file_cache.h

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/*
 * Copyright 2010 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http:///www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


#ifndef PAGESPEED_KERNEL_CACHE_FILE_CACHE_H_
#define PAGESPEED_KERNEL_CACHE_FILE_CACHE_H_

#include "pagespeed/kernel/base/abstract_mutex.h"
#include "pagespeed/kernel/base/basictypes.h"
#include "pagespeed/kernel/base/cache_interface.h"
#include "pagespeed/kernel/base/file_system.h"
#include "pagespeed/kernel/base/scoped_ptr.h"
#include "pagespeed/kernel/base/shared_string.h"
#include "pagespeed/kernel/base/string.h"
#include "pagespeed/kernel/base/thread_annotations.h"
#include "pagespeed/kernel/base/thread_system.h"

namespace net_instaweb {

class Hasher;
class MessageHandler;
class SlowWorker;
class Statistics;
class Timer;
class Variable;

class FileCache : public CacheInterface {
 public:
  struct CachePolicy {
    CachePolicy(Timer* timer, Hasher* hasher, int64 clean_interval_ms,
                int64 target_size_bytes, int64 target_inode_count)
        : timer(timer), hasher(hasher), clean_interval_ms(clean_interval_ms),
          target_size_bytes(target_size_bytes),
          target_inode_count(target_inode_count) {}
    const Timer* timer;
    const Hasher* hasher;
    int64 clean_interval_ms;
    int64 target_size_bytes;
    int64 target_inode_count;
    bool cleaning_enabled() { return clean_interval_ms != kDisableCleaning; }
   private:
    
  };

  FileCache(const GoogleString& path, FileSystem* file_system,
            ThreadSystem* thread_system, SlowWorker* worker,
            CachePolicy* policy, Statistics* stats, MessageHandler* handler);
  virtual ~FileCache();

  static void InitStats(Statistics* statistics);

  virtual void Get(const GoogleString& key, Callback* callback);
  virtual void Put(const GoogleString& key, const SharedString& value);
  virtual void Delete(const GoogleString& key);
  void set_worker(SlowWorker* worker) { worker_ = worker; }
  SlowWorker* worker() { return worker_; }

  static GoogleString FormatName() { return "FileCache"; }
  virtual GoogleString Name() const { return FormatName(); }

  virtual bool IsBlocking() const { return true; }
  virtual bool IsHealthy() const { return true; }
  virtual void ShutDown() {}  

  const CachePolicy* cache_policy() const { return cache_policy_.get(); }
  CachePolicy* mutable_cache_policy() { return cache_policy_.get(); }
  const GoogleString& path() const { return path_; }

  static const char kBytesFreedInCleanup[];
  static const char kCleanups[];
  static const char kDiskChecks[];
  static const char kEvictions[];
  static const char kSkippedCleanups[];
  static const char kStartedCleanups[];
  static const char kWriteErrors[];

  static const int kDisableCleaning = -1;

 private:
  class CacheCleanFunction;
  friend class FileCacheTest;
  friend class CacheCleanFunction;

  bool Clean(int64 target_size_bytes, int64 target_inode_count);

  void CleanWithLocking(int64 next_clean_time_ms) LOCKS_EXCLUDED(mutex_);

  bool ShouldClean(int64* suggested_next_clean_time_ms) LOCKS_EXCLUDED(mutex_);

  void CleanIfNeeded() LOCKS_EXCLUDED(mutex_);

  bool EncodeFilename(const GoogleString& key, GoogleString* filename);

  const GoogleString path_;
  FileSystem* file_system_;
  SlowWorker* worker_;
  MessageHandler* message_handler_;
  const scoped_ptr<CachePolicy> cache_policy_;
  scoped_ptr<AbstractMutex> mutex_;
  int64 next_clean_ms_ GUARDED_BY(mutex_);
  int path_length_limit_; 
  GoogleString clean_time_path_;
  GoogleString clean_lock_path_;
  FileSystem::ProgressNotifier* notifier_for_tests_;

  Variable* disk_checks_;
  Variable* cleanups_;
  Variable* evictions_;
  Variable* bytes_freed_in_cleanup_;
  Variable* skipped_cleanups_;
  Variable* started_cleanups_;
  Variable* write_errors_;

  static const char kCleanTimeName[];
  static const char kCleanLockName[];

  static const int kLockTimeoutMs;

  
};

}  

#endif