DDS::DataWriterProtocolQosPolicy Struct Reference

Protocol that applies only to DDS::DataWriter instances. More...

#include <managed_infrastructure.h>

Static Public Member Functions
static System::String^	get_datawriterprotocol_qos_policy_name ()
	Stringified human-readable name for DDS::DataWriterProtocolQosPolicy.

Public Attributes
GUID_t	virtual_guid
	The virtual GUID (Global Unique Identifier).
System::UInt32	rtps_object_id
	The RTPS Object ID.
RtpsReliableWriterProtocol_t	rtps_reliable_writer
	The reliable protocol defined in RTPS.

Properties
System::Boolean	push_on_write [get, set]
	Whether to push sample out when write is called.
System::Boolean	disable_positive_acks [get, set]
	Controls whether or not the writer expects positive acknowledgements from matching readers.
System::Boolean	disable_inline_keyhash [get, set]
	Controls whether or not a keyhash is propagated on the wire with each sample.
System::Boolean	serialize_key_with_dispose [get, set]
	Controls whether or not the serialized key is propagated on the wire with dispose samples.

Detailed Description

Protocol that applies only to DDS::DataWriter instances.

DDS has a standard protocol for packet (user and meta data) exchange between applications using DDS for communications. This QoS policy and DDS::DataWriterProtocolQosPolicy give you control over configurable portions of the protocol, including the configuration of the reliable data delivery mechanism of the protocol on a per DataWriter or DataReader basis.

These configuration parameters control timing, timeouts, and give you the ability to tradeoff between speed of data loss detection and repair versus network and CPU bandwidth used to maintain reliability.

It is important to tune the reliability protocol (on a per DDS::DataWriter and DDS::DataReader basis) to meet the requirements of the end-user application so that data can be sent between DataWriters and DataReaders in an efficient and optimal manner in the presence of data loss.

You can also use this QoS policy to control how RTI Connext responds to "slow" reliable DataReaders or ones that disconnect or are otherwise lost. See DDS::ReliabilityQosPolicy for more information on the per-DataReader/DataWriter reliability configuration. DDS::HistoryQosPolicy and DDS::ResourceLimitsQosPolicy also play an important role in the DDS reliable protocol.

This QoS policy is an extension to the DDS standard.

Entity:

DDS::DataWriter

Properties:

RxO = N/A
Changeable = NO

Member Data Documentation

GUID_t DDS::DataWriterProtocolQosPolicy::virtual_guid

The virtual GUID (Global Unique Identifier).

The virtual GUID is used to uniquely identify different incarnations of the same DDS::DataWriter.

RTI Connext uses the virtual GUID to associate a persisted writer history to a specific DDS::DataWriter.

The RTI Connext Persistence Service uses the virtual GUID to send samples on behalf of the original DDS::DataWriter.

[default] DDS::Guid_t::GUID_AUTO

System::UInt32 DDS::DataWriterProtocolQosPolicy::rtps_object_id

The RTPS Object ID.

This value is used to determine the RTPS object ID of a data writer according to the DDS-RTPS Interoperability Wire Protocol.

Only the last 3 bytes are used; the most significant byte is ignored.

If the default value is specified, RTI Connext will automatically assign the object ID based on a counter value (per participant) starting at 0x00800000. That value is incremented for each new data writer.

A rtps_object_id value in the interval [0x00800000,0x00ffffff] may collide with the automatic values assigned by RTI Connext. In those cases, the recomendation is not to use automatic object ID assigment.

[default] DDS::WireProtocolQosPolicy::RTPS_AUTO_ID

[range] [0,0x00ffffff]

RtpsReliableWriterProtocol_t DDS::DataWriterProtocolQosPolicy::rtps_reliable_writer

The reliable protocol defined in RTPS.

[default] low_watermark 0;
high_watermark 1;
heartbeat_period 3.0 seconds;
fast_heartbeat_period 3.0 seconds;
late_joiner_heartbeat_period 3.0 seconds;
virtual_heartbeat_period DDS::Duration_t::DURATION_AUTO;
samples_per_virtual_heartbeat DDS::ResourceLimitsQosPolicy::LENGTH_UNLIMITED;
max_heartbeat_retries 10;
inactivate_nonprogressing_readers false;
heartbeats_per_max_samples 8;
min_nack_response_delay 0.0 seconds;
max_nack_response_delay 0.2 seconds;
max_bytes_per_nack_response 131072

Property Documentation

System:: Boolean DDS::DataWriterProtocolQosPolicy::push_on_write

getset

Whether to push sample out when write is called.

If set to true (the default), the writer will send a sample every time write is called. Otherwise, the sample is put into the queue waiting for a NACK from remote reader(s) to be sent out.

[default] true

System:: Boolean DDS::DataWriterProtocolQosPolicy::disable_positive_acks

getset

Controls whether or not the writer expects positive acknowledgements from matching readers.

If set to true, the writer does not expect readers to send send positive acknowledgments to the writer. Consequently, instead of keeping a sample queued until all readers have positively acknowledged it, the writer will keep a sample for at least DDS::RtpsReliableWriterProtocol_t::disable_positive_acks_min_sample_keep_duration, after which the sample is logically considered as positively acknowledged.

If set to false (the default), the writer expects to receive positive acknowledgements from its acknowledging readers (DDS::DataReaderProtocolQosPolicy::disable_positive_acks = false) and it applies the keep-duration to its non-acknowledging readers (DDS::DataReaderProtocolQosPolicy::disable_positive_acks = true).

A writer with both acknowledging and non-acknowledging readers keeps a sample queued until acknowledgements have been received from all acknowledging readers and the keep-duration has elapsed for non-acknowledging readers.

[default] false

System:: Boolean DDS::DataWriterProtocolQosPolicy::disable_inline_keyhash

getset

Controls whether or not a keyhash is propagated on the wire with each sample.

This field only applies to keyed writers.

With each key, RTI Connext associates an internal 16-byte representation, called a keyhash.

When this field is false, the keyhash is sent on the wire with every data instance.

When this field is true, the keyhash is not sent on the wire and the readers must compute the value using the received data.

If the reader is CPU bound, sending the keyhash on the wire may increase performance, because the reader does not have to get the keyhash from the data.

If the writer is CPU bound, sending the keyhash on the wire may decrease performance, because it requires more bandwidth (16 more bytes per sample).

Note: Setting disable_inline_keyhash to true is not compatible with using RTI Real-Time Connect or RTI Recorder.

[default] false

System:: Boolean DDS::DataWriterProtocolQosPolicy::serialize_key_with_dispose

getset

Controls whether or not the serialized key is propagated on the wire with dispose samples.

This field only applies to keyed writers.

We recommend setting this field to true if there are DataReaders where DDS::DataReaderProtocolQosPolicy::propagate_dispose_of_unregistered_instances is also true.

Important: When this field is true, batching will not be compatible with RTI Connext 4.3e, 4.4b, or 4.4c. The DDS::DataReader entities will receive incorrect data and/or encounter deserialization errors.

[default] false