Scenario: stand-alone invocation tasks that support the asynchronous invocations of services

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Scenario: stand-alone invocation tasks that support the asynchronous invocations of services

This scenario considers the asynchronous invocations of tasks and services only. It describes the SCA settings and the expected transactional and fault behavior for this type of invocation.
This scenario is applicable to Human Task Manager API clients, for example, Business Process Choreographer Explorer, that make use only of asynchronous invocations. It avoids the need for assessing the execution duration of the service associated with the task when you model the task.

Task component settings

The task component can take the following settings. If you use IBM Integration Designer to define the task component, valid values for the attribute type are generated automatically.

Qualifier type: attribute type Value
Reference attribute: Multiplicity 1:1 (mandatory)
Reference qualifier: DeliverAsyncAt commit (mandatory)
Implementation qualifier^{*: Transaction} global (mandatory)
Reference qualifier^{**: SuspendTransaction} Not applicable
Implementation qualifier^{***: ActivitySession} true (mandatory)
Reference qualifier^{***: SuspendActivitySession} false (default)
Reference qualifier: Reliability assured (mandatory)
Reference qualifier: RequestExpiration any
Reference qualifier: ResponseExpiration any

^{*: use global if you use transactions
settings, and local if you use activity session settings.}
^{**: if the transaction is set to global, only the transaction settings are used}
^{***: if the transaction is set to local, only the settings for the activity sessions are used}

Service component settings

The service component can take the following settings. If you use IBM Integration Designer to define the task component, valid values for the attribute type are generated automatically.

Qualifier type: attribute type Value
Interface attribute: PreferredInteractionStyle Ignored
Implementation qualifier^{*: Transaction}
local (default)
global
Interface qualifier^{**: JoinTransaction}
false (default)
true
Implementation qualifier^{***: ActivitySession} any (default)
Interface qualifier^{***: JoinActivitySession} false (default)

^{*: use global if you use transactions
settings, and local if you use activity session settings.}
^{**: if the transaction is set to global, only the transaction settings are used}
^{***: if the transaction is set to local, only the settings for the activity sessions are used}

The following list gives the valid combinations of settings for the service Transaction and JoinTransaction qualifiers:

The Transaction qualifier is set to local and the JoinTransaction is set to false. With these settings, the task and service invocation run in separate transactions.
The Transaction qualifier is set to global and the JoinTransaction is set to false. With these settings, the task and service invocation run in separate transactions.
The Transaction qualifier is set to global and the JoinTransaction is set to true. With these settings, the task and service invocation run in the same transaction.

Transactional and fault behavior

In this asynchronous invocation scenario, the startTask method is used for API invocation only. Task and service invocations occur in different transactions. The following applies when a runtime exception occurs, which is not handled by the service implementation. This scenario has the following transactional behavior and exception handling.

Operation type When the SCA runtime exception occurs Behavior of tasks and services
One-way operation During service invocation but before the start of the service execution The task receives an SCA runtime exception. The Human Task Manager API method throws a CoreOTaskServiceRuntimeExceptionReceivedException exception. The task transaction is rolled back and the task stays in the inactive state.
One-way operation During service execution The invocation task is not notified. The task moves to the finished state. A failed event is generated that can be handled by using the failed event manager.
Request-response operation During service invocation but before the start of the service execution The task receives an SCA runtime exception. The Human Task Manager API method throws a CoreOTaskServiceRuntimeExceptionReceivedException exception. The task transaction is rolled back and the task stays in the inactive state.
Request-response operation During service execution The task is notified of the SCA runtime exception and stores it in the task context in the database. If a reply handler is available, it is used to notify the client. The task is put into the failed state.

The operation definition can include one or more fault messages that can be thrown by the service component during execution.
The task component is notified about a fault message as follows:

The fault message is stored in the database in the context of the task
The task is put into the failed state
If the task was invoked synchronously and a reply handler was specified, the reply handler is invoked to return the fault occurrence to the client
If the task was invoked asynchronously, the fault message is returned to the client as a FaultReplyException exception

Fault handling does not impact transactional behavior. The transactions are not rolled back.

Scenarios for invoking tasks

Related concepts:
Scenarios for invoking tasks
Service qualifiers

Qualifier type: attribute type	Value
Reference attribute: Multiplicity	1:1 (mandatory)
Reference qualifier: DeliverAsyncAt	commit (mandatory)
Implementation qualifier^{*: Transaction}	global (mandatory)
Reference qualifier^{**: SuspendTransaction}	Not applicable
Implementation qualifier^{***: ActivitySession}	true (mandatory)
Reference qualifier^{***: SuspendActivitySession}	false (default)
Reference qualifier: Reliability	assured (mandatory)
Reference qualifier: RequestExpiration	any
Reference qualifier: ResponseExpiration	any

Qualifier type: attribute type	Value
Interface attribute: PreferredInteractionStyle	Ignored
Implementation qualifier^{*: Transaction}	local (default) global
Interface qualifier^{**: JoinTransaction}	false (default) true
Implementation qualifier^{***: ActivitySession}	any (default)
Interface qualifier^{***: JoinActivitySession}	false (default)

Operation type	When the SCA runtime exception occurs	Behavior of tasks and services
One-way operation	During service invocation but before the start of the service execution	The task receives an SCA runtime exception. The Human Task Manager API method throws a CoreOTaskServiceRuntimeExceptionReceivedException exception. The task transaction is rolled back and the task stays in the inactive state.
One-way operation	During service execution	The invocation task is not notified. The task moves to the finished state. A failed event is generated that can be handled by using the failed event manager.
Request-response operation	During service invocation but before the start of the service execution	The task receives an SCA runtime exception. The Human Task Manager API method throws a CoreOTaskServiceRuntimeExceptionReceivedException exception. The task transaction is rolled back and the task stays in the inactive state.
Request-response operation	During service execution	The task is notified of the SCA runtime exception and stores it in the task context in the database. If a reply handler is available, it is used to notify the client. The task is put into the failed state.