Add 10 minute random fuzz to automatic update check event schedule.

main.cc

 // Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <string>
 #include <tr1/memory>
 #include <vector>
 
 #include <gflags/gflags.h>
 #include <glib.h>
 
+#include "base/at_exit.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/string_util.h"
 #include "metrics/metrics_library.h"
 #include "update_engine/dbus_constants.h"
 #include "update_engine/dbus_service.h"
 #include "update_engine/prefs.h"
 #include "update_engine/subprocess.h"
 #include "update_engine/update_attempter.h"
 #include "update_engine/utils.h"
@@ skipping 16 matching lines @@
 gboolean UpdateBootFlags(void* arg) {
   // This purely best effort. Failures should be logged by Subprocess.
   int unused = 0;
   vector<string> cmd(1, "/usr/sbin/chromeos-setgoodkernel");
   Subprocess::SynchronousExec(cmd, &unused);
   return FALSE;  // Don't call this callback again
 }
 
 namespace {
 
+const int kTimeoutOnce = 7 * 60;  // at 7 minutes
+const int kTimeoutPeriodic = 45 * 60;  // every 45 minutes
+const int kTimeoutFuzz = 10 * 60;  // +/- 5 minutes
+
+// Schedules an update check |seconds| from now, while adding some fuzz.
+void ScheduleUpdateCheck(int seconds,
+                         GSourceFunc update_function,
+                         UpdateAttempter* update_attempter) {
+  seconds = utils::FuzzInt(seconds, kTimeoutFuzz);
+  g_timeout_add_seconds(seconds, update_function, update_attempter);
+}
+
 gboolean UpdateOnce(void* arg) {
   UpdateAttempter* update_attempter = reinterpret_cast<UpdateAttempter*>(arg);
   update_attempter->Update("", "");
-  return FALSE;
+  return FALSE;  // Don't run again.
 }
 
 gboolean UpdatePeriodically(void* arg) {
   UpdateAttempter* update_attempter = reinterpret_cast<UpdateAttempter*>(arg);
   update_attempter->Update("", "");
-  return TRUE;
+  ScheduleUpdateCheck(kTimeoutPeriodic, &UpdatePeriodically, update_attempter);
+  return FALSE;  // Don't run again.
 }
 
 void SchedulePeriodicUpdateChecks(UpdateAttempter* update_attempter) {
   if (!utils::IsOfficialBuild()) {
     LOG(WARNING) << "Non-official build: periodic update checks disabled.";
     return;
   }
-
   if (utils::IsRemovableDevice(utils::RootDevice(utils::BootDevice()))) {
     LOG(WARNING) << "Removable device boot: periodic update checks disabled.";
     return;
   }
-
-  // Kick off periodic updating. First, update after 2 minutes. Also, update
-  // every 30 minutes.
-  g_timeout_add_seconds(2 * 60, &UpdateOnce, update_attempter);
-  g_timeout_add_seconds(30 * 60, &UpdatePeriodically, update_attempter);
+  // Kick off periodic updating.
+  ScheduleUpdateCheck(kTimeoutOnce, &UpdateOnce, update_attempter);
+  ScheduleUpdateCheck(kTimeoutPeriodic, &UpdatePeriodically, update_attempter);
 }
 
 void SetupDbusService(UpdateEngineService* service) {
   DBusGConnection *bus;
   DBusGProxy *proxy;
   GError *error = NULL;
 
   bus = dbus_g_bus_get(DBUS_BUS_SYSTEM, &error);
   if (!bus) {
     LOG(FATAL) << "Failed to get bus";
@@ skipping 26 matching lines @@
 }  // namespace {}
 
 }  // namespace chromeos_update_engine
 
 #include "update_engine/subprocess.h"
 
 int main(int argc, char** argv) {
   ::g_type_init();
   g_thread_init(NULL);
   dbus_g_thread_init();
+  base::AtExitManager exit_manager;  // Required for base/rand_util.h.
   chromeos_update_engine::Subprocess::Init();
   google::ParseCommandLineFlags(&argc, &argv, true);
   CommandLine::Init(argc, argv);
   logging::InitLogging("/var/log/update_engine.log",
                        (FLAGS_logtostderr ?
                         logging::LOG_ONLY_TO_SYSTEM_DEBUG_LOG :
                         logging::LOG_ONLY_TO_FILE),
                        logging::DONT_LOCK_LOG_FILE,
                        logging::APPEND_TO_OLD_LOG_FILE);
   if (!FLAGS_foreground)
@@ skipping 33 matching lines @@
   g_main_loop_run(loop);
 
   // Cleanup:
   g_main_loop_unref(loop);
   update_attempter.set_dbus_service(NULL);
   g_object_unref(G_OBJECT(service));
 
   LOG(INFO) << "Chrome OS Update Engine terminating";
   return 0;
 }