1 files changed, 185 insertions, 0 deletions
diff --git a/comm/mailnews/base/src/MsgDBCacheManager.jsm b/comm/mailnews/base/src/MsgDBCacheManager.jsm
new file mode 100644
index 0000000000..9506f08e5e
--- /dev/null
+++ b/comm/mailnews/base/src/MsgDBCacheManager.jsm
@@ -0,0 +1,185 @@
+/* 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 ::::::::::::::: */
+
+const EXPORTED_SYMBOLS = ["msgDBCacheManager"];
+
+var { MailServices } = ChromeUtils.import(
+  "resource:///modules/MailServices.jsm"
+);
+
+var log = console.createInstance({
+  prefix: "mailnews.database.dbcache",
+  maxLogLevel: "Warn",
+  maxLogLevelPref: "mailnews.database.dbcache.loglevel",
+});
+
+/**
+ */
+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() {
+    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");
+
+    this.startPeriodicCheck();
+
+    this._initialized = true;
+  },
+
+  /* ........ Timer Callback ................*/
+
+  _dbCacheCheckTimerCallback() {
+    msgDBCacheManager.checkCachedDBs();
+  },
+
+  /* ........ Observer Notification Handler ................*/
+
+  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() {
+    if (this._dbCacheCheckTimer) {
+      this._dbCacheCheckTimer.cancel();
+
+      delete this._dbCacheCheckTimer;
+      this._dbCacheCheckTimer = null;
+    }
+  },
+
+  /**
+   * Starts periodic db cache check
+   */
+  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() {
+    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 db of cachedDBs) {
+      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--;
+      }
+    }
+  },
+};