August 17, 2023

tLoop – Docs for ESB 5.x

tLoop

tFor.png

tLoop Properties

Component family

Orchestration

 

Function

tLoop iterates on a task
execution.

Purpose

tLoop allows you to execute a
task or a Job automatically, based on a loop

Basic settings

Loop Type

Select a type of loop to be carried out: either For or While.

For: The task or Job is carried out
for the defined number of iteration

While: The task or Job is carried
until the condition is met.

For

From

Type in the first instance number which the loop should start
from. A start instance number of 2 with a step of 2 means the loop
takes on every even number instance.

 

To

Type in the last instance number which the loop should finish
with.

 

Step

Type in the step the loop should be incremented of. A step of 2
means every second instance.

 

Values are increasing

Select this check box to only allow an increasing sequence.
Deselect this check box to only allow a decreasing sequence.

While

Declaration

Type in an expression initiating the loop.

 

Condition

Type in the condition that should be met for the loop to
end.

 

Iteration

Type in the expression showing the operation to be performed at
each loop.

Usage

tLoop is to be used as a start
component and can only be used with an iterate connection to the
next component.

Global Variables

ERROR_MESSAGE: the error message generated by the
component when an error occurs. This is an After variable and it returns a string. This
variable functions only if the Die on error check box is
cleared, if the component has this check box.

CURRENT_VALUE: the current value. Only available for a
For type loop. This is a Flow variable and it returns
an integer.

CURRENT_ITERATION: the sequence number of the current
iteration. This is a Flow variable and it returns an integer.

A Flow variable functions during the execution of a component while an After variable
functions after the execution of the component.

To fill up a field or expression with a variable, press Ctrl +
Space
to access the variable list and choose the variable to use from it.

For further information about variables, see Talend Studio
User Guide.

Connections

Outgoing links (from this component to another):

Row: Iterate.

Trigger: On Subjob Ok; On Subjob
Error; Run if; On Component Ok; On Component Error.

Incoming links (from one component to this one):

Row: Iterate;

Trigger: On Subjob Ok; On Subjob
Error; Run if; On Component Ok; On Component Error; Synchronize;
Parallelize.

For further information regarding connections, see
Talend Studio User
Guide
.

Log4j

The activity of this component can be logged using the log4j feature. For more information on this feature, see Talend Studio User
Guide
.

For more information on the log4j logging levels, see the Apache documentation at http://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/Level.html.

Limitation

n/a

Scenario: Job execution in a loop

This scenario describes a Job composed of a parent Job and a child Job. The parent Job
implements a loop which executes a child Job five times, with a pause of three seconds
between each two executions.

  1. Create a Parent Job, and drop tLoop, tRunJob, and tSleep components to the workspace.

  2. Connect tLoop to tRunJob using a Row > Iterate connection, and connect tRunJob to tSleep using a
    Row > Main
    connection.

    use_case_tloop1.png
  3. Create a Child Job, and drop tRowGenerator and tLogRow
    components to the workspace.

  4. Connect tRowGenerator to tLogRow using a Row
    > Main connection.

    use_case_tloop2.png
  5. On the Basic settings view of the tLoop component, choose For loop type and type in the instance number to start from
    (1), to finish with (5) and the
    step (1).

    use_case_tloop3.png
  6. On the Basic settings view of the tRunJob component, select Child
    Job in the Job field.

    use_case_tloop4.png
  7. On the Basic settings view of the tSleep component, enter 3 in the
    Pause field.

  8. Double-click tRowGenerator to open the schema
    editor. Then click the plus button to add four new columns:

    • id, to generate sequence numbers

    • firstname, to generate random first names

    • lastname, to generate random last names

    • city, to generate random city names

    For more information about tRowGenerator, see
    tRowGenerator.

    use_case_tloop5.png
  9. Press F6 to run the
    Parent Job.

    The Child Job will be executed five times with a
    three-second pause between each two executions, displaying random personal
    information on the Run console as configured in
    the tRowGenerator component.


Document get from Talend https://help.talend.com
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