cache_batcher.h

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/*
 * Copyright 2012 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_CACHE_BATCHER_H_
#define PAGESPEED_KERNEL_CACHE_CACHE_BATCHER_H_

#include <cstddef>

#include <unordered_map>
#include <vector>

#include "pagespeed/kernel/base/abstract_mutex.h"
#include "pagespeed/kernel/base/basictypes.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/string_util.h"
#include "pagespeed/kernel/base/thread_annotations.h"
#include "pagespeed/kernel/cache/cache_interface.h"

namespace net_instaweb {

class Statistics;
class Variable;

class CacheBatcher : public CacheInterface {
 public:
  static const int kDefaultMaxParallelLookups = 1;

  static const size_t kDefaultMaxPendingGets = 1000;

  struct Options {
    Options()
        : max_parallel_lookups(kDefaultMaxParallelLookups),
          max_pending_gets(kDefaultMaxPendingGets) {
    }

    int max_parallel_lookups;
    int max_pending_gets;
  };

  CacheBatcher(const Options& options, CacheInterface* cache,
               AbstractMutex* mutex, Statistics* statistics);
  virtual ~CacheBatcher();

  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);
  virtual GoogleString Name() const;
  static GoogleString FormatName(StringPiece cache, int parallelism, int max);

  virtual bool IsBlocking() const { return cache_->IsBlocking(); }

  virtual bool IsHealthy() const { return cache_->IsHealthy(); }
  virtual void ShutDown();

 private:
  typedef std::unordered_map<GoogleString, std::vector<Callback*>> CallbackMap;

  class Group;
  class MultiCallback;

  bool CanIssueGet() const EXCLUSIVE_LOCKS_REQUIRED(mutex_);
  bool CanQueueCallback() const EXCLUSIVE_LOCKS_REQUIRED(mutex_);
  void GroupComplete();

  MultiGetRequest* ConvertMapToRequest(const CallbackMap& map)
      EXCLUSIVE_LOCKS_REQUIRED(mutex_);
  MultiGetRequest* CreateRequestForQueuedKeys()
      EXCLUSIVE_LOCKS_REQUIRED(mutex_);
  void MoveQueuedKeys() EXCLUSIVE_LOCKS_REQUIRED(mutex_);
  void ExtractInFlightKeys(const GoogleString& key,
                   std::vector<CacheInterface::Callback*>* callbacks)
      LOCKS_EXCLUDED(mutex_);

  void DecrementInFlightGets(int n) LOCKS_EXCLUDED(mutex_);

  friend class CacheBatcherTestingPeer;
  int last_batch_size() const LOCKS_EXCLUDED(mutex_);
  int num_in_flight_keys() LOCKS_EXCLUDED(mutex_);

  CacheInterface* cache_;
  Variable* dropped_gets_;
  Variable* coalesced_gets_;
  Variable* queued_gets_;
  CallbackMap in_flight_ GUARDED_BY(mutex_);
  int last_batch_size_ GUARDED_BY(mutex_);
  scoped_ptr<AbstractMutex> mutex_;
  int num_in_flight_groups_ GUARDED_BY(mutex_);
  int num_in_flight_keys_ GUARDED_BY(mutex_);
  int num_pending_gets_ GUARDED_BY(mutex_);
  const Options options_;
  CallbackMap queued_ GUARDED_BY(mutex_);
  bool shutdown_ GUARDED_BY(mutex_);

  
};

}  

#endif