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

#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:

# yaml
    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 >:

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 ()
ComponentHealth	GetComponentHealth () const override
void	OnLoadingCancelled () override
void	OnAllComponentsLoaded () override
void	OnAllComponentsAreStopping () override

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

Protected Types
using	LoggableComponentBase = ComponentBase
	Legacy alias, use ComponentBase instead.

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.

LoggableComponentBase

using components::ComponentBase::LoggableComponentBase = ComponentBase

protectedinherited

Legacy alias, use ComponentBase instead.

Definition at line 69 of file 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.

GetComponentHealth()

ComponentHealth components::ComponentBase::GetComponentHealth ( ) const

inlineoverridevirtualinherited

Override this function to inform the world of the state of your component.

Warning

The function is called concurrently from multiple threads.

Reimplemented from components::RawComponentBase.

Definition at line 35 of file 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.

OnAllComponentsAreStopping()

void components::ComponentBase::OnAllComponentsAreStopping ( )

inlineoverridevirtualinherited

Component may use this function to stop doing work before the stop of the components that depend on it.

Base components may override it and make final to do some work before the derived object constructor is called. Don't use it otherwise.

Reimplemented from components::RawComponentBase.

Reimplemented in urabbitmq::ConsumerComponentBase, and components::Server.

Definition at line 60 of file component_base.hpp.

OnAllComponentsLoaded()

void components::ComponentBase::OnAllComponentsLoaded ( )

inlineoverridevirtualinherited

Component may use this function to finalize registration of other components that depend on it (for example, handler components register in server component, and the latter uses OnAllComponentsLoaded() to start processing requests).

Base components may override it and make final to do some work after the derived object constructor is called. Don't use it otherwise.

Reimplemented from components::RawComponentBase.

Reimplemented in urabbitmq::ConsumerComponentBase, components::Server, and server::handlers::Ping.

Definition at line 53 of file component_base.hpp.

OnLoadingCancelled()

void components::ComponentBase::OnLoadingCancelled ( )

inlineoverridevirtualinherited

Called once if the creation of any other component failed. If the current component expects some other component to take any action with the current component, this call is a signal that such action may never happen due to components loading was cancelled. Application components might not want to override it.

Reimplemented from components::RawComponentBase.

Definition at line 44 of file component_base.hpp.

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

• userver/cache/lru_cache_component_base.hpp