ozo::failover::retry_strategy< Options > Class Template Reference

#include <ozo/failover/retry.h>

Description

template<typename Options = decltype(hana::make_map())>
class ozo::failover::retry_strategy< Options >

Retry strategy.

Retry strategy is a factory for ozo::fallback::basic_try object. This class is an options' factory (see ozo::options_factory_base).

Inherits ozo::options_factory_base< retry_strategy< decltype(hana::make_map()) >, decltype(hana::make_map()) >.

Public Member Functions
constexpr	retry_strategy (Options options=Options{})
	Construct a new retry strategy object. More...
template<typename Operation , typename Allocator , typename ConnectionProvider , typename TimeConstraint , typename ... Args>
auto	get_first_try (const Operation &, const Allocator &, ConnectionProvider &&provider, TimeConstraint t, Args &&...args) const
	Get the first try object. More...
constexpr decltype(auto)	tries (int n) const &
	Specify number of tries. More...
constexpr int	get_tries () const
	Number of maximum tries count are setted with ozo::retry_strategy::tries() More...
constexpr auto	get_conditions () const
	Retry error conditions of the strategy. More...
constexpr decltype(auto)	operator* (int n) const &
	Sintactic sugar for ozo::retry_strategy::tries() More...
Public Member Functions inherited from ozo::options_factory_base< retry_strategy< decltype(hana::make_map()) >, decltype(hana::make_map()) >
constexpr	options_factory_base (decltype(hana::make_map()) v)
constexpr decltype(auto)	set (decltype(hana::make_map()) &&...options) &&
constexpr auto	has (ozo::option< Key > op) const
constexpr decltype(auto)	get (ozo::option< Key > op) const
constexpr const decltype(hana::make_map()) &	options () const &
constexpr decltype(hana::make_map()) &	options () &
constexpr decltype(hana::make_map()) &&	options () &&

Friends
class	ozo::options_factory_base< retry_strategy< Options >, Options >

Constructors

retry_strategy()

template<typename Options = decltype(hana::make_map())>

constexpr ozo::failover::retry_strategy< Options >::retry_strategy ( Options  options = Options{} )

constexpr

Construct a new retry strategy object.

Parameters

options

— boost::hana::map of ozo::failover::retry_options and values.

Member Function Documentation

get_conditions()

template<typename Options = decltype(hana::make_map())>

constexpr auto ozo::failover::retry_strategy< Options >::get_conditions ( ) const

constexpr

Retry error conditions of the strategy.

Returns

boost::hana::tuple — tuple of retryable error conditions setted for this strategy.

References ozo::failover::retry_options::conditions, and ozo::options_factory_base< retry_strategy< decltype(hana::make_map()) >, decltype(hana::make_map()) >::get().

get_first_try()

template<typename Options = decltype(hana::make_map())>

template<typename Operation , typename Allocator , typename ConnectionProvider , typename TimeConstraint , typename ... Args>

auto ozo::failover::retry_strategy< Options >::get_first_try	(	const Operation &	,
		const Allocator &	,
		ConnectionProvider &&	provider,
		TimeConstraint	t,
		Args &&...	args
	)		const

Get the first try object.

Default implementation for ozo::fallback::get_first_try() failover strategy interface function.

Parameters

alloc	— allocator which should be used for try context.
args	— operation arguments.

Returns

basic_try — first try object.

References ozo::deadline(), ozo::options_factory_base< retry_strategy< decltype(hana::make_map()) >, decltype(hana::make_map()) >::has(), ozo::options_factory_base< retry_strategy< decltype(hana::make_map()) >, decltype(hana::make_map()) >::options(), and ozo::failover::retry_options::tries.

get_tries()

template<typename Options = decltype(hana::make_map())>

constexpr int ozo::failover::retry_strategy< Options >::get_tries ( ) const

constexpr

Number of maximum tries count are setted with ozo::retry_strategy::tries()

Returns

int — number of operation tries

References ozo::options_factory_base< retry_strategy< decltype(hana::make_map()) >, decltype(hana::make_map()) >::get(), and ozo::failover::retry_options::tries.

operator*()

template<typename Options = decltype(hana::make_map())>

constexpr decltype(auto) ozo::failover::retry_strategy< Options >::operator* ( int  n ) const &

constexpr

Sintactic sugar for ozo::retry_strategy::tries()

Parameters

n	— number of tries

Returns

retry_strategy specialization object

References ozo::failover::retry_strategy< Options >::tries().

tries()

template<typename Options = decltype(hana::make_map())>

constexpr decltype(auto) ozo::failover::retry_strategy< Options >::tries ( int  n ) const &

constexpr

Specify number of tries.

Specify number of tries for an operation.

Parameters

n	— number of tries

Returns

retry_strategy specialization object

If operation has time constraint T each try would have its own time constraint according to the rule, there ti — actual time of ith try:

Try number	Time constraint
1	T/n
2	(T - t1) / (n - 1)
3	(T - (t1 + t2)) / (n - 2)
...
N	(T - (t1 + t2 + ... + tn-1)))

Example

Retry on a network problem and operation timed-out no more than 3 tries. Each try has own time duration constraint calculated as:

• for the 1st try: 0,5/3 sec.
• for the 2nd try: (0,5 - t1) / 2 >= 0,5/3 sec.
• for the 3rd try: 0,5 - (t1 + t2) >= 0,5/3 sec.

auto retry = failover::retry(errc::network, errc::timeout);
ozo::request[retry*3](pool, query, .5s, out, yield);

References ozo::options_factory_base< retry_strategy< decltype(hana::make_map()) >, decltype(hana::make_map()) >::set(), and ozo::failover::retry_options::tries.

Referenced by ozo::failover::retry_strategy< Options >::operator*().