By Ricardo Ferreira-Oracle on Oct 11, 2011
This article will show how COBOL developers can create, with minimum effort, robust distributed and service-oriented applications using the facilities offered by Oracle Tuxedo. Through a step by step example, you will learn how to configure and setup an Oracle Tuxedo development environment, how to implement COBOL code that enable client and server interactions and how to deploy and test the application into Oracle Tuxedo. For this article, is expected that you have a basic knowledge of the Linux operating system and basic knowledge about programming, if you are not a COBOL developer of course.
What is exactly the Oracle Tuxedo?
Simply put, Oracle Tuxedo is an application server for non-Java developers. This means that developers of programming languages like C/C++, COBOL, Python and Ruby can implement distributed applications using enterprise features like messaging, clustering, security, load-balancing, scalability and thread management from an middleware implementation. The main difference is that the platform itself are not based on Java, and the programming language used to develop the applications are not restricted to Java.
Historically speaking, the concept of an application server had been used in distributed architectures to promote loosely coupling between client and server applications (reason because it's commonly named as middleware) and the reuse of common features that, in the old days, developers had to write every time they need to create a distributed application, features like messaging, clustering, security, load-balancing scalability and thread management, most of them, features that represent critical non-functional requirements. Instead of create every time those features, you can just delegate to a middleware that host those features and reuse across different applications, since they will offer the same behavior for every application. Another key thing about application servers is the fact that they introduce a programing model that forces developers to focus only in business logic instead of basic infrastructure.
With this programming model in mind, you can write distributed applications without worrying about that they are distributed, meaning that you don't have to worry about how client applications invokes services from server applications, how the message are serialized and unserialized between remote computers and how cross-cutting concerns (aspects) are applied at every interaction. Oracle Tuxedo has been very popular in the market as an application server, and it has more than 25 years of maturity and evolution.
In fact, the firsts line of code of Tuxedo was written in 1983 at the AT&T laboratories. Years later, Novell acquired the Unix System Laboratories, the AT&T division responsible for the Tuxedo development. In a exclusive formal agreement, BEA Systems started the development of Tuxedo in non-Netware platforms and became the principal maintainer and distributor of Tuxedo technology. Since the acquisition by Oracle in 2008, Tuxedo was renamed to Oracle Tuxedo and now are part of the Oracle Fusion Middleware stack, being massively optimized year after year.
COBOL? Why not C/C++ or Java?
You probably are wondering why this article will be focused in the COBOL programming language instead of more popular and equally powerful programming languages like C/C++ or Java. COBOL is a structured programming language largely used worldwide at many organizations, due to it's popularity in the 80's and the 90's and the highly mainframe adoption. In fact, most banking organizations today runs their critical transactions at mainframes and those transactions are written in COBOL. Even in the x86 architectures we found many applications written at this programming language, so it is a little bit fair with COBOL developers dedicate this article for them.
In the C/C++ world, the concept and usage of application servers are pretty common. In the Java world is almost a rule of development, so it's natural for Java developers (actually, Java EE developers) use application servers. Unfortunately, this scenario does not apply for COBOL developers. Having said that, Oracle Tuxedo was designed from the source to handle C/C++ implementations, and if you are a C/C++ developer, you will not find any difficulties to work with Oracle Tuxedo. It is unnecessary to say that, if you are a Java developer, there are a bunch of application server implementations available in the market today, like Oracle WebLogic and Oracle GlassFish. There is no need to use Oracle Tuxedo as application server.
Setting Up an Oracle Tuxedo Development Environment for COBOL
Let's start the development of a simple distributed application using Oracle Tuxedo and the COBOL programming language. For this article, I have used a Linux operating system (Fedora 14) as platform. If you intend to use another operating system, check if both Oracle Tuxedo and the COBOL compiler supports it. The first thing to configure is a proper COBOL compiler. Oracle Tuxedo does not distribute any compiler, neither for C/C++. You need to use a certified compiler in order to develop using Oracle Tuxedo. Fortunately, there are many COBOL compilers available today. Oracle certifies two compilers in particular: Micro Focus COBOL compiler and COBOL-IT compiler suite. The main difference between this two implementations are the fact that Micro Focus COBOL compiler are proprietary, and demands that you pay licenses to use it. COBOL-IT on the other hand are free and open source. The company basically gives you support and consultancy through subscriptions. For this article, we will use COBOL-IT in the development of the example.
You will need a C/C++ compiler too. During the compilation of COBOL source code files, Oracle Tuxedo translate COBOL code to native C/C++ code, and after that, it compiles it to the target platform as a native executable. This means that implicitly, a C/C++ program compilation occurs, even being you used COBOL as programming language. There no restrictions about which C/C++ compiler to use. If you are a Linux user, the ANSI GNU compiler will be available already in the platform. Depending of your Linux distribution, some other packages must be installed too.
Download the COBOL-IT compiler suite clicking here. The COBOL-IT compiler suite installation is pretty simple. Just download the zipped files and unzip into a folder of your preference. In my environment, I have unzipped in the /home/riferrei/cobol-it-std-64 folder. After unzip the files, you need to define two environment variables:
After defining these two environment variables, you are ready to use your COBOL-IT compiler suite. Let's create a simple "Hello World" COBOL application to certify that the COBOL-IT compiler are really working. Create a file in your environment named hello.cbl, and in this file write the following COBOL code:
To compile this source code and to generate a native executable program, you need to use the COBOL-IT compiler, using the following command:
cobc -x hello.cbl
As you can see, the COBOL-IT compiler used in the command cobc available in the /bin installation directory of COBOL-IT compiler suite. After type this command, you should see a native executable program generated in the same directory of the file hello.cbl. Executing this program should generate, unsurprisingly, a console output with the following message: "Hello World using COBOL".
Now that your COBOL-IT compiler suite are up and running, it is time to move forward and start the configuration of Oracle Tuxedo. For this article, I have used the 11g R1 version of Oracle Tuxedo, which in the time of the development of this article was the latest version available. Oracle Tuxedo is freely available for learning and evaluation. You can download the installation software here. Install the software following the recommendations documented in the Oracle Tuxedo installation guide. I will not repeat those instructions here since you can easily follow from the official documentation.
The configuration of Oracle Tuxedo is very straightforward. In the essence, you have to define a series of environment variables that change the behavior about how Oracle Tuxedo will compile, execute and manage the COBOL applications. It is important no remember that the instructions available here applies exclusively for COBOL development with Oracle Tuxedo. If you want to use Oracle Tuxedo with C/C++ programming language, there are another instructions available. I summarized the list of environment variables that, for the development of this article, you need to define.
It is a good idea to put those environment variables in the system scope. If you are a Linux operating system user, could be e good idea define those environment variables in the .bash_profile configuration file of your home directory.
Creating a COBOL-based Application using Oracle Tuxedo
When you develop applications using Oracle Tuxedo, you actually create a distributed application. This means that you should create at least two applications: The client-tier, which will be the "presentation layer" for the end-user, and the server-tier, which provides one or more services interfaces to be consumed from the client-tier. If you look closely, It is basically the same architecture that Java EE provides. The programming model used in Oracle Tuxedo can be ATMI and CORBA. For this article, I will use ATMI since is the only programming model available for COBOL programming language. But for most advanced applications, specially those ones based on C/C++ programming language, I encourage you to use CORBA instead of ATMI. This approach frees your code from Oracle Tuxedo specific API's, turning your business logic actually portable between other CORBA implementations like Progress Orbix, Micro Focus Visibroker, etc.
We will create a simple example of distributed application where the server-tier expose a service that takes a string as parameter and converts to the upper case mode. The client-tier will actually take an string from the command-line and send it as parameter to the server-tier for processing. The first thing to do is to create a folder that will be our application directory. Create a folder named MY_TUX_APP. After this, you need to define two environment variables:
These two environment variables are used in the deployment phase of the Oracle Tuxedo development, which means that they are applied to every application that are deployed. The other environment variables are defined only once and reused across different deployments. Enter in the $APPDIR directory. Let's start the development of the application by the server-tier layer. Create a file named serverApp.cbl and write the following COBOL code:
This COBOL application receives a string parameters and converts to the upper case mode. You can see in the code that every interaction or "phase" are sent to a logger mechanism called user-log. This a interesting approach supported by Oracle Tuxedo that enable developers to debug "what is happening" in runtime. Functions like TPSVCSTART and USERLOG are included in the source code dynamically, are are part of the Oracle Tuxedo ATMI API. To compile this application and generate a native executable program, type the following command:
buildserver -C -o serverApp -f serverApp.cbl -s serverApp
An native executable program named serverApp will be generated in the current directory. Let's understand which each parameter of the buildserver command does. The "-C" parameter tells to Oracle Tuxedo that a COBOL compilation will be done. Without this parameter, Oracle Tuxedo assumes that a C/C++ compilation will occur. The "-o" parameter tells what will be the name of the native executable program. The "-f" parameter tells which source code must be compiled. Finally, the "-s" parameter tells what service will be published when this server get up and running.
Let's create the client-tier application. Being in the same folder ($APPDIR), create a file named clientApp.cbl, and inside this file, write the following COBOL code:
Let's compile this client-tier application. To do this, just type the following command:
buildclient -C -o clientApp -f clientApp.cbl
As you can see, the parameters used in the compilation are the same that we used in the compilation of the server-tier, with the exception of the parameter "-s" in which of the client-tier are unnecessary. At this point, you should have two executable applications in the directory, one name clientApp and another named serverApp. To start the deployment phase of this application, it is necessary to create the configuration file for it. This configuration file are called UBBCONFIG file. The UBBCONFIG file acts as the external configuration descriptor that defines the application. If you are familiar with Java EE development, think in this configuration file as a deployment descriptor. In the directory of the application, create a file named ubbConfig and edit this file as showed in the listing below:
There are one section of this configuration file that you must change to get the example working, the "MACHINES-DEFAULT" section. Change the variables "APPDIR", "TUXCONFIG" and "TUXDIR" to reflect your file system format and directories location. You also need to change the hostname of the server. As you can see in the UBBCONFIG file, there is a mapping between the machine "riferrei_linux_64" to the element "LMID=simple". Change the hostname to reflect the hostname of your machine. I have found some problems when I used hostnames with special characters like "-" or ".". If some problems occurs in the UBBCONFIG loading, maybe this could be the cause.
Deploying and Testing the Application in Oracle Tuxedo
It is time to deploy and test the application. Every application in Oracle Tuxedo must have a binary version of their UBBCONFIG file. To generate this binary version, Oracle Tuxedo gives you a very simple utility program named tmloadcf. Being in the application directory of the application, type the following command:
A binary version of the UBBCONFIG file named tuxconfig will be generated in the current directory. Now we are all set. Let's start the deployment of the application and begin the tests. To deploy the application and start the server service, type the following command:
You should see in the console that a few messages will appear. Which these messages basically says is about the correct execution of the admin and server services, which means that they will be ready to accept client requests and ready to process the incoming messages. Type the following command:
./clientApp "Oracle Tuxedo"
With this command, we actually execute the client-tier application and we pass a string from the command line parameters. After type the command above, you should see in the console the following output:
This means that our server-tier application received the message and passed to the serverApp service. The service on the other hand transformed the string passed as parameter to the upper case format and sent back to the caller application. In the "middle" of these two applications, Oracle Tuxedo did take care of the messaging and transaction execution. To shutdown the services and the server application, type the following command:
I have recorded a video that capture the entire application development since the compilation process. If you feel that some step was not done correctly, run the video below to follow step by step the sequence of commands needed to compile, deploy and test the application created at this article.
This article gave you an overview about Oracle Tuxedo e how it can be used to create distributed applications using the COBOL programming language. It showed how to set up a development environment that enable COBOL developers to build a simple but complete application in Oracle Tuxedo. I hope that this article could help you and your team to explore the features that only Oracle Tuxedo offers.