## Simple CIAO tutorial

Note:

- CoSMIC tools are not used in this tutorial.
- This is only a GENERAL way of building up a CIAO application and deploying it with DAnCE. The user could always change the process in his own way. For example: the IDL file content, the project structure etc.
- To download the code of this example please refer to the CVS repository at `$CIAO_ROOT/DAnCE/examples/Hello`.

## Example Description

This Hello example is contructed in the following ways:

- 1. There are 2 components in the system: Sender and Receiver
- 2. The Sender will send out the timeout event to the Receiver.
- 3. Upon receiving the timeout event, the Receiver will go and fetch data from the Sender.
- 4. The user could deploy multiple instances of the Receiver without changing any C++/idl source code.

## Step-By-Step

### Hello_Base

1. Write an IDL file (`Hello_Base.idl`) which contains all the interfaces and events common to all the components. The reason we do this is becuse the generated lib of this idl file will be linked in by all the components in the system. To reduce the size of the component lib we have to include only the necesary part. In this example, we have an eventtype `timeout` and an interface `ReadMessage`, which are used by both the Sender and the Receiver, so we put both of them in Hello.idl.

2. Look at the `Hello_Base.mpc` file to get an idea how the Hello_Base_stub and Hello_Base_svnt projects are organized. MPC is a utility we used to generate makefiles or VC project/solution files for all ACE, TAO and CIAO libraries.

### For Every Components

1. Use:
   `$CIAO_ROOT/bin/generate_component_mpc.pl -p Hello_Base Sender
   $CIAO_ROOT/bin/generate_component_mpc.pl -p Hello_Base Receiver`
   Note:
   - I have different directories for `"Hello_Base", "Sender", "Receiver"` respectively.
   - For every `_stub` project, add:
     `"libs += Hello_Base_DnC_stub"`

2. Use the export script to generate the export files. (3 files per component).

3. Write an idl file for every compoent. Here you can put the component specific IDL definitions in this file. In this example we have a interface `trigger` specific to the Sender. Please note that the Sender component `"supports"` (IDL keyword) this interface.

4. Write the CIDL file for every component.

5. Write `_exec.h` and `_exec.cpp` files which actually implement the component.

Writing all those files could be troublesome to a new CCM user. The best way of learning this is to read the example source code. If you are familliar with CORBA programming, it should not take too much time before you can declare yourself as a CCM programmer.

### The Entry Point

After both components are implemented we still need a small program to initialize the process. In Sender.idl there is a Sender specific interface with a single method in it created for this purpose. Hence there is a CORBA client application called `starter`. The `starter` will make a invocation on a supported interface called `trigger` on the Sender component to get the whole distributed application started. The `starter` will first obtain the Sender component object reference through the ior string supplied as a command argument. Please see the the last part of `Hello/Sender/Sender.mpc` file for details.

### Make

- Go to the directory `$CIAO_ROOT/DAnCE` and do:
  `$ACE_ROOT/bin/mwc.pl` (use -type option if you are using a compiler/IDE other than gnuace -which by default generates GNU makefiles)
For example, using `$ACE_ROOT/bin/mwc.pl -type vc71` if you are using Visual C++ 7.1 IDE.

- Look at the generated Makefile(*unx) , Solution/workspace files(Windows) and you got it.

### Assemble

Now we can step forward to build the assembly. Here we are going to build the simplest case only, which is 1 Receiver and 1 Sender. If you are interested in CIAO you could try 1 Sender with multiple Receiver. However, you need to change the Sender.idl to make it publishes timeout event instead of emits event.

- You need to create an XML descriptor file to describe your deployment plan, which is defined in a Deployment Plan Descriptor (.cdp). In this file, you need to declaratively specify how the component assembly is constructed. Specificly, you need to specify the component types, component instances, component connections, implementation artifact descriptions, and whether you want to register component instances with naming service.

- Please make sure that the Modified_Deployment.xsd and XMI.xsd files are in the Hello/descriptors directory. The former file could be found in $CIAO_ROOT/docs/schema directory.

- Create the NodeManagerMap.dat file containing the CORBALOC IIOP address of each `NodeManager` where it is running. Please refer to the existing `NodeManagerMap.dat` for details, as you can see, we only specify 2 `NodeManagers`, which means these two components will be installed in the different `NodeApplication` server. Please refer to the flattened_deploymentplan.cdp file to see how a deployer could specify the mapping between components and nodes.
Note: Creating the deployment plan descriptor is a tedious and error-prone job, you can download CoSMIC to assist you in this step.

### Deploy with DAnCE

Finally you are ready to deploy the component-based application you have developed.

- If you wish to register one or more of your component instances with CORBA naming service, then please start your naming service first with multicast mode first ("-m 1" option).

- Go into the descriptors directory Start NodeManagers (NodeDameon) by running `run_NodeDaemons.pl`

- Start the execution manager: `$CIAO_ROOT/DAnCE/ExecutionManager/Execution_Manager -o EM.ior -i NodeManagerMap.dat`

- NOTE: As one can see, we use the "NodeManagerMap.dat" file to instruct the Execution_Manager how to find the endpoint of each individual NodeManager (i.e., Node Daemon) where component(s) will be deployed, so this is non-standard. We plan to use Naming Service to do this in the future.

- Start the plan launcher: `$CIAO_ROOT/DAnCE/Plan_Launcher/plan_launcher -p flattened_deploymentplan.cdp -k file://EM.ior`
  - If you don't want to register component(s) with CORBA naming service, then you don't have to start your naming service, and you can use the below code to start the executor: `$CIAO_ROOT/DAnCE/Plan_Launcher/plan_launcher -p flattened_deploymentplan_without_ns.cdp -k file://EM.ior`

    After this, components should be deployed successfully.

- You can go into the $CIAO_ROOT/DAnCE/examples/Hello/descriptor directory and run the `$CIAO_ROOT/DAnCE/examples/Hello/Sender/starter` to start the application. Please make sure that the component IOR file for the Sender component (`Sender.ior`) is present when you run this client.

### More Features

Recently DAnCE is enabled with a feature called Redeployment and Reconfiguration (ReDaC). For more information about how to use this feature, please refer to the ReDaC-Usage-Example.html under $CIAO_ROOT/examples/Hello/.

Email: ciao-users@cse.wustl.edu