Add device status reports to policy requests.

chrome/browser/policy/device_status_collector.cc

+// Copyright (c) 2011 The Chromium 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 "chrome/browser/policy/device_status_collector.h"
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/message_loop.h"
+#include "base/task.h"
+#include "base/time.h"
+#include "chrome/browser/idle.h"
+#include "chrome/browser/policy/proto/device_management_backend.pb.h"
+#include "chrome/browser/prefs/pref_service.h"
+#include "chrome/browser/prefs/scoped_user_pref_update.h"
+
+using base::Time;
+using base::TimeDelta;
+
+namespace em = enterprise_management;
+
+namespace {
+// How many seconds of inactivity triggers the idle state.
+const unsigned int kIdleStateThresholdSeconds = 300;
+
+// The maximum number of time periods stored in the local state.
+const unsigned int kMaxStoredActivePeriods = 500;
+
+// Stores the baseline timestamp, to which the active periods are relative.
+const char* const kPrefBaselineTime = "device_status.baseline_timestamp";
+
+// Stores a list of timestamps representing device active periods.
+const char* const kPrefDeviceActivePeriods = "device_status.active_periods";
+}
+
+namespace policy {
+
+DeviceStatusCollector::DeviceStatusCollector(PrefService* local_state)
+    : local_state_(local_state),
+      last_idle_check_(Time()),
+      last_idle_state_(IDLE_STATE_UNKNOWN) {
+  // Only start the timer if we have a message loop. The only time this should
+  // matter is in unit_tests.
+  if (MessageLoop::current()) {
+    timer_.Start(FROM_HERE,
+                 TimeDelta::FromSeconds(
+                     DeviceStatusCollector::kPollIntervalSeconds),
+                 this, &DeviceStatusCollector::CheckIdleState);
+  }
+}
+
+// static
+void DeviceStatusCollector::RegisterPrefs(PrefService* local_state) {
+  local_state->RegisterInt64Pref(kPrefBaselineTime, Time::Now().ToTimeT());
+  local_state->RegisterListPref(kPrefDeviceActivePeriods, new ListValue);
+}
+
+unsigned int DeviceStatusCollector::max_stored_active_periods() const {
+  return kMaxStoredActivePeriods;
+}
+
+void DeviceStatusCollector::CheckIdleState() {
+  CalculateIdleState(kIdleStateThresholdSeconds,
+      base::Bind(&DeviceStatusCollector::IdleStateCallback,
+                 base::Unretained(this)));
+}
+
+bool DeviceStatusCollector::ToInternalTime(const Time& time, int& out_val) {
+  Time baseline = Time::FromTimeT(
+      local_state_->GetInt64(kPrefBaselineTime));
+  int64 offset_millis = (time - baseline).InMilliseconds();
+  // Fail if the time cannot be represented by an integer.
+  // Assuming 32-bit integers, this would only happen if we haven't uploaded
+  // status in more than 49 days. This should never happen, and if it does,
+  // it's reasonsable to stop recording the status.

[Mattias Nissler (ping if slow), 2011/11/30 12:44:29]

What if somebody is on vacation for 2 months and doesn't use their device? Or,
in education, the device isn't used during the summer months?

[Patrick Dubroy, 2011/12/06 14:30:36]

This doesn't matter anymore -- the method has been removed.

+  if (offset_millis > static_cast<int64>(INT_MAX))
+    return false;
+  out_val = (int)offset_millis;

[Mattias Nissler (ping if slow), 2011/11/30 12:44:29]

space after )

[Patrick Dubroy, 2011/12/06 14:30:36]

Done.

+  return true;
+}
+
+Time DeviceStatusCollector::FromInternalTime(int internal_time) {
+  Time baseline = Time::FromTimeT(
+      local_state_->GetInt64(kPrefBaselineTime));
+  return baseline + TimeDelta::FromMilliseconds(internal_time);
+}
+
+Time DeviceStatusCollector::GetCurrentTime() {
+  return Time::Now();
+}
+
+void DeviceStatusCollector::AddActivePeriod(Time start, Time end) {
+  // Maintain the list of active periods in a local_state pref.
+  ListPrefUpdate update(local_state_, kPrefDeviceActivePeriods);
+  ListValue* active_periods = update.Get();
+
+  // Cap the number of active periods that we store.
+  if (active_periods->GetSize() >= 2 * max_stored_active_periods())
+    return;
+
+  int start_offset, end_offset;
+  if (!ToInternalTime(start, start_offset) ||
+      !ToInternalTime(end, end_offset)) {
+    NOTREACHED();
+    return;
+  }
+
+  int list_size = active_periods->GetSize();
+  DCHECK(list_size % 2 == 0);
+
+  // Check if this period can be combined with the previous one.
+  if (list_size > 0 && last_idle_state_ == IDLE_STATE_ACTIVE) {
+    int last_period_end;
+    if (active_periods->GetInteger(list_size - 1, &last_period_end) &&
+        last_period_end == start_offset) {
+      active_periods->Set(list_size - 1,
+                          Value::CreateIntegerValue(end_offset));
+      return;
+    }
+  }
+  // Add a new period to the list.
+  active_periods->Append(Value::CreateIntegerValue(start_offset));
+  active_periods->Append(Value::CreateIntegerValue(end_offset));
+}
+
+void DeviceStatusCollector::IdleStateCallback(IdleState state) {
+  Time now = GetCurrentTime();
+
+  if (state == IDLE_STATE_ACTIVE) {
+    unsigned int poll_interval = DeviceStatusCollector::kPollIntervalSeconds;
+
+    // If it's been too long since the last report, assume that the system was
+    // in standby, and only count a single interval of activity.
+    if ((now - last_idle_check_).InSeconds() >= (2 * poll_interval))
+      AddActivePeriod(now - TimeDelta::FromSeconds(poll_interval), now);
+    else
+      AddActivePeriod(last_idle_check_, now);
+  }
+  last_idle_check_ = now;
+  last_idle_state_ = state;
+}
+
+void DeviceStatusCollector::GetStatus(em::DeviceStatusReportRequest* request) {
+  const ListValue* active_periods =
+      local_state_->GetList(kPrefDeviceActivePeriods);
+  em::TimePeriod* time_period;
+
+  DCHECK(active_periods->GetSize() % 2 == 0);
+
+  int period_count = active_periods->GetSize() / 2;
+  for (int i = 0; i < period_count; i++) {
+    int start, end;
+
+    if (!active_periods->GetInteger(2 * i, &start) ||
+        !active_periods->GetInteger(2 * i + 1, &end) ||
+        end < start) {
+      // Something is amiss -- bail out.
+      NOTREACHED();
+      break;
+    }
+    time_period = request->add_active_time();
+    time_period->set_start_timestamp(
+        (FromInternalTime(start) - Time::UnixEpoch()).InMilliseconds());
+    time_period->set_end_timestamp(
+        (FromInternalTime(end) - Time::UnixEpoch()).InMilliseconds());
+  }
+  ListPrefUpdate update(local_state_, kPrefDeviceActivePeriods);
+  update.Get()->Clear();
+
+  // Reset the baseline time every time we report. If this isn't done
+  // periodically, the times will overflow.

[Mattias Nissler (ping if slow), 2011/11/30 12:44:29]

It seems likes maintaining the baseline time makes this all a bit complex. Can't
we rather just store the times as strings? That's what PrefService::SetInt64
does.

[Patrick Dubroy, 2011/12/06 14:30:36]

You're right. It's simpler to store as strings. Done.

+  local_state_->SetInt64(kPrefBaselineTime,
+                         GetCurrentTime().ToTimeT());
+}
+
+}  // namespace policy