DDS_BuiltinTopicReaderResourceLimits_t Struct Reference

Built-in topic reader's resource limits. More...

Data Fields
DDS_Long	initial_samples
	Initial number of samples.
DDS_Long	max_samples
	Maximum number of samples.
DDS_Long	initial_infos
	Initial number of sample infos.
DDS_Long	max_infos
	Maximum number of sample infos.
DDS_Long	initial_outstanding_reads
	The initial number of outstanding reads that have not call finish yet on the same built-in topic DDS_DataReader.
DDS_Long	max_outstanding_reads
	The maximum number of outstanding reads that have not called finish yet on the same built-in topic DDS_DataReader.
DDS_Long	max_samples_per_read
	Maximum number of samples that can be read/taken on a same built-in topic DDS_DataReader.
DDS_Boolean	disable_fragmentation_support
	Determines whether the built-in topic DDS_DataReader can receive fragmented samples.
DDS_Long	max_fragmented_samples
	The maximum number of samples for which the built-in topic DDS_DataReader may store fragments at a given point in time.
DDS_Long	initial_fragmented_samples
	The initial number of samples for which a built-in topic DDS_DataReader may store fragments.
DDS_Long	max_fragmented_samples_per_remote_writer
	The maximum number of samples per remote writer for which a built-in topic DDS_DataReader may store fragments.
DDS_Long	max_fragments_per_sample
	Maximum number of fragments for a single sample.
DDS_Boolean	dynamically_allocate_fragmented_samples
	Determines whether the built-in topic DDS_DataReader pre-allocates storage for storing fragmented samples.

Detailed Description

Built-in topic reader's resource limits.

Defines the resources that can be used for a built-in-topic data reader.

A built-in topic data reader subscribes reliably to built-in topics containing declarations of new entities or updates to existing entities in the domain. Keys are used to differentiate among entities of the same type. RTI Connext assigns a unique key to each entity in a domain.

Properties:

RxO = N/A
Changeable = NO

QoS:

DDS_DiscoveryConfigQosPolicy

Field Documentation

DDS_Long DDS_BuiltinTopicReaderResourceLimits_t::initial_samples

Initial number of samples.

This should be a value between 1 and initial number of instance of the built-in-topic reader, depending on how many instances are sending data concurrently.

[default] 64

[range] [1, 1 million], <= max_samples

DDS_Long DDS_BuiltinTopicReaderResourceLimits_t::max_samples

Maximum number of samples.

This should be a value between 1 and max number of instance of the built-in-topic reader, depending on how many instances are sending data concurrently. Also, it should not be less than initial_samples.

[default] DDS_LENGTH_UNLIMITED

[range] [1, 1 million] or DDS_LENGTH_UNLIMITED, >= initial_samples

DDS_Long DDS_BuiltinTopicReaderResourceLimits_t::initial_infos

Initial number of sample infos.

The initial number of info units that a built-in topic DDS_DataReader can have. Info units are used to store DDS_SampleInfo.

[default] 64

[range] [1, 1 million] <= max_infos

DDS_Long DDS_BuiltinTopicReaderResourceLimits_t::max_infos

Maximum number of sample infos.

The maximum number of info units that a built-in topic DDS_DataReader can use to store DDS_SampleInfo.

[default] DDS_LENGTH_UNLIMITED

[range] [1, 1 million] or DDS_LENGTH_UNLIMITED, >= initial_infos

DDS_Long DDS_BuiltinTopicReaderResourceLimits_t::initial_outstanding_reads

The initial number of outstanding reads that have not call finish yet on the same built-in topic DDS_DataReader.

[default] 2

[range] [1, 65536] or DDS_LENGTH_UNLIMITED <= max_outstanding_reads

DDS_Long DDS_BuiltinTopicReaderResourceLimits_t::max_outstanding_reads

The maximum number of outstanding reads that have not called finish yet on the same built-in topic DDS_DataReader.

[default] DDS_LENGTH_UNLIMITED

[range] [1, 65536] or DDS_LENGTH_UNLIMITED, >= initial_outstanding_reads

DDS_Long DDS_BuiltinTopicReaderResourceLimits_t::max_samples_per_read

Maximum number of samples that can be read/taken on a same built-in topic DDS_DataReader.

[default] 1024

[range] [1, 65536]

DDS_Boolean DDS_BuiltinTopicReaderResourceLimits_t::disable_fragmentation_support

Determines whether the built-in topic DDS_DataReader can receive fragmented samples.

When fragmentation support is not needed, disabling fragmentation support will save some memory resources.

[default] DDS_BOOLEAN_FALSE

DDS_Long DDS_BuiltinTopicReaderResourceLimits_t::max_fragmented_samples

The maximum number of samples for which the built-in topic DDS_DataReader may store fragments at a given point in time.

At any given time, a built-in topic DDS_DataReader may store fragments for up to max_fragmented_samples samples while waiting for the remaining fragments. These samples need not have consecutive sequence numbers and may have been sent by different built-in topic DDS_DataWriter instances.

Once all fragments of a sample have been received, the sample is treated as a regular sample and becomes subject to standard QoS settings such as DDS_BuiltinTopicReaderResourceLimits_t::max_samples.

The middleware will drop fragments if the max_fragmented_samples limit has been reached. For best-effort communication, the middleware will accept a fragment for a new sample, but drop the oldest fragmented sample from the same remote writer. For reliable communication, the middleware will drop fragments for any new samples until all fragments for at least one older sample from that writer have been received.

Only applies if DDS_BuiltinTopicReaderResourceLimits_t::disable_fragmentation_support is DDS_BOOLEAN_FALSE.

[default] 1024

[range] [1, 1 million]

DDS_Long DDS_BuiltinTopicReaderResourceLimits_t::initial_fragmented_samples

The initial number of samples for which a built-in topic DDS_DataReader may store fragments.

Only applies if DDS_BuiltinTopicReaderResourceLimits_t::disable_fragmentation_support is DDS_BOOLEAN_FALSE.

[default] 4

[range] [1,1024], <= max_fragmented_samples

DDS_Long DDS_BuiltinTopicReaderResourceLimits_t::max_fragmented_samples_per_remote_writer

The maximum number of samples per remote writer for which a built-in topic DDS_DataReader may store fragments.

Logical limit so a single remote writer cannot consume all available resources.

Only applies if DDS_BuiltinTopicReaderResourceLimits_t::disable_fragmentation_support is DDS_BOOLEAN_FALSE.

[default] 256

[range] [1, 1 million], <= max_fragmented_samples

DDS_Long DDS_BuiltinTopicReaderResourceLimits_t::max_fragments_per_sample

Maximum number of fragments for a single sample.

Only applies if DDS_BuiltinTopicReaderResourceLimits_t::disable_fragmentation_support is DDS_BOOLEAN_FALSE.

[default] DDS_LENGTH_UNLIMITED

[range] [1, 1 million] or DDS_LENGTH_UNLIMITED

DDS_Boolean DDS_BuiltinTopicReaderResourceLimits_t::dynamically_allocate_fragmented_samples

Determines whether the built-in topic DDS_DataReader pre-allocates storage for storing fragmented samples.

By default, the middleware does not allocate memory upfront, but instead allocates memory from the heap upon receiving the first fragment of a new sample. The amount of memory allocated equals the amount of memory needed to store all fragments in the sample. Once all fragments of a sample have been received, the sample is deserialized and stored in the regular receive queue. At that time, the dynamically allocated memory is freed again.

This QoS setting is useful for large, but variable-sized data types where upfront memory allocation for multiple samples based on the maximum possible sample size may be expensive. The main disadvantage of not pre-allocating memory is that one can no longer guarantee the middleware will have sufficient resources at run-time.

If dynamically_allocate_fragmented_samples is set to DDS_BOOLEAN_FALSE, the middleware will allocate memory upfront for storing fragments for up to DDS_DataReaderResourceLimitsQosPolicy::initial_fragmented_samples samples. This memory may grow up to DDS_DataReaderResourceLimitsQosPolicy::max_fragmented_samples if needed.

Only applies if DDS_DataReaderResourceLimitsQosPolicy::disable_fragmentation_support is DDS_BOOLEAN_FALSE.

[default] DDS_BOOLEAN_TRUE