Quality of Service (QoS) policies. More...
Modules | |
| ASYNCHRONOUS_PUBLISHER | |
| <<extension>> Specifies the asynchronous publishing settings of the DDSPublisher instances. | |
| AVAILABILITY | |
| <<extension>> Configures the availability of data. | |
| BATCH | |
| <<extension>> Batch QoS policy used to enable batching in DDSDataWriter instances. | |
| DATABASE | |
| <<extension>> Various threads and resource limits settings used by RTI Connext to control its internal database. | |
| DATA_READER_PROTOCOL | |
| <<extension>> Specifies the DataReader-specific protocol QoS. | |
| DATA_READER_RESOURCE_LIMITS | |
| <<extension>> Various settings that configure how DataReaders allocate and use physical memory for internal resources. | |
| DATA_REPRESENTATION | |
| A list of data representations and compression methods supported by a DDSDataWriter or DDSDataReader. | |
| DATA_TAG | |
| Stores (name, value) pairs that can be used to determine access permissions. | |
| DATA_WRITER_PROTOCOL | |
| <<extension>> Along with DDS_WireProtocolQosPolicy and DDS_DataReaderProtocolQosPolicy, this QoS policy configures the DDS on-the-network protocol (RTPS). | |
| DATA_WRITER_RESOURCE_LIMITS | |
| <<extension>> Various settings that configure how a DDSDataWriter allocates and uses physical memory for internal resources. | |
| DATA_WRITER_TRANSFER_MODE | |
| <<extension>> Specifies the DataWriter transfer mode QoS. | |
| DEADLINE | |
| Expresses the maximum duration (deadline) within which an instance is expected to be updated. | |
| DESTINATION_ORDER | |
| Controls the criteria used to determine the logical order among changes made by DDSPublisher entities to the same instance of data (i.e., matching DDSTopic and key). | |
| DISCOVERY | |
| <<extension>> Specifies the attributes required to discover participants in the domain. | |
| DISCOVERY_CONFIG | |
| <<extension>> Specifies the discovery configuration QoS. | |
| DOMAIN_PARTICIPANT_RESOURCE_LIMITS | |
| <<extension>> Various settings that configure how a DDSDomainParticipant allocates and uses physical memory for internal resources, including the maximum sizes of various properties. | |
| DURABILITY | |
| This QoS policy specifies whether or not RTI Connext will store and deliver previously published data samples to new DDSDataReader entities that join the network later. | |
| DURABILITY_SERVICE | |
| Various settings to configure the external RTI Persistence Service used by RTI Connext for DataWriters with a DDS_DurabilityQosPolicy setting of DDS_PERSISTENT_DURABILITY_QOS or DDS_TRANSIENT_DURABILITY_QOS. | |
| ENTITY_FACTORY | |
| A QoS policy for all DDSEntity types that can act as factories for one or more other DDSEntity types. | |
| ENTITY_NAME | |
| <<extension>> Assigns a name to a DDSDomainParticipant, DDSPublisher, DDSSubscriber, DDSDataWriter or DDSDataReader. Except for DDSPublisher and DDSSubscriber, these names are visible during the discovery process and in RTI tools to help you visualize and debug your system. | |
| EVENT | |
| <<extension>> Configures the internal thread in a DomainParticipant that handles timed events. | |
| HISTORY | |
| Specifies the behavior of RTI Connext in the case where the value of an instance changes (one or more times) before it can be successfully communicated to one or more existing subscribers. | |
| GROUP_DATA | |
| Attaches a buffer of opaque data that is distributed by means of Built-in Topics during discovery. | |
| LATENCY_BUDGET | |
| Provides a hint as to the maximum acceptable delay from the time the data is written to the time it is received by the subscribing applications. | |
| LIFESPAN | |
| Specifies how long the data written by the DDSDataWriter is considered valid. | |
| LIVELINESS | |
| Specifies and configures the mechanism that allows DDSDataReader entities to detect when DDSDataWriter entities become disconnected or "dead.". | |
| LOCATORFILTER | |
| <<extension>> The QoS policy used to report the configuration of a MultiChannel DataWriter as part of DDS_PublicationBuiltinTopicData. | |
| LOGGING | |
| <<extension>> Configures the RTI Connext logging facility. | |
| MONITORING | |
| Configures the use of RTI Monitoring Library 2.0 to collect and distribute RTI Connext telemetry data. | |
| MULTICHANNEL | |
| <<extension>> Configures the ability of a DataWriter to send data on different multicast groups (addresses) based on the value of the data. | |
| OWNERSHIP | |
| Specifies whether it is allowed for multiple DDSDataWriter (s) to write the same instance of the data and if so, how these modifications should be arbitrated. | |
| OWNERSHIP_STRENGTH | |
| Specifies the value of the strength used to arbitrate among multiple DDSDataWriter objects that attempt to modify the same instance of a data type (identified by DDSTopic + key). | |
| PARTITION | |
| Set of strings that introduces logical partitions in DDSDomainParticipant, DDSPublisher, or DDSSubscriber entities. | |
| PRESENTATION | |
| Specifies how the samples representing changes to data instances are presented to a subscribing application. | |
| PROFILE | |
| <<extension>> Configures the way that XML documents containing QoS profiles are loaded by RTI Connext. | |
| PROPERTY | |
| <<extension>> Stores (name, value) pairs that can be used to configure certain parameters of RTI Connext that are not exposed through formal QoS policies. Can also be used to store and propagate application-specific name/value pairs that can be retrieved by user code during discovery. | |
| PUBLISH_MODE | |
| <<extension>> Specifies how RTI Connext sends application data on the network. This QoS policy can be used to tell RTI Connext to use its own thread to send data, instead of the user thread. | |
| READER_DATA_LIFECYCLE | |
| Controls how a DataReader manages the lifecycle of the data that it has received. | |
| RECEIVER_POOL | |
| <<extension>> Configures threads used by RTI Connext to receive and process data from transports (for example, UDP sockets). | |
| RELIABILITY | |
| Indicates the level of reliability offered/requested by RTI Connext. | |
| RESOURCE_LIMITS | |
| Controls the amount of physical memory allocated for DDS entities, if dynamic allocations are allowed, and how they occur. Also controls memory usage among different instance values for keyed topics. | |
| SERVICE | |
| <<extension>> Service QoS policy is used to indicate what kind of service is associated with the DDS entity. | |
| SYSTEM_RESOURCE_LIMITS | |
| <<extension>> Configures DomainParticipant-independent resources used by RTI Connext. | |
| TIME_BASED_FILTER | |
| Filter that allows a DDSDataReader to specify that it is interested only in (potentially) a subset of the values of the data. | |
| TOPIC_DATA | |
| Attaches a buffer of opaque data that is distributed by means of Built-in Topics during discovery. | |
| TOPIC_QUERY_DISPATCH | |
| Configures the ability of a DDSDataWriter to publish historical samples. | |
| TRANSPORT_BUILTIN | |
| <<extension>> Specifies which built-in transports are used. | |
| TRANSPORT_MULTICAST | |
| <<extension>> Specifies the multicast address on which a DDSDataReader wants to receive its data. It can also specify a port number, as well as a subset of the available (at the DDSDomainParticipant level) transports with which to receive the multicast data. | |
| TRANSPORT_MULTICAST_MAPPING | |
| <<extension>> Specifies a list of topic expressions and addresses that can be used by an Entity with a specific topic name to receive data. | |
| TRANSPORT_PRIORITY | |
| This QoS policy allows the application to take advantage of transport that are capable of sending messages with different priorities. | |
| TRANSPORT_SELECTION | |
| <<extension>> Specifies the physical transports that a DDSDataWriter or DDSDataReader may use to send or receive data. | |
| TRANSPORT_UNICAST | |
| <<extension>> Specifies a subset of transports and a port number that can be used by an Entity to receive data. | |
| TYPE_CONSISTENCY_ENFORCEMENT | |
| Defines the rules for determining whether the type used to publish a given topic is consistent with that used to subscribe to it. | |
| TYPESUPPORT | |
| <<extension>> Allows you to attach application-specific values to a DDSDataWriter or DDSDataReader, which are passed to the serialization or deserialization routine of the associated data type and choose whether to set padding bytes to zero during serialization. | |
| USER_DATA | |
| Attaches a buffer of opaque data that is distributed by means of Built-in Topics during discovery. | |
| WRITER_DATA_LIFECYCLE | |
| Controls how a DataWriter handles the lifecycle of the instances (keys) that it is registered to manage. | |
| WIRE_PROTOCOL | |
| <<extension>> Specifies the wire protocol related attributes for the DDSDomainParticipant. | |
| Extended Qos Support | |
| <<extension>> Types and defines used in extended QoS policies. | |
Classes | |
| struct | DDS_QosPrintFormat |
| A collection of attributes used to configure how a QoS appears when printed. More... | |
| struct | DDS_QosPolicyCount |
| Type to hold a counter for a DDS_QosPolicyId_t. More... | |
| struct | DDS_QosPolicyCountSeq |
Declares IDL sequence < DDS_QosPolicyCount > More... | |
Macros | |
| #define | DDS_QosPrintFormat_INITIALIZER |
| Static initializer for DDS_QosPrintFormat. More... | |
| #define | DDS_QOS_POLICY_COUNT |
| Number of QoS policies in DDS_QosPolicyId_t. More... | |
Detailed Description
Quality of Service (QoS) policies.
Data Distribution Service (DDS) relies on the use of QoS. A QoS is a set of characteristics that controls some aspect of the behavior of DDS. A QoS is comprised of individual QoS policies (objects conceptually deriving from an abstract QosPolicy class).
"Supported QoS policies"
The QosPolicy provides the basic mechanism for an application to specify quality of service parameters. It has an attribute name that is used to uniquely identify each QosPolicy.
QosPolicy implementation is comprised of a name, an ID, and a type. The type of a QosPolicy value may be atomic, such as an integer or float, or compound (a structure). Compound types are used whenever multiple parameters must be set coherently to define a consistent value for a QosPolicy.
QoS (i.e., a list of QosPolicy objects) may be associated with all DDSEntity objects in the system such as DDSTopic, DDSDataWriter, DDSDataReader, DDSPublisher, DDSSubscriber, and DDSDomainParticipant.
Specifying QoS on entities
QosPolicies can be set programmatically when an DDSEntity is created, or modified with the DDSEntity's set_qos (abstract) method.
QosPolicies can also be configured from XML resources (files, strings). With this approach, you can change the QoS without recompiling the application. For more information, see Configuring QoS Profiles with XML.
To customize a DDSEntity's QoS before creating the entity, the correct pattern is:
- First, initialize a QoS object with the appropriate INITIALIZER constructor.
- Call the relevant get_<entity>_default_qos() method.
- Modify the QoS values as desired.
- Finally, create the entity.
Each QosPolicy is treated independently from the others. This approach has the advantage of being very extensible. However, there may be cases where several policies are in conflict. Consistency checking is performed each time the policies are modified via the set_qos (abstract) operation, or when the DDSEntity is created.
When a policy is changed after being set to a given value, it is not required that the new value be applied instantaneously; RTI Connext is allowed to apply it after a transition phase. In addition, some QosPolicy have immutable semantics, meaning that they can only be specified either at DDSEntity creation time or else prior to calling the DDSEntity::enable operation on the entity.
Each DDSEntity can be configured with a list of QosPolicy objects. However, not all QosPolicies are supported by each DDSEntity. For instance, a DDSDomainParticipant supports a different set of QosPolicies than a DDSTopic or a DDSPublisher.
Additional properties that are not exposed through the formal QoS policies can also be set for an DDSEntity via the DDS_PropertyQosPolicy. These properties are described in the Property Reference Guide.
QoS compatibility
In several cases, for communications to occur properly (or efficiently), a QosPolicy on the publisher side must be compatible with a corresponding policy on the subscriber side. For example, if a DDSSubscriber requests to receive data reliably while the corresponding DDSPublisher defines a best-effort policy, communication will not happen as requested.
To address this issue and maintain the desirable decoupling of publication and subscription as much as possible, the QosPolicy specification follows the subscriber-requested, publisher-offered pattern.
In this pattern, the subscriber side can specify a "requested" value for a particular QosPolicy. The publisher side specifes an "offered" value for that QosPolicy. RTI Connext will then determine whether the value requested by the subscriber side is compatible with what is offered by the publisher side. If the two policies are compatible, then communication will be established. If the two policies are not compatible, RTI Connext will not establish communications between the two DDSEntity objects and will record this fact by means of the DDS_OFFERED_INCOMPATIBLE_QOS_STATUS on the publisher end and DDS_REQUESTED_INCOMPATIBLE_QOS_STATUS on the subscriber end. The application can detect this fact by means of a DDSListener or a DDSCondition.
The following properties are defined on a QosPolicy.
-
RxO property
The QosPolicy objects that need to be set in a compatible manner between the publisher and subscriber end are indicated by the setting of the RxO property:-
RxO = YES
indicates that the policy can be set both at the publishing and subscribing ends and the values must be set in a compatible manner. In this case the compatible values are explicitly defined. -
RxO = NO
indicates that the policy can be set both at the publishing and subscribing ends but the two settings are independent. That is, all combinations of values are compatible. -
RxO = N/A
indicates that the policy can only be specified at either the publishing or the subscribing end, but not at both ends. So compatibility does not apply.
-
RxO = YES
-
Changeable property
Determines whether a QosPolicy can be changed.- NO -- policy can only be specified at DDSEntity creation time.
- UNTIL ENABLE -- policy can only be changed before the DDSEntity is enabled.
- YES -- policy can be changed at any time.
Macro Definition Documentation
◆ DDS_QosPrintFormat_INITIALIZER
| #define DDS_QosPrintFormat_INITIALIZER |
Static initializer for DDS_QosPrintFormat.
Use this initializer to ensure that new objects do not have uninitialized contents.
- See also
- DDS_QosPrintFormat
◆ DDS_QOS_POLICY_COUNT
| #define DDS_QOS_POLICY_COUNT |
Number of QoS policies in DDS_QosPolicyId_t.
Enumeration Type Documentation
◆ DDS_QosPolicyId_t
| enum DDS_QosPolicyId_t |
Type to identify QosPolicies.
| Enumerator | |
|---|---|
| DDS_INVALID_QOS_POLICY_ID | Identifier for an invalid QoS policy. |
| DDS_USERDATA_QOS_POLICY_ID | Identifier for DDS_UserDataQosPolicy. |
| DDS_DURABILITY_QOS_POLICY_ID | Identifier for DDS_DurabilityQosPolicy. |
| DDS_PRESENTATION_QOS_POLICY_ID | Identifier for DDS_PresentationQosPolicy. |
| DDS_DEADLINE_QOS_POLICY_ID | Identifier for DDS_DeadlineQosPolicy. |
| DDS_LATENCYBUDGET_QOS_POLICY_ID | Identifier for DDS_LatencyBudgetQosPolicy. |
| DDS_OWNERSHIP_QOS_POLICY_ID | Identifier for DDS_OwnershipQosPolicy. |
| DDS_OWNERSHIPSTRENGTH_QOS_POLICY_ID | Identifier for DDS_OwnershipStrengthQosPolicy. |
| DDS_LIVELINESS_QOS_POLICY_ID | Identifier for DDS_LivelinessQosPolicy. |
| DDS_TIMEBASEDFILTER_QOS_POLICY_ID | Identifier for DDS_TimeBasedFilterQosPolicy. |
| DDS_PARTITION_QOS_POLICY_ID | Identifier for DDS_PartitionQosPolicy. |
| DDS_RELIABILITY_QOS_POLICY_ID | Identifier for DDS_ReliabilityQosPolicy. |
| DDS_DESTINATIONORDER_QOS_POLICY_ID | Identifier for DDS_DestinationOrderQosPolicy. |
| DDS_HISTORY_QOS_POLICY_ID | Identifier for DDS_HistoryQosPolicy. |
| DDS_RESOURCELIMITS_QOS_POLICY_ID | Identifier for DDS_ResourceLimitsQosPolicy. |
| DDS_ENTITYFACTORY_QOS_POLICY_ID | Identifier for DDS_EntityFactoryQosPolicy. |
| DDS_WRITERDATALIFECYCLE_QOS_POLICY_ID | Identifier for DDS_WriterDataLifecycleQosPolicy. |
| DDS_READERDATALIFECYCLE_QOS_POLICY_ID | Identifier for DDS_ReaderDataLifecycleQosPolicy. |
| DDS_TOPICDATA_QOS_POLICY_ID | Identifier for DDS_TopicDataQosPolicy. |
| DDS_GROUPDATA_QOS_POLICY_ID | Identifier for DDS_GroupDataQosPolicy. |
| DDS_TRANSPORTPRIORITY_QOS_POLICY_ID | Identifier for DDS_TransportPriorityQosPolicy. |
| DDS_LIFESPAN_QOS_POLICY_ID | Identifier for DDS_LifespanQosPolicy. |
| DDS_DURABILITYSERVICE_QOS_POLICY_ID | Identifier for DDS_DurabilityServiceQosPolicy. |
| DDS_DATA_REPRESENTATION_QOS_POLICY_ID | Identifier for DDS_DataRepresentationQosPolicy. |
| DDS_TYPE_CONSISTENCY_ENFORCEMENT_QOS_POLICY_ID | Identifier for DDS_TypeConsistencyEnforcementQosPolicy. |
| DDS_DATATAG_QOS_POLICY_ID | Identifier for DDS_DataTagQosPolicy. |
| DDS_WIREPROTOCOL_QOS_POLICY_ID | <<extension>> Identifier for DDS_WireProtocolQosPolicy |
| DDS_DISCOVERY_QOS_POLICY_ID | <<extension>> Identifier for DDS_DiscoveryQosPolicy |
| DDS_DATAREADERRESOURCELIMITS_QOS_POLICY_ID | <<extension>> Identifier for DDS_DataReaderResourceLimitsQosPolicy |
| DDS_DATAWRITERRESOURCELIMITS_QOS_POLICY_ID | <<extension>> Identifier for DDS_DataWriterResourceLimitsQosPolicy |
| DDS_DATAREADERPROTOCOL_QOS_POLICY_ID | <<extension>> Identifier for DDS_DataReaderProtocolQosPolicy |
| DDS_DATAWRITERPROTOCOL_QOS_POLICY_ID | <<extension>> Identifier for DDS_DataWriterProtocolQosPolicy |
| DDS_DOMAINPARTICIPANTRESOURCELIMITS_QOS_POLICY_ID | <<extension>> Identifier for DDS_DomainParticipantResourceLimitsQosPolicy |
| DDS_EVENT_QOS_POLICY_ID | <<extension>> Identifier for DDS_EventQosPolicy |
| DDS_DATABASE_QOS_POLICY_ID | <<extension>> Identifier for DDS_DatabaseQosPolicy |
| DDS_RECEIVERPOOL_QOS_POLICY_ID | <<extension>> Identifier for DDS_ReceiverPoolQosPolicy |
| DDS_DISCOVERYCONFIG_QOS_POLICY_ID | <<extension>> Identifier for DDS_DiscoveryConfigQosPolicy |
| DDS_SYSTEMRESOURCELIMITS_QOS_POLICY_ID | <<extension>> Identifier for DDS_SystemResourceLimitsQosPolicy |
| DDS_TRANSPORTSELECTION_QOS_POLICY_ID | <<extension>> Identifier for DDS_TransportSelectionQosPolicy |
| DDS_TRANSPORTUNICAST_QOS_POLICY_ID | <<extension>> Identifier for DDS_TransportUnicastQosPolicy |
| DDS_TRANSPORTMULTICAST_QOS_POLICY_ID | <<extension>> Identifier for DDS_TransportMulticastQosPolicy |
| DDS_TRANSPORTBUILTIN_QOS_POLICY_ID | <<extension>> Identifier for DDS_TransportBuiltinQosPolicy |
| DDS_TYPESUPPORT_QOS_POLICY_ID | <<extension>> Identifier for DDS_TypeSupportQosPolicy |
| DDS_PROPERTY_QOS_POLICY_ID | <<extension>> Identifier for DDS_PropertyQosPolicy |
| DDS_PUBLISHMODE_QOS_POLICY_ID | <<extension>> Identifier for DDS_PublishModeQosPolicy |
| DDS_ASYNCHRONOUSPUBLISHER_QOS_POLICY_ID | <<extension>> Identifier for DDS_AsynchronousPublisherQosPolicy |
| DDS_ENTITYNAME_QOS_POLICY_ID | <<extension>> Identifier for DDS_EntityNameQosPolicy |
| DDS_BATCH_QOS_POLICY_ID | <<extension>> Identifier for DDS_BatchQosPolicy |
| DDS_PROFILE_QOS_POLICY_ID | <<extension>> Identifier for DDS_ProfileQosPolicy |
| DDS_LOCATORFILTER_QOS_POLICY_ID | <<extension>> Identifier for DDS_LocatorFilterQosPolicy |
| DDS_MULTICHANNEL_QOS_POLICY_ID | <<extension>> Identifier for DDS_MultiChannelQosPolicy |
| DDS_AVAILABILITY_QOS_POLICY_ID | <<extension>> Identifier for DDS_AvailabilityQosPolicy |
| DDS_TRANSPORTMULTICASTMAPPING_QOS_POLICY_ID | <<extension>> Identifier for DDS_TransportMulticastMappingQosPolicy |
| DDS_LOGGING_QOS_POLICY_ID | <<extension>> Identifier for DDS_LoggingQosPolicy |
| DDS_TOPICQUERYDISPATCH_QOS_POLICY_ID | <<extension>> Identifier for DDS_TopicQueryDispatchQosPolicy |
| DDS_DATAWRITERTRANSFERMODE_QOS_POLICY_ID | <<extension>> Identifier for DDS_DataWriterTransferModeQosPolicy |
| DDS_MONITORING_QOS_POLICY_ID | <<extension>> Identifier for DDS_MonitoringQosPolicy |