#include <userver/dynamic_config/updater/component.hpp>

Detailed Description

Component that does a periodic update of runtime configs.

Note that the service with dynamic config update component and without configs cache requires successful update to start. See dynamic_config_fallback for details and explanation.

Optional update event deduplication

Config update types to deduplicate. If enabled, JSON of the whole config is compared to the previous one; if same, no config update event is sent to the subscribers of dynamic_config::Source (OnConfigUpdate functions).

deduplicate-update-types static config option specifies the update types of the config cache, for which event deduplication should be performed. Possible values:

none (the default)
only-full
only-incremental
full-and-incremental

Full updates will always send an event unless deduplicated. Incremental updates may send an extra event for some config service implementations.

Note: This is not a silver bullet against extra events, because the events will be sent to every dynamic config subscriber if any part of the config has updated, not if the interesting part has updated.

Static options components::DynamicConfigClientUpdater :

Name	Description	Default value
updates-sink	Name of the component derived from components::DynamicConfigUpdatesSinkBase to be used for storing received updates.	dynamic-config
store-enabled	Store the retrieved values into the updates sink component.	true
load-only-my-values	Request from the client only the values used by this service.	true
deduplicate-update-types	Config update types for best-effort deduplication. Possible values: none, only-full, only-incremental, full-and-incremental.	full-and-incremental

Options inherited from components::CachingComponentBase :

Name	Description	Default value
update-types	Specifies whether incremental and/or full updates are used. Possible values: full-and-incremental, only-full, only-incremental.	–
update-interval	(required) interval between Update invocations.	–
update-jitter	Max. amount of time by which update-interval may be adjusted for requests dispersal.	update_interval / 10
updates-enabled	If false, cache updates are disabled (except for the first one if !first-update-fail-ok).	true
full-update-interval	Interval between full updates.	–
full-update-jitter	Max. amount of time by which full-update-interval may be adjusted for requests dispersal.	full-update-interval / 10
exception-interval	Sleep interval after an unhandled exception.	update_interval
first-update-fail-ok	Whether first update failure is non-fatal.	false
task-processor	The name of the TaskProcessor for running DoWork.	main-task-processor
config-settings	Enables dynamic reconfiguration with CacheConfigSet.	true
additional-cleanup-interval	How often to run background RCU garbage collector, in milliseconds.	10000
is-strong-period	Whether to include Update execution time in update-interval.	false
has-pre-assign-check	Enables the check before changing the value in the cache, by default it is the check that the new value is not empty.	false
testsuite-force-periodic-update	Override testsuite-periodic-update-enabled in TestsuiteSupport component config.	–
failed-updates-before-expiration	The number of consecutive failed updates for data expiration.	–
alert-on-failing-to-update-times	Fire an alert if the cache update failed specified amount of times in a row. If zero - alerts are disabled. Value from dynamic config takes priority over static.	0
safe-data-lifetime	Enables awaiting data destructors in the component's destructor. Can be set to false if the stored data does not refer to the component and its dependencies.	true
dump	Manages cache behavior after dump load.	–
dump.first-update-mode	Behavior of update after successful load from dump. skip - after successful load from dump, do nothing; required - make a synchronous update of type first-update-type, stop the service on failure; best-effort - make a synchronous update of type first-update-type, keep working and use data from dump on failure. Possible values: skip, required, best-effort.	skip
dump.first-update-type	Update type after successful load from dump. Possible values: full, incremental, incremental-then-async-full.	full

Options inherited from components::ComponentBase :

Name	Description	Default value
load-enabled	Set to false to disable loading of the component.	true

See also the options for components::CachingComponentBase.

Static configuration example:

# yaml
    dynamic-config-client-updater:
      store-enabled: true
      load-only-my-values: true
 
      # options from components::CachingComponentBase
      update-types: full-and-incremental
      update-interval: 5s
      update-jitter: 2s
      full-update-interval: 5m
      first-update-fail-ok: true
      config-settings: false
      additional-cleanup-interval: 5m

Definition at line 70 of file component.hpp.

Inheritance diagram for components::DynamicConfigClientUpdater:

Public Types
using	DataType

Public Member Functions
	DynamicConfigClientUpdater (const ComponentConfig &, const ComponentContext &)
dynamic_config::AdditionalKeysToken	SetAdditionalKeys (std::vector< std::string > keys)
const std::string &	Name () const noexcept
void	InvalidateAsync (UpdateType update_type)
	Non-blocking forced cache update of specified type.
void	InvalidateAsync (UpdateType update_type)
	Non-blocking forced cache update of specified type.
utils::SharedReadablePtr< dynamic_config::DocsMap >	Get () const final
utils::SharedReadablePtr< dynamic_config::DocsMap >	GetUnsafe () const
concurrent::AsyncEventSubscriberScope	UpdateAndListen (Class obj, std::string name, void(Class::func)(const std::shared_ptr< const dynamic_config::DocsMap > &))
concurrent::AsyncEventChannel< const std::shared_ptr< const dynamic_config::DocsMap > & > &	GetEventChannel ()
ComponentHealth	GetComponentHealth () const override
void	OnLoadingCancelled () override
void	OnAllComponentsLoaded () override
void	OnGracefulShutdown (engine::Deadline serving_shutdown_deadline) override
void	OnAllComponentsAreStopping () override
void	UpdateSyncDebug (UpdateType update_type)
	Forces a synchronous cache update of specified type.

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

Static Public Attributes
static constexpr std::string_view	kName = "dynamic-config-client-updater"
	The default name of components::DynamicConfigClientUpdater.

Protected Types
using	LoggableComponentBase
enum	Flag
	Periodic update flags. More...

Protected Member Functions
void	Set (std::unique_ptr< const dynamic_config::DocsMap > value_ptr)
	Sets the new value of cache. As a result, Get member function starts returning the new value.
void	Attach (const std::shared_ptr< const dynamic_config::DocsMap > &value_ptr)
void	Emplace (Args &&... args)
void	Clear ()
	Clears the content of the cache by string a default constructed T.
virtual bool	MayReturnNull () const
	Whether Get is expected to return nullptr.
virtual void	PreAssignCheck (const dynamic_config::DocsMap old_value_ptr, const dynamic_config::DocsMap new_value_ptr) const
	If the option has-pre-assign-check is set true in static config, this function is called before assigning the new value to the cache.
void	UpdateSyncDebug (UpdateType update_type)
	Forces a synchronous cache update of specified type.
AllowedUpdateTypes	GetAllowedUpdateTypes () const
	Update types configured for the cache.
void	OnCacheModified () noexcept
virtual utils::Flags< Flag >	GetStartFlags () const
	Returns flags for cache start.
void	EarlyStartPeriodicUpdates (utils::Flags< Flag > flags)
	Call this to start periodic updates just now, not after the constructor.
void	EarlyStartPeriodicUpdates (utils::Flags< Flag > flags)
	Call this to start periodic updates just now, not after the constructor.

virtual void	WriteContents (dump::Writer &writer, const dynamic_config::DocsMap &contents) const
virtual std::unique_ptr< const dynamic_config::DocsMap >	ReadContents (dump::Reader &reader) const

Member Typedef Documentation

◆ DataType

using components::CachingComponentBase< dynamic_config::DocsMap >::DataType

inherited

Definition at line 144 of file caching_component_base.hpp.

◆ LoggableComponentBase

using components::ComponentBase::LoggableComponentBase

protectedinherited

Deprecated: use components::ComponentBase instead.

Definition at line 79 of file component_base.hpp.

Member Enumeration Documentation

◆ Flag

enum cache::CacheUpdateTrait::Flag

strongprotectedinherited

Periodic update flags.

Definition at line 89 of file cache_update_trait.hpp.

Member Function Documentation

◆ Attach()

void components::CachingComponentBase< dynamic_config::DocsMap >::Attach ( const std::shared_ptr< const dynamic_config::DocsMap > & value_ptr )

protectedinherited

Attach the value of cache. As a result the Get() member function starts returning the value passed into this function after the Update() finishes. Does not take over into sole ownership. Do not use unless absolutely necessary. The object must be strictly thread-safe.

Warning: Do not forget to update cache::UpdateStatisticsScope, otherwise the behavior is undefined.

Definition at line 186 of file caching_component_base.hpp.

◆ Clear()

void components::CachingComponentBase< dynamic_config::DocsMap >::Clear ( )

protectedinherited

Clears the content of the cache by string a default constructed T.

Definition at line 193 of file caching_component_base.hpp.

◆ Emplace()

void components::CachingComponentBase< dynamic_config::DocsMap >::Emplace ( Args &&... args )

protectedinherited

Definition at line 190 of file caching_component_base.hpp.

◆ Get()

utils::SharedReadablePtr< dynamic_config::DocsMap > components::CachingComponentBase< dynamic_config::DocsMap >::Get ( ) const

finalvirtualinherited

Returns: cache contents. May be nullptr if and only if MayReturnNull returns true.

Exceptions

cache::EmptyCacheError if the contents are nullptr, and MayReturnNull returns false (which is the default behavior).

Implements cache::DataProvider< dynamic_config::DocsMap >.

Definition at line 150 of file caching_component_base.hpp.

◆ GetComponentHealth()

ComponentHealth components::ComponentBase::GetComponentHealth ( ) const

inlineoverrideinherited

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

Warning: The function is called concurrently from multiple threads.

Definition at line 35 of file component_base.hpp.

◆ GetEventChannel()

concurrent::AsyncEventChannel< const std::shared_ptr< const dynamic_config::DocsMap > & > & components::CachingComponentBase< dynamic_config::DocsMap >::GetEventChannel ( )

inherited

Definition at line 164 of file caching_component_base.hpp.

◆ GetUnsafe()

utils::SharedReadablePtr< dynamic_config::DocsMap > components::CachingComponentBase< dynamic_config::DocsMap >::GetUnsafe ( ) const

inherited

Returns: cache contents. May be nullptr regardless of MayReturnNull.

Definition at line 153 of file caching_component_base.hpp.

◆ InvalidateAsync() [1/2]

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

inherited

Non-blocking forced cache update of specified type.

See also: PeriodicTask::ForceStepAsync for behavior details

◆ InvalidateAsync() [2/2]

( UpdateType update_type )

inherited

Non-blocking forced cache update of specified type.

See also: PeriodicTask::ForceStepAsync for behavior details

◆ MayReturnNull()

bool components::CachingComponentBase< dynamic_config::DocsMap >::MayReturnNull ( ) const

protectedvirtualinherited

Whether Get is expected to return nullptr.

Definition at line 196 of file caching_component_base.hpp.

◆ Name()

( ) const

inherited

Returns: name of the component

◆ OnAllComponentsAreStopping()

void components::ComponentBase::OnAllComponentsAreStopping ( )

inlineoverrideinherited

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.

Definition at line 70 of file component_base.hpp.

◆ OnAllComponentsLoaded()

void components::ComponentBase::OnAllComponentsLoaded ( )

inlineoverrideinherited

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.

Definition at line 51 of file component_base.hpp.

◆ OnCacheModified()

void cache::CacheUpdateTrait::OnCacheModified ( )

protectednoexceptinherited

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

◆ OnGracefulShutdown()

void components::ComponentBase::OnGracefulShutdown ( engine::Deadline serving_shutdown_deadline )

overrideinherited

Serving components like HTTP and gRPC servers may use this function to stop accepting new requests and shutdown serving in the given time interval. Application components likely do not need to override it.

Parameters

[in] serving_shutdown_deadline The deadline until already running requests should be allowed to complete. The component is supposed to stop accepting new requests and continue processing of already active requests until this deadline (unless those requests finish earlier). And it might completely shutdown requests processing when the deadline is reached (or when no active requests left).

◆ OnLoadingCancelled()

void components::ComponentBase::OnLoadingCancelled ( )

inlineoverrideinherited

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.

Definition at line 42 of file component_base.hpp.

◆ PreAssignCheck()

void components::CachingComponentBase< dynamic_config::DocsMap >::PreAssignCheck	(	const dynamic_config::DocsMap *	old_value_ptr,
		const dynamic_config::DocsMap *	new_value_ptr ) const

protectedvirtualinherited

If the option has-pre-assign-check is set true in static config, this function is called before assigning the new value to the cache.

Note: old_value_ptr and new_value_ptr can be nullptr.

Definition at line 208 of file caching_component_base.hpp.

◆ ReadContents()

std::unique_ptr< const dynamic_config::DocsMap > components::CachingComponentBase< dynamic_config::DocsMap >::ReadContents ( dump::Reader & reader ) const

protectedvirtualinherited

Definition at line 202 of file caching_component_base.hpp.

◆ Set()

void components::CachingComponentBase< dynamic_config::DocsMap >::Set ( std::unique_ptr< const dynamic_config::DocsMap > value_ptr )

protectedinherited

Sets the new value of cache. As a result, Get member function starts returning the new value.

Notifies subscribers after setting the new value, see UpdateAndListen. Should only be called from Update normally.

Warning: Do not forget to update cache::UpdateStatisticsScope, otherwise the behavior is undefined.

Definition at line 175 of file caching_component_base.hpp.

◆ UpdateAndListen()

concurrent::AsyncEventSubscriberScope components::CachingComponentBase< dynamic_config::DocsMap >::UpdateAndListen	(	Class *	obj,
		std::string	name,
		void(Class::*	func )(const std::shared_ptr< const dynamic_config::DocsMap > &) )

inherited

Subscribes to cache updates using a member function. Also immediately invokes the function with the current cache contents.

Definition at line 158 of file caching_component_base.hpp.

◆ UpdateSyncDebug() [1/2]

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

inherited

Forces a synchronous cache update of specified type.

Warning: This method is intended for tests and debugging only. In production code use InvalidateAsync instead. The reasons are:

InvalidateAsync shifts the time of the next update as if a periodic update has just happened. UpdateSyncDebug does not do that: it locks the mutex and performs an additional update on the side, which puts extra load on the CPU and on the data source.
The cache we subscribe to sends events as part of its own update. If the callback does something lengthy, e.g. updating another cache, this affects the cache we subscribe to: it may disrupt its updates and cause a traffic jam in the whole chain of caches. InvalidateAsync is not subject to this. On top of that, UpdateSyncDebug will block the cache we subscribe to for the time we wait for the previous update of the dependent cache to finish (if one was in progress).
InvalidateAsync robustly handles situations with repeated update requests, see the docs of PeriodicTask::ForceStepAsync, on top of which it is implemented. UpdateSyncDebug tries to lock the mutex over and over and performs as many updates as were requested, even if they were requested many times in a row.
If UpdateSyncDebug is called before the periodic updates of the current cache have started (they start after the constructor of the derived cache finishes), the behavior is undefined, because the state of the periodic updates is not set up yet, while an update was already requested. InvalidateAsync handles this case: in that situation nothing happens.

See also: InvalidateAsync

Exceptions

If	Update throws

◆ UpdateSyncDebug() [2/2]

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

inherited

Forces a synchronous cache update of specified type.

Warning: This method is intended for tests and debugging only. In production code use InvalidateAsync instead. The reasons are:

InvalidateAsync shifts the time of the next update as if a periodic update has just happened. UpdateSyncDebug does not do that: it locks the mutex and performs an additional update on the side, which puts extra load on the CPU and on the data source.
The cache we subscribe to sends events as part of its own update. If the callback does something lengthy, e.g. updating another cache, this affects the cache we subscribe to: it may disrupt its updates and cause a traffic jam in the whole chain of caches. InvalidateAsync is not subject to this. On top of that, UpdateSyncDebug will block the cache we subscribe to for the time we wait for the previous update of the dependent cache to finish (if one was in progress).
InvalidateAsync robustly handles situations with repeated update requests, see the docs of PeriodicTask::ForceStepAsync, on top of which it is implemented. UpdateSyncDebug tries to lock the mutex over and over and performs as many updates as were requested, even if they were requested many times in a row.
If UpdateSyncDebug is called before the periodic updates of the current cache have started (they start after the constructor of the derived cache finishes), the behavior is undefined, because the state of the periodic updates is not set up yet, while an update was already requested. InvalidateAsync handles this case: in that situation nothing happens.

See also: InvalidateAsync

Exceptions

If	Update throws

◆ WriteContents()

void components::CachingComponentBase< dynamic_config::DocsMap >::WriteContents	(	dump::Writer &	writer,
		const dynamic_config::DocsMap &	contents ) const

protectedvirtualinherited

Override to use custom serialization for cache dumps

Definition at line 200 of file caching_component_base.hpp.

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

userver/dynamic_config/updater/component.hpp

Detailed Description

Optional update event deduplication

Static options components::DynamicConfigClientUpdater :

Static configuration example:

Public Types

Public Member Functions

Static Public Member Functions

Static Public Attributes

Protected Types

Protected Member Functions

Member Typedef Documentation

◆ DataType

◆ LoggableComponentBase

Member Enumeration Documentation

◆ Flag

Member Function Documentation

◆ Attach()

◆ Clear()

◆ Emplace()

◆ Get()

◆ GetComponentHealth()

◆ GetEventChannel()

◆ GetUnsafe()

◆ InvalidateAsync() [1/2]

◆ InvalidateAsync() [2/2]

◆ MayReturnNull()

◆ Name()

◆ OnAllComponentsAreStopping()

◆ OnAllComponentsLoaded()

◆ OnCacheModified()

◆ OnGracefulShutdown()

◆ OnLoadingCancelled()

◆ PreAssignCheck()

◆ ReadContents()

◆ Set()

◆ UpdateAndListen()

◆ UpdateSyncDebug() [1/2]

◆ UpdateSyncDebug() [2/2]

◆ WriteContents()