Base class for LRU-cache components. More...

#include <userver/cache/lru_cache_component_base.hpp>

Inheritance diagram for cache::LruCacheComponent< Key, Value, Hash, Equal >:

Collaboration diagram for cache::LruCacheComponent< Key, Value, Hash, Equal >:

Public Types
using	Cache = ExpirableLruCache< Key, Value, Hash, Equal >

using	CacheWrapper = LruCacheWrapper< Key, Value, Hash, Equal >

Public Member Functions
	LruCacheComponent (const components::ComponentConfig &, const components::ComponentContext &)

CacheWrapper	GetCache ()

Public Member Functions inherited from components::LoggableComponentBase
	LoggableComponentBase (const ComponentConfig &, const ComponentContext &)

	LoggableComponentBase (LoggableComponentBase &&)=delete

	LoggableComponentBase (const LoggableComponentBase &)=delete

	~LoggableComponentBase () override=default

ComponentHealth	GetComponentHealth () const override

void	OnLoadingCancelled () override

void	OnAllComponentsLoaded () override

void	OnAllComponentsAreStopping () override

Static Public Member Functions
static yaml_config::Schema	GetStaticConfigSchema ()

Static Public Member Functions inherited from components::LoggableComponentBase
static yaml_config::Schema	GetStaticConfigSchema ()

Protected Member Functions
virtual Value	DoGetByKey (const Key &key)=0

std::shared_ptr< Cache >	GetCacheRaw ()

Detailed Description

template<typename Key, typename Value, typename Hash = std::hash<Key>, typename Equal = std::equal_to<Key>>
class cache::LruCacheComponent< Key, Value, Hash, Equal >

Base class for LRU-cache components.

Provides facilities for creating LRU caches. You need to override LruCacheComponent::DoGetByKey to handle cache misses.

Caching components must be configured in service config (see options below) and may be reconfigured dynamically via components::DynamicConfig.

Dynamic config

USERVER_LRU_CACHES

Static options:

Name	Description	Default value
size	max amount of items to store in cache	–
ways	number of ways for associative cache	–
lifetime	TTL for cache entries (0 is unlimited)	0
config-settings	enables dynamic reconfiguration with CacheConfigSet	true

Example usage:

#include <userver/cache/lru_cache_component_base.hpp>
#include <userver/components/component_list.hpp>
 
using Key = std::string;
using Value = std::size_t;
 
class ExampleCacheComponent final
    : public cache::LruCacheComponent<Key, Value> {
 public:
  static constexpr auto kName = "example-cache";
 
  ExampleCacheComponent(const components::ComponentConfig& config,
                        const components::ComponentContext& context)
      : ::cache::LruCacheComponent<Key, Value>(config, context) {}
 
 private:
  Value DoGetByKey(const Key& key) override {
    return GetValueForExpiredKeyFromRemote(key);
  }
 
  Value GetValueForExpiredKeyFromRemote(const Key& key);
};

Do not forget to add the component to component list:

auto component_list = components::MinimalComponentList();

component_list.Append<ExampleCacheComponent>();

Example config:

# yaml
    example-cache:
      size: 1
      ways: 1
      lifetime: 1s # 0 (unlimited) by default
      config-settings: false # true by default

Definition at line 80 of file lru_cache_component_base.hpp.

Member Typedef Documentation

◆ Cache

template<typename Key , typename Value , typename Hash = std::hash<Key>, typename Equal = std::equal_to<Key>>

using cache::LruCacheComponent< Key, Value, Hash, Equal >::Cache = ExpirableLruCache<Key, Value, Hash, Equal>

Definition at line 83 of file lru_cache_component_base.hpp.

◆ CacheWrapper

template<typename Key , typename Value , typename Hash = std::hash<Key>, typename Equal = std::equal_to<Key>>

using cache::LruCacheComponent< Key, Value, Hash, Equal >::CacheWrapper = LruCacheWrapper<Key, Value, Hash, Equal>

Definition at line 84 of file lru_cache_component_base.hpp.

Constructor & Destructor Documentation

◆ LruCacheComponent()

template<typename Key , typename Value , typename Hash , typename Equal >

cache::LruCacheComponent< Key, Value, Hash, Equal >::LruCacheComponent	(	const components::ComponentConfig &	config,
		const components::ComponentContext &	context
	)