Refactor the WebStorage size management:

- Abandon the Quota UI: it does not make sense to ask the users to decide individual database quota increases. It is unlikely anyone will be able to make a meaningul decision.
- Introduce a global limit for all WebStorage content. This is shared between Database and AppCache.
- Make the quota increase decision automatic
- Treat out-of-space situations by creaying a system notification (TODO).

1 files changed, 282 insertions, 0 deletions

diff --git a/src/com/android/browser/WebStorageSizeManager.java b/src/com/android/browser/WebStorageSizeManager.java
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+++ b/src/com/android/browser/WebStorageSizeManager.java
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+/*
+ * Copyright (C) 2009 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.browser;
+
+import android.content.Context;
+import android.os.StatFs;
+import android.util.Log;
+import android.webkit.WebStorage;
+
+import java.io.File;
+import java.util.Set;
+
+
+/**
+ * Package level class for managing the disk size consumed by the WebDatabase
+ * and ApplicationCaches APIs (henceforth called Web storage).
+ *
+ * Currently, the situation on the WebKit side is as follows:
+ *  - WebDatabase enforces a quota for each origin.
+ *  - Session/LocalStorage do not enforce any disk limits.
+ *  - ApplicationCaches enforces a maximum size for all origins.
+ *
+ * The WebStorageSizeManager maintains a global limit for the disk space
+ * consumed by the WebDatabase and ApplicationCaches. As soon as WebKit will
+ * have a limit for Session/LocalStorage, this class will manage the space used
+ * by those APIs as well.
+ *
+ * The global limit is computed as a function of the size of the partition where
+ * these APIs store their data (they must store it on the same partition for
+ * this to work) and the size of the available space on that partition.
+ * The global limit is not subject to user configuration but we do provide
+ * a debug-only setting.
+ * TODO(andreip): implement the debug setting.
+ *
+ * The size of the disk space used for Web storage is initially divided between
+ * WebDatabase and ApplicationCaches as follows:
+ *
+ * 75% for WebDatabase
+ * 25% for ApplicationCaches
+ *
+ * When an origin's database usage reaches its current quota, WebKit invokes
+ * the following callback function:
+ * - exceededDatabaseQuota(Frame* frame, const String& database_name);
+ * Note that the default quota for a new origin is 0, so we will receive the
+ * 'exceededDatabaseQuota' callback before a new origin gets the chance to
+ * create its first database.
+ *
+ * When the total ApplicationCaches usage reaches its current quota, WebKit
+ * invokes the following callback function:
+ * - void reachedMaxAppCacheSize(int64_t spaceNeeded);
+ *
+ * The WebStorageSizeManager's main job is to respond to the above two callbacks
+ * by inspecting the amount of unused Web storage quota (i.e. global limit -
+ * sum of all other origins' quota) and deciding if a quota increase for the
+ * out-of-space origin is allowed or not.
+ *
+ * The default quota for an origin is min(ORIGIN_DEFAULT_QUOTA, unused_quota).
+ * Quota increases are done in steps, where the increase step is
+ * min(QUOTA_INCREASE_STEP, unused_quota).
+ *
+ * This approach has the drawback that space may remain unused if there
+ * are many websites that store a lot less content than ORIGIN_DEFAULT_QUOTA.
+ * We deal with this by picking a value for ORIGIN_DEFAULT_QUOTA that is smaller
+ * than what the HTML 5 spec recommends. At the same time, picking a very small
+ * value for ORIGIN_DEFAULT_QUOTA may create performance problems since it's
+ * more likely for origins to have to rollback and restart transactions as a
+ * result of reaching the quota more often.
+ *
+ * When all the Web storage space is used, the WebStorageSizeManager creates
+ * a system notification that will guide the user to the WebSettings UI. There,
+ * the user can free some of the Web storage space by deleting all the data used
+ * by an origin.
+ * TODO(andreip): implement the notification.
+ */
+class WebStorageSizeManager {
+    // Logging flags.
+    private final static boolean LOGV_ENABLED = com.android.browser.Browser.LOGV_ENABLED;
+    private final static boolean LOGD_ENABLED = com.android.browser.Browser.LOGD_ENABLED;
+    private final static String LOGTAG = "browser";
+    // The default quota value for an origin.
+    private final static long ORIGIN_DEFAULT_QUOTA = 4 * 1024 * 1024;  // 4MB
+    // The default value for quota increases.
+    private final static long QUOTA_INCREASE_STEP = 2 * 1024 * 1024;  // 2MB
+    // The name of the application cache file. Keep in sync with
+    // WebCore/loader/appcache/ApplicationCacheStorage.cpp
+    private final static String APPCACHE_FILE = "ApplicationCache.db";
+    // The WebStorageSizeManager singleton.
+    private static WebStorageSizeManager mManager;
+    // The application context.
+    private Context mContext;
+    // The global Web storage limit.
+    private long mGlobalLimit;
+    // The maximum size of the application cache file.
+    private long mAppCacheMaxSize;
+
+    /**
+     * Factory method.
+     * @param path is a path on the partition where the app cache data is kept.
+     * @param ctx is the browser application context.
+     * @param storage is the WebStorage singleton.
+     *
+     */
+    public static WebStorageSizeManager getInstance(String appCachePath,
+            Context ctx) {
+       if (mManager == null) {
+           mManager = new WebStorageSizeManager(appCachePath, ctx);
+       }
+       return mManager;
+    }
+
+    /**
+     * Returns the maximum size of the application cache.
+     */
+    public long getAppCacheMaxSize() {
+        return mAppCacheMaxSize;
+    }
+
+    /**
+     * The origin has exceeded its database quota.
+     * @param url the URL that exceeded the quota
+     * @param databaseIdentifier the identifier of the database on
+     *     which the transaction that caused the quota overflow was run
+     * @param currentQuota the current quota for the origin.
+     * @param totalUsedQuota is the sum of all origins' quota.
+     * @param quotaUpdater The callback to run when a decision to allow or
+     *     deny quota has been made. Don't forget to call this!
+     */
+    public void onExceededDatabaseQuota(String url,
+        String databaseIdentifier, long currentQuota, long totalUsedQuota,
+        WebStorage.QuotaUpdater quotaUpdater) {
+        if(LOGV_ENABLED) {
+            Log.v(LOGTAG,
+                  "Received onExceededDatabaseQuota for "
+                  + url
+                  + ":"
+                  + databaseIdentifier
+                  + "(current quota: "
+                  + currentQuota
+                  + ")");
+        }
+        long totalUnusedQuota = mGlobalLimit - totalUsedQuota - mAppCacheMaxSize;
+
+        if (totalUnusedQuota < QUOTA_INCREASE_STEP) {
+            // There definitely isn't any more space. Fire notifications
+            // and exit.
+            scheduleOutOfSpaceNotification();
+            quotaUpdater.updateQuota(currentQuota);
+            if(LOGV_ENABLED) {
+                Log.v(LOGTAG, "onExceededDatabaseQuota: out of space.");
+            }
+            return;
+        }
+        // We have enough space inside mGlobalLimit.
+        long newOriginQuota = currentQuota;
+        if (newOriginQuota == 0) {
+            // This is a new origin. It wants an initial quota. It is guaranteed
+            // to get at least ORIGIN_INCREASE_STEP bytes.
+            newOriginQuota =
+                Math.min(ORIGIN_DEFAULT_QUOTA, totalUnusedQuota);
+        } else {
+            // This is an origin we have seen before. It wants a quota
+            // increase.
+            newOriginQuota +=
+                Math.min(QUOTA_INCREASE_STEP, totalUnusedQuota);
+        }
+        quotaUpdater.updateQuota(newOriginQuota);
+
+        if(LOGV_ENABLED) {
+            Log.v(LOGTAG, "onExceededDatabaseQuota set new quota to "
+                    + newOriginQuota);
+        }
+    }
+
+    /**
+     * The Application Cache has exceeded its max size.
+     * @param spaceNeeded is the amount of disk space that would be needed
+     * in order for the last appcache operation to succeed.
+     * @param totalUsedQuota is the sum of all origins' quota.
+     * @param quotaUpdater A callback to inform the WebCore thread that a new
+     * app cache size is available. This callback must always be executed at
+     * some point to ensure that the sleeping WebCore thread is woken up.
+     */
+    public void onReachedMaxAppCacheSize(long spaceNeeded, long totalUsedQuota,
+            WebStorage.QuotaUpdater quotaUpdater) {
+        if(LOGV_ENABLED) {
+            Log.v(LOGTAG, "Received onReachedMaxAppCacheSize with spaceNeeded "
+                  + spaceNeeded + " bytes.");
+        }
+
+        long totalUnusedQuota = mGlobalLimit - totalUsedQuota - mAppCacheMaxSize;
+
+        if (totalUnusedQuota < spaceNeeded) {
+            // There definitely isn't any more space. Fire notifications
+            // and exit.
+            scheduleOutOfSpaceNotification();
+            quotaUpdater.updateQuota(0);
+            if(LOGV_ENABLED) {
+                Log.v(LOGTAG, "onReachedMaxAppCacheSize: out of space.");
+            }
+            return;
+        }
+        // There is enough space to accommodate spaceNeeded bytes.
+        mAppCacheMaxSize += spaceNeeded;
+        quotaUpdater.updateQuota(mAppCacheMaxSize);
+
+        if(LOGV_ENABLED) {
+            Log.v(LOGTAG, "onReachedMaxAppCacheSize set new max size to "
+                    + mAppCacheMaxSize);
+        }
+    }
+
+    // Computes the global limit as a function of the size of the data
+    // partition and the amount of free space on that partition.
+    private long getGlobalLimit(String path) {
+        StatFs dataPartition = new StatFs(path);
+        long freeSpace = dataPartition.getAvailableBlocks()
+            * dataPartition.getBlockSize();
+        long fileSystemSize = dataPartition.getBlockCount()
+            * dataPartition.getBlockSize();
+        return calculateGlobalLimit(fileSystemSize, freeSpace);
+    }
+
+    // Returns the current size (in bytes) of the application cache file.
+    private long getCurrentAppCacheSize(String path) {
+        File file = new File(path + File.separator + APPCACHE_FILE);
+        return file.length();
+    }
+
+    /*package*/ static long calculateGlobalLimit(long fileSystemSizeBytes,
+            long freeSpaceBytes) {
+        if (fileSystemSizeBytes <= 0
+                || freeSpaceBytes <= 0
+                || freeSpaceBytes > fileSystemSizeBytes) {
+            return 0;
+        }
+
+        long fileSystemSizeRatio =
+            2 << ((int) Math.floor(Math.log10(
+                    fileSystemSizeBytes / (1024 * 1024))));
+        long maxSizeBytes = (long) Math.min(Math.floor(
+                fileSystemSizeBytes / fileSystemSizeRatio),
+                Math.floor(freeSpaceBytes / 2));
+        // Round maxSizeBytes up to a multiple of 1024KB (but only if
+        // maxSizeBytes > 1MB).
+        long maxSizeStepBytes = 1024 * 1024;
+        if (maxSizeBytes < maxSizeStepBytes) {
+            return 0;
+        }
+        long roundingExtra = maxSizeBytes % maxSizeStepBytes == 0 ? 0 : 1;
+        return (maxSizeStepBytes
+                * ((maxSizeBytes / maxSizeStepBytes) + roundingExtra));
+    }
+
+    // Schedules a system notification that takes the user to the WebSettings
+    // activity when clicked.
+    private void scheduleOutOfSpaceNotification() {
+        // TODO(andreip): implement.
+    }
+    // Private ctor.
+    private WebStorageSizeManager(String appCachePath, Context ctx) {
+        mContext = ctx;
+        mGlobalLimit = getGlobalLimit(appCachePath);
+        // The initial max size of the app cache is either 25% of the global
+        // limit or the current size of the app cache file, whichever is bigger.
+        mAppCacheMaxSize = Math.max(mGlobalLimit / 4,
+                getCurrentAppCacheSize(appCachePath));
+    }
+}
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