DDS_BatchQosPolicy Struct Reference

Used to configure batching of multiple samples into a single network packet in order to increase throughput for small samples. More...

Data Fields
DDS_Boolean	enable
	Specifies whether or not batching is enabled.
DDS_Long	max_data_bytes
	The maximum cumulative length of all serialized samples in a batch.
DDS_Long	max_samples
	The maximum number of samples in a batch.
struct DDS_Duration_t	max_flush_delay
	The maximum flush delay.
struct DDS_Duration_t	source_timestamp_resolution
	Batch source timestamp resolution.
DDS_Boolean	thread_safe_write
	Determines whether or not the write operation is thread safe.

Detailed Description

Used to configure batching of multiple samples into a single network packet in order to increase throughput for small samples.

This QoS policy configures the ability of the middleware to collect multiple user data samples to be sent in a single network packet, to take advantage of the efficiency of sending larger packets and thus increase effective throughput.

This QoS policy can be used to dramatically increase effective throughput for small data samples. Usually, throughput for small samples (size < 2048 bytes) is limited by CPU capacity and not by network bandwidth. Batching many smaller samples to be sent in a single large packet will increase network utilization, and thus throughput, in terms of samples per second.

Entity:

DDS_DataWriter

Properties:

RxO = NO
Changeable = UNTIL ENABLE

Field Documentation

DDS_Boolean DDS_BatchQosPolicy::enable

Specifies whether or not batching is enabled.

[default] DDS_BOOLEAN_FALSE

DDS_Long DDS_BatchQosPolicy::max_data_bytes

The maximum cumulative length of all serialized samples in a batch.

A batch is flushed automatically when this maximum is reached.

max_data_bytes does not include the meta data associated with the batch samples. Each sample has at least 8 bytes of meta data containing information such as the timestamp and sequence number. The meta data can be as large as 52 bytes for keyed topics and 20 bytes for unkeyed topics.

Note: Batches must contain whole samples. If a new batch is started and its initial sample causes the serialized size to exceed max_data_bytes, RTI Connext will send the sample in a single batch.

[default] 1024

[range] [1,DDS_LENGTH_UNLIMITED]

Consistency

The setting of DDS_BatchQosPolicy::max_data_bytes must be consistent with DDS_BatchQosPolicy::max_samples. For these two values to be consistent, they cannot be both DDS_LENGTH_UNLIMITED.

DDS_Long DDS_BatchQosPolicy::max_samples

The maximum number of samples in a batch.

A batch is flushed automatically when this maximum is reached.

[default] DDS_LENGTH_UNLIMITED

[range] [1,DDS_LENGTH_UNLIMITED]

Consistency

The setting of DDS_BatchQosPolicy::max_samples must be consistent with DDS_BatchQosPolicy::max_data_bytes. For these two values to be consistent, they cannot be both DDS_LENGTH_UNLIMITED.

struct DDS_Duration_t DDS_BatchQosPolicy::max_flush_delay

The maximum flush delay.

A batch is flushed automatically after the delay specified by this parameter.

The delay is measured from the time the first sample in the batch is written by the application.

[default] DDS_DURATION_INFINITE

[range] [0,DDS_DURATION_INFINITE]

Consistency

The setting of DDS_BatchQosPolicy::max_flush_delay must be consistent with DDS_AsynchronousPublisherQosPolicy::disable_asynchronous_batch and DDS_BatchQosPolicy::thread_safe_write. If the delay is different than DDS_DURATION_INFINITE, DDS_AsynchronousPublisherQosPolicy::disable_asynchronous_batch must be set to DDS_BOOLEAN_FALSE and DDS_BatchQosPolicy::thread_safe_write must be set to DDS_BOOLEAN_TRUE.

struct DDS_Duration_t DDS_BatchQosPolicy::source_timestamp_resolution

Batch source timestamp resolution.

The value of this field determines how the source timestamp is associated with the samples in a batch.

A sample written with timestamp 't' inherits the source timestamp 't2' associated with the previous sample unless ('t' - 't2') > source_timestamp_resolution.

If source_timestamp_resolution is set to DDS_DURATION_INFINITE, every sample in the batch will share the source timestamp associated with the first sample.

If source_timestamp_resolution is set to zero, every sample in the batch will contain its own source timestamp corresponding to the moment when the sample was written.

The performance of the batching process is better when source_timestamp_resolution is set to DDS_DURATION_INFINITE.

[default] DDS_DURATION_INFINITE

[range] [0,DDS_DURATION_INFINITE]

Consistency

The setting of DDS_BatchQosPolicy::source_timestamp_resolution must be consistent with DDS_BatchQosPolicy::thread_safe_write. If DDS_BatchQosPolicy::thread_safe_write is set to DDS_BOOLEAN_FALSE, DDS_BatchQosPolicy::source_timestamp_resolution must be set to DDS_DURATION_INFINITE.

DDS_Boolean DDS_BatchQosPolicy::thread_safe_write

Determines whether or not the write operation is thread safe.

If this parameter is set to DDS_BOOLEAN_TRUE, multiple threads can call write on the DDS_DataWriter concurrently.

[default] DDS_BOOLEAN_TRUE

Consistency

The setting of DDS_BatchQosPolicy::thread_safe_write must be consistent with DDS_BatchQosPolicy::source_timestamp_resolution. If DDS_BatchQosPolicy::thread_safe_write is set to DDS_BOOLEAN_FALSE, DDS_BatchQosPolicy::source_timestamp_resolution must be set to DDS_DURATION_INFINITE.