Triggers design patterns¶

Applications of type Triggers (see Application Types) are implemented using the following design patterns.

Queue design pattern¶

The design of a Queue Application implies steps for:

Data discovery,
Data selection,
Parameters definition,
Data Item(s) creation,
Data Item(s) submission to the Processing Queue.

An example of control flow is the following:

!define DIAG_NAME Trigger Queue example
!include includes/skins.iuml
skinparam backgroundColor #FFFFFF
skinparam componentStyle uml2

start

:Discover Data;

while (Are there Data objects?) is (yes)
if (Does Data object satisfy processing criteria?) then (yes)
:Define processing parameters;
:Create Data Item;
:Add Data Item to Processing Queue;
else (no)
endif
endwhile (no)

stop

Tip

It’s important to note that Queue Applications, when discovering and selecting data, deal with metadata only, leveraging an Opensearch catalog (see Catalog). Stage-in data is not usually required.

Pipe design pattern¶

Since Pipe Applications are not developed by the Users but provided as a service by the platform, the design pattern is provided as an additional information, that can be used to understand its behaviour.

A Pipe Application performs the following steps:

Data Items retrieval,
Data Items analysis,
Stand-alone Processing Application execution submission,
Stand-alone Processing Application execution monitor.

An example of control flow is the following: