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// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <map>
#include <memory>
#include <string>
#include <vector>
#include "base/callback.h"
#include "base/gtest_prod_util.h"
#include "base/macros.h"
#include "base/optional.h"
#include "base/time/time.h"
#include "content/common/content_export.h"
#include "content/common/leveldb_wrapper.mojom.h"
#include "mojo/public/cpp/bindings/binding_set.h"
#include "mojo/public/cpp/bindings/interface_ptr_set.h"
namespace base {
namespace trace_event {
class ProcessMemoryDump;
namespace content {
// This is a wrapper around a leveldb::mojom::LevelDBDatabase. Multiple
// interface
// pointers can be bound to the same object. The wrapper adds a couple of
// features not found directly in leveldb.
// 1) Adds the given prefix, if any, to all keys. This allows the sharing of one
// database across many, possibly untrusted, consumers and ensuring that they
// can't access each other's values.
// 2) Enforces a max_size constraint.
// 3) Informs observers when values scoped by prefix are modified.
// 4) Throttles requests to avoid overwhelming the disk.
// The wrapper supports two different caching modes.
class CONTENT_EXPORT LevelDBWrapperImpl : public mojom::LevelDBWrapper {
using ValueMap = std::map<std::vector<uint8_t>, std::vector<uint8_t>>;
using ValueMapCallback = base::OnceCallback<void(std::unique_ptr<ValueMap>)>;
using Change =
std::pair<std::vector<uint8_t>, base::Optional<std::vector<uint8_t>>>;
using KeysOnlyMap = std::map<std::vector<uint8_t>, size_t>;
class CONTENT_EXPORT Delegate {
virtual ~Delegate();
virtual void OnNoBindings() = 0;
virtual std::vector<leveldb::mojom::BatchedOperationPtr>
PrepareToCommit() = 0;
virtual void DidCommit(leveldb::mojom::DatabaseError error) = 0;
// Called during loading if no data was found. Needs to call |callback|.
virtual void MigrateData(ValueMapCallback callback);
// Called during loading to give delegate a chance to modify the data as
// stored in the database.
virtual std::vector<Change> FixUpData(const ValueMap& data);
virtual void OnMapLoaded(leveldb::mojom::DatabaseError error);
enum class CacheMode {
// The cache stores only keys (required to maintain max size constraints)
// when there is only one client binding to save memory. The client is
// asked to send old values on mutations for sending notifications to
// observers.
// The cache always stores keys and values.
// Options provided to constructor.
struct Options {
CacheMode cache_mode = CacheMode::KEYS_AND_VALUES;
// Max bytes of storage that can be used by key value pairs.
size_t max_size = 0;
// Minimum time between 2 commits to disk.
base::TimeDelta default_commit_delay;
// Maximum number of bytes written to disk in one hour.
int max_bytes_per_hour = 0;
// Maximum number of disk write batches in one hour.
int max_commits_per_hour = 0;
// |Delegate::OnNoBindings| will be called when this object has no more
// bindings and all pending modifications have been processed.
LevelDBWrapperImpl(leveldb::mojom::LevelDBDatabase* database,
const std::string& prefix,
Delegate* delegate,
const Options& options);
LevelDBWrapperImpl(leveldb::mojom::LevelDBDatabase* database,
std::vector<uint8_t> prefix,
Delegate* delegate,
const Options& options);
~LevelDBWrapperImpl() override;
void Bind(mojom::LevelDBWrapperRequest request);
// Forks, or copies, all data in this prefix to another prefix.
// Note: this object (the parent) must stay alive until the forked wrapper
// has been loaded (see initialized()).
std::unique_ptr<LevelDBWrapperImpl> ForkToNewPrefix(
const std::string& new_prefix,
Delegate* delegate,
const Options& options);
std::unique_ptr<LevelDBWrapperImpl> ForkToNewPrefix(
std::vector<uint8_t> new_prefix,
Delegate* delegate,
const Options& options);
// Cancels all pending load tasks. Useful for emergency destructions. If the
// wrapper is unloaded (initialized() returns false), this will DROP all
// pending changes to the database, and any uninitialized wrappers created
// through |ForkToNewPrefix| will stay BROKEN and unresponsive.
void CancelAllPendingRequests();
// The total bytes used by items which counts towards the quota.
size_t storage_used() const { return storage_used_; }
// The physical memory used by the cache.
size_t memory_used() const { return memory_used_; }
bool empty() const { return storage_used_ == 0; }
// If this wrapper is loaded and sending changes to the database.
bool initialized() const { return IsMapLoaded(); }
CacheMode cache_mode() const { return cache_mode_; }
// Tasks that are waiting for the map to be loaded.
bool has_pending_load_tasks() const {
return !on_load_complete_tasks_.empty();
bool has_changes_to_commit() const { return commit_batch_.get(); }
const std::vector<uint8_t>& prefix() { return prefix_; }
leveldb::mojom::LevelDBDatabase* database() { return database_; }
// Commence aggressive flushing. This should be called early during startup,
// before any localStorage writing. Currently scheduled writes will not be
// rescheduled and will be flushed at the scheduled time after which
// aggressive flushing will commence.
static void EnableAggressiveCommitDelay();
// Commits any uncommitted data to the database as soon as possible. This
// usually means data will be committed immediately, but if we're currently
// waiting on the result of initializing our map the commit won't happen
// until the load has finished.
void ScheduleImmediateCommit();
// Clears the in-memory cache if currently no changes are pending. If there
// are uncommitted changes this method does nothing.
void PurgeMemory();
// Adds memory statistics to |pmd| for memory infra.
void OnMemoryDump(const std::string& name,
base::trace_event::ProcessMemoryDump* pmd);
// Sets cache mode to either store only keys or keys and values. See
// SetCacheMode().
void SetCacheModeForTesting(CacheMode cache_mode);
// Returns a pointer ID for use with HasObserver and RemoveObserver.
mojo::InterfacePtrSetElementId AddObserver(
mojom::LevelDBObserverAssociatedPtr observer);
bool HasObserver(mojo::InterfacePtrSetElementId id);
mojom::LevelDBObserverAssociatedPtr RemoveObserver(
mojo::InterfacePtrSetElementId id);
// LevelDBWrapper:
void AddObserver(mojom::LevelDBObserverAssociatedPtrInfo observer) override;
void Put(const std::vector<uint8_t>& key,
const std::vector<uint8_t>& value,
const base::Optional<std::vector<uint8_t>>& client_old_value,
const std::string& source,
PutCallback callback) override;
void Delete(const std::vector<uint8_t>& key,
const base::Optional<std::vector<uint8_t>>& client_old_value,
const std::string& source,
DeleteCallback callback) override;
void DeleteAll(const std::string& source,
DeleteAllCallback callback) override;
void Get(const std::vector<uint8_t>& key, GetCallback callback) override;
void GetAll(
mojom::LevelDBWrapperGetAllCallbackAssociatedPtrInfo complete_callback,
GetAllCallback callback) override;
FRIEND_TEST_ALL_PREFIXES(LevelDBWrapperImplTest, GetAllAfterSetCacheMode);
FRIEND_TEST_ALL_PREFIXES(LevelDBWrapperImplTest, SetCacheModeConsistent);
// Used to rate limit commits.
class RateLimiter {
RateLimiter(size_t desired_rate, base::TimeDelta time_quantum);
void add_samples(size_t samples) { samples_ += samples; }
// Computes the total time needed to process the total samples seen
// at the desired rate.
base::TimeDelta ComputeTimeNeeded() const;
// Given the elapsed time since the start of the rate limiting session,
// computes the delay needed to mimic having processed the total samples
// seen at the desired rate.
base::TimeDelta ComputeDelayNeeded(
const base::TimeDelta elapsed_time) const;
float rate() const { return rate_; }
float rate_;
float samples_;
base::TimeDelta time_quantum_;
// There can be only one fork operation per commit batch.
struct CommitBatch {
bool clear_all_first;
// Prefix copying is performed before applying changes.
base::Optional<std::vector<uint8_t>> copy_to_prefix;
// Used if the map_type_ is LOADED_KEYS_ONLY.
std::map<std::vector<uint8_t>, std::vector<uint8_t>> changed_values;
// Used if the map_type_ is LOADED_KEYS_AND_VALUES.
std::set<std::vector<uint8_t>> changed_keys;
enum class MapState {
// Loading from the database connection.
// Loading from another LevelDBWrapperImpl that we have forked from.
using LoadStateForForkCallback = base::OnceCallback<
void(bool database_enabled, const ValueMap&, const KeysOnlyMap&)>;
using ForkSourceEarlyDeathCallback =
base::OnceCallback<void(std::vector<uint8_t> source_prefix)>;
// Changes the cache mode of the wrapper. If applicable, this will change the
// internal storage type after the next commit. The keys-only mode can only
// be set only when there is one client binding. It automatically changes to
// keys-and-values mode when more than one binding exists.
// Notifications to observers when an item is mutated depends on the
// |client_old_value| when in keys-only mode. Using GetAll during
// keys-only mode will cause extra disk access.
void SetCacheMode(CacheMode cache_mode);
void OnConnectionError();
// Always loads the |keys_values_map_|, sets the |map_state_| to
// LOADED_KEYS_AND_VALUES, and calls through all the completion callbacks.
// Then if the |cache_mode_| is keys-only, it unloads the map to the
// |keys_only_map_| and sets the |map_state_| to LOADED_KEYS_ONLY
void LoadMap(base::OnceClosure completion_callback);
void OnMapLoaded(leveldb::mojom::DatabaseError status,
std::vector<leveldb::mojom::KeyValuePtr> data);
void OnGotMigrationData(std::unique_ptr<ValueMap> data);
void CalculateStorageAndMemoryUsed();
void OnLoadComplete();
void CreateCommitBatchIfNeeded();
void StartCommitTimer();
base::TimeDelta ComputeCommitDelay() const;
void CommitChanges();
void OnCommitComplete(leveldb::mojom::DatabaseError error);
void UnloadMapIfPossible();
bool IsMapUpgradeNeeded() const {
return map_state_ == MapState::LOADED_KEYS_ONLY &&
cache_mode_ == CacheMode::KEYS_AND_VALUES;
bool IsMapLoaded() const {
return map_state_ == MapState::LOADED_KEYS_ONLY ||
map_state_ == MapState::LOADED_KEYS_AND_VALUES;
bool IsMapLoadedAndEmpty() const {
return (map_state_ == MapState::LOADED_KEYS_ONLY &&
keys_only_map_.empty()) ||
(map_state_ == MapState::LOADED_KEYS_AND_VALUES &&
void DoForkOperation(const base::WeakPtr<LevelDBWrapperImpl>& forked_wrapper);
void OnForkStateLoaded(bool database_enabled,
const ValueMap& map,
const KeysOnlyMap& key_only_map);
std::vector<uint8_t> prefix_;
mojo::BindingSet<mojom::LevelDBWrapper> bindings_;
mojo::AssociatedInterfacePtrSet<mojom::LevelDBObserver> observers_;
Delegate* delegate_;
leveldb::mojom::LevelDBDatabase* database_;
// For commits to work correctly the map loaded state (keys vs keys & values)
// must stay consistent for a given commit batch.
MapState map_state_ = MapState::UNLOADED;
CacheMode cache_mode_;
ValueMap keys_values_map_;
KeysOnlyMap keys_only_map_;
// These are always consumed & cleared when the map is loaded.
std::vector<base::OnceClosure> on_load_complete_tasks_;
size_t storage_used_;
size_t max_size_;
size_t memory_used_;
base::TimeTicks start_time_;
base::TimeDelta default_commit_delay_;
RateLimiter data_rate_limiter_;
RateLimiter commit_rate_limiter_;
int commit_batches_in_flight_ = 0;
std::unique_ptr<CommitBatch> commit_batch_;
base::WeakPtrFactory<LevelDBWrapperImpl> weak_ptr_factory_;
static bool s_aggressive_flushing_enabled_;
} // namespace content