rti::core::policy::TopicQueryDispatch Class Reference

<<extension>> Configures the ability of a dds::pub::DataWriter to publish samples in response to a rti::sub::TopicQuery More...

#include <rti/core/policy/CorePolicy.hpp>

Public Member Functions
	TopicQueryDispatch ()
	Creates the default policy. More...
	TopicQueryDispatch (bool the_enable, const dds::core::Duration &the_publication_period, int32_t the_samples_per_period)
	Creates a policy with the provided values for enable, publication_period and samples_per_period. More...
TopicQueryDispatch &	enable (bool the_enable)
	Allows this writer to dispatch TopicQueries. More...
bool	enable () const
	Getter (see setter with the same name) More...
TopicQueryDispatch &	publication_period (const dds::core::Duration &the_publication_period)
	Sets the periodic interval at which samples are published. More...
dds::core::Duration	publication_period () const
	Getter (see setter with the same name) More...
TopicQueryDispatch &	samples_per_period (int32_t the_samples_per_period)
	Sets the maximum number of samples to publish in each publication_period. More...
int32_t	samples_per_period () const
	Getter (see setter with the same name) More...

Detailed Description

<<extension>> Configures the ability of a dds::pub::DataWriter to publish samples in response to a rti::sub::TopicQuery

Enables the ability of a dds::pub::DataWriter to publish historical samples upon reception of a rti::sub::TopicQuery and how often they are published.

Since a TopicQuery selects previously written samples, the DataWriter must have a dds::core::policy::Durability::kind different from dds::core::policy::DurabilityKind::VOLATILE. Also, dds::core::policy::Reliability::kind must be set to dds::core::policy::ReliabilityKind_def::RELIABLE.

Only samples that fall within the dds::core::policy::Durability::writer_depth for an instance are evaluated against the TopicQuery filter. While the DataWriter is waiting for acknowledgements from one or more DataReaders, there may temporarily be more than dds::core::policy::Durability::writer_depth samples per instance in the DataWriter's queue if the dds::core::policy::History::depth is set to a higher value than dds::core::policy::Durability::writer_depth. Those additional samples past dds::core::policy::Durability::writer_depth are not eligible to be sent in response to the TopicQuery.

A TopicQuery may select multiple samples at once. The writer will publish them periodically, independently from newly written samples. rti::core::policy::TopicQueryDispatch::publication_period configures the frequency of that period and rti::core::policy::TopicQueryDispatch::samples_per_period configures the maximum number of samples to publish each period.

If the DataWriter blocks during the publication of one of these samples, it will stop and try again the next period. (See dds::pub::DataWriter::write() for the conditions that may cause the write operation to block.)

All the DataWriters that belong to a single dds::pub::Publisher and enable TopicQueries share the same event thread, but each DataWriter schedules separate events. To configure that thread, see rti::core::policy::AsynchronousPublisher::topic_query_publication_thread.

If the DataWriter is dispatching more than one TopicQuery at the same time, the configuration of this periodic event applies to all of them. For example, if a DataWriter receives two TopicQueries around the same time, the period is 1 second, the number of samples per period is 10, the first TopicQuery selects 5 samples, and the second one selects 8, the DataWriter will immediately attempt to publish all 5 for the first TopicQuery and 5 for the second one. After one second, it will publish the remaining 3 samples.

Entity:

dds::pub::DataWriter

Properties:

RxO = N/A
Changeable = NO

See also

dds::pub::Publisher

Constructor & Destructor Documentation

TopicQueryDispatch() [1/2]

rti::core::policy::TopicQueryDispatch::TopicQueryDispatch ( )

inline

Creates the default policy.

TopicQueryDispatch() [2/2]

rti::core::policy::TopicQueryDispatch::TopicQueryDispatch ( bool  the_enable, const dds::core::Duration &  the_publication_period, int32_t  the_samples_per_period  )

inline

Creates a policy with the provided values for enable, publication_period and samples_per_period.

Member Function Documentation

enable() [1/2]

TopicQueryDispatch & rti::core::policy::TopicQueryDispatch::enable

(

bool

the_enable

)

Allows this writer to dispatch TopicQueries.

When set to true, this writer can receive and dispatch TopicQueries.

[default] false

enable() [2/2]

bool rti::core::policy::TopicQueryDispatch::enable

(

)

const

Getter (see setter with the same name)

publication_period() [1/2]

TopicQueryDispatch & rti::core::policy::TopicQueryDispatch::publication_period

(

const dds::core::Duration &

the_publication_period

)

Sets the periodic interval at which samples are published.

[default] 1 second

[range] [0,1 year]

publication_period() [2/2]

dds::core::Duration rti::core::policy::TopicQueryDispatch::publication_period

(

)

const

Getter (see setter with the same name)

samples_per_period() [1/2]

TopicQueryDispatch & rti::core::policy::TopicQueryDispatch::samples_per_period

(

int32_t

the_samples_per_period

)

Sets the maximum number of samples to publish in each publication_period.

[default] dds::core::LENGTH_UNLIMITED

[range] [1, 100000000] or dds::core::LENGTH_UNLIMITED

samples_per_period() [2/2]

int32_t rti::core::policy::TopicQueryDispatch::samples_per_period

(

)

const

Getter (see setter with the same name)