RTI Connext Java API  Version 5.1.0
QoS Policies

Quality of Service (QoS) policies. More...


 <<eXtension>> Specifies the asynchronous publishing settings of the com.rti.dds.publication.Publisher instances.
 <<eXtension>> Configures the availability of data.
 <<eXtension>> Batch QoS policy used to enable batching in com.rti.dds.publication.DataWriter instances.
 <<eXtension>> Various threads and resource limits settings used by RTI Connext to control its internal database.
 <<eXtension>> Specifies the DataReader-specific protocol QoS.
 <<eXtension>> Various settings that configure how DataReaders allocate and use physical memory for internal resources.
 <<eXtension>> Along with com.rti.dds.infrastructure.WireProtocolQosPolicy and com.rti.dds.infrastructure.DataReaderProtocolQosPolicy, this QoS policy configures the DDS on-the-network protocol (RTPS).
 <<eXtension>> Various settings that configure how a com.rti.dds.publication.DataWriter allocates and uses physical memory for internal resources.
 Expresses the maximum duration (deadline) within which an instance is expected to be updated.
 Controls the criteria used to determine the logical order among changes made by com.rti.dds.publication.Publisher entities to the same instance of data (i.e., matching com.rti.dds.topic.Topic and key).
 <<eXtension>> Specifies the discovery configuration QoS.
 <<eXtension>> Specifies the attributes required to discover participants in the domain.
 <<eXtension>> Various settings that configure how a com.rti.dds.domain.DomainParticipant allocates and uses physical memory for internal resources, including the maximum sizes of various properties.
 This QoS policy specifies whether or not RTI Connext will store and deliver previously published data samples to new com.rti.dds.subscription.DataReader entities that join the network later.
 Various settings to configure the external RTI Persistence Service used by RTI Connext for DataWriters with a com.rti.dds.infrastructure.DurabilityQosPolicy setting of com.rti.dds.infrastructure.DurabilityQosPolicyKind.DurabilityQosPolicyKind.PERSISTENT_DURABILITY_QOS or com.rti.dds.infrastructure.DurabilityQosPolicyKind.DurabilityQosPolicyKind.TRANSIENT_DURABILITY_QOS.
 A QoS policy for all com.rti.dds.infrastructure.Entity types that can act as factories for one or more other com.rti.dds.infrastructure.Entity types.
 <<eXtension>> Assigns a name to a com.rti.dds.domain.DomainParticipant, com.rti.dds.publication.Publisher, com.rti.dds.subscription.Subscriber, com.rti.dds.publication.DataWriter or com.rti.dds.subscription.DataReader. Except for com.rti.dds.publication.Publisher and com.rti.dds.subscription.Subscriber, these names are visible during the discovery process and in RTI tools to help you visualize and debug your system.
 <<eXtension>> Configures the internal thread in a DomainParticipant that handles timed events.
 <<eXtension>> Configures multi-thread concurrency and deadlock prevention capabilities.
 Attaches a buffer of opaque data that is distributed by means of Built-in Topics during discovery.
 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.
 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.
 Specifies how long the data written by the com.rti.dds.publication.DataWriter is considered valid.
 Specifies and configures the mechanism that allows com.rti.dds.subscription.DataReader entities to detect when com.rti.dds.publication.DataWriter entities become disconnected or "dead.".
 <<eXtension>> The QoS policy used to report the configuration of a MultiChannel DataWriter as part of builtin.PublicationBuiltinTopicData.
 <<eXtension>> Configures the RTI Connext logging facility.
 <<eXtension>> Configures the ability of a DataWriter to send data on different multicast groups (addresses) based on the value of the data.
 Specifies whether it is allowed for multiple com.rti.dds.publication.DataWriter (s) to write the same instance of the data and if so, how these modifications should be arbitrated.
 Specifies the value of the strength used to arbitrate among multiple com.rti.dds.publication.DataWriter objects that attempt to modify the same instance of a data type (identified by com.rti.dds.topic.Topic + key).
 Set of strings that introduces a logical partition among the topics visible by a com.rti.dds.publication.Publisher and a com.rti.dds.subscription.Subscriber.
 Specifies how the samples representing changes to data instances are presented to a subscribing application.
 <<eXtension>> Configures the way that XML documents containing QoS profiles are loaded by RTI Connext.
 <<eXtension>> Stores name/value (string) 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.
 <<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.
 Controls how a DataReader manages the lifecycle of the data that it has received.
 <<eXtension>> Configures threads used by RTI Connext to receive and process data from transports (for example, UDP sockets).
 Indicates the level of reliability offered/requested by RTI Connext.
 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.
 <<eXtension>> Configures DomainParticipant-independent resources used by RTI Connext.
 Filter that allows a com.rti.dds.subscription.DataReader to specify that it is interested only in (potentially) a subset of the values of the data.
 Attaches a buffer of opaque data that is distributed by means of Built-in Topics during discovery.
 <<eXtension>> Specifies which built-in transports are used.
 <<eXtension>> Specifies a list of topic expressions and addresses that can be used by an Entity with a specific topic name to receive data.
 <<eXtension>> Specifies the multicast address on which a com.rti.dds.subscription.DataReader wants to receive its data. It can also specify a port number, as well as a subset of the available (at the com.rti.dds.domain.DomainParticipant level) transports with which to receive the multicast data.
 This QoS policy allows the application to take advantage of transport that are capable of sending messages with different priorities.
 <<eXtension>> Specifies the physical transports that a com.rti.dds.publication.DataWriter or com.rti.dds.subscription.DataReader may use to send or receive data.
 <<eXtension>> Specifies a subset of transports and a port number that can be used by an Entity to receive data.
 Defines the rules for determining whether the type used to publish a given topic is consistent with that used to subscribe to it.
 <<eXtension>> Allows you to attach application-specific values to a com.rti.dds.publication.DataWriter or com.rti.dds.subscription.DataReader, 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.
 Attaches a buffer of opaque data that is distributed by means of Built-in Topics during discovery.
 <<eXtension>> Specifies the wire protocol related attributes for the com.rti.dds.domain.DomainParticipant.
 Controls how a DataWriter handles the lifecycle of the instances (keys) that it is registered to manage.


class  Qos
 An abstract base class for all QoS types. More...
class  QosPolicy
 The base class for all QoS policies. More...
class  QosPolicyCount
 Type to hold a counter for a com.rti.dds.infrastructure.QosPolicyId_t. More...
class  QosPolicyCountSeq
 Declares IDL sequence < com.rti.dds.infrastructure.QosPolicyCount > More...
class  QosPolicyId_t
 Type to identify QosPolicies. 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 com.rti.dds.infrastructure.Entity objects in the system such as com.rti.dds.topic.Topic, com.rti.dds.publication.DataWriter, com.rti.dds.subscription.DataReader, com.rti.dds.publication.Publisher, com.rti.dds.subscription.Subscriber, and com.rti.dds.domain.DomainParticipant.

Specifying QoS on entities

QosPolicies can be set programmatically when an com.rti.dds.infrastructure.Entity is created, or modified with the com.rti.dds.infrastructure.Entity'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 com.rti.dds.infrastructure.Entity's QoS before creating the entity, the correct pattern is:

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 com.rti.dds.infrastructure.Entity 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 com.rti.dds.infrastructure.Entity creation time or else prior to calling the com.rti.dds.infrastructure.Entity.enable operation on the entity.

Each com.rti.dds.infrastructure.Entity can be configured with a list of QosPolicy objects. However, not all QosPolicies are supported by each com.rti.dds.infrastructure.Entity. For instance, a com.rti.dds.domain.DomainParticipant supports a different set of QosPolicies than a com.rti.dds.topic.Topic or a com.rti.dds.publication.Publisher.

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 com.rti.dds.subscription.Subscriber requests to receive data reliably while the corresponding com.rti.dds.publication.Publisher 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 com.rti.dds.infrastructure.Entity objects and will record this fact by means of the com.rti.dds.infrastructure.StatusKind.StatusKind.OFFERED_INCOMPATIBLE_QOS_STATUS on the publisher end and com.rti.dds.infrastructure.StatusKind.StatusKind.REQUESTED_INCOMPATIBLE_QOS_STATUS on the subscriber end. The application can detect this fact by means of a com.rti.dds.infrastructure.Listener or a com.rti.dds.infrastructure.Condition.

The following properties are defined on a QosPolicy.

RTI Connext Java API Version 5.1.0 Copyright © Mon Feb 3 2014 Real-Time Innovations, Inc