file_based_policy_loader.h revision 21d179b334e59e9a3bfcaed4c4430bef1bc5759d 
1// Copyright (c) 2010 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef CHROME_BROWSER_POLICY_FILE_BASED_POLICY_LOADER_H_
6#define CHROME_BROWSER_POLICY_FILE_BASED_POLICY_LOADER_H_
7#pragma once
8
9#include "chrome/browser/file_path_watcher/file_path_watcher.h"
10#include "chrome/browser/policy/asynchronous_policy_loader.h"
11#include "chrome/browser/policy/file_based_policy_provider.h"
12
13namespace policy {
14
15// A customized asynchronous policy loader that handles loading policy from a
16// file using a FilePathWatcher. The loader creates a fallback task to load
17// policy periodically in case the watcher fails and retries policy loads when
18// the watched file is in flux.
19class FileBasedPolicyLoader : public AsynchronousPolicyLoader {
20 public:
21  FileBasedPolicyLoader(
22      FileBasedPolicyProvider::ProviderDelegate* provider_delegate);
23
24  // AsynchronousPolicyLoader overrides:
25  virtual void Reload();
26
27  void OnFilePathChanged(const FilePath& path);
28  void OnError();
29
30 protected:
31  // FileBasedPolicyLoader objects should only be deleted by
32  // RefCountedThreadSafe.
33  friend class base::RefCountedThreadSafe<AsynchronousPolicyLoader>;
34  virtual ~FileBasedPolicyLoader();
35
36  const FilePath& config_file_path() { return config_file_path_; }
37
38  // AsynchronousPolicyLoader overrides:
39
40  // Creates the file path watcher and configures it to watch
41  // |config_file_path_|.  Must be called on the file thread.
42  virtual void InitOnFileThread();
43  virtual void StopOnFileThread();
44
45 private:
46  // Checks whether policy information is safe to read. If not, returns false
47  // and then delays until it is considered safe to reload in |delay|.
48  // Must be called on the file thread.
49  bool IsSafeToReloadPolicy(const base::Time& now, base::TimeDelta* delay);
50
51  // The path at which we look for configuration files.
52  const FilePath config_file_path_;
53
54  // Managed with a scoped_ptr rather than being declared as an inline member to
55  // decouple the watcher's life cycle from the loader's. This decoupling makes
56  // it possible to destroy the watcher before the loader's destructor is called
57  // (e.g. during Stop), since |watcher_| internally holds a reference to the
58  // loader and keeps it alive.
59  scoped_ptr<FilePathWatcher> watcher_;
60
61  // Settle interval.
62  const base::TimeDelta settle_interval_;
63
64  // Records last known modification timestamp of |config_file_path_|.
65  base::Time last_modification_file_;
66
67  // The wall clock time at which the last modification timestamp was
68  // recorded.  It's better to not assume the file notification time and the
69  // wall clock times come from the same source, just in case there is some
70  // non-local filesystem involved.
71  base::Time last_modification_clock_;
72
73  DISALLOW_COPY_AND_ASSIGN(FileBasedPolicyLoader);
74};
75
76}  // namespace policy
77
78#endif  // CHROME_BROWSER_POLICY_FILE_BASED_POLICY_LOADER_H_
79