCache実装、またはボレーライブラリの改善方法に関する提案です。


更新:(2014-01-06)

Volleyキャッシュが多くの小さな(1バイト)を使用していることに気づいたIO読み取り/書き込み。DiskBasedCache.Javaを複製し、すべてのFileInputStreamsとFileOutputStreamsをBufferedInputStreamとBufferedOutputStreamsでカプセル化しました。この最適化が3-10倍のスピードアップを与えてくれました。

この変更では、中央のインデックスファイルを使用して新しいディスクキャッシュを書き込む場合と比較して、バグのリスクが低くなります。


更新:(2014-01-10)

これが、私が現在使用している新しいクラスBufferedDiskBasedCache.Javaです。

package no.ludde.Android.ds.Android.volley;

/*
 * Copyright (C) 2011 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.
 */

import Android.os.SystemClock;

import com.Android.volley.Cache;
import com.Android.volley.VolleyLog;

import Java.io.BufferedInputStream;
import Java.io.BufferedOutputStream;
import Java.io.EOFException;
import Java.io.File;
import Java.io.FileInputStream;
import Java.io.FileOutputStream;
import Java.io.FilterInputStream;
import Java.io.IOException;
import Java.io.InputStream;
import Java.io.OutputStream;
import Java.util.Collections;
import Java.util.HashMap;
import Java.util.Iterator;
import Java.util.LinkedHashMap;
import Java.util.Map;

/**
 * Cache implementation that caches files directly onto the hard disk in the specified
 * directory. The default disk usage size is 5MB, but is configurable.
 */
public class BufferedDiskBasedCache implements Cache {

    /** Map of the Key, CacheHeader pairs */
    private final Map<String, CacheHeader> mEntries =
            new LinkedHashMap<String, CacheHeader>(16, .75f, true);

    /** Total amount of space currently used by the cache in bytes. */
    private long mTotalSize = 0;

    /** The root directory to use for the cache. */
    private final File mRootDirectory;

    /** The maximum size of the cache in bytes. */
    private final int mMaxCacheSizeInBytes;

    /** Default maximum disk usage in bytes. */
    private static final int DEFAULT_DISK_USAGE_BYTES = 5 * 1024 * 1024;

    /** High water mark percentage for the cache */
    private static final float HYSTERESIS_FACTOR = 0.9f;

    /** Magic number for current version of cache file format. */
    private static final int CACHE_MAGIC = 0x20120504;

    /**
     * Constructs an instance of the DiskBasedCache at the specified directory.
     * @param rootDirectory The root directory of the cache.
     * @param maxCacheSizeInBytes The maximum size of the cache in bytes.
     */
    public BufferedDiskBasedCache(File rootDirectory, int maxCacheSizeInBytes) {
        mRootDirectory = rootDirectory;
        mMaxCacheSizeInBytes = maxCacheSizeInBytes;
    }

    /**
     * Constructs an instance of the DiskBasedCache at the specified directory using
     * the default maximum cache size of 5MB.
     * @param rootDirectory The root directory of the cache.
     */
    public BufferedDiskBasedCache(File rootDirectory) {
        this(rootDirectory, DEFAULT_DISK_USAGE_BYTES);
    }

    /**
     * Clears the cache. Deletes all cached files from disk.
     */
    @Override
    public synchronized void clear() {
        File[] files = mRootDirectory.listFiles();
        if (files != null) {
            for (File file : files) {
                file.delete();
            }
        }
        mEntries.clear();
        mTotalSize = 0;
        VolleyLog.d("Cache cleared.");
    }

    /**
     * Returns the cache entry with the specified key if it exists, null otherwise. 
     */
    @Override
    public synchronized Entry get(String key) {
        CacheHeader entry = mEntries.get(key);
        // if the entry does not exist, return.
        if (entry == null) {
            return null;
        }

        File file = getFileForKey(key);
        CountingInputStream cis = null;
        try {
            cis = new CountingInputStream(new BufferedInputStream(new FileInputStream(file)));
            CacheHeader.readHeader(cis); // eat header
            byte[] data = streamToBytes(cis, (int) (file.length() - cis.bytesRead));
            return entry.toCacheEntry(data);
        } catch (IOException e) {
            VolleyLog.d("%s: %s", file.getAbsolutePath(), e.toString());
            remove(key);
            return null;
        } finally {
            if (cis != null) {
                try {
                    cis.close();
                } catch (IOException ioe) {
                    return null;
                }
            }
        }
    }

    /**
     * Initializes the DiskBasedCache by scanning for all files currently in the
     * specified root directory. Creates the root directory if necessary.
     */
    @Override
    public synchronized void initialize() {
        if (!mRootDirectory.exists()) {
            if (!mRootDirectory.mkdirs()) {
                VolleyLog.e("Unable to create cache dir %s", mRootDirectory.getAbsolutePath());
            }
            return;
        }

        File[] files = mRootDirectory.listFiles();
        if (files == null) {
            return;
        }
        for (File file : files) {
            BufferedInputStream fis = null;
            try {
                fis = new BufferedInputStream(new FileInputStream(file));
                CacheHeader entry = CacheHeader.readHeader(fis);
                entry.size = file.length();
                putEntry(entry.key, entry);
            } catch (IOException e) {
                if (file != null) {
                   file.delete();
                }
            } finally {
                try {
                    if (fis != null) {
                        fis.close();
                    }
                } catch (IOException ignored) { }
            }
        }
    }

    /**
     * Invalidates an entry in the cache.
     * @param key Cache key
     * @param fullExpire True to fully expire the entry, false to soft expire
     */
    @Override
    public synchronized void invalidate(String key, boolean fullExpire) {
        Entry entry = get(key);
        if (entry != null) {
            entry.softTtl = 0;
            if (fullExpire) {
                entry.ttl = 0;
            }
            put(key, entry);
        }

    }

    /**
     * Puts the entry with the specified key into the cache.
     */
    @Override
    public synchronized void put(String key, Entry entry) {
        pruneIfNeeded(entry.data.length);
        File file = getFileForKey(key);
        try {
            BufferedOutputStream fos = new BufferedOutputStream(new FileOutputStream(file));
            CacheHeader e = new CacheHeader(key, entry);
            e.writeHeader(fos);
            fos.write(entry.data);
            fos.close();
            putEntry(key, e);
            return;
        } catch (IOException e) {
        }
        boolean deleted = file.delete();
        if (!deleted) {
            VolleyLog.d("Could not clean up file %s", file.getAbsolutePath());
        }
    }

    /**
     * Removes the specified key from the cache if it exists.
     */
    @Override
    public synchronized void remove(String key) {
        boolean deleted = getFileForKey(key).delete();
        removeEntry(key);
        if (!deleted) {
            VolleyLog.d("Could not delete cache entry for key=%s, filename=%s",
                    key, getFilenameForKey(key));
        }
    }

    /**
     * Creates a pseudo-unique filename for the specified cache key.
     * @param key The key to generate a file name for.
     * @return A pseudo-unique filename.
     */
    private String getFilenameForKey(String key) {
        int firstHalfLength = key.length() / 2;
        String localFilename = String.valueOf(key.substring(0, firstHalfLength).hashCode());
        localFilename += String.valueOf(key.substring(firstHalfLength).hashCode());
        return localFilename;
    }

    /**
     * Returns a file object for the given cache key.
     */
    public File getFileForKey(String key) {
        return new File(mRootDirectory, getFilenameForKey(key));
    }

    /**
     * Prunes the cache to fit the amount of bytes specified.
     * @param neededSpace The amount of bytes we are trying to fit into the cache.
     */
    private void pruneIfNeeded(int neededSpace) {
        if ((mTotalSize + neededSpace) < mMaxCacheSizeInBytes) {
            return;
        }
        if (VolleyLog.DEBUG) {
            VolleyLog.v("Pruning old cache entries.");
        }

        long before = mTotalSize;
        int prunedFiles = 0;
        long startTime = SystemClock.elapsedRealtime();

        Iterator<Map.Entry<String, CacheHeader>> iterator = mEntries.entrySet().iterator();
        while (iterator.hasNext()) {
            Map.Entry<String, CacheHeader> entry = iterator.next();
            CacheHeader e = entry.getValue();
            boolean deleted = getFileForKey(e.key).delete();
            if (deleted) {
                mTotalSize -= e.size;
            } else {
               VolleyLog.d("Could not delete cache entry for key=%s, filename=%s",
                       e.key, getFilenameForKey(e.key));
            }
            iterator.remove();
            prunedFiles++;

            if ((mTotalSize + neededSpace) < mMaxCacheSizeInBytes * HYSTERESIS_FACTOR) {
                break;
            }
        }

        if (VolleyLog.DEBUG) {
            VolleyLog.v("pruned %d files, %d bytes, %d ms",
                    prunedFiles, (mTotalSize - before), SystemClock.elapsedRealtime() - startTime);
        }
    }

    /**
     * Puts the entry with the specified key into the cache.
     * @param key The key to identify the entry by.
     * @param entry The entry to cache.
     */
    private void putEntry(String key, CacheHeader entry) {
        if (!mEntries.containsKey(key)) {
            mTotalSize += entry.size;
        } else {
            CacheHeader oldEntry = mEntries.get(key);
            mTotalSize += (entry.size - oldEntry.size);
        }
        mEntries.put(key, entry);
    }

    /**
     * Removes the entry identified by 'key' from the cache.
     */
    private void removeEntry(String key) {
        CacheHeader entry = mEntries.get(key);
        if (entry != null) {
            mTotalSize -= entry.size;
            mEntries.remove(key);
        }
    }

    /**
     * Reads the contents of an InputStream into a byte[].
     * */
    private static byte[] streamToBytes(InputStream in, int length) throws IOException {
        byte[] bytes = new byte[length];
        int count;
        int pos = 0;
        while (pos < length && ((count = in.read(bytes, pos, length - pos)) != -1)) {
            pos += count;
        }
        if (pos != length) {
            throw new IOException("Expected " + length + " bytes, read " + pos + " bytes");
        }
        return bytes;
    }

    /**
     * Handles holding onto the cache headers for an entry.
     */
    // Visible for testing.
    static class CacheHeader {
        /** The size of the data identified by this CacheHeader. (This is not
         * serialized to disk. */
        public long size;

        /** The key that identifies the cache entry. */
        public String key;

        /** ETag for cache coherence. */
        public String etag;

        /** Date of this response as reported by the server. */
        public long serverDate;

        /** TTL for this record. */
        public long ttl;

        /** Soft TTL for this record. */
        public long softTtl;

        /** Headers from the response resulting in this cache entry. */
        public Map<String, String> responseHeaders;

        private CacheHeader() { }

        /**
         * Instantiates a new CacheHeader object
         * @param key The key that identifies the cache entry
         * @param entry The cache entry.
         */
        public CacheHeader(String key, Entry entry) {
            this.key = key;
            this.size = entry.data.length;
            this.etag = entry.etag;
            this.serverDate = entry.serverDate;
            this.ttl = entry.ttl;
            this.softTtl = entry.softTtl;
            this.responseHeaders = entry.responseHeaders;
        }

        /**
         * Reads the header off of an InputStream and returns a CacheHeader object.
         * @param is The InputStream to read from.
         * @throws IOException
         */
        public static CacheHeader readHeader(InputStream is) throws IOException {
            CacheHeader entry = new CacheHeader();
            int magic = readInt(is);
            if (magic != CACHE_MAGIC) {
                // don't bother deleting, it'll get pruned eventually
                throw new IOException();
            }
            entry.key = readString(is);
            entry.etag = readString(is);
            if (entry.etag.equals("")) {
                entry.etag = null;
            }
            entry.serverDate = readLong(is);
            entry.ttl = readLong(is);
            entry.softTtl = readLong(is);
            entry.responseHeaders = readStringStringMap(is);
            return entry;
        }

        /**
         * Creates a cache entry for the specified data.
         */
        public Entry toCacheEntry(byte[] data) {
            Entry e = new Entry();
            e.data = data;
            e.etag = etag;
            e.serverDate = serverDate;
            e.ttl = ttl;
            e.softTtl = softTtl;
            e.responseHeaders = responseHeaders;
            return e;
        }


        /**
         * Writes the contents of this CacheHeader to the specified OutputStream.
         */
        public boolean writeHeader(OutputStream os) {
            try {
                writeInt(os, CACHE_MAGIC);
                writeString(os, key);
                writeString(os, etag == null ? "" : etag);
                writeLong(os, serverDate);
                writeLong(os, ttl);
                writeLong(os, softTtl);
                writeStringStringMap(responseHeaders, os);
                os.flush();
                return true;
            } catch (IOException e) {
                VolleyLog.d("%s", e.toString());
                return false;
            }
        }

    }

    private static class CountingInputStream extends FilterInputStream {
        private int bytesRead = 0;

        private CountingInputStream(InputStream in) {
            super(in);
        }

        @Override
        public int read() throws IOException {
            int result = super.read();
            if (result != -1) {
                bytesRead++;
            }
            return result;
        }

        @Override
        public int read(byte[] buffer, int offset, int count) throws IOException {
            int result = super.read(buffer, offset, count);
            if (result != -1) {
                bytesRead += result;
            }
            return result;
        }
    }

    /*
     * Homebrewed simple serialization system used for reading and writing cache
     * headers on disk. Once upon a time, this used the standard Java
     * Object{Input,Output}Stream, but the default implementation relies heavily
     * on reflection (even for standard types) and generates a ton of garbage.
     */

    /**
     * Simple wrapper around {@link InputStream#read()} that throws EOFException
     * instead of returning -1.
     */
    private static int read(InputStream is) throws IOException {
        int b = is.read();
        if (b == -1) {
            throw new EOFException();
        }
        return b;
    }

    static void writeInt(OutputStream os, int n) throws IOException {
        os.write((n >> 0) & 0xff);
        os.write((n >> 8) & 0xff);
        os.write((n >> 16) & 0xff);
        os.write((n >> 24) & 0xff);
    }

    static int readInt(InputStream is) throws IOException {
        int n = 0;
        n |= (read(is) << 0);
        n |= (read(is) << 8);
        n |= (read(is) << 16);
        n |= (read(is) << 24);
        return n;
    }

    static void writeLong(OutputStream os, long n) throws IOException {
        os.write((byte)(n >>> 0));
        os.write((byte)(n >>> 8));
        os.write((byte)(n >>> 16));
        os.write((byte)(n >>> 24));
        os.write((byte)(n >>> 32));
        os.write((byte)(n >>> 40));
        os.write((byte)(n >>> 48));
        os.write((byte)(n >>> 56));
    }

    static long readLong(InputStream is) throws IOException {
        long n = 0;
        n |= ((read(is) & 0xFFL) << 0);
        n |= ((read(is) & 0xFFL) << 8);
        n |= ((read(is) & 0xFFL) << 16);
        n |= ((read(is) & 0xFFL) << 24);
        n |= ((read(is) & 0xFFL) << 32);
        n |= ((read(is) & 0xFFL) << 40);
        n |= ((read(is) & 0xFFL) << 48);
        n |= ((read(is) & 0xFFL) << 56);
        return n;
    }

    static void writeString(OutputStream os, String s) throws IOException {
        byte[] b = s.getBytes("UTF-8");
        writeLong(os, b.length);
        os.write(b, 0, b.length);
    }

    static String readString(InputStream is) throws IOException {
        int n = (int) readLong(is);
        byte[] b = streamToBytes(is, n);
        return new String(b, "UTF-8");
    }

    static void writeStringStringMap(Map<String, String> map, OutputStream os) throws IOException {
        if (map != null) {
            writeInt(os, map.size());
            for (Map.Entry<String, String> entry : map.entrySet()) {
                writeString(os, entry.getKey());
                writeString(os, entry.getValue());
            }
        } else {
            writeInt(os, 0);
        }
    }

    static Map<String, String> readStringStringMap(InputStream is) throws IOException {
        int size = readInt(is);
        Map<String, String> result = (size == 0)
                ? Collections.<String, String>emptyMap()
                : new HashMap<String, String>(size);
        for (int i = 0; i < size; i++) {
            String key = readString(is).intern();
            String value = readString(is).intern();
            result.put(key, value);
        }
        return result;
    }


}
33
Ludde
2
Jacob Nordfalk

StreamToBytes()では、最初にキャッシュファイルの長さで新しいバイトが返されますが、キャッシュファイルがアプリケーションの最大ヒープサイズよりも大きすぎませんか?

private static byte[] streamToBytes(InputStream in, int length) throws IOException {
    byte[] bytes = new byte[length];
    ...
}

public synchronized Entry get(String key) {
    CacheHeader entry = mEntries.get(key);

    File file = getFileForKey(key);
    byte[] data = streamToBytes(..., file.length());
}

キャッシュをクリアしたい場合は、DiskBasedCache参照を保持し、クリア時刻になった後、ClearCacheRequestを使用して、そのキャッシュインスタンスをに渡します。

File cacheDir = new File(context.getCacheDir(), DEFAULT_CACHE_DIR);
DiskBasedCache cache = new DiskBasedCache(cacheDir);
RequestQueue queue = new RequestQueue(cache, network);
queue.start();
// clear all volley caches.
queue.add(new ClearCacheRequest(cache, null));

この方法ではすべてのキャッシュがクリアされるため、慎重に使用することをお勧めします。もちろん、条件付きチェックを行うことができます。ただcacheDirファイルを繰り返し、どれが大きすぎるかを見積もり、それを削除します。

for (File cacheFile : cacheDir.listFiles()) {
    if (cacheFile.isFile() && cacheFile.length() > 10000000) cacheFile.delete();
}

Volleyはビッグデータキャッシュソリューションとして設計されていません。これは一般的なリクエストキャッシュであり、いつでも大きなデータを保存することはありません。

------------- 2014-07-17に更新-------------

実際、すべてのキャッシュをクリアするのが最終的な方法であり、賢明な方法でもありません。確かにそうであるかどうかわからない場合は、これらの大きなリクエスト使用キャッシュを抑制する必要があります。応答データのサイズが大きいかどうかを判断できるので、setShouldCache(false)を呼び出して無効にします。

public class TheRequest extends Request {
    @Override
    protected Response<String> parseNetworkResponse(NetworkResponse response) {
        // if response data was too large, disable caching is still time.
        if (response.data.length > 10000) setShouldCache(false);
        ...
    }
}
0
A-Droid Tech

私が最初に考えたのは、Jake Whartonが作成したDiskLruCacheを使用し、その上にcom.Android.volley.Cacheラッパーを作成することでした。

しかし、私は最終的に、アプリケーションコンテキストから呼び出されたAsyncTaskでのキャッシュ作成と組み合わせて、Volleyのシングルトンパターンを実装しました

public static synchronized VolleyClient getInstance(Context context)
{
    if (mInstance == null)
    {
        mInstance = new VolleyClient(context);
    }
    return mInstance;
}

private VolleyClient(Context context)
{
    this.context = context;
    VolleyCacheInitializer volleyCacheInitializer = new VolleyCacheInitializer();
    volleyCacheInitializer.execute();
}

private class VolleyCacheInitializer extends AsyncTask<Void, Void, Boolean>
{
    @Override
    protected Boolean doInBackground(Void... params)
    {
        // Instantiate the cache with 50MB Cache Size
        Cache diskBasedCache = new DiskBasedCache(context.getCacheDir(), 50 * 1024 * 1024);

        // Instantiate the RequestQueue with the cache and network.
        mRequestQueue = new RequestQueue(diskBasedCache, network);

        // Start the queue which calls the DiskBasedCache.initialize()
        mRequestQueue.start();

        return true;
    }

    @Override
    protected void onPostExecute(Boolean aBoolean)
    {
        super.onPostExecute(aBoolean);

        if(aBoolean)
            Log.d(TAG, "Volley request queue initialized");
        else
            Log.d(TAG, "Volley request queue initialization failed");
    }
}

MyApplicationクラスの内部

@Override
public void onCreate()
{
    super.onCreate();

    // Initialize an application level volley request queue
    VolleyClient volleyHttpClient = VolleyClient.getInstance(this);
}
0
Chebyr