9. Extending RTI Perftest to Other Middlewares¶
The RTI Perftest C++ implementation is designed in a way that it can be extended to test other middlewares or communication mechanisms.
An example is the RAW transport support RTI Perftest offers when compiling against RTI Connext DDS Professional. In this case, although using specific functions from the OS/Network abstraction layer from RTI Connext DDS, RTI Perftest is testing pure socket-to-socket communication (in this case, even simpler than a middleware).
9.1. Interface infrastructure¶
The main entry point for the RTI Perftest Classic C++ implementation is the perftest_cpp class, under srcCpp/. There, instead of interacting directly with the data types, the DDS entities, and their methods, the code abstracts everything and uses the following class interfaces (defined in srcCpp/MessagingIF):
This interface contains the different attributes required to interact with the messages. It can be described as a wrapper of the message that the middleware sends/receives. Objects of this class will be passed to the write methods of the publication entities.
This interface abstracts the middleware itself. It contains the methods used to initialize/finish the middleware. For a DDS implementation, these methods are the creation/destruction of Participants, Publishers, and Subscribers. This interface also controls the creation of IMessagingWriter and IMessagingReader entities.
This interface abstracts the entity in the middleware in charge of sending the data. For a DDS implementation, this will be a wrapper for the DataWriter.
This interface abstracts the entity in the middleware in charge of receiving the data. For a DDS implementation, this will be a wrapper for the DataReader.
This interface is in charge of processing the messages received by the IMessagingReader interface. That way, independently of how the data was obtained (by pulling data, by a callback in the middleware, or by any other way), the same actions will be done.
9.2. Common Infrastructure¶
RTI Connext DDS Professional and RTI Connext DDS Micro offer specific OS abstraction layers in order to be able to use semaphores, timers, threads, and other OS-dependent functions, etc., independently of the OS where the middleware is running. When RTI Perftest is being compiled against those middlewares, it will try to use that infrastructure. However, when RTI Perftest is compiled for anything else, a default implementation for those functions is provided, based on the C++11 standard.
The Common infrastructure classes can be found in srcCpp/Infrastructure_common.h and srcCpp/Infrastructure_common.cxx.
When adding support for other middlewares or communication mechanisms, these functions can be used and extended, or, alternatively, a specific implementation can be developed to avoid the restriction of using C++11 compilers (this may make sense if the target OS/platform does not have a modern compiler).
9.3. Message type (idl)¶
RTI Perftest generates its code for RTI Connext DDS Professional and RTI Connext DDS Micro using the rtiddsgen tool, which generates the code from some .idl files.
These .idl files are used to represent the types that RTI Perftest uses to send messages between publisher and subscriber sides. The TestMessage interface mentioned above acts as a wrapper for these types in the .idl.
The files can be found under srcIdl. All of them represent the same structure, but with differences based on attributes that imply the IDL representation to change. For example, in order to test with keyed data and unkeyed data, two different structures are needed (one with a member marked as @key and the other without the @key designation).
These files can be used by other middlewares, if they accept .idl files as input.
9.4. Discovery mechanisms¶
The RTI Perftest implementation for RTI Connext DDS relies on the discovery mechanisms provided by the middleware. However, this is not a hard restriction, and communication patterns without discovery can be used as well.
A good example of this is the RAW transport implementation RTI Perftest provides.
9.5. Command-line options¶
Command line options are parsed in srcCppCommon/Parameter.h/cxx and srcCppCommon/ParameterManager.h/cxx, where the infrastructure allows the use of different masks to determine if a parameter may or may not be parsed and be available for a certain middleware. This is controlled by Middleware::<MiddlewareMask. Therefore, enabling existing parameters for different middleware implementations or creating new ones should just imply adding the right mask to the parameter.
9.6. Build infrastructure¶
RTI Perftest relies on two scripts for building, build.sh and build.bat. These scripts build against RTI Connext DDS for each of the different language implementations.
In every case, RTI Perftest for RTI Connext DDS uses rtiddsgen to generate the right makefiles/solutions, and then uses those files to build natively.
rtiddsgen may not work for other middlewares, so RTI Perftest cannot currently offer an implementation for building other middlewares; that has to be implemented by the developer.
9.7. Selecting and protecting code¶
RTI Perftest for RTI Connext DDS Professional and Micro need to protect certain parts of the code to avoid interferences, or to let the compiler know what files it should include or not. This is done by checking if certain defines are present and provided at compilation time.
Currently, for this protection, RTI Perftest makes use of the PERFTEST_RTI_PRO and PERFTEST_RTI_MICRO definitions.