caf::actor_pool Class Reference

An actor poool is a lightweight abstraction for a set of workers. More...

#include <actor_pool.hpp>

Inheritance diagram for caf::actor_pool:

Public Types
using	actor_vec = std::vector< actor >
using	factory = std::function< actor()>
using	guard_type = std::unique_lock< std::mutex >
using	policy = std::function< void(actor_system &, guard_type &, const actor_vec &, mailbox_element_ptr &, execution_unit *)>

Public Member Functions
bool	enqueue (mailbox_element_ptr what, execution_unit *eu) override
	Enqueues a new message wrapped in a mailbox_element to the actor.
	actor_pool (actor_config &cfg)
void	on_destroy () override
	Cleans up any remaining state before the destructor is called.
void	setup_metrics ()
Public Member Functions inherited from caf::monitorable_actor
virtual const char *	name () const
	Returns an implementation-dependent name for logging purposes, which is only valid as long as the actor is running.
void	attach (attachable_ptr ptr) override
	Attaches ptr to this actor.
size_t	detach (const attachable::token &what) override
	Detaches the first attached object that matches what.
void	link_to (const actor_addr &x)
	Links this actor to x.
template<class ActorHandle >
void	link_to (const ActorHandle &x)
	Links this actor to x.
void	unlink_from (const actor_addr &x)
	Unlinks this actor from x.
template<class ActorHandle >
void	unlink_from (const ActorHandle &x)
	Links this actor to x.
Public Member Functions inherited from caf::abstract_actor
actor_control_block *	ctrl () const
	abstract_actor (const abstract_actor &)=delete
abstract_actor &	operator= (const abstract_actor &)=delete
virtual void	on_destroy ()
	Cleans up any remaining state before the destructor is called.
bool	enqueue (strong_actor_ptr sender, message_id mid, message msg, execution_unit *host) override
	Enqueues a new message without forwarding stack to the channel.
virtual bool	enqueue (mailbox_element_ptr what, execution_unit *host)=0
	Enqueues a new message wrapped in a mailbox_element to the actor.
virtual void	attach (attachable_ptr ptr)=0
	Attaches ptr to this actor.
template<class F >
void	attach_functor (F f)
	Convenience function that attaches the functor f to this actor.
actor_addr	address () const noexcept
	Returns the logical actor address.
virtual size_t	detach (const attachable::token &what)=0
	Detaches the first attached object that matches what.
virtual std::set< std::string >	message_types () const
	Returns the set of accepted messages types as strings or an empty set if this actor is untyped.
actor_id	id () const noexcept
	Returns the ID of this actor.
node_id	node () const noexcept
	Returns the node this actor is living on.
actor_system &	home_system () const noexcept
	Returns the system that created this actor (or proxy).
Public Member Functions inherited from caf::abstract_channel
virtual bool	enqueue (strong_actor_ptr sender, message_id mid, message content, execution_unit *host=nullptr)=0
	Enqueues a new message without forwarding stack to the channel.
bool	is_abstract_actor () const
bool	is_abstract_group () const
bool	is_actor_decorator () const

Static Public Member Functions
static policy	round_robin ()
	Returns a simple round robin dispatching policy.
static policy	broadcast ()
	Returns a broadcast dispatching policy.
static policy	random ()
	Returns a random dispatching policy.
template<class T , class Join , class Split = detail::nop_split>
static policy	split_join (Join jf, Split sf=Split(), T init=T())
	Returns a split/join dispatching policy.
static actor	make (execution_unit *eu, policy pol)
	Returns an actor pool without workers using the dispatch policy pol.
static actor	make (execution_unit *eu, size_t num_workers, const factory &fac, policy pol)
	Returns an actor pool with n workers created by the factory function fac using the dispatch policy pol.

Protected Member Functions
void	on_cleanup (const error &reason) override
	Allows subclasses to add additional cleanup code to the critical section in cleanup.
Protected Member Functions inherited from caf::monitorable_actor
virtual void	on_cleanup (const error &reason)
	Allows subclasses to add additional cleanup code to the critical section in cleanup.
void	bounce (mailbox_element_ptr &what)
	Sends a response message if what is a request.
void	bounce (mailbox_element_ptr &what, const error &err)
	Sends a response message if what is a request.
	monitorable_actor (actor_config &cfg)
	Creates a new actor instance.
void	attach_impl (attachable_ptr &ptr)
size_t	detach_impl (const attachable::token &what, bool stop_on_hit=false, bool dry_run=false)
bool	handle_system_message (mailbox_element &x, execution_unit *ctx, bool trap_exit)
template<class F >
bool	handle_system_message (mailbox_element &x, execution_unit *context, bool trap_exit, F &down_msg_handler)
Protected Member Functions inherited from caf::abstract_actor
	abstract_actor (actor_config &cfg)
Protected Member Functions inherited from caf::abstract_channel
int	flags () const
void	flags (int new_value)

Additional Inherited Members
Static Public Attributes inherited from caf::abstract_channel
static constexpr int	is_abstract_actor_flag = 0x01000000
static constexpr int	is_abstract_group_flag = 0x02000000
static constexpr int	is_actor_bind_decorator_flag = 0x04000000
static constexpr int	is_actor_dot_decorator_flag = 0x08000000
static constexpr int	is_actor_decorator_mask = 0x0C000000
static constexpr int	is_hidden_flag = 0x10000000
Protected Attributes inherited from caf::monitorable_actor
error	fail_state_
std::condition_variable	cv_
attachable_ptr	attachables_head_
Protected Attributes inherited from caf::abstract_actor
std::mutex	mtx_
Related Symbols inherited from caf::abstract_actor
using	actor_id = uint64_t
	A unique actor ID.

Detailed Description

An actor poool is a lightweight abstraction for a set of workers.

The pool itself is an actor, meaning that it can be passed around in an actor system to hide the actual set of workers.

After construction, new workers can be added via ‘{'SYS’, 'PUT', actor} messages, e.g.,send(my_pool, sys_atom::value, put_atom::value, worker). {'SYS', 'DELETE', actor}messages remove a specific worker from the set, {'SYS', 'DELETE'}removes all workers, and{'SYS', 'GET'}returns a vector<actor>` containing all workers.

Note that the pool always sends exit messages to all of its workers when forced to quit. The pool monitors all of its workers. Messages queued up in a worker's mailbox are lost, i.e., the pool itself does not buffer and resend messages. Advanced caching or resend strategies can be implemented in a policy.

It is worth mentioning that the pool is not an event-based actor. Neither does it live in its own thread. Messages are dispatched immediately during the enqueue operation. Any user-defined policy thus has to dispatch messages with as little overhead as possible, because the dispatching runs in the context of the sender.

Attention

This feature is experimental.

Member Function Documentation

enqueue()

bool caf::actor_pool::enqueue ( mailbox_element_ptr  what, execution_unit *  host  )

overridevirtual

Enqueues a new message wrapped in a mailbox_element to the actor.

This enqueue variant allows to define forwarding chains.

Returns

true if the message has added to the mailbox, false otherwise. In the latter case, the actor terminated and the message has been dropped. Once this function returns false, it returns false for all future invocations.

Note

The returned value is purely informational and may be used to discard actor handles early. Messages may still get dropped later even if this function returns true. In particular when dealing with remote actors.

Implements caf::abstract_actor.

on_cleanup()

void caf::actor_pool::on_cleanup ( const error &  reason )

overrideprotectedvirtual

Allows subclasses to add additional cleanup code to the critical section in cleanup.

This member function is called inside of a critical section.

Reimplemented from caf::monitorable_actor.

on_destroy()

void caf::actor_pool::on_destroy ( )

overridevirtual

Cleans up any remaining state before the destructor is called.

This function makes sure it is safe to call virtual functions in sub classes before destroying the object, because calling virtual function in the destructor itself is not safe. Any override implementation is required to call super::destroy() at the end.

Reimplemented from caf::abstract_actor.

split_join()

template<class T , class Join , class Split = detail::nop_split>

static policy caf::actor_pool::split_join ( Join  jf, Split  sf = Split(), T  init = T()  )

static

Returns a split/join dispatching policy.

The function object sf distributes a work item to all workers (split step) and the function object jf joins individual results into a single one with init as initial value of the operation.

Template Parameters

T	Result type of the join step.
Join	Function object with signature void (T&, message&).
Split	Function object with signature void (vector<pair<actor, message>>&, message&). The first argument is a mapping from actors (workers) to tasks (messages). The second argument is the input message. The default split policy broadcasts the work item to all workers.

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

• libcaf_core/caf/actor_pool.hpp
• libcaf_core/caf/actor_pool.cpp