DDS_DiscoveryConfigQosPolicy Struct Reference

Settings for discovery configuration. More...

Data Fields
struct DDS_Duration_t	participant_liveliness_lease_duration
	The liveliness lease duration for the participant.
struct DDS_Duration_t	participant_liveliness_assert_period
	The period to assert liveliness for the participant.
DDS_RemoteParticipantPurgeKind	remote_participant_purge_kind
	The participant's behavior for maintaining knowledge of remote participants (and their contained entities) with which discovery communication has been lost.
struct DDS_Duration_t	max_liveliness_loss_detection_period
	The maximum amount of time between when a remote entity stops maintaining its liveliness and when the matched local entity realizes that fact.
DDS_Long	initial_participant_announcements
	The number of initial announcements sent when a participant is first enabled or when a remote participant is newly discovered.
struct DDS_Duration_t	min_initial_participant_announcement_period
	The minimum period between initial announcements when a participant is first enabled or when a remote participant is newly discovered.
struct DDS_Duration_t	max_initial_participant_announcement_period
	The maximum period between initial announcements when a participant is first enabled or when a remote participant is newly discovered.
struct DDS_BuiltinTopicReaderResourceLimits_t	participant_reader_resource_limits
	Resource limits.
struct DDS_RtpsReliableReaderProtocol_t	publication_reader
	RTPS protocol-related configuration settings for a built-in publication reader.
struct DDS_BuiltinTopicReaderResourceLimits_t	publication_reader_resource_limits
	Resource limits.
struct DDS_RtpsReliableReaderProtocol_t	subscription_reader
	RTPS protocol-related configuration settings for a built-in subscription reader.
struct DDS_BuiltinTopicReaderResourceLimits_t	subscription_reader_resource_limits
	Resource limits.
struct DDS_RtpsReliableWriterProtocol_t	publication_writer
	RTPS protocol-related configuration settings for a built-in publication writer.
struct DDS_WriterDataLifecycleQosPolicy	publication_writer_data_lifecycle
	Writer data lifecycle settings for a built-in publication writer.
struct DDS_RtpsReliableWriterProtocol_t	subscription_writer
	RTPS protocol-related configuration settings for a built-in subscription writer.
struct DDS_WriterDataLifecycleQosPolicy	subscription_writer_data_lifecycle
	Writer data lifecycle settings for a built-in subscription writer.
DDS_DiscoveryConfigBuiltinPluginKindMask	builtin_discovery_plugins
	The kind mask for built-in discovery plugins.
struct DDS_RtpsReliableReaderProtocol_t	participant_message_reader
	RTPS protocol-related configuration settings for a built-in participant message reader.
struct DDS_RtpsReliableWriterProtocol_t	participant_message_writer
	RTPS protocol-related configuration settings for a built-in participant message writer.
struct DDS_PublishModeQosPolicy	publication_writer_publish_mode
	Publish mode policy for the built-in publication writer.
struct DDS_PublishModeQosPolicy	subscription_writer_publish_mode
	Publish mode policy for the built-in subscription writer.
struct DDS_AsynchronousPublisherQosPolicy	asynchronous_publisher
	Asynchronous publishing settings for the discovery DDS_Publisher and all entities that are created by it.

Detailed Description

Settings for discovery configuration.

This QoS policy is an extension to the DDS standard.

This QoS policy controls the amount of delay in discovering entities in the system and the amount of discovery traffic in the network.

The amount of network traffic required by the discovery process can vary widely, based on how your application has chosen to configure the middleware's network addressing (e.g., unicast vs. multicast, multicast TTL, etc.), the size of the system, whether all applications are started at the same time or whether start times are staggered, and other factors. Your application can use this policy to make tradeoffs between discovery completion time and network bandwidth utilization. In addition, you can introduce random back-off periods into the discovery process to decrease the probability of network contention when many applications start simultaneously.

Entity:

DDS_DomainParticipant

Properties:

RxO = N/A
Changeable = NO

Field Documentation

struct DDS_Duration_t DDS_DiscoveryConfigQosPolicy::participant_liveliness_lease_duration

The liveliness lease duration for the participant.

This is the same as the expiration time of the DomainParticipant as defined in the RTPS protocol.

If the participant has not refreshed its own liveliness to other participants at least once within this period, it may be considered as stale by other participants in the network.

Should be strictly greater than DDS_DiscoveryConfigQosPolicy::participant_liveliness_assert_period.

[default] 100 seconds

[range] [1 nanosec,1 year], > participant_liveliness_assert_period

struct DDS_Duration_t DDS_DiscoveryConfigQosPolicy::participant_liveliness_assert_period

The period to assert liveliness for the participant.

The period at which the participant will refresh its liveliness to all the peers.

Should be strictly less than DDS_DiscoveryConfigQosPolicy::participant_liveliness_lease_duration.

[default] 30 seconds

[range] [1 nanosec,1 year), < participant_liveliness_lease_duration

DDS_RemoteParticipantPurgeKind DDS_DiscoveryConfigQosPolicy::remote_participant_purge_kind

The participant's behavior for maintaining knowledge of remote participants (and their contained entities) with which discovery communication has been lost.

Most users will not need to change this value from its default, DDS_LIVELINESS_BASED_REMOTE_PARTICIPANT_PURGE. However, DDS_NO_REMOTE_PARTICIPANT_PURGE may be a good choice if the following conditions apply:

1. Discovery communication with a remote participant may be lost while data communication remains intact. Such will not typically be the case if discovery takes place over the Simple Discovery Protocol, but may be the case if the RTI Enterprise Discovery Service is used.
2. Extensive and prolonged lack of discovery communication between participants is not expected to be common, either because participant loss itself is expected to be rare, or because participants may be lost sporadically but will typically return again.
3. Maintaining inter-participant liveliness is problematic, perhaps because a participant has no writers with the appropriate DDS_LivelinessQosPolicyKind.

[default] DDS_LIVELINESS_BASED_REMOTE_PARTICIPANT_PURGE

struct DDS_Duration_t DDS_DiscoveryConfigQosPolicy::max_liveliness_loss_detection_period

The maximum amount of time between when a remote entity stops maintaining its liveliness and when the matched local entity realizes that fact.

Notification of the loss of liveliness of a remote entity may come more quickly that this duration, depending on the liveliness contract between the local and remote entities and the capabilities of the discovery mechanism in use. For example, a DDS_DataReader will learn of the loss of liveliness of a matched DDS_DataWriter within the reader's offered liveliness lease duration.

Shortening this duration will increase the responsiveness of entities to communication failures. However, it will also increase the CPU usage of the application, as the liveliness of remote entities will be examined more frequently.

[default] 60 seconds

[range] [0, 1 year]

DDS_Long DDS_DiscoveryConfigQosPolicy::initial_participant_announcements

The number of initial announcements sent when a participant is first enabled or when a remote participant is newly discovered.

Also, when a new remote participant appears, the local participant can announce itself to the peers multiple times controlled by this parameter.

[default] 5

[range] [0,1 million]

struct DDS_Duration_t DDS_DiscoveryConfigQosPolicy::min_initial_participant_announcement_period

The minimum period between initial announcements when a participant is first enabled or when a remote participant is newly discovered.

A random delay between this and DDS_DiscoveryConfigQosPolicy::max_initial_participant_announcement_period is introduced in between initial announcements when a new remote participant is discovered.

The setting of DDS_DiscoveryConfigQosPolicy::min_initial_participant_announcement_period must be consistent with DDS_DiscoveryConfigQosPolicy::max_initial_participant_announcement_period. For these two values to be consistent, they must verify that:

DDS_DiscoveryConfigQosPolicy::min_initial_participant_announcement_period <= DDS_DiscoveryConfigQosPolicy::max_initial_participant_announcement_period.

[default] 1 second

[range] [1 nanosec,1 year]

struct DDS_Duration_t DDS_DiscoveryConfigQosPolicy::max_initial_participant_announcement_period

The maximum period between initial announcements when a participant is first enabled or when a remote participant is newly discovered.

A random delay between DDS_DiscoveryConfigQosPolicy::min_initial_participant_announcement_period and this is introduced in between initial announcements when a new remote participant is discovered.

The setting of DDS_DiscoveryConfigQosPolicy::max_initial_participant_announcement_period must be consistent with DDS_DiscoveryConfigQosPolicy::min_initial_participant_announcement_period. For these two values to be consistent, they must verify that:

DDS_DiscoveryConfigQosPolicy::min_initial_participant_announcement_period <= DDS_DiscoveryConfigQosPolicy::max_initial_participant_announcement_period.

[default] 1 second

[range] [1 nanosec,1 year]

struct DDS_BuiltinTopicReaderResourceLimits_t DDS_DiscoveryConfigQosPolicy::participant_reader_resource_limits

Resource limits.

Resource limit of the built-in topic participant reader. For details, see DDS_BuiltinTopicReaderResourceLimits_t.

struct DDS_RtpsReliableReaderProtocol_t DDS_DiscoveryConfigQosPolicy::publication_reader

RTPS protocol-related configuration settings for a built-in publication reader.

For details, refer to the DDS_DataReaderQos

struct DDS_BuiltinTopicReaderResourceLimits_t DDS_DiscoveryConfigQosPolicy::publication_reader_resource_limits

Resource limits.

Resource limit of the built-in topic publication reader. For details, see DDS_BuiltinTopicReaderResourceLimits_t.

struct DDS_RtpsReliableReaderProtocol_t DDS_DiscoveryConfigQosPolicy::subscription_reader

RTPS protocol-related configuration settings for a built-in subscription reader.

For details, refer to the DDS_DataReaderQos

struct DDS_BuiltinTopicReaderResourceLimits_t DDS_DiscoveryConfigQosPolicy::subscription_reader_resource_limits

Resource limits.

Resource limit of the built-in topic subscription reader. For details, see DDS_BuiltinTopicReaderResourceLimits_t.

struct DDS_RtpsReliableWriterProtocol_t DDS_DiscoveryConfigQosPolicy::publication_writer

RTPS protocol-related configuration settings for a built-in publication writer.

For details, refer to the DDS_DataWriterQos

struct DDS_WriterDataLifecycleQosPolicy DDS_DiscoveryConfigQosPolicy::publication_writer_data_lifecycle

Writer data lifecycle settings for a built-in publication writer.

For details, refer to the DDS_WriterDataLifecycleQosPolicy. DDS_WriterDataLifecycleQosPolicy::autodispose_unregistered_instances will always be forced to DDS_BOOLEAN_TRUE.

struct DDS_RtpsReliableWriterProtocol_t DDS_DiscoveryConfigQosPolicy::subscription_writer

RTPS protocol-related configuration settings for a built-in subscription writer.

For details, refer to the DDS_DataWriterQos

struct DDS_WriterDataLifecycleQosPolicy DDS_DiscoveryConfigQosPolicy::subscription_writer_data_lifecycle

Writer data lifecycle settings for a built-in subscription writer.

For details, refer to the DDS_WriterDataLifecycleQosPolicy. DDS_WriterDataLifecycleQosPolicy::autodispose_unregistered_instances will always be forced to DDS_BOOLEAN_TRUE.

DDS_DiscoveryConfigBuiltinPluginKindMask DDS_DiscoveryConfigQosPolicy::builtin_discovery_plugins

The kind mask for built-in discovery plugins.

There are several built-in discovery plugin. This mask enables the different plugins. Any plugin not enabled will not be created.

[default] DDS_DISCOVERYCONFIG_BUILTIN_SDP

struct DDS_RtpsReliableReaderProtocol_t DDS_DiscoveryConfigQosPolicy::participant_message_reader

RTPS protocol-related configuration settings for a built-in participant message reader.

For details, refer to the DDS_DataReaderQos

struct DDS_RtpsReliableWriterProtocol_t DDS_DiscoveryConfigQosPolicy::participant_message_writer

RTPS protocol-related configuration settings for a built-in participant message writer.

For details, refer to the DDS_DataWriterQos

struct DDS_PublishModeQosPolicy DDS_DiscoveryConfigQosPolicy::publication_writer_publish_mode

Publish mode policy for the built-in publication writer.

Determines whether the Discovery built-in publication DDS_DataWriter publishes data synchronously or asynchronously and how.

struct DDS_PublishModeQosPolicy DDS_DiscoveryConfigQosPolicy::subscription_writer_publish_mode

Publish mode policy for the built-in subscription writer.

Determines whether the Discovery built-in subscription DDS_DataWriter publishes data synchronously or asynchronously and how.

struct DDS_AsynchronousPublisherQosPolicy DDS_DiscoveryConfigQosPolicy::asynchronous_publisher

Asynchronous publishing settings for the discovery DDS_Publisher and all entities that are created by it.