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// Copyright (c) 2012 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/async_policy_loader.h"
#include "base/bind.h"
#include "chrome/browser/policy/policy_bundle.h"
#include "content/public/browser/browser_thread.h"
using base::Time;
using base::TimeDelta;
using content::BrowserThread;
namespace policy {
namespace {
// Amount of time to wait for the files on disk to settle before trying to load
// them. This alleviates the problem of reading partially written files and
// makes it possible to batch quasi-simultaneous changes.
const int kSettleIntervalSeconds = 5;
// The time interval for rechecking policy. This is the fallback in case the
// implementation never detects changes.
const int kReloadIntervalSeconds = 15 * 60;
} // namespace
AsyncPolicyLoader::AsyncPolicyLoader()
: ALLOW_THIS_IN_INITIALIZER_LIST(weak_factory_(this)) {}
AsyncPolicyLoader::~AsyncPolicyLoader() {}
base::Time AsyncPolicyLoader::LastModificationTime() {
return base::Time();
}
void AsyncPolicyLoader::Reload(bool force) {
DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
TimeDelta delay;
Time now = Time::Now();
// Check if there was a recent modification to the underlying files.
if (!force && !IsSafeToReload(now, &delay)) {
ScheduleNextReload(delay);
return;
}
scoped_ptr<PolicyBundle> bundle(Load());
// Check if there was a modification while reading.
if (!force && !IsSafeToReload(now, &delay)) {
ScheduleNextReload(delay);
return;
}
update_callback_.Run(bundle.Pass());
ScheduleNextReload(TimeDelta::FromSeconds(kReloadIntervalSeconds));
}
scoped_ptr<PolicyBundle> AsyncPolicyLoader::InitialLoad() {
// This is the first load, early during startup. Use this to record the
// initial |last_modification_time_|, so that potential changes made before
// installing the watches can be detected.
last_modification_time_ = LastModificationTime();
return Load();
}
void AsyncPolicyLoader::Init(const UpdateCallback& update_callback) {
DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
DCHECK(update_callback_.is_null());
DCHECK(!update_callback.is_null());
update_callback_ = update_callback;
InitOnFile();
// There might have been changes to the underlying files since the initial
// load and before the watchers have been created.
if (LastModificationTime() != last_modification_time_)
Reload(false);
// Start periodic refreshes.
ScheduleNextReload(TimeDelta::FromSeconds(kReloadIntervalSeconds));
}
void AsyncPolicyLoader::ScheduleNextReload(TimeDelta delay) {
DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
weak_factory_.InvalidateWeakPtrs();
BrowserThread::PostDelayedTask(
BrowserThread::FILE, FROM_HERE,
base::Bind(&AsyncPolicyLoader::Reload,
weak_factory_.GetWeakPtr(),
false /* force */),
delay);
}
bool AsyncPolicyLoader::IsSafeToReload(const Time& now, TimeDelta* delay) {
Time last_modification = LastModificationTime();
if (last_modification.is_null())
return true;
// If there was a change since the last recorded modification, wait some more.
const TimeDelta kSettleInterval(
TimeDelta::FromSeconds(kSettleIntervalSeconds));
if (last_modification != last_modification_time_) {
last_modification_time_ = last_modification;
last_modification_clock_ = now;
*delay = kSettleInterval;
return false;
}
// Check whether the settle interval has elapsed.
const base::TimeDelta age = now - last_modification_clock_;
if (age < kSettleInterval) {
*delay = kSettleInterval - age;
return false;
}
return true;
}
} // namespace policy
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