1 files changed, 175 insertions, 0 deletions
diff --git a/mailnews/base/util/msgDBCacheManager.js b/mailnews/base/util/msgDBCacheManager.js
new file mode 100644
index 000000000..267962375
--- /dev/null
+++ b/mailnews/base/util/msgDBCacheManager.js
@@ -0,0 +1,175 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * Message DB Cache manager
+ */
+
+/* :::::::: Constants and Helpers ::::::::::::::: */
+
+this.EXPORTED_SYMBOLS = ["msgDBCacheManager"];
+
+var Cc = Components.classes;
+var Ci = Components.interfaces;
+var Cu = Components.utils;
+
+Cu.import("resource:///modules/mailServices.js");
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource:///modules/gloda/log4moz.js");
+var log = Log4Moz.getConfiguredLogger("mailnews.database.dbcache");
+
+/**
+ */
+var DBCACHE_INTERVAL_DEFAULT_MS = 60000; // 1 minute
+
+/* :::::::: The Module ::::::::::::::: */
+
+var msgDBCacheManager =
+{
+  _initialized: false,
+
+  _msgDBCacheTimer: null,
+
+  _msgDBCacheTimerIntervalMS: DBCACHE_INTERVAL_DEFAULT_MS,
+
+  _dbService: null,
+
+  /**
+   * This is called on startup
+   */
+  init: function dbcachemgr_init()
+  {
+    if (this._initialized)
+      return;
+
+    this._dbService = Cc["@mozilla.org/msgDatabase/msgDBService;1"]
+                        .getService(Ci.nsIMsgDBService);
+
+    // we listen for "quit-application-granted" instead of
+    // "quit-application-requested" because other observers of the
+    // latter can cancel the shutdown.
+    Services.obs.addObserver(this, "quit-application-granted", false);
+
+    this.startPeriodicCheck();
+
+    this._initialized = true;
+  },
+
+/* ........ Timer Callback ................*/
+
+  _dbCacheCheckTimerCallback: function dbCache_CheckTimerCallback()
+  {
+    msgDBCacheManager.checkCachedDBs();
+  },
+
+/* ........ Observer Notification Handler ................*/
+
+  observe: function dbCache_observe(aSubject, aTopic, aData) {
+    switch (aTopic) {
+    // This is observed before any windows start unloading if something other
+    // than the last 3pane window closing requested the application be
+    // shutdown. For example, when the user quits via the file menu.
+    case "quit-application-granted":
+      Services.obs.removeObserver(this, "quit-application-granted");
+      this.stopPeriodicCheck();
+      break;
+    }
+  },
+
+/* ........ Public API ................*/
+
+  /**
+   * Stops db cache check
+   */
+  stopPeriodicCheck: function dbcache_stopPeriodicCheck()
+  {
+    if (this._dbCacheCheckTimer) {
+      this._dbCacheCheckTimer.cancel();
+
+      delete this._dbCacheCheckTimer;
+      this._dbCacheCheckTimer = null;
+    }
+  },
+
+  /**
+   * Starts periodic db cache check
+   */
+  startPeriodicCheck: function dbcache_startPeriodicCheck()
+  {
+    if (!this._dbCacheCheckTimer) {
+      this._dbCacheCheckTimer = Cc["@mozilla.org/timer;1"]
+                                   .createInstance(Ci.nsITimer);
+
+      this._dbCacheCheckTimer.initWithCallback(
+                                   this._dbCacheCheckTimerCallback,
+                                   this._msgDBCacheTimerIntervalMS,
+                                   Ci.nsITimer.TYPE_REPEATING_SLACK);
+    }
+  },
+
+  /**
+   * Checks if any DBs need to be closed due to inactivity or too many of them open.
+   */
+  checkCachedDBs: function()
+  {
+    let idleLimit = Services.prefs.getIntPref("mail.db.idle_limit");
+    let maxOpenDBs = Services.prefs.getIntPref("mail.db.max_open");
+
+    // db.lastUseTime below is in microseconds while Date.now and idleLimit pref
+    // is in milliseconds.
+    let closeThreshold = (Date.now() - idleLimit) * 1000;
+    let cachedDBs = this._dbService.openDBs;
+    log.info("Periodic check of cached folder databases (DBs), count=" + cachedDBs.length);
+    // Count databases that are already closed or get closed now due to inactivity.
+    let numClosing = 0;
+    // Count databases whose folder is open in a window.
+    let numOpenInWindow = 0;
+    let dbs = [];
+    for (let i = 0; i < cachedDBs.length; i++) {
+      let db = cachedDBs.queryElementAt(i, Ci.nsIMsgDatabase);
+      if (!db.folder.databaseOpen) {
+        // The DB isn't really open anymore.
+        log.debug("Skipping, DB not open for folder: " + db.folder.name);
+        numClosing++;
+        continue;
+      }
+
+      if (MailServices.mailSession.IsFolderOpenInWindow(db.folder)) {
+        // The folder is open in a window so this DB must not be closed.
+        log.debug("Skipping, DB open in window for folder: " + db.folder.name);
+        numOpenInWindow++;
+        continue;
+      }
+
+      if (db.lastUseTime < closeThreshold)
+      {
+        // DB open too log without activity.
+        log.debug("Closing expired DB for folder: " + db.folder.name);
+        db.folder.msgDatabase = null;
+        numClosing++;
+        continue;
+      }
+
+      // Database eligible for closing.
+      dbs.push(db);
+    }
+    log.info("DBs open in a window: " + numOpenInWindow + ", DBs open: " + dbs.length + ", DBs already closing: " + numClosing);
+    let dbsToClose = Math.max(dbs.length - Math.max(maxOpenDBs - numOpenInWindow, 0), 0);
+    if (dbsToClose > 0) {
+      // Close some DBs so that we do not have more than maxOpenDBs.
+      // However, we skipped DBs for folders that are open in a window
+      // so if there are so many windows open, it may be possible for
+      // more than maxOpenDBs folders to stay open after this loop.
+      log.info("Need to close " + dbsToClose + " more DBs");
+      // Order databases by lowest lastUseTime (oldest) at the end.
+      dbs.sort((a, b) => b.lastUseTime - a.lastUseTime);
+      while (dbsToClose > 0) {
+        let db = dbs.pop();
+        log.debug("Closing DB for folder: " + db.folder.name);
+        db.folder.msgDatabase = null;
+        dbsToClose--;
+      }
+    }
+  },
+};