#include <userver/cache/cache_update_trait.hpp>

Detailed Description

Base class for periodically updated caches.

Note: Don't use directly, inherit from components::CachingComponentBase instead

Definition at line 30 of file cache_update_trait.hpp.

Inheritance diagram for cache::CacheUpdateTrait:

Public Member Functions
	CacheUpdateTrait (CacheUpdateTrait &&)=delete

CacheUpdateTrait &	operator= (CacheUpdateTrait &&)=delete

void	InvalidateAsync (UpdateType update_type)
	Non-blocking forced cache update of specified type.

void	UpdateSyncDebug (UpdateType update_type)
	Forces a cache update of specified type.

const std::string &	Name () const

Protected Types
enum class	Flag { kNone = 0 , kNoFirstUpdate = 1 << 0 }
	Periodic update flags. More...

Protected Member Functions
AllowedUpdateTypes	GetAllowedUpdateTypes () const
	Update types configured for the cache.

void	StartPeriodicUpdates (utils::Flags< Flag > flags={})
	Starts periodic updates.

void	StopPeriodicUpdates ()
	Stops periodic updates.

void	AssertPeriodicUpdateStarted ()

void	AssertPeriodicUpdateStopped ()

void	OnCacheModified ()

virtual void	Update (UpdateType type, const std::chrono::system_clock::time_point &last_update, const std::chrono::system_clock::time_point &now, UpdateStatisticsScope &stats_scope)=0
	Should be overridden in a derived class to align the stored data with some data source.

Member Enumeration Documentation

◆ Flag

enum class cache::CacheUpdateTrait::Flag

strongprotected

Periodic update flags.

Enumerator

kNoFirstUpdate

Disable initial update on start.

Deprecated: Use first-update-fail-ok: true instead

Definition at line 61 of file cache_update_trait.hpp.

Member Function Documentation

◆ InvalidateAsync()

void cache::CacheUpdateTrait::InvalidateAsync ( UpdateType update_type )

Non-blocking forced cache update of specified type.

See also: PeriodicTask::ForceStepAsync for behavior details

◆ Name()

const std::string & cache::CacheUpdateTrait::Name ( ) const

Returns: name of the component

◆ OnCacheModified()

void cache::CacheUpdateTrait::OnCacheModified ( )

protected

Called in CachingComponentBase::Set during update to indicate that the cached data has been modified

◆ StopPeriodicUpdates()

void cache::CacheUpdateTrait::StopPeriodicUpdates ( )

protected

Stops periodic updates.

Warning: Should be called in destructor of derived class.

◆ Update()

virtual void cache::CacheUpdateTrait::Update	(	UpdateType	type,
		const std::chrono::system_clock::time_point &	last_update,
		const std::chrono::system_clock::time_point &	now,
		UpdateStatisticsScope &	stats_scope )

protectedpure virtual

Should be overridden in a derived class to align the stored data with some data source.

Update implementation should do one of the following:

A. If the update succeeded and has changes...

call CachingComponentBase::Set to update the stored value and send a notification to subscribers
call UpdateStatisticsScope::Finish
return normally (an exception is allowed in edge cases)

B. If the update succeeded and verified that there are no changes...

DON'T call CachingComponentBase::Set
call UpdateStatisticsScope::FinishNoChanges
return normally (an exception is allowed in edge cases)

C. If the update failed...

DON'T call CachingComponentBase::Set
call UpdateStatisticsScope::FinishWithError, or...
throw an exception, which will be logged nicely (if there already is an exception, prefer rethrowing it instead of calling UpdateStatisticsScope::FinishWithError)

Parameters

type	type of the update
last_update	time of the last update (value of `now` from previous invocation of Update or default constructed value if this is the first Update).
now	current time point
stats_scope	the scope that expects one of `Finish`, `FinishNoChanges`, `FinishWithError` or an exception.

Exceptions

std::exception on update failure

Warning: If Update returns without throwing an exception and without calling one of the Finish* methods, the behavior is undefined.

See also: Basics of Caches

◆ UpdateSyncDebug()

void cache::CacheUpdateTrait::UpdateSyncDebug ( UpdateType update_type )

Forces a cache update of specified type.