TP Framework

This topic includes the following sections:

The TP Framework is required when developing BEA Tuxedo CORBA servers. Later releases will relax this requirement, though it is expected that most customers will use the TP Framework as an integral part of their applications.

BEA Tuxedo provides the infrastructure for providing load balancing, transactional capabilities, and administrative infrastructure. The base API used by the TP Framework is the CORBA API with BEA extensions. The TP Framework API is exposed to customers. The BEA Tuxedo ATMI is an optional API that can be mixed in with TP Framework APIs, allowing a customer to deploy distributed applications using a mix of CORBA servers and ATMI servers.

Before BEA Tuxedo CORBA, ORB products did not approach BEA Tuxedo's performance in large-scale environments. BEA Tuxedo systems support applications that can process hundreds of transactions per second. These applications are built using the BEA Tuxedo stateless-service programming model that minimizes the amount of system resources used for each request, and thus maximizes throughput and price performance.

Now, BEA Tuxedo CORBA and its TP Framework give customers a way to develop CORBA applications with performance similar to BEA Tuxedo ATMI applications. BEA Tuxedo CORBA servers provide throughput, response time, and price performance approaching the BEA Tuxedo stateless-service programming model, while using the CORBA programming model.

A Simple Programming Model

The TP Framework provides a simple, useful subset of the wide range of possible CORBA object implementation choices. You use it for the development of server-side object implementations only. When using any client-side CORBA ORB, clients interact with CORBA objects whose server-side implementations are managed by the TP Framework. Clients are unaware of the existence of the TP Framework—a client written to access a CORBA object executing in a non-BEA Tuxedo server environment will be able to access that same CORBA object executing in a BEA Tuxedo server environment without any changes or restrictions to the client interface.

The TP Framework provides a server environment and an API that is easier to use and understand than the CORBA Portable Object Adapter (POA) API, and is specifically geared towards enterprise applications. It is a simple server programming model and an orthodox implementation of the CORBA model, which will be familiar to programmers using ORBs such as ORBIX or VisiBroker.

The TP Framework simplifies the programming of BEA Tuxedo CORBA servers by reducing the complexity of the server environment in the following ways:

The TP Framework provides the following functionality:

Control Flow

The TP Framework, in conjunction with the ORB and the POA, controls the flow of the application program by doing the following:

Object State Management

The TP Framework API provides callback methods for application code to implement flexible state management schemes for CORBA objects. State management involves the saving and restoring of object state on object deactivation and activation. It also concerns the duration of activation of objects, which influences the performance of servers and their resource usage. The default duration of object activation is controlled by policies assigned to implementations at IDL compile time.

Transaction Integration

TP Framework transaction integration provides the following features:

Object Housekeeping

When a server is shut down, the TP Framework rolls back any transactions that the server is involved in and deactivates any CORBA objects that are currently active.

High-level Services

The TP interface in the TP Framework API provides methods for performing object registrations and utility functions. The following services are provided:

The purpose of these high-level service methods is to eliminate the need for developers to understand the CORBA POA, CORBA Naming Service, and BEA Tuxedo APIs, which they use for their underlying implementations. By encapsulating the underlying API calls with a high-level set of methods, programmers can focus their efforts on providing business logic rather than understanding and using the more complex underlying facilities.

State Management

State management involves the saving and restoring of object state on object deactivation and activation. It also concerns the duration of activation of objects, which influences the performance of servers and their resource usage. The external API of the TP Framework provides activate_object and deactivate_object methods, which are a possible location for state management code.

Activation Policy

State management is provided in the TP Framework by the activation policy. This policy controls the activation and deactivation of servants for a particular IDL interface (as opposed to the creation and destruction of the servants). This policy is applicable only to CORBA objects using the TP Framework.

The activation policy determines the default in-memory activation duration for a CORBA object. A CORBA object is active in a POA if the POA's active object map contains an entry that associates an object ID with an existing servant. Object deactivation removes the association of an object ID with its active servant. You can choose from one of three activation policies: method (the default), transaction, or process.

The activation policies are described below:

Application-controlled Activation and Deactivation

Ordinarily, activation and deactivation decisions are made by the TP Framework, as discussed earlier in this chapter. The techniques in this section show how to use alternate mechanisms. The application can control the timing of activation and deactivation explicitly for objects with particular policies.

Explicit Activation

Application code can bypass the on-demand activation feature of the TP Framework for objects that use the process activation policy. The application can "preactivate" an object (that is, activate it before any invocation) using the TP::create_active_object_reference call.

Preactivation works as follows. Before the application creates an object reference, the application instantiates a servant and initializes that servant's state. The application uses TP::create_active_object_reference to put the object into the Active Object Map (that is, associate the servant with an ObjectId). Then, when the first invocation is made, the TP Framework immediately directs the request to the process that created the object reference and then to the existing servant, bypassing the necessity to call Server::create_servant and then the servant's activate_object method (just as if this were the second or later invocation on the object). Note that the object reference for such an object will not be directed to another server and the object will never go through on-demand activation as long as the object remains activated.

Since the preactivated object has the process activation policy, it will remain active until one of two events occurs: (1) the ending of the process or (2) a TP::deactivateEnable call.

Usage Notes

Preactivation is especially useful if the application needs to establish the servant with an initial state in the same process, perhaps using shared memory to initialize state. Waiting to initialize state until a later time and in a potentially different process may be very difficult if that state includes pointers, object references, or complex data structures. TP::create_active_object_reference guarantees that the preactivated object is in the same process as the code that is doing the preactivation. While this is convenient, preactivation should be used sparingly, as should all process objects, because it preallocates precious resources. However, when needed and used properly, preallocation is more efficient than alternatives.

Examples of such usage might be an object using the "iterator" pattern. For example, there might a potentially long list of items that could be returned (in an unbound IDL sequence) from a "database_query" method (for example, the contents of the telephone book). Returning all such items in the sequence is impractical because the message size and the memory requirements would be too large.

On an initial call to get the list, an object using the iterator pattern returns only a limited number of items in the sequence and also returns a reference to an "iterator" object that can be invoked to receive further elements. This iterator object is initialized by the initial object; that is, the initial object creates a servant and sets its state to keep track of where in the long list of items the iteration currently stands (the pointer to the database, the query parameters, the cursor, and so forth).

The initial object preactivates this iterator object by using TP::create_active_object_reference. It also creates an object reference to that object to return to the client. The client then invokes repeatedly on the iterator object to receive, say, the next 100 items in the list each time. The advantage of preactivation in this situation is that the state might be complex. It is often easiest to set such state initially, from a method that has all the information in its context (call frame), when the initial object still has control.

When the client is finished with the iterator object, it invokes a final method on the initial object which deacativates the iterator object. The initial object deactivates the iterator object by invoking a method on the iterator object that calls the TP::deactivateEnable method, that is, the iterator object calls TP::deactivateEnable on itself.

Caution to Users

For objects to be preactivated in this fashion, the state usually cannot be recovered if a crash occurs. (This is because the state was considered too complex or inconvenient to set upon initial, delayed activation.) This is a valid object technique, essentially stating that the object is valid only for a single activation period.

However, a problem may arise because of the "one-time" usage. Since a client still holds an object reference that leads to the process containing that state, and since the state cannot be recreated after the crash, care must be taken that the client's next invocation does not automatically provoke a new activation of the object, because that object would have inapplicable state.

The solution is to refuse to allow the object to be activated automatically by the TP Framework. If the user provides the TobjS::ActivateObjectFailed exception to the TP Framework as a result of the activate_object call, the TP Framework will not complete the activation and will return an exception to the client, CORBA::OBJECT_NOT_EXIST. The client has presumably been warned about this possibility, since it knows about the iterator (or similar) pattern. The client must be prepared to restart the iteration.

Note: This defensive measure may not be necessary in the future; the TP Framework itself may detect that the object reference is no longer valid. In particular, you should not depend on the possibility that the activate_object method might be called. If the TP Framework does in fact change, activate_object will not be called and the framework itself will generate the OBJECT_NOT_EXIST exception.

Self Deactivation

Just as it is possible to preactivate an object with the process activation policy, it is possible to request the deactivation of an object with the process activation policy. The ability to preactivate and the ability to request deactivation are independent; regardless of how an object was activated, it can be deactivated explicitly.

A method in the application can request (via TP::deactivateEnable) that the object be deactivated. When TP::deactivateEnable is called and the object is subsequently deactivated, no guarantee is made that subsequent invocations on the CORBA object will result in reactivation in the same process as a previous activation. The association between the ObjectId and the servant exists from the activation of the CORBA object until one of the following events occurs: (1) the shutdown of the server process or (2) the application calls TP::deactivateEnable. After the association is broken, when the object is invoked again, it can be reactivated anywhere that is allowed by the BEA Tuxedo configuration parameters.

There are two forms of TP::deactivateEnable. In the first form (with no parameters), the object currently executing will be deactivated after completion of the method in which the call is made. The object itself makes the decision that it should be deactivated. This is often done during a method call that acts as a "signoff" signal.

The second form of TP::deactivateEnable allows a server to request deactivation of any active object, whether it is the object that is executing or not; that is, any part of the server can ask that the object be deactivated. This form takes parameters identifying the object to be deactivated. Explicit deactivation is not allowed for objects with an activation policy of transaction, because such objects cannot be safely deactivated until the end of a transaction.

In the TP::deactivateEnable call, the TP Framework calls the servant's deactivate_object method. Exactly when the TP Framework invokes deactivate_object depends on the state of the object to be deactivated. If the object is not currently in execution, the TP Framework deactivates it before returning to the caller. The object might be currently executing a method; this is always the case for TP::deactivateEnable with no parameters (since it refers to the currently executing object). In this case, TP::deactivateEnable is not told whether the object was deactivated immediately or not.

Note: The TP::deactivateEnable(interface, object id, servant) method can be used to deactivate an object. However, if that object is currently in a transaction, the object will be deactivated when the transaction commits or rolls back. If an invoke occurs on the object before the transaction is committed or rolled back, the object will not be deactivated.

To ensure the desired behavior, make sure that the object is not in a transaction or ensure that no invokes occur on the object after the TP::deactivateEnable() call until the transaction is complete.

Servant Lifetime

A servant is a C++ class that contains methods to implement an IDL interface's operations. The user writes the servant code. The TP Framework invokes methods in the servant code to satisfy requests. The servant is created by the C++ "new" statement and is destroyed by the C++ "delete" statement. Exactly who does the creation and who does the deletion, and the timing of creation and deletion, is the subject of this section.

The Normal Case

In the normal case, the TP Framework completely controls the lifetime of a servant. The basic model is that, when a request for an inactive object arrives, the TP Framework obtains a servant and then activates it (by calling its activate_object method). At deactivation time, the TP Framework calls the servant's deactivate_object method and then disposes of the servant.

The phase "the TP Framework obtains a servant" means that when the TP Framework needs a servant to be created, it calls a user-written Server method, either Server::create_servant or ServerBase::create_servant_with_id. At that time, the application code must return a pointer to the requested servant. The application almost always does this by using the C++ "new" statement to create a new instance of a servant. The phrase "disposes of the servant" means that the TP Framework removes the reference to the servant, which actually deletes it.

The application must be aware that this current behavior of always creating and removing a servant may change in future versions of this product. The application should not depend on the current behavior, but should write servant code that allows reuse of a servant. Specifically, the servant code must work even if the servant has not been freshly created (by the C++ "new" statement). The TP Framework reserves the right not to remove a servant after it has been deactivated and then to reactivate it. This means that the servant must completely initialize itself at the time of the callback on the servant's activate_object method, not at the time of servant creation (not in the constructor).

Special Cases

There are two techniques an application can use to alter the normal TP Framework use of servants. The first has to do with obtaining a servant and the second has to do with disposing of the servant.

The application can alter the "obtaining" mechanism by using explicit preactivation. In this case, the application creates and initializes a servant before asking the TP Framework to declare it activated. Once such a servant has been turned over to the TP Framework (by the TP::create_active_object_reference call), that servant is treated by the TP Framework just like every other servant. The only difference is in its method of creation and initialization.

The application can alter the "disposing" mechanism by taking the responsibility for disposing of a servant instead of leaving that responsibility with the TP Framework. Once a servant is known to the TP Framework (through Server::create_servant, ServerBase::create_servant_with_id, or TP::create_active_object_reference), the TP Framework's default behavior is to remove that servant itself. In this case, the application code must no longer use references to the servant after deactivation.

However, the application may tell the TP Framework not to dispose of the servant after the TP Framework deactivates it. Taking responsibility for a servant is done on an individual servant basis, not for a whole class of servants, by calling Tobj_ServantBase::_add_ref with a parameter identifying the servant.

Note: In applications written using BEA Tuxedo release 8.0 or later, use the Tobj_ServantBase::_add_ref method instead of the TP::application_responsibility() method. Unlike the TP::application_responsibility() method, the add_ref() method takes no arguments.

The advantage of the application taking responsibility for the servant is that the servant does not have to be created anew. If obtaining the servant is an expensive proposition, the application may choose to save the servant and reuse it later. This is especially likely to be true for servants for preactivated objects, but is true in general. For example, the next time the TP Framework makes a call on Server::create_servant or ServerBase::create_servant_with_id, the application might return a previously saved servant.

Saving and Restoring Object State

While CORBA objects are active, their state is contained in a servant. Unless an application uses TP::create_active_object_reference, state must be initialized when the object is first invoked (that is, the first time a method is invoked on a CORBA object after its object reference is created), and on subsequent invocations after they have been deactivated. While a CORBA object is deactivated, its state must be saved outside the process in which the servant was active. The object's state can be saved in shared memory, in a file, or in a database. Before a CORBA object is deactivated, its state must be saved, and when it is activated, its state must be restored.

The programmer determines what constitutes an object's state and what must be saved before an object is deactivated, and restored when an object is activated.

Note On Use of Constructors and Destructors for CORBA Objects

The state of CORBA objects must not be initialized, saved, or restored in the constructors or destructors for the servant classes. This is because the TP Framework may reuse an instance of a servant rather than deleting it at deactivation. No guarantee is made as to the timing of the creation and deletion of servant instances.

Transactions

The following sections provide information about transaction policies and how to use transactions.

Transaction Policies

Eligibility of CORBA objects to participate in global transactions is controlled by the transaction policies assigned to implementations at compile time. The following policies can be assigned.

Note: The optional policy is the only transaction policy that can be influenced by administrative configuration. If the system administrator sets the AUTOTRAN attribute for the interface by means of the UBBCONFIG file or by using administrative tools, the system automatically starts a transaction upon invocation of the object, if it is not already infected with a transaction (that is, the behavior is as if the always policy were specified).

Transaction Initiation

Transactions are initiated in one of two ways:

Transaction Termination

In general, the handling of the outcome of a transaction is the responsibility of the initiator. Therefore, the following are true:

The following behavior is enforced by the BEA Tuxedo system:

Transaction Suspend and Resume

The CORBA object must follow strict rules with respect to suspending and resuming a transaction within a method invocation. These rules and the error conditions that result from their violation are described below.

When a CORBA object method begins execution, it can be in one of the following three states with respect to transactions:

Restrictions on Transactions

The following restrictions apply to BEA Tuxedo CORBA transactions:

SQL and Global Transactions

Adhere to the following guidelines when using SQL and Global Transactions:

Voting on Transaction Outcome

CORBA objects can affect transaction outcome during two stages of transaction processing:

Note: Users of SQL cursors must be careful when using an object with the method or process activation policy. A process opens an SQL cursor within a client-initiated transaction. For typical SQL database products, once the client commits the transaction, all cursors that were opened within that transaction are automatically closed; however, the object will not receive any notification that its cursor has been closed.

Transaction Timeouts

When a transaction timeout occurs, the transaction is marked so that the only possible outcome is to roll back the transaction, and the CORBA::TRANSACTION_ROLLEDBACK standard exception is returned to the client. Any attempts to send new requests will also fail with the CORBA::TRANSACTION_ROLLEDBACK exception until the transaction has been aborted.

Parallel Objects

Support for parallel objects was added to BEA Tuxedo CORBA in release 8.0 as a performance enhancement. The parallel objects feature enables you to designate all business objects in a particular application as stateless objects. The effect is that, unlike stateful business objects, which can only run on one server in a single domain, stateless business objects can run on all servers in a single domain. Thus, the benefits of parallel objects are as follows:

To implement parallel objects, the concurrency policy option has been added to the ICF file. To select parallel objects for a particular application, you set the concurrency policy option to user-controlled. When you select user-controlled concurrency, the business object are not registered with the Active Object Map (AOM) and, therefore, are stateless and can be active on more than one server at a time. Thus, these objects are referred to as parallel objects.

If user-controlled concurrency is selected, the servant implementation must comply with one of the following statements:

Listing 3-1 ICF Syntax

[#pragma activation_policy method|transaction|process]
[#pragma transaction_policy never|ignore|optional|always]
[#pragma concurrency_policy user_controlled|system_controlled]
[Module module-name {]
   implementation [implementation-name]
     {
     implements (module-name::interface-name);
     [activation_policy (method|transaction|process);]
     [transaction_policy (never|ignore|optional|always);]
     [concurrency_policy (user_controlled|system_controlled);]
     };
  [};]

User-controlled concurrency can be used with factory-based routing, all activation policies, and all transaction policies. The interaction with these features is as follows:

Note: There is one restriction with user-controlled concurrency. TP::create_active_object_reference throws a TobjS::IllegalOperation exception if it is passed an interface with user-controlled concurrency set. Since the AOM is not used when user-controlled concurrency is set, there is no way for the TP Framework to connect an active object to this server.

TP Framework API

The TP Framework comprises the following components:

The visible part of the TP Framework consists of two categories of operations:

Server Interface

The Server interface provides callback methods that can be used for application-specific server initialization and termination logic. This interface also provides a callback method that is used to create servants when servants are required for object activation.

The Server interface has the following characteristics:

C++ Declarations

ServerBase Interface

The serverBase interface allows you to take full advantage of multithreading capabilities. You can create your own Server classes that inherit from the ServerBase class. This provides you with the following:

The ServerBase class provides the same operations that were available in the Server class in earlier releases. The Server class inherits from the ServerBase class.

These methods can be used with single-threaded and multithreaded applications:

These methods can be used with multithreaded server applications only:

Note: Programmers must provide definitions of the Server class methods. The ServerBase class methods have default implementations.

C++ Declarations (in Server.h)

The C++ mapping is as follows:

class OBBEXPDLLUSER ServerBase {
public:

    virtual CORBA::Boolean
        initialize(int argc, char** argv) = 0;

    virtual void
        release() = 0;

    virtual Tobj_Servant
        create_servant(const char* interfaceName) = 0;

       // Default Implementations Supplied
       virtual Tobj_Servant
           create_servant_with_id(const char* interfaceName,
                                   const char* stroid);

       virtual CORBA::Boolean
           thread_initialize(int argc, char** argv);

       virtual void
           thread_release();

};

class Server : public ServerBase {
public:

    CORBA::Boolean initialize(int argc, char** argv);
    void release();
    Tobj_Servant create_servant(const char* interfaceName);
};

Server::create_servant()

Synopsis

Creates a servant to instantiate a C++ object.

C++ Binding

class Server {
public:
      Tobj_Servant     create_servant(const char* interfaceName);
};

Argument

Exception

If an exception is thrown in Server::create_servant(), the TP Framework catches the exception. Activation fails. A CORBA::OBJECT_NOT_EXIST() exception is raised back to the client. In addition, an error message is written to the user log (ULOG) file, as follows, for each exception type:

Description

The create_servant method is invoked by the TP Framework when a request arrives at the server and there is no available servant to satisfy the request. The TP Framework calls the create_servant method with the interface name for the servant to be created. The server application instantiates an appropriate C++ object and returns a pointer to it. Typically, the method contains a switch statement on the interface name and creates a new object, depending on the interface name.

Caution: The server application must not depend on this method being invoked for every activation of a CORBA object. The server application must not do any handling of CORBA object state in the constructors or destructors of any servant classes for CORBA objects. This is because the TP Framework may possibly reuse servants on activation and may possibly not destroy servants on deactivation.

Return Value

ServerBase::create_servant_with_id()

Synopsis

Creates a servant for this target object. This method supports the development of single-headed and multithreaded server applications.

C++ Binding

Tobj_Servant create_servant_with_id (const char* interfaceName,
                                     const char* stroid);

Arguments

Description

The TP Framework invokes the create_servant_with_id method when a request arrives at the server and there no servant is available to satisfy the request. The TP Framework passes in the interface name for the servant to be created and the object ID associated with the object with which the servant will be associated. The server application instantiates an appropriate C++ object and returns a pointer to it. Typically, the method contains a switch statement on the interface name and creates a new object, depending on the interface name. Providing the object ID allows a servant implementation to make decisions during the creation of the servant instance that require knowledge of the target object. Reentrancy support is one example of how a servant implementation might employ knowledge of the target object.

The ServerBase class provides a default implementation of create_servant_with_id which calls the standard create_servant method passing the interface name. This default implementation ignores the target object ID parameter.

Caution: The server application must not depend on the invocation of this method for every activation of a CORBA object. The server application must not handle the CORBA object state in the constructors or destructors of any servant classes for CORBA objects. This is because the TP Framework might reuse servants on activation and might not destroy servants on deactivation.

Return Value

Example

Tobj_Servant simple_per_request_server::create_servant_with_id(
const char* intf_repos_id, const char* stroid)
{
TP::userlog("create_servant_with_id called in thread %ld",
(unsigned long)SIMPTHR_GETCURRENTTHREADID);

// Perform any necessary initialization based on
// this object ID

return create_servant(intf_repos_id);
}

Server::initialize()

Synopsis

Allows the application to perform application-specific initialization procedures, such as logging into a database, creating and registering well-known object factories, initializing global variables, and so forth.

C++ Binding

class Server {
public:

        CORBA::Boolean  initialize(int argc, char** argv);

};

Arguments

The argc and argv arguments are passed from the command line. The argc argument contains the name of the server. The argv argument contains the first command-line option that is specific to the application, if there are any.

Exceptions

If an exception is raised in Server::initialize(), the TP Framework catches the exception. The TP Framework behavior is the same as if initialize() returned FALSE (that is, an exception is considered to be a failure). In addition, an error message is written to the user log (ULOG) file, as follows, for each exception type:

Description

The initialize callback method, which is invoked as the last step in server initialization, allows the application to perform application-specific initialization.

Typically, a server application does the following tasks in Server::initialize:

It is the responsibility of the server application to open any required XA resource managers. This is done by invoking either of the following methods:

Note: You must use the TP::open_xa_rm() method if you use the INS bootstrap mechanism to obtain initial object references.

Return Value

Boolean TRUE or FALSE. TRUE indicates success. FALSE indicates failure. If an error occurs in initialize(), the application code should return FALSE. The application code should not call the system call exit(). Calling exit() does not give the TP Framework a chance to release resources allocated during startup and may cause unpredictable results.

If the return value is FALSE:

ServerBase::thread_initialize()

Synopsis

Performs any necessary application-specific initialization for a thread created using the BEA Tuxedo software. This method supports the development of a multithreaded server application.

C++ Binding

CORBA::Boolean thread_initialize(int argc, char** argv)

Arguments

Description

In managing the thread pool, the BEA Tuxedo software creates and releases threads using the operating system thread library services. Depending on application requirements, these threads might need to be initialized before they are used to process requests.

The thread_initialize callback method is invoked each time a thread is created, to initialize the thread. Note that the BEA Tuxedo software manages a number of system-owned threads that are used for dispatching requests; these system-owned threads are in addition to those threads in the thread pool. Under some circumstances the servant methods you implement are also executed in these system-owned threads; for this reason the BEA Tuxedo software invokes the thread_initialize method to initialize the system-owned threads.

The ServerBase class provides a default implementation of the thread_initialize method that opens the XA resource manager in the initialized thread.

Return Value

Example

CORBA::Boolean simple_per_request_server::thread_initialize(
int argc, char** argv)
{
TP::userlog("thread_initialize called in thread %ld",
(unsigned long)SIMPTHR_GETCURRENTTHREADID);
return CORBA_TRUE;
}

Server::release()

Synopsis

Allows the application to perform any application-specific cleanup, such as logging off a database, unregistering well-known factories, or deallocating resources.

C++ Binding

typedef Tobj_ServantBase* Tobj_Servant;

class Server {
public:
        void      release();
};

Arguments

None.

Exceptions

If an exception is raised in release(), the TP Framework catches the exception. Each exception causes an error message to be written to the user log (ULOG) file, as follows:

In all cases, the server continues to exit.

Description

The release callback method, which is invoked as the first step in server shutdown, allows the server application to perform any application-specific cleanup. The user must override the virtual function definition.

Typical tasks performed by the application in this method are as follows:

This method is normally called in response to a tmshutdown command from the administrator or operator.

The TP Framework provides a default implementation of Server::release(). The default implementation closes XA resource managers for the server. The implementation does this by issuing a tx_close() invocation, which uses the default CLOSEINFO configured for the server's group in the UBBCONFIG file.

It is the responsibility of the application to close any open XA resource managers. This is done by issuing either of the following calls:

Note: You must use the TP::close_xa_rm() method if you use the INS bootstrap mechanism to obtain initial object references.

Note: Once a server receives a request from the tmshutdown(1) command to shut down, it can no longer receive requests from other remote objects. This may require servers to be shut down in a specific order. For example, if the Server::release() method in Server 1 needs to access a method of an object that resides in Server 2, Server 2 should be shut down after Sever 1 is shut down. In particular, the TP::unregister_factory() method accesses the FactoryFinder Registrar object that resides in a separate server. The TP::unregister_factory() method is typically invoked from the release() method; therefore, the FactoryFinder server should be shut down after all servers that call TP::unregister_factory() in their Server::release() method.

Return Value

None.

ServerBase::thread_release()

Synopsis

Performs application-specific cleanup when a thread that was created by the BEA Tuxedo software is released. This method supports the development of a multithreaded server application.

C++ Binding

void thread_release()

Arguments

None.

Description

The thread_release callback method is invoked each time a thread is released. Implement the thread_release method as necessary to perform application-specific resource cleanup.

The ServerBase class provides a default implementation of the thread_release method that closes the XA resource manager in the released thread.

Return Value

None.

Example

void simple_per_request_server::thread_release()
{
TP::userlog("thread_release called in thread %ld",
(unsigned long)SIMPTHR_GETCURRENTTHREADID);
}

Tobj_ServantBase Interface

The Tobj_ServantBase interface inherits from the PortableServer::RefCountServantBase class and defines operations that allow a CORBA object to assist in the management of its state in a thread-safe manner. Every implementation skeleton generated by the IDL compiler automatically inherits from the Tobj_ServantBase class. The Tobj_ServantBase class contains two virtual methods, activate_object() and deactivate_object(), that may be optionally implemented by the programmer.

Whenever a request comes in for an inactive CORBA object, the object is activated and the activate_object() method is invoked on the servant. When the CORBA object is deactivated, the deactivate_object() method is invoked on the servant. The timing of deactivation is driven by the implementation's activation policy. When the deactivate_object() method is invoked, the TP Framework passes in a reason code to indicate why the call was made.

These methods support the development of a multithreaded server application:

Note: Tobj_ServantBase::activate_object() and Tobj_ServantBase::deactivate_object() are the only methods that the TP Framework guarantees will be invoked for CORBA object activation and deactivation. The servant class constructor and destructor may or may not be invoked at activation or deactivation time (through the Server::create_servant call for C++). Therefore, the server application code must not do any state handling for CORBA objects in either the constructor or destructor of the servant class.

Note: The programmer does not need to use a cast or reference to Tobj_ServantBase directly. The Tobj_ServantBase methods show up as part of the skeleton and, therefore, in the implementation class for a servant. The programmer may provide definitions for the activate_object and deactivate_object methods, but the programmer should never make direct invocations on those methods; only the TP Framework should call those methods.

C++ Declaration (in Tobj_ServantBase.h)

The C++ mapping for the Tobj_servantBase interface is as follows:

class Tobj_ServantBase : public PortableServer::RefCountServantBase {
public:

    Tobj_ServantBase& operator=(const Tobj_ServantBase&);
    Tobj_ServantBase() {}
    Tobj_ServantBase(const Tobj_ServantBase& s) :
        PortableServer::RefCountServantBase(s) {}

    virtual void activate_object(const char *) {}

    virtual void deactivate_object(const char*, 
        TobjS::DeactivateReasonValue) {}

    virtual CORBA::Boolean _is_reentrant() { return CORBA_FALSE; }
};

typedef Tobj_ServantBase * Tobj_Servant;

Tobj_ServantBase:: activate_object()

Synopsis

Associates an object ID with a servant. This method gives the application an opportunity to restore the object's state when the object is activated. The state may be restored from shared memory, from an ordinary flat file, or from a database file.

C++ Binding

class Tobj_ServantBase : public PortableServer::ServantBase {
public:	
        virtual void activate_object(const char * stroid) {}
};

Argument

Description

Object activation is triggered by a client invoking a method on an inactive CORBA object. This causes the Portable Object Adapter (POA) to assign a servant to the CORBA object. The activate_object() method is invoked before the method invoked by the client is invoked. If activate_object() returns successfully, that is, without raising an exception, the requested method is executed on the servant.

If the object is currently infected with a global transaction, activate_object() executes within the scope of that same global transaction.

It is the responsibility of the programmer of the object to check that the stored state of the object is consistent. In other words, it is up to the application code to save a persistent flag that indicates whether or not deactivate_object() successfully saved the state of the object. That flag should be checked in activate_object().

Return Value

None.

Exceptions

If an error occurs while executing activate_object(), the application code should raise either a CORBA standard exception or a TobjS::ActivateObjectFailed exception. When an exception is raised, the TP Framework catches the exception, and the following events occur:

Tobj_ServantBase::_add_ref()

Synopsis

Adds a reference to a servant. This method supports the development of a multithreaded server application.

Note: In applications written using BEA Tuxedo release 8.0 or later, use this method instead of the TP::application_responsibility() method.

C++ Binding

void _add_ref()

Arguments

None.

Description

Invoke this method when a reference to a servant is needed. Invoking this method causes the reference count for the servant to increment by one.

Return Value

None.

Example

myServant * servant = new intf_i();
if(servant != NULL)
   servant->_add_ref();

Tobj_ServantBase::deactivate_object()

Synopsis

Removes the association of an object ID with its servant. This method gives the application an opportunity to save all or part of the object's state before the object is deactivated. The state may be saved in shared memory, in an ordinary flat file, or in a database file.

C++ Binding

class Tobj_ServantBase : public PortableServer::ServantBase {
public:	
        virtual void deactivate_object(const char* stroid,
                       TobjS::DeactivateReasonValue  reason) {}
};

Arguments