1 files changed, 87 insertions, 0 deletions
diff --git a/browser/components/sessionstore/SessionLogger.sys.mjs b/browser/components/sessionstore/SessionLogger.sys.mjs
new file mode 100644
index 0000000000..a7c99f911e
--- /dev/null
+++ b/browser/components/sessionstore/SessionLogger.sys.mjs
@@ -0,0 +1,87 @@
+/* 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/. */
+
+import { LogManager } from "resource://gre/modules/LogManager.sys.mjs";
+// See Bug 1889052
+// eslint-disable-next-line mozilla/use-console-createInstance
+import { Log } from "resource://gre/modules/Log.sys.mjs";
+
+const lazy = {};
+ChromeUtils.defineESModuleGetters(lazy, {
+  AsyncShutdown: "resource://gre/modules/AsyncShutdown.sys.mjs",
+  cancelIdleCallback: "resource://gre/modules/Timer.sys.mjs",
+  requestIdleCallback: "resource://gre/modules/Timer.sys.mjs",
+});
+
+const loggerNames = ["SessionStore"];
+
+export const sessionStoreLogger = Log.repository.getLogger("SessionStore");
+sessionStoreLogger.manageLevelFromPref("browser.sessionstore.loglevel");
+
+class SessionLogManager extends LogManager {
+  #idleCallbackId = null;
+  #observers = new Set();
+
+  QueryInterface = ChromeUtils.generateQI([Ci.nsIObserver]);
+
+  constructor(options = {}) {
+    super(options);
+
+    Services.obs.addObserver(this, "sessionstore-windows-restored");
+    this.#observers.add("sessionstore-windows-restored");
+
+    lazy.AsyncShutdown.profileBeforeChange.addBlocker(
+      "SessionLogManager: finalize and flush any logs to disk",
+      () => {
+        return this.stop();
+      }
+    );
+  }
+
+  async stop() {
+    if (this.#observers.has("sessionstore-windows-restored")) {
+      Services.obs.removeObserver(this, "sessionstore-windows-restored");
+      this.#observers.delete("sessionstore-windows-restored");
+    }
+    await this.requestLogFlush(true);
+    this.finalize();
+  }
+
+  observe(subject, topic, _) {
+    switch (topic) {
+      case "sessionstore-windows-restored":
+        // this represents the moment session restore is nominally complete
+        // and is a good time to ensure any log messages are flushed to disk
+        Services.obs.removeObserver(this, "sessionstore-windows-restored");
+        this.#observers.delete("sessionstore-windows-restored");
+        this.requestLogFlush();
+        break;
+    }
+  }
+
+  async requestLogFlush(immediate = false) {
+    if (this.#idleCallbackId && !immediate) {
+      return;
+    }
+    if (this.#idleCallbackId) {
+      lazy.cancelIdleCallback(this.#idleCallbackId);
+      this.#idleCallbackId = null;
+    }
+    if (!immediate) {
+      await new Promise(resolve => {
+        this.#idleCallbackId = lazy.requestIdleCallback(resolve);
+      });
+      this.#idleCallbackId = null;
+    }
+    await this.resetFileLog();
+  }
+}
+
+export const logManager = new SessionLogManager({
+  prefRoot: "browser.sessionstore.",
+  logNames: loggerNames,
+  logFilePrefix: "sessionrestore",
+  logFileSubDirectoryEntries: ["sessionstore-logs"],
+  testTopicPrefix: "sessionrestore:log-manager:",
+});