cache::LruCacheComponent< Key, Value, Hash, Equal > Class Template Reference

Table of Contents

• Detailed Description
• Dynamic config
• Static options:
• Example usage:
• Example config:
• Public Types
• Public Member Functions
• Static Public Member Functions
• Protected Member Functions
• Member Typedef Documentation
• Cache
• CacheWrapper
• Constructor & Destructor Documentation
• LruCacheComponent()
• ~LruCacheComponent()
• Member Function Documentation
• GetCache()
• GetCacheRaw()
• GetStaticConfigSchema()

#include <userver/cache/lru_cache_component_base.hpp>

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 std::string_view 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:

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

Definition at line 77 of file 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 ()

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 80 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 81 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 )

Definition at line 125 of file lru_cache_component_base.hpp.

~LruCacheComponent()

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

cache::LruCacheComponent< Key, Value, Hash, Equal >::~LruCacheComponent ( )

override

Definition at line 164 of file lru_cache_component_base.hpp.

Member Function Documentation

GetCache()

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

LruCacheComponent< Key, Value, Hash, Equal >::CacheWrapper cache::LruCacheComponent< Key, Value, Hash, Equal >::GetCache

(

)

Definition at line 176 of file lru_cache_component_base.hpp.

GetCacheRaw()

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

std::shared_ptr< Cache > cache::LruCacheComponent< Key, Value, Hash, Equal >::GetCacheRaw ( )

inlineprotected

Definition at line 95 of file lru_cache_component_base.hpp.

GetStaticConfigSchema()

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

yaml_config::Schema cache::LruCacheComponent< Key, Value, Hash, Equal >::GetStaticConfigSchema ( )

static

Definition at line 213 of file lru_cache_component_base.hpp.

---

The documentation for this class was generated from the following file:

• userver/cache/lru_cache_component_base.hpp