Version

    Loop

    Short Description
    Ports
    Metadata
    Loop Attributes
    Details
    Examples
    Compatibility
    See also

    Short Description

    The Loop component allows repeated execution of a group of components or repeated processing of records.

    ComponentSame input metadataSorted inputsInputsOutputsEach to all outputsJavaCTLAuto-propagated metadata
    Loop✓⨯22⨯⨯✓✓
    [Important]Important

    It is highly important to manage token flow correctly. For example each token sent to the loop body must be navigated back to the Loop component. The token cannot be duplicated or cannot disappear. If these rules are not strictly followed, your jobflow processing can easily stuck in a deadlock situation.

    Ports

    Port typeNumberRequiredDescriptionMetadata
    Input0✓Entry point for loop processing.Any
    1✓Tokens from the loop body must be returned back to the Loop component via this port.Any
    Output0✓Tokens which do not satisfy While condition are sent to this port to end up the looping.Any
    1⨯Tokens which satisfy While condition are sent to this port to start loop body.Any

    Metadata

    All input and output ports have arbitrary but identical metadata.

    Loop Attributes

    AttributeReqDescriptionPossible values
    Basic
    While conditionyes

    While this condition is satisfied, the iterating token is repeatedly sent to the loop body (second output port), otherwise the token is sent out of the loop (first output port).

    While condition is a CTL2 expression which is evaluated against two records.

    The first record ($in.0) is the token incoming from one of the input ports (either a loop initializing token or a token incoming from the loop body).

    The second record ($in.1) is an artificial input for the condition evaluator with just a single field $in.1.iterationNumber which is automatically populated by the number of iteration of the current token. So for example, if the loop should be executed exactly five times, the condition could look like $in.1.iterationNumber < 5.

    		CTL expression
    Advanced
    Logging levelnoDecides on which level token processing information should be logged.INFO (default) | DEBUG | TRACE | OFF

    Details

    The Loop component processes records (or tokens) one by one.

    1. The record enters the Loop component.

    2. The record is checked to fulfill the loop condition. If the condition is not fulfilled, the record is sent out to the first output port and the processing continues from step 1 using the next record. If the condition is met, the record is sent out to the second output port.

    3. The record is processed by components in the loop body.

    4. The record enters the Loop component through the second input port.

    5. Processing continues from the step 2.

    Edge Types

    All edges in loop are automatically converted to fast-propagate version. See Types of Edges.

    Examples

    Repeating Actions in Jobflow - Login

    Example of Loop component usage

    Figure 59.3. Example of Loop component usage


    This jobflow simply generates an initial token by the DataGenerator component. The Loop component applies While condition on this initial token. If the condition is not satisfied, the token is sent out of the loop. On the other hand, if the condition is satisfied, the token is sent to the loop body, where the token is processed by other components. The token must be routed back to the Loop component, where While condition is evaluated again. The token looping is performed until the condition is not satisfied. Once the token is sent out of loop, another initial token is read from the first input port.

    Compatibility

    VersionCompatibility Notice
    4.0.0

    Loop is now also available as an ordinary Component. Before, Loop was available as a Jobflow Component only.