Component Based DDS with C++11 and R2DDS

Component Based DDS using
C++11
R2DDS (Ruby to DDS)
RTI London Connext Conference 2014
Johnny Willemsen
CTO Remedy IT
jwillemsen@remedy.nl

Remedy IT
Remedy IT is specialized in communication
middleware and component technologies
Strong focus on open standards based solutions
Actively involved in the Object Management Group,
leading several OMG open standardization efforts
Our customers are in various domains including
telecom, aerospace and defense, transportation,
industrial automation
For more information take a look at our website
www.remedy.nl
Copyright © Remedy IT2

What we do
Develop implementations of OMG open standards
• Open source; TAO, CIAO, R2CORBA
• Commercial; TAOX11, AXCIOMA
Deliver services related to OMG standards including
CORBA, CCM, DDS
Deliver services for specific implementations,
including RTI Connext DDS
Develop open standards as part of the OMG

Component Based DDS
DDS is a great technology but
• It provides a messaging protocol, not a complete
architecture
• Provides a lot of freedom to the developer which can
lead to misuse
• Lots of things are left to the application like
deployment and threading model design
• Vendor portability can be a challenge
• No vendor support for the IDL to C++11 language
mapping

CBDDS Standards
CBDDS combines eleven OMG standards into a
comprehensive software suite
• IDL4, IDL2C++11
• CORBA
• DDS, DDS X-Types, DDS Security, RPC4DDS
• LwCCM, DDS4CCM, AMI4CCM
• D&C

CBDDS Principles
Interoperable Open Architecture (IOA)
Component Based Architecture (CBA)
Service Oriented Architecture (SOA)
Event Driven Architecture (EDA)
Model Driven Architecture (MDA)

What is a Component?
Independent revisable unit of software with well
defined interfaces called “ports”
Able to be packaged as an independent deployable
set of files
Smallest decomposable unit that defines standard
ports is a “monolithic component”
A “component assembly” is an aggregation of
monolithic components or other component
assemblies

Why Component Based
Development?
Modularity
Reuse
Interoperability
Extensibility
Scalability
Reduced Complexity
Faster and Cheaper Development
Quality and Reliability
Deployability

Interaction Patterns
CBDDS uses so called interaction patterns to define
the interaction between user components
CBDDS defines request/reply, state, and event
interaction patterns
An interaction pattern is realized at deployment time
using a specific communication middleware, legacy
system, or hardware
Copyright © 20139

Request/Reply Interaction
Pattern
Support for synchronous and asynchronous
invocations
Delivered with a function style API
Defined in IDL using operations with arguments and
an optional return value
The application code that uses this interaction
pattern is unaware of how the interaction pattern is
realized
Copyright © 201310

Event Interaction Pattern
The event interaction pattern defines extended ports
for the following roles
• Basic many-to-many publish subscribe messaging
• Event distribution with optional user defined data
Copyright © 201311

State Interaction Pattern
The state interaction pattern defines extended ports
for the following roles
• Distributed state management and access
• Distributed database functionality with eventual
consistency
Copyright © 201312

Deployment
CBDDS also includes deployment tooling
Supports single process, single node, and distributed
deployments
Applications can be deployed using a deployment
plan
Which DDS QoS is used is a deployment decision,
not hardcoded into the business logic
Various options to define a deployment plan

IDL to C++11
IDL to C++11 is a formal OMG standard that greatly
simplifies the development of IDL based applications
Reuse as much as possible from the C++11 standard
• Standard basic types
• Uses STL containers like std::string, std::vector,
std::array
• Uses C++11 move semantics to provide a safe and
fast API
Standardized IDL::traits<T> to simplify template
programming
Automatic reference counting by using
std::shared_ptr and std::weak_ptr semantics
No new/delete and no plain C++ pointers!

The Technical Side
CBDDS with C++11 is implemented as part of our
AXCIOMA product
Component related glue code is generated by our
Ruby based IDL compiler
• No dependency on remote CORBA support, all local
interfaces
C++11 representation of the user defined types,
including all types that are used for DDS
communication
But, no DDS vendor supports the IDL to C++11
language mapping out of the box

C++11 to C++ Conversion
Framework
Based on the user defined IDL types, an implied IDL
definition is generated by RIDLC
• This implied IDL definition is passed to rtiddsgen
RIDLC generates a set of conversion traits to convert
between the RTI Connext DDS C++ type definition
and the C++11 type definition
• By using C++11 move semantics this is in most
cases just a move of memory, no copy!
C++11 representation of the DDS entities uses the
RTI Connext DDS C++ representation and the
conversion traits
At the moment RTI supports IDL to C++11 the
conversion traits will expand to nothing!

Some Code!
Sender ReceiverDDS
// Sender component class which publishes one sample to DDS
class Sender_i : public IDL::traits<Sender>::base_type
{
public:
// Register an instance to DDS
virtual void configuration_complete () override {
IDL::traits<Shapes::ShapeType_conn::Writer>::ref_type writer =
context_->get_connection_info_write_data();
instance_handle_ = writer->register_instance (square_);
}
// Write one sample to DDS
virtual void ccm_activate () override {
IDL::traits<Shapes::ShapeType_conn::Writer>::ref_type writer =
context_->get_connection_info_write_data();
writer->write_one (square_, instance_handle_);
}
private:
DDS::InstanceHandle_t instance_handle_;
// Use C++11 uniform initialization to initialize the member
ShapeType square {“GREEN”, 10, 10, 1};
};

Receiver Code (1)
// Receiver component which receives the samples from DDS
class Receiver_i : public IDL::traits<Receiver>::base_type
{
public:
virtual void configuration_complete () override {}
// We want sample by sample
virtual void ccm_activate () override {
IDL::traits<CCM_DDS::DataListenerControl>::ref_type lc =
context_->get_connection_info_data_control();
lc->mode (CCM_DDS::ListenerMode::ONE_BY_ONE);
}
private:
IDL::traits<Shapes::CCM_Sender_Context>::ref_type context_;
IDL::traits<Shapes::ShapeType_conn::CCM_Listener>::ref_type
data_listener_;
};

Receiver Code (2)
// Receive the sample from DDS and just dump it to the console
class info_out_i: public
IDL::traits<Shapes::ShapeType_conn::CCM_Listener>::base_type
{
public:
// Sample has been received by DDS
virtual void on_one_data (const ShapeType& shape,
CCM_DDS::ReadInfo&) override {
std::cout << “Received ” << shape << std::endl;
}
private:
IDL::traits<Shapes::CCM_Sender_Context>::ref_type context_;
};

Ruby to DDS

Ruby to DDS
Ruby is a powerful scripting language
Integrated part of the Ruby on Rails framework for
developing web based applications
R2CORBA makes it possible to use and provide
CORBA functionality using Ruby
R2DDS is a prototype developed by Remedy IT to
use DDS from Ruby
Push data from DDS to the web browser using Ruby
on Rails
Currently generates C++ code based on the IDL type
definition, could potentially use Dynamic Data in the
future

Some Ruby DDS Code
// Create all needed DDS entities (without QoS for simplicity)
dfp = DDS.DomainParticipantFactory_init()
dp = dfp.create_participant()
topic = dp.create_topic()
pub = dp.create_publisher()
sub = dp.create_subscriber()
dw = pub.create_datawriter(topic)
dr = sub.create_datareader(topic, listener)
// Create an ORANGE shape and publish it 10 times with increasing
// size and position
shape = ShapeType.new("ORANGE", 10, 10, 10)
$i = 1
while $i <= 10 do
dw.write(shape)
shape.shapesize = $i * 10
shape.x = $i * 10
shape.y = $i * 10
$i=$i+1
sleep(1)
end

Ruby DDS listener Code
// Define a new Listener that prints the received shape to the
// console
class ShapeListener < DDS::DataReaderListener
def initialize()
end
def on_data_available(reader)
shape = ShapeType.new()
reader.read (shape);
puts "Read sample #{shape.color()} #{shape.x()} #{shape.y()}
#{shape.shapesize()}";
end
end
// Create an instance and create a new DDS datareader with this
// listener
listener = ShapeListener.new()
dr = sub.create_datareader(topic, listener)

Questions?

Want to know more?
Let us meet here at the RTI London Connext
Conference 2014!
See our website at http://www.remedy.nl
Check our slideshare presentations at
http://www.slideshare.net/RemedyIT
Email me at jwillemsen@remedy.nl
Call us at +31-10-5220139
Follow us on Twitter @RemedyIT

Contact
26
Remedy IT
Melkrijder 11
3861 SG Nijkerk (Gld)
The Netherlands
tel.: +31(0)88 053 0000
e-mail: sales@remedy.nl
website: www.remedy.nl
Twitter: @RemedyIT
Slideshare: RemedyIT
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Copyright © Remedy IT

Component Based DDS with C++11 and R2DDS

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