Qos (Quality of Service)用于指定服务的行为，允许用户指定每个实体怎样表现或运行。通过XML文件(Profiles)来配置或者在代码中直接指定。

XML profiles

xml配置文件可以有多个。

加载

Fast DDS在初始化阶段自动加载XML：

• 在当前可执行文件的路径下加载 DEFAULT_FASTRTPS_PROFILES.xml
• 加载环境变量FASTRTPS_DEFAULT_PROFILES_FILE指定的xml
• 加载配置参数指定的xml文件
• 直接加载xml格式的字符串

创建

<?xml version="1.0" encoding="UTF-8" ?>
<dds xmlns="http://www.eprosima.com/XMLSchemas/fastRTPS_Profiles"><profiles><domainparticipant_factory profile_name="domainparticipant_factory_profile"><!-- ... --></domainparticipant_factory><participant profile_name="participant_profile"><!-- ... --></participant><data_writer profile_name="datawriter_profile"><!-- ... --></data_writer><data_reader profile_name="datareader_profile"><!-- ... --></data_reader><topic profile_name="topic_profile"><!-- ... --></topic><transport_descriptors><!-- ... --></transport_descriptors></profiles><library_settings><!-- ... --></library_settings><log><!-- ... --></log><types><!-- ... --></types>
</dds>

1. <dds>, <profiles>, <library_settings>, <types>, and <log> 这些标签可以独立定义。
2. <participant>, <data_reader>, <data_writer>, <topic>, and <transport_descriptors> 这些标签必须作为<profiles>的子元素

修改

if (ReturnCode_t::RETCODE_OK ==DomainParticipantFactory::get_instance()->load_XML_profiles_file("my_profiles.xml"))
{DomainParticipantQos participant_qos;DomainParticipantFactory::get_instance()->get_participant_qos_from_profile("participant_xml_profile",participant_qos);// Name obtained in another section of the codeparticipant_qos.name() = custom_name;// Modify number of preallocations (this overrides the one set in the XML profile)participant_qos.allocation().send_buffers.preallocated_number = 10;// Create participant using the modified XML QosDomainParticipant* participant =DomainParticipantFactory::get_instance()->create_participant(0, participant_qos);
}

可配置内容

• DomainParticipantFactory profiles
• DomainParticipant profiles
• DataWriter profiles
• DataReader profiles
• Topic profiles
• transport_descriptor
• Intra-process delivery profiles
• Log profiles
• Dynamic Types profiles

Qos

每个Qos都有一个唯一的ID（定义在枚举QosPolicyId_t中），这个ID值用于一些Status中，以识别状态所引用的特定Qos策略。
Fast DDS中支持的Policies在这里

DeadlineQosPolicy

当新的数据样本的频率低于设定的阈值时，此QoS策略会发出警报。它对于预期定期更新数据的情况非常有用。

Data Member Name	Type	Default Value
period	Duration_t	c_TimeInfinite

DestinationOrderQosPolicy

DurabilityQosPolicy

DurabilityServiceQosPolicy

EntityFactoryQosPolicy

GroupDataQosPolicy

HistoryQosPolicy

LatencyBudgetQosPolicy

LivelinessQosPolicy

OwnershipQosPolicy

OwnershipStrengthQosPolicy

PartitionQosPolicy

PresentationQosPolicy

ReaderDataLifecycleQosPolicy

ReliabilityQosPolicy

ResourceLimitsQosPolicy

TimeBasedFilterQosPolicy

TopicDataQosPolicy

TransportPriorityQosPolicy

UserDataQosPolicy

WriterDataLifecycleQosPolicy

eProsima扩展的Qos