From d1993a0ecf25a7aab55855574c8d9803fa93fd30 Mon Sep 17 00:00:00 2001 From: Philip Rauwolf Date: Wed, 7 Aug 2013 17:13:23 +0200 Subject: Added tutorial Added a tutorial file in AsciiDoc format. References to existing guides, documentation etc. currently still partially missing. Change-Id: I88e50c9d31b4812659072e3953c7be9c0f489c03 --- Tutorial | 412 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 412 insertions(+) create mode 100644 Tutorial diff --git a/Tutorial b/Tutorial new file mode 100644 index 0000000..9a1e41f --- /dev/null +++ b/Tutorial @@ -0,0 +1,412 @@ +GENIVI_CommonAPI +================ +:Author: Juergen Gehring - juergen.gehring@bmw.de, Manfred Bathelt - manfred.bathelt@bmw.de +:doctitle: GENIVI_CommonAPI_Tutorial + +Copyright +--------- +Copyright (C) 2013, GENIVI Alliance, Inc. +Copyright (C) 2013, BMW AG + +This file is part of GENIVI Project IPC Common API. + +Contributions are licensed to the GENIVI Alliance under one or more +Contribution License Agreements or MPL 2.0 . + +(C) Copyright +This Source Code Form is subject to the terms of the +Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed with +this file, You can obtain one at http://mozilla.org/MPL/2.0/. + +For further information see https://collab.genivi.org/wiki/display/genivi/SysInfraEGCommonIDLCommon APIGuide + +== License +This project is licensed under MPL 2.0 + +Contribution is done under GENIVI CLA or MPL2.0. + +== Version +The current version can be taken from the git. + +== Common API Overview + +Common API and its mechanism specific bindings (e.g. Common API D-Bus) provide a set of libraries and tools to work with +RMI communication in a way independent of wich mechanism is used. The main intention is to ease porting your project to +new communication mechanisms and to enable testing of your application way before setting it up on the precise environment +and the communication mechanism it is meant to use. + +Common API consists of two main parts: +* The Common API runtime, which is the basic library required to enable Common API functionality. +* The Common API generator Eclipse plugin, which allows the generation of Common API proxy and stub code out of Franca IDL files. + +The application will use both the Common API runtime and the generated code to implement client and/or service. + +In order to enable communication via a specific communication mechanism, the corresponding Common API middleware library +and middleware generator plugin is required in addition. However, both the middleware specific library and the middleware +specific generated code will NEVER be seen or used by the application code. It is solely the responsibility of the basic +Common API library to enable communication by using this specific middleware library and code. + + +== Getting started with Common API + +The following subsections are meant as a step by step tutorial on how to set up Common API on your system. Additionally, +the Common API middleware library for D-Bus will be installed and an example application will be created that will +communicate via D-Bus. + +Note that you later can switch D-Bus for any other communication layer (provided it has Common API support) +_without the need to touch your code or your binary at all!_. + +Further information on Common API and Common API D-Bus is provided in the individual README files accompanying both packages. + + +=== Setting up the Environment + +==== Requirements + +First, make sure all requirements to build the CommonAPI runtime are installed and in the correct version. +CommonAPI was developed using gcc 4.6 and gcc 4.7, but is feature compatible to gcc 4.5 and compiler compatible to gcc 4.4. + + +==== Setting up Common API + +Download the Common API runtime via git from the download site of http://projects.genivi.org/commonapi/, then compile and install the library on your computer: +---- +$ git clone git://git.projects.genivi.org/ipc/common-api-runtime.git +$ cd common-api-runtime +$ autoreconf -i +$ ./configure +$ make +$ sudo make install (or alternative install process, eg. checkinstall on debian-based distributions, such as Ubuntu) +---- + +With this, the Common API runtime library will be installed in /usr/local/lib. The package is accessible for your application +e.g. via pkgconfig. The pkgconfig data is located at /usr/local/lib/pkgconfig. + + +==== Setting up Common API D-Bus + +To build Common API D-Bus, the Common API runtime and libdbus version 1.4.16 patched with the marshaling patch must be available through PkgConfig. +The marshalling patch is provided within the Common API D-Bus package. + +Download the Common API D-Bus library via git from the download site of http://projects.genivi.org/commonapi/: +---- +$ git clone git://git.projects.genivi.org/ipc/common-api-dbus-runtime.git +---- + +Download, patch and install version 1.4.16 of libdbus (*WARNING*: _Not_ following these instructions may result in corruption of the preinstalled libdbus +library of your computer, thereby rendering your system unusable): +---- +$ wget http://dbus.freedesktop.org/releases/dbus/dbus-1.4.16.tar.gz +$ tar -xzf dbus-1.4.16.tar.gz +$ cd dbus-1.4.16 +$ patch -p1 < /common-api-dbus-runtime/dbus-DBusMessage-add-support-for-custom-marshaling.patch +$ ./configure --prefix=/usr/local +$ make -C dbus +$ sudo make -C dbus install +$ sudo make install-pkgconfigDATA +---- + +The path to CommonAPI and patched libdbus pkgconfig files must be added to the PKG_CONFIG_PATH for the rest of the entire build process. +If you followed the instructions above, both will be located in _/usr/local/lib/pkgconfig_, so you can just type: +---- +$ export PKG_CONFIG_PATH="/usr/local/lib/pkgconfig:$PKG_CONFIG_PATH" +---- + +Now, compile and install the Common API D-Bus library on your computer +---- +$ cd /common-api-dbus-runtime +$ autoreconf -i +$ ./configure +$ make +$ sudo make install (or alternative install process, eg. checkinstall on debian-based distributions, such as Ubuntu) +---- + +With this, the libraries for Common API and Common API D-Bus are installed and ready for use. The next steps will provide you with the means +to efficiently design and implement your Common API applications via Eclipse. + + +==== Setting up Eclipse + +In order to generate the Common API code that will be used by your client and your service, the Common API generator plugin is +required. This plugin is an Eclipse plugin, and is provided as an Eclipse update site. For convenience, the generator plugins +for Common API and Common API D-Bus are packed together. + +First, get an appropriate Eclipse up and running. The version of the Common API generator plugin contained in this package was tested +with the Eclipse Modeling Tools package of Eclipse Juno (4.1) and Eclipse Kepler (4.2). You can get one of them from www.eclipse.org: +---- +Eclipse Juno: http://www.eclipse.org/downloads/packages/eclipse-modeling-tools/junosr1 +Eclipse Kepler: http://www.eclipse.org/downloads/packages/eclipse-modeling-tools/keplerrc3 +---- + +Because the generator plugin generates code from Franca IDL files (https://code.google.com/a/eclipselabs.org/p/franca/), +you will need to have installed the Franca IDL feature in your Eclipse. The plugin was created for Franca IDL version 0.8.9. +Franca IDL is a language to efficiently design the RMI interface of your applications, independent from specific communication +mechanisms and also independent from specific programming languages. + +Get the appropriate zipped Franca IDL update site (named site_franca_0.8.9.xxx.zip) from +---- +https://code.google.com/a/eclipselabs.org/p/franca/downloads/list +---- +Also, download the Common API D-Bus Tooling via git from the download site of http://projects.genivi.org/commonapi/: +---- +$ git clone git://git.projects.genivi.org/ipc/common-api-dbus-tools.git +---- + +Install the Franca IDL plugin and the CommonAPI generator plugins in your Eclipse: +---- +Help->Install New Software...->Add...->Archive... +---- +From Franca IDL, you will only need to install the sub-category "Franca Feature" for the Common API and Common API D-Bus generators to work. +The update site of the Common API generator plugin is located at +---- +/common-api-dbus-tools/org.genivi.commonapi.dbus.feature/org.genivi.commonapi.dbus.updatesite.zip +---- +To develop your application, you will only need the _GENIVI Common API C++ Core Generator_. However, for this tutorial to work and/or if you +intend to enable your Common API application to communicate via D-Bus, you will also need the _GENIVI Common API C++ D-Bus Generator_. + +Restart Eclipse when you are prompted to do so. Now you should be able to use the CommonAPI generators in your Eclipse. + + +=== Creating the Example + +The example that will be created in this tutorial from now onwards is provided as ready-to-use source package in +---- +/common-api-dbus-tools/CommonAPI-Examples +---- +The example found here is more verbose than the one we will create, but functionally it will be the same. + +It is assumed that you have created a C++ project in your Eclipse in which all further development will happen. + + +==== Creating the RMI interface definition + +The first step in developing a Common API application likely will be the definition of the RMI interface the client will use to communicate with +the server. In the context of CommonAPI, the definition of this interface always happens via the Franca IDL, regardless of which communication +mechanism you intend to use in the end. For this tutorial, create an arbitrarily namend file ending in _.fidl_ in your Eclipse project. It is +not relevant where in your project you have placed this file, as the the code generated from this file will always be put in the automatically +created src-gen folder at the top level of the project hierarchy. + +Open your newly created _.fidl_-file, and type the following lines: +---- +package commonapi.examples + +interface HelloWorldInterface { + version { major 1 minor 0 } + + method sayHello { + in { + String name + } + out { + String message + } + } +} +---- +Note that the _version_ parameter in every interface is mandatory! No code will be generated if it is malformed or not present! + +Now, save the _.fidl_ file and right click it. As you have installed the Common API and Common API D-Bus generators, you will see +a menu item saying _"Common API"_, with sub menu items for generating either the Common API level code only ("_Generate C++ Code_") +or for generating both the Common API level code and the glue code required to run applications with using Common API D-Bus +("_Generate D-Bus C++ Code_"). + + +==== Generating code + +We do want to use D-Bus as middleware, so we will need the D-Bus specific glue code as well as the Common API level code which we will +program agains. Therefore, you might want to chose the latter of the two options provided by the generator plugin ("_Generate D-Bus C++ Code_"). +After having done so, you will see the newly created src-gen folder and it's contents. The files will be created according to their +fully qualified names relative to src-gen as the top level folder, as defined in the _.fidl_-file: +---- +HelloWorldInterface.h +HelloWorldInterfaceProxy.h +HelloWorldInterfaceProxyBase.h +HelloWorldInterfaceStub.h +HelloWorldInterfaceStubDefault.cpp +HelloWorldInterfaceStubDefault.h + +HelloWorldInterfaceDBusProxy.cpp +HelloWorldInterfaceDBusProxy.h +HelloWorldInterfaceDBusStubAdapter.cpp +HelloWorldInterfaceDBusStubAdapter.h +---- + +All files that have a "DBus" in their name are glue code required by the D-Bus binding and are not relevant while developing your application, +they only need to be compiled with your application (there are ways to NOT compile these sources with your applications and include them at +runtime instead; see the README of Common API D-Bus for details). + +All other files that have a _Proxy_ in their name are relevant for you if you develop a client, all other files that have a _Stub_ in their name +are relevant for you if you develop a service. + +A proxy is a class that provides method calls that will result in remote method invocations on the service, plus registration methods for events +that can be broadcasted by the service. + +A stub is the part of the service that will be called when a remote method invocation from a client arrives. It also contains methods to fire +events (broadcasts) to several or all clients. The Stub comes in two flavors: One default stub that contains empty implementations of all methods, +thereby allowing you to implement only the ones you are interested in, and a Stub skeleton where you have to implement everything yourself before +you can use it. A service will have to implement a subclass of either of the two in order to make itself available to the outside world +(or just use the default stub if your service should not be able to do anything except firing events). + +In this tutorial, we will create both a client and a service in order to be able to see some communication going on. + + +==== Implement the Client + +Start by creating a new .cpp source file in your project (e.g. helloworld-proxy.cpp). Make sure you have a main method in order to start the client application. + +Here, you will need two includes in order to access the Common API client functionality: +---- +#include //Defined in the Common API Runtime library +#include //Part of the code we just generated + +#include +#include +---- + +The first thing each and every Common API application will do is to load a runtime: +---- +std::shared_ptr runtime = CommonAPI::Runtime::load(); +---- +If you link the Common API DBus library to and compile the generated DBus specific code with your executable, this runtime "magically" will be a +runtime that provides access to the DBus communication infrastructure via a strictly CommonAPI level interface. If you link the library and add +the generated code of another Common API middleware binding instead, this runtime will provide access to this other communication infrastructure. +To not interrupt this tutorial, further explanation on this mechanism is done below in a separate chapter in "Further Reading". + +In order to be able to communicate with a specific service, we need a proxy. We can create a proxy by using a factory, which in turn we can get from +the runtime we just created: +---- +std::shared_ptr factory = runtime->createFactory(); +const std::string& commonApiAddress = "local:commonapi.examples.HelloWorld:commonapi.examples.HelloWorld"; +std::shared_ptr> helloWorldProxy = factory->buildProxy(commonApiAddress); +---- +The parameter _commonApiAddress_ is the address at which the service that shall be accessed will be available. This address will be translated +internally to an actual DBus-Address - or whatever format fits the communication infrastructure you use. Semantically, this address consists of three parts, +separated by colons: +* Domain: The first part, defines in which domain the service is located. For DBus use cases, only "local" makes any sense, as no services that are more remote than + "on the same operating system" are accessible. +* ServiceID: The second part. This defines the name or type of the service that shall be accessed. +* InstanceID: The third part. This defines the specific instance of this service that shall be accessed. + +There are ways to influence the translation of the Common API address to the specific address (of course once again without the need to change your code). +Please have a look at the README of Common API DBus if you want to know more about this possibility in the context of DBus, or the corresponding documentation +of the other middleware binding you are using. + +With this, the client is set up and ready to use. We should wait for the service to be available, then we can start issuing calls: +---- +while (!helloWorldProxy->isAvailable()) { + usleep(10); +} + +const std::string name = "World"; +CommonAPI::CallStatus callStatus; +std::string helloWorldReturnMessage; + +helloWorldProxy->sayHello(name, callStatus, helloWorldReturnMessage); +if (callStatus != CommonAPI::CallStatus::SUCCESS) { + std::cerr << "Remote call failed!\n"; + return -1; +} + +std::cout << "Got message: '" << helloWorldReturnMessage << "'\n"; +---- + + +==== Implement the Service + +Works about the same way as implementing the client. The includes that are required are the following: +---- +#include +#include + +#include +#include +#include +---- + +And we also need a stub that actually does something when the method we call in the client gets called: +---- +class MyHelloWorldStub: public commonapi::examples::HelloWorldInterfaceStubDefault { + public: + virtual void sayHello(std::string name, std::string& message) { + std::stringstream messageStream; + + messageStream << "Hello " << name << "!"; + message = messageStream.str(); + + std::cout << "sayHello('" << name << "'): '" << message << "'\n"; + } +}; +---- + +The rest looks quite similar to the client side, with the difference that we do not issue calls via a proxy, but instead register a service that then +will be provided to the outside world. The service is registered using the same Common API address, which allows the proxy to actually find the service. +Afterwards, we just wait for calls: +---- +std::shared_ptr runtime = CommonAPI::Runtime::load(); +std::shared_ptr factory = runtime->createFactory(); +std::shared_ptr servicePublisher = runtime->getServicePublisher(); + +const std::string& commonApiAddress = "local:commonapi.examples.HelloWorld:commonapi.examples.HelloWorld"; +std::shared_ptr helloWorldStub = std::make_shared(); +servicePublisher->registerService(helloWorldStub, commonApiAddress, factory); + +while(true) { + std::cout << "Waiting for calls... (Abort with CTRL+C)\n"; + std::this_thread::sleep_for(std::chrono::seconds(60)); +} +---- + + +=== Running the Demo + +Build the two applications using your favourite build system. If all worked well, you should see communication ongoing via DBus (e.g. via dbus-monitor), +and you should get output from your client once, saying +---- +"Got Message: 'Hello World'". +---- + + +== Further reading + +Aside from the README files of Common API and the specific bindings. + + +=== The middleware loading mechanism of Common API + + +==== CommonAPI::Runtime::load() returns no runtime object, why? + +As it was mentioned before, when you call _CommonAPI::Runtime::load()_. +you "magically" will have access to a specific middleware library. In a very basic case, the library and thereby communication mechanism you will have access to +will be the only Common API middleware library you linked to your executable during compilation. + +However, this call to _load()_ most likely will *FAIL* if you have no generated middleware specific code that is compiled with your application. Why that? +The reason is simple, once understood: Most linkers are lazy. They do not link libraries that seem to be unused. Due to the fact that there is no reference +whatsoever from Common API (and therefore your application) to any of the middleware libraries, the linker considers any and all middleware libraries +as unused if not referenced by middleware specific generated code, and therefore will not add them to the executable. + +You can disable this behavior by passing the linker flag _whole-archive_ during the build process. Note however that this behavior _normally_ is a good optimization +without repercussions - except probably in the context of CommonAPI. + + +==== Using more than one middleware binding + +CommonAPI provides the possibility to use more than one middleware binding at once. In this case, you should no longer use _CommonAPI::Runtime::load()_, +but instead _CommonAPI::Runtime::load("NameOfSomeMiddleware")_. + +The "NameOfSomeMiddleware" is the well known name of the middleware you want to load. It is defined and made public by each of the middlewares that support +Common API. For DBus, this name is simply "DBus". + + +==== Fully dynamic loading and additional information + +This topic is handled in-depth in the README of Common API. Please refer to this file for any further information. + + +=== Online Documentation and Guides + +For an in-depth introduction to Franca IDL, please refer to the current user manual found on +---- +https://code.google.com/a/eclipselabs.org/p/franca/downloads/list +---- +At the time of writing of this tutorial, _FrancaUserGuide-0.3.0.pdf_ is the most recent version. -- cgit v1.2.1