1 files changed, 71 insertions, 0 deletions
diff --git a/remote/shared/Log.sys.mjs b/remote/shared/Log.sys.mjs
new file mode 100644
index 0000000000..f1b3706391
--- /dev/null
+++ b/remote/shared/Log.sys.mjs
@@ -0,0 +1,71 @@
+/* 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 { Log as StdLog } from "resource://gre/modules/Log.sys.mjs";
+
+const PREF_REMOTE_LOG_LEVEL = "remote.log.level";
+
+const lazy = {};
+
+// Lazy getter which returns a cached value of the remote log level. Should be
+// used for static getters used to guard hot paths for logging, eg
+// isTraceLevelOrMore.
+ChromeUtils.defineLazyGetter(lazy, "logLevel", () =>
+  Services.prefs.getCharPref(PREF_REMOTE_LOG_LEVEL, StdLog.Level.Fatal)
+);
+
+/** E10s compatible wrapper for the standard logger from Log.sys.mjs. */
+export class Log {
+  static TYPES = {
+    CDP: "CDP",
+    MARIONETTE: "Marionette",
+    REMOTE_AGENT: "RemoteAgent",
+    WEBDRIVER_BIDI: "WebDriver BiDi",
+  };
+
+  /**
+   * Get a logger instance. For each provided type, a dedicated logger instance
+   * will be returned, but all loggers are relying on the same preference.
+   *
+   * @param {string} type
+   *     The type of logger to use. Protocol-specific modules should use the
+   *     corresponding logger type. Eg. files under /marionette should use
+   *     Log.TYPES.MARIONETTE.
+   */
+  static get(type = Log.TYPES.REMOTE_AGENT) {
+    const logger = StdLog.repository.getLogger(type);
+    if (!logger.ownAppenders.length) {
+      logger.addAppender(new StdLog.DumpAppender());
+      logger.manageLevelFromPref(PREF_REMOTE_LOG_LEVEL);
+    }
+    return logger;
+  }
+
+  /**
+   * Check if the current log level matches the Debug log level, or any level
+   * above that. This should be used to guard logger.debug calls and avoid
+   * instanciating logger instances unnecessarily.
+   */
+  static get isDebugLevelOrMore() {
+    // Debug is assigned 20, more verbose log levels have lower values.
+    return StdLog.Level[lazy.logLevel] <= StdLog.Level.Debug;
+  }
+
+  /**
+   * Check if the current log level matches the Trace log level, or any level
+   * above that. This should be used to guard logger.trace calls and avoid
+   * instanciating logger instances unnecessarily.
+   */
+  static get isTraceLevelOrMore() {
+    // Trace is assigned 10, more verbose log levels have lower values.
+    return StdLog.Level[lazy.logLevel] <= StdLog.Level.Trace;
+  }
+
+  static get verbose() {
+    // we can't use Preferences.sys.mjs before first paint,
+    // see ../browser/base/content/test/performance/browser_startup.js
+    const level = Services.prefs.getStringPref(PREF_REMOTE_LOG_LEVEL, "Info");
+    return StdLog.Level[level] >= StdLog.Level.Info;
+  }
+}