Sun Microsystems iPlanet Integration Server 3.0, Руководство по системе управления

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Process Execution
166 iPlanet Integration Server • Process System Guide • August 2001
Process instance execution Process execution involves creation of any number of
activities, including one or more Offered activities (which are offered to and
performed by client applications), Queued activities (which are placed on a queue
and performed by client applications—but not, in this case, by applications
integrated through proxies), Subprocess activities (which create an instance of
another process), and Automatic activities (which are performed by the engine
rather than client applications).
Process instance termination Process termination involves the completion of a
Last activity.
The different activity types are discussed in the context of each stage of the
execution life cycle, explained in more detail in the sections below.
Process Instance Creation
The engine creates a new instance of a process in three situations:
• A client application requests a new instance of a process
The request must provide the name of a process definition registered with the
engine. The engine invokes the assignment rules for process creation to
determine if the user making the request is authorized to create an instance of
the process. If so, a First activity is created. A First activity passes automatically
through the PENDING, READY, and ACTIVE states, and is placed directly
into a COMPLETED state. Its OnComplete router methods, if any, are
executed, and process execution proceeds.
• A Subprocess activity becomes ACTIVE
A Subprocess activity specifies a process and engine name. If the specified
process is registered with the specified engine and all the required data can be
located, the specified engine creates a new instance of the process. As in the
previous case, a First activity is created, and process execution then proceeds.
• An engine recovers current state
During a failover scenario, or whenever a backup engine unit comes online, the
engine needs to recover current state information from the engine database. In
this situation, process instances that were active when the engine went off line
are recreated and restored to their former states.