9.4.1. What’s New in 4.0.0

The following features are new since Connext Micro 3.0.3.

9.4.1.1. Enhanced performance for asynchronous DataWriters

This release reduces the contention between DataWriters and the asynchronous publication thread (used for flow-control of samples and publishing fragmented samples). Previously, DataWriters would block while the asynchronous publication thread was sending data. In this release, the asynchronous publication thread uses a separate critical section from the DataWriter’s write API, which allows the DataWriter to write samples while the asynchronous publication thread is sending data.

Please note the following limitations:

• It is not possible to send and receive data at the same time.

• The asynchronous publication thread and the DataWriter will contend for the same critical section when the asynchronous publication thread starts or finishes sending a sample. This is because the DataWriter is loaning samples to the asynchronous publication thread instead of copying them, and the ownership transfer of samples from the DataWriter to the asynchronous publication thread (and from the asynchronous publication thread to the DataWriter) is protected.

In addition, The User’s Manual has not been updated for this release; some sections do not reflect the impact of these changes. Specifically, note the following:

• Each DataWriter allocates 1 additional mutex.

• Each DomainParticipant allocates 2 additional mutexes, plus 1 mutex per flow-controller (3 by default).

• Each DataWriter allocates an additional (max_routes_per_reader * max_fragmented_samples * max_remote_readers * 464) bytes. Future releases may reduce this.

9.4.1.2. Further control which entities communicate with each other using new Partition QoS policy

The PARTITION QoS policy provides a method to prevent Entities that have otherwise compatible QoS policies from matching—and thus communicating with—each other. Much in the same way that only applications within the same DDS domain will communicate with each other, only Entities that belong to the same partition can talk to each other.

See information on Partitions in the User’s Manual chapter for more information.

9.4.1.3. Store additional entity-related information that is passed between applications during discovery using new User/Topic/Group Data QoS policies

Connext Micro now provides areas where your application can store additional information related to DDS Entities. How this information is used is up to user code. Connext Micro distributes this information to other applications as part of the discovery proces; however, Connext Micro does not interpret the information. Use cases are usually application-to-application identification, authentication, authorization, and encryption.

There are three User Discovery Data QoS policies:

• USER_DATA: associated with DomainParticipants, DataWriters, and DataReaders.

• TOPIC_DATA: associated with Topics.

• GROUP_DATA: associated with Publishers and Subscribers.

See information on User Discovery Data in the User’s Manual chapter for more information.

9.4.1.4. Verify that locally created participant GUIDs are unique within a DomainParticipantFactory

When a DomainParticipant is created, Connext Micro now checks that the GUID is not already in use by another DomainParticipant created from the same DomainParticipantFactory.

9.4.1.5. Micro Application Generator (MAG)

9.4.1.5.1. Support for Partition QoS policy in MAG

Micro Application Generator (MAG) now supports the PARTITION QoS policy. Instead of ignoring the Partition QoS values, as it did in previous releases, MAG now parses the values configured in XML and adds those values when generating the code.

The following partition-related DomainParticipant QoS resource limits are also now supported:

• max_partitions

• max_partition_cumulative_characters

• max_partition_string_size

• max_partition_string_allocation

See the Partitions chapter in the User’s Manual for more information on this QoS policy.

9.4.1.5.2. Support for GROUP_DATA, USER_DATA, and TOPIC_DATA QoS policies in MAG

Micro Application Generator (MAG) now supports the GROUP_DATA, USER_DATA, and TOPIC_DATA QoS policies. Instead of ignoring these QoS values, as it did in previous releases, MAG now parses the values configured in XML and adds those values when generating the code.

MAG also supports the group_data, user_data, and topic_data elements:

• user_data in the DomainParticipant, DataWriter, and DataReader QoS

• topic_data in the Topic QoS

• group_data in the Publisher and Subscriber QoS

• The following DomainParticipant QoS resource limits:

  • participant_user_data_max_length

  • participant_user_data_max_count

  • topic_data_max_length

  • topic_data_max_count

  • publisher_group_data_max_length

  • publisher_group_data_max_count

  • subscriber_group_data_max_length

  • subscriber_group_data_max_count

  • writer_user_data_max_length

  • writer_user_data_max_count

  • reader_user_data_max_length

  • reader_user_data_max_count

See the User Discovery Data chapter in the User’s Manual for more information on these QoS policies.

9.4.1.5.3. Support for environment variable expansion in MAG

Now you can refer to an environment variable set in the command shell within an XML tag. When MAG parses the configuration file, it will expand the environment variable. The way to refer to the environment variable is as follows:

$(MY_VARIABLE)

For example:

<name>$(MY_VARIABLE)</name>

Being able to refer to an environment variable within an XML file increases XML reusability. For example, this will allow you to specify the initial peers, so you do not need to use multiple XML files or XML profiles per application.

9.4.1.5.4. Only check for QoS policies that are used by your system definition

In previous releases, MAG checked whether all of the QoS policies passed to the tool were supported by Connext Micro. This has been changed to only check for QoS policies that are used by the system defined in the <domain_participant_library>.

9.4.1.5.5. XML fields of type duration have unset tags default to 0 with a warning log message

The duration type tag has two subfields, <sec> and <nanosec>. Some QoS policies that use these fields, such as the DEADLINE QoS Policy, set the default duration to INFINITE. Therefore, if you had set just one of these fields (such as <sec>, but not <nanosec>, or vice-versa), the resulting duration value was still INFINITE.

Now if you set only one of these fields (<sec> or <nanosec>) in the XML file, the other value defaults to 0. (If you set neither one of them, the default duration for that policy would be used.) A warning message will also be logged by the parser specifying the parent tag, the missing subfield, and the line number.

9.4.1.5.6. Support for resource limits in DomainParticipantFactoryQos

This release allows you to configure the resource limits of the DomainParticipantFactoryQos (max_participants) in XML.

By default, MAG updates the resource limits of the DomainParticipantFactoryQos so that MAG can at least support the entities defined in the XML file. However, if your applications communicate with more remote entities than those specified in the XML file, you may need to manually update the resource limits. In that case, you need to use the -dontUpdateResourceLimits command-line option. That will prevent MAG from automatically updating the resource limits for the DomainParticipantFactory, DomainParticipants, DataReaders, and DataWriters.

9.4.1.5.7. Instance replacement changes affect XML files in MAG

The type used by <instance_replacement> in MAG has been changed from a single type to a complex type. Because of this change, XML files used by MAG in previous releases won’t work out of the box in this release. For example, the following XML based on MAG in previous releases won’t work in the current release:

<datareader_qos>
    <reader_resource_limits>
        <instance_replacement>OLDEST_INSTANCE_REPLACEMENT</instance_replacement>
    </reader_resource_limits>
</datareader_qos>

You need to update it to the following:

<datareader_qos>
    <reader_resource_limits>
        <instance_replacement>
            <alive_instance_removal>ANY_INSTANCE_REMOVAL</alive_instance_removal>
            <disposed_instance_removal>ANY_INSTANCE_REMOVAL</disposed_instance_removal>
            <no_writers_instance_removal>ANY_INSTANCE_REMOVAL</no_writers_instance_removal>
        </instance_replacement>
    </reader_resource_limits>
</datareader_qos>