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.
5 // See net/disk_cache/disk_cache.h for the public interface of the cache.
7 #ifndef NET_DISK_CACHE_BACKEND_IMPL_H_
8 #define NET_DISK_CACHE_BACKEND_IMPL_H_
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"
26 namespace disk_cache {
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.
40 // This class implements the Backend interface. An object of this
41 // class handles the operations of the cache for a particular profile.
42 class NET_EXPORT_PRIVATE BackendImpl : public Backend {
43 friend class Eviction;
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();
52 // Performs general initialization for this current instance of the cache.
53 int Init(const CompletionCallback& callback);
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);
59 // Sets the maximum size for the total amount of data stored by this instance.
60 bool SetMaxSize(int max_bytes);
62 // Sets the cache type for this backend.
63 void SetType(net::CacheType type);
65 // Creates a new storage block of size block_count.
66 bool CreateBlock(FileType block_type, int block_count,
69 // Updates the ranking information for an entry.
70 void UpdateRank(EntryImpl* entry, bool modified);
72 // Permanently deletes an entry, but still keeps track of it.
73 void InternalDoomEntry(EntryImpl* entry);
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
78 void OnEntryDestroyBegin(Addr address);
80 // This method must be called after all resources for an entry have been
82 void OnEntryDestroyEnd();
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;
89 // Returns the id being used on this run of the cache.
90 int32 GetCurrentEntryId() const;
92 // Returns the maximum size for a file to reside on the cache.
93 int MaxFileSize() const;
95 // A user data block is being created, extended or truncated.
96 void ModifyStorageSize(int32 old_size, int32 new_size);
98 // Logs requests that are denied due to being too big.
99 void TooMuchStorageRequested(int32 size);
101 // Returns true if a temporary buffer is allowed to be extended.
102 bool IsAllocAllowed(int current_size, int new_size);
104 // Tracks the release of |size| bytes by an entry buffer.
105 void BufferDeleted(int size);
107 // Only intended for testing the two previous methods.
108 int GetTotalBuffersSize() const {
109 return buffer_bytes_;
112 // Returns true if this instance seems to be under heavy load.
113 bool IsLoaded() const;
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;
120 net::CacheType cache_type() const {
124 bool read_only() const {
128 // Returns a weak pointer to this object.
129 base::WeakPtr<BackendImpl> GetWeakPtr();
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();
136 // Reports some data when we filled up the cache.
137 void FirstEviction();
139 // Called when an interesting event should be logged (counted).
140 void OnEvent(Stats::Counters an_event);
142 // Keeps track of payload access (doesn't include metadata).
143 void OnRead(int bytes);
144 void OnWrite(int bytes);
146 // Timer callback to calculate usage statistics.
149 // Sets internal parameters to enable unit testing mode.
150 void SetUnitTestMode();
152 // Sets internal parameters to enable upgrade mode (for internal tools).
153 void SetUpgradeMode();
155 // Sets the eviction algorithm to version 2.
156 void SetNewEviction();
158 // Sets an explicit set of BackendFlags.
159 void SetFlags(uint32 flags);
161 // Sends a dummy operation through the operation queue, for unit tests.
162 int FlushQueueForTest(const CompletionCallback& callback);
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);
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);
172 // Performs a simple self-check, and returns the number of dirty items
173 // or an error code (negative value).
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,
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;
198 typedef base::hash_map<CacheAddr, EntryImpl*> EntriesMap;
200 void AdjustMaxCacheSize(int table_len);
205 // Deletes the cache and starts again.
206 void RestartCache(bool failure);
207 void PrepareForRestart();
211 // Creates a new entry object. Returns zero on success, or a disk_cache error
213 int NewEntry(Addr address, EntryImpl** entry);
215 // Opens the next or previous entry on a cache iteration.
216 EntryImpl* OpenFollowingEntry(bool forward, void** iter);
218 // Handles the used storage count.
219 void AddStorageSize(int32 bytes);
220 void SubstractStorageSize(int32 bytes);
222 // Update the number of referenced cache entries.
223 void IncreaseNumRefs();
224 void DecreaseNumRefs();
225 void IncreaseNumEntries();
226 void DecreaseNumEntries();
228 // Dumps current cache statistics to the log.
234 // Reports an uncommon, recoverable error.
235 void ReportError(int error);
237 // Performs basic checks on the index file. Returns false on failure.
240 // Part of the self test. Returns the number or dirty entries, or an error.
241 int CheckAllEntries();
243 // Part of the self test. Returns false if the entry is corrupt.
244 bool CheckEntry(EntryImpl* cache_entry);
246 // Returns the maximum total memory for the memory buffers.
247 int MaxBuffersSize();
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.
267 bool read_only_; // Prevents updates of the rankings data (used by tools).
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.
273 net::NetLog* net_log_;
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_;
280 DISALLOW_COPY_AND_ASSIGN(BackendImpl);
283 // Returns the preferred max cache size given the available disk space.
284 NET_EXPORT_PRIVATE int PreferedCacheSize(int64 available);
286 } // namespace disk_cache
288 #endif // NET_DISK_CACHE_BACKEND_IMPL_H_