1// Copyright (c) 2012 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// See net/disk_cache/disk_cache.h for the public interface of the cache.
6
7#ifndef NET_DISK_CACHE_BACKEND_IMPL_H_
8#define NET_DISK_CACHE_BACKEND_IMPL_H_
9
10#include "base/containers/hash_tables.h"
11#include "base/files/file_path.h"
12#include "base/timer/timer.h"
13#include "net/disk_cache/block_files.h"
14#include "net/disk_cache/disk_cache.h"
15#include "net/disk_cache/eviction.h"
16#include "net/disk_cache/in_flight_backend_io.h"
17#include "net/disk_cache/rankings.h"
18#include "net/disk_cache/stats.h"
19#include "net/disk_cache/stress_support.h"
20#include "net/disk_cache/trace.h"
21
22namespace net {
23class NetLog;
24}  // namespace net
25
26namespace disk_cache {
27
28enum BackendFlags {
29  kNone = 0,
30  kMask = 1,                    // A mask (for the index table) was specified.
31  kMaxSize = 1 << 1,            // A maximum size was provided.
32  kUnitTestMode = 1 << 2,       // We are modifying the behavior for testing.
33  kUpgradeMode = 1 << 3,        // This is the upgrade tool (dump).
34  kNewEviction = 1 << 4,        // Use of new eviction was specified.
35  kNoRandom = 1 << 5,           // Don't add randomness to the behavior.
36  kNoLoadProtection = 1 << 6,   // Don't act conservatively under load.
37  kNoBuffering = 1 << 7         // Disable extended IO buffering.
38};
39
40// This class implements the Backend interface. An object of this
41// class handles the operations of the cache for a particular profile.
42class NET_EXPORT_PRIVATE BackendImpl : public Backend {
43  friend class Eviction;
44 public:
45  BackendImpl(const base::FilePath& path, base::MessageLoopProxy* cache_thread,
46              net::NetLog* net_log);
47  // mask can be used to limit the usable size of the hash table, for testing.
48  BackendImpl(const base::FilePath& path, uint32 mask,
49              base::MessageLoopProxy* cache_thread, net::NetLog* net_log);
50  virtual ~BackendImpl();
51
52  // Performs general initialization for this current instance of the cache.
53  int Init(const CompletionCallback& callback);
54
55  // Same behavior as OpenNextEntry but walks the list from back to front.
56  int OpenPrevEntry(void** iter, Entry** prev_entry,
57                    const CompletionCallback& callback);
58
59  // Sets the maximum size for the total amount of data stored by this instance.
60  bool SetMaxSize(int max_bytes);
61
62  // Sets the cache type for this backend.
63  void SetType(net::CacheType type);
64
65  // Creates a new storage block of size block_count.
66  bool CreateBlock(FileType block_type, int block_count,
67                   Addr* block_address);
68
69  // Updates the ranking information for an entry.
70  void UpdateRank(EntryImpl* entry, bool modified);
71
72  // Permanently deletes an entry, but still keeps track of it.
73  void InternalDoomEntry(EntryImpl* entry);
74
75  // This method must be called when an entry is released for the last time, so
76  // the entry should not be used anymore. |address| is the cache address of the
77  // entry.
78  void OnEntryDestroyBegin(Addr address);
79
80  // This method must be called after all resources for an entry have been
81  // released.
82  void OnEntryDestroyEnd();
83
84  // If the data stored by the provided |rankings| points to an open entry,
85  // returns a pointer to that entry, otherwise returns NULL. Note that this
86  // method does NOT increase the ref counter for the entry.
87  EntryImpl* GetOpenEntry(CacheRankingsBlock* rankings) const;
88
89  // Returns the id being used on this run of the cache.
90  int32 GetCurrentEntryId() const;
91
92  // Returns the maximum size for a file to reside on the cache.
93  int MaxFileSize() const;
94
95  // A user data block is being created, extended or truncated.
96  void ModifyStorageSize(int32 old_size, int32 new_size);
97
98  // Logs requests that are denied due to being too big.
99  void TooMuchStorageRequested(int32 size);
100
101  // Returns true if a temporary buffer is allowed to be extended.
102  bool IsAllocAllowed(int current_size, int new_size);
103
104  // Tracks the release of |size| bytes by an entry buffer.
105  void BufferDeleted(int size);
106
107  // Only intended for testing the two previous methods.
108  int GetTotalBuffersSize() const {
109    return buffer_bytes_;
110  }
111
112  // Returns true if this instance seems to be under heavy load.
113  bool IsLoaded() const;
114
115  // Returns the full histogram name, for the given base |name| and experiment,
116  // and the current cache type. The name will be "DiskCache.t.name_e" where n
117  // is the cache type and e the provided |experiment|.
118  std::string HistogramName(const char* name, int experiment) const;
119
120  net::CacheType cache_type() const {
121    return cache_type_;
122  }
123
124  bool read_only() const {
125    return read_only_;
126  }
127
128  // Returns a weak pointer to this object.
129  base::WeakPtr<BackendImpl> GetWeakPtr();
130
131  // Returns true if we should send histograms for this user again. The caller
132  // must call this function only once per run (because it returns always the
133  // same thing on a given run).
134  bool ShouldReportAgain();
135
136  // Reports some data when we filled up the cache.
137  void FirstEviction();
138
139  // Called when an interesting event should be logged (counted).
140  void OnEvent(Stats::Counters an_event);
141
142  // Keeps track of payload access (doesn't include metadata).
143  void OnRead(int bytes);
144  void OnWrite(int bytes);
145
146  // Timer callback to calculate usage statistics.
147  void OnStatsTimer();
148
149  // Sets internal parameters to enable unit testing mode.
150  void SetUnitTestMode();
151
152  // Sets internal parameters to enable upgrade mode (for internal tools).
153  void SetUpgradeMode();
154
155  // Sets the eviction algorithm to version 2.
156  void SetNewEviction();
157
158  // Sets an explicit set of BackendFlags.
159  void SetFlags(uint32 flags);
160
161  // Sends a dummy operation through the operation queue, for unit tests.
162  int FlushQueueForTest(const CompletionCallback& callback);
163
164  // Trims an entry (all if |empty| is true) from the list of deleted
165  // entries. This method should be called directly on the cache thread.
166  void TrimForTest(bool empty);
167
168  // Trims an entry (all if |empty| is true) from the list of deleted
169  // entries. This method should be called directly on the cache thread.
170  void TrimDeletedListForTest(bool empty);
171
172  // Performs a simple self-check, and returns the number of dirty items
173  // or an error code (negative value).
174  int SelfCheck();
175
176  // Backend implementation.
177  virtual net::CacheType GetCacheType() const OVERRIDE;
178  virtual int32 GetEntryCount() const OVERRIDE;
179  virtual int OpenEntry(const std::string& key, Entry** entry,
180                        const CompletionCallback& callback) OVERRIDE;
181  virtual int CreateEntry(const std::string& key, Entry** entry,
182                          const CompletionCallback& callback) OVERRIDE;
183  virtual int DoomEntry(const std::string& key,
184                        const CompletionCallback& callback) OVERRIDE;
185  virtual int DoomAllEntries(const CompletionCallback& callback) OVERRIDE;
186  virtual int DoomEntriesBetween(base::Time initial_time,
187                                 base::Time end_time,
188                                 const CompletionCallback& callback) OVERRIDE;
189  virtual int DoomEntriesSince(base::Time initial_time,
190                               const CompletionCallback& callback) OVERRIDE;
191  virtual int OpenNextEntry(void** iter, Entry** next_entry,
192                            const CompletionCallback& callback) OVERRIDE;
193  virtual void EndEnumeration(void** iter) OVERRIDE;
194  virtual void GetStats(StatsItems* stats) OVERRIDE;
195  virtual void OnExternalCacheHit(const std::string& key) OVERRIDE;
196
197 private:
198  typedef base::hash_map<CacheAddr, EntryImpl*> EntriesMap;
199
200  void AdjustMaxCacheSize(int table_len);
201
202  bool InitStats();
203  void StoreStats();
204
205  // Deletes the cache and starts again.
206  void RestartCache(bool failure);
207  void PrepareForRestart();
208
209  void CleanupCache();
210
211  // Creates a new entry object. Returns zero on success, or a disk_cache error
212  // on failure.
213  int NewEntry(Addr address, EntryImpl** entry);
214
215  // Opens the next or previous entry on a cache iteration.
216  EntryImpl* OpenFollowingEntry(bool forward, void** iter);
217
218  // Handles the used storage count.
219  void AddStorageSize(int32 bytes);
220  void SubstractStorageSize(int32 bytes);
221
222  // Update the number of referenced cache entries.
223  void IncreaseNumRefs();
224  void DecreaseNumRefs();
225  void IncreaseNumEntries();
226  void DecreaseNumEntries();
227
228  // Dumps current cache statistics to the log.
229  void LogStats();
230
231  // Send UMA stats.
232  void ReportStats();
233
234  // Reports an uncommon, recoverable error.
235  void ReportError(int error);
236
237  // Performs basic checks on the index file. Returns false on failure.
238  bool CheckIndex();
239
240  // Part of the self test. Returns the number or dirty entries, or an error.
241  int CheckAllEntries();
242
243  // Part of the self test. Returns false if the entry is corrupt.
244  bool CheckEntry(EntryImpl* cache_entry);
245
246  // Returns the maximum total memory for the memory buffers.
247  int MaxBuffersSize();
248
249  scoped_refptr<MappedFile> index_;  // The main cache index.
250  base::FilePath path_;  // Path to the folder used as backing storage.
251  BlockFiles block_files_;  // Set of files used to store all data.
252  int32 max_size_;  // Maximum data size for this instance.
253  Eviction eviction_;  // Handler of the eviction algorithm.
254  EntriesMap open_entries_;  // Map of open entries.
255  int num_refs_;  // Number of referenced cache entries.
256  int max_refs_;  // Max number of referenced cache entries.
257  int entry_count_;  // Number of entries accessed lately.
258  int byte_count_;  // Number of bytes read/written lately.
259  int buffer_bytes_;  // Total size of the temporary entries' buffers.
260  int up_ticks_;  // The number of timer ticks received (OnStatsTimer).
261  net::CacheType cache_type_;
262  int uma_report_;  // Controls transmission of UMA data.
263  uint32 user_flags_;  // Flags set by the user.
264  bool init_;  // controls the initialization of the system.
265  bool restarted_;
266  bool unit_test_;
267  bool read_only_;  // Prevents updates of the rankings data (used by tools).
268  bool disabled_;
269  bool new_eviction_;  // What eviction algorithm should be used.
270  bool first_timer_;  // True if the timer has not been called.
271  bool user_load_;  // True if we see a high load coming from the caller.
272
273  net::NetLog* net_log_;
274
275  Stats stats_;  // Usage statistics.
276  scoped_ptr<base::RepeatingTimer<BackendImpl> > timer_;  // Usage timer.
277  scoped_refptr<TraceObject> trace_object_;  // Initializes internal tracing.
278  base::WeakPtrFactory<BackendImpl> ptr_factory_;
279
280  DISALLOW_COPY_AND_ASSIGN(BackendImpl);
281};
282
283// Returns the preferred max cache size given the available disk space.
284NET_EXPORT_PRIVATE int PreferedCacheSize(int64 available);
285
286}  // namespace disk_cache
287
288#endif  // NET_DISK_CACHE_BACKEND_IMPL_H_
289