PipeLoop

Overview

You can use this Snap to enable looping on pipeline executions based on a stop condition or iteration limit. The output document of each iteration is fed into the next iteration as the input document, and execution continues until the stop condition is met or the iteration limit is reached. Learn more.



Limitations

  • Reuse is currently not supported because of the requirement to close an input view to force flush all documents out.

  • Reads only the first output document for a specific input document (the remaining documents are ignored and dropped).

  • Supports expressions on the pipeline specification, but only evaluates the input document to PipeLoop, not for each iteration.

Snap views

View Description Examples of upstream and downstream Snaps
Input The document or binary data to send to the child pipeline. For a single document input, only the first output document is captured in the output document and the remaining documents are ignored.
Output If you select the Debug iterations output checkbox, an additional _iteration_documents is added to the output document alongside the output documents and passthrough documents.

_iteration_documents contains the following fields:

  • iteration: The index of the loop iteration.

  • child_pipeline_output: The output document of the respective iteration.

  • stop_condition_evaluation: The evaluated result of the stop condition.
Error

Error handling is a generic way to handle errors without losing data or failing the Snap execution. You can handle the errors that the Snap might encounter when running the pipeline by choosing one of the following options from the When errors occur list under the Views tab. The available options are:

  • Stop Pipeline Execution Stops the current pipeline execution when an error occurs.
  • Discard Error Data and Continue Ignores the error, discards that record, and continues with the remaining records.
  • Route Error Data to Error View Routes the error data to an error view without stopping the Snap execution.

Learn more about Error handling in Pipelines.

Snap settings

Legend:
  • Expression icon (): Allows using pipeline parameters to set field values dynamically (if enabled). SnapLogic Expressions are not supported. If disabled, you can provide a static value.
  • SnapGPT (): Generates SnapLogic Expressions based on natural language using SnapGPT. Learn more.
  • Suggestion icon (): Populates a list of values dynamically based on your Snap configuration. You can select only one attribute at a time using the icon. Type into the field if it supports a comma-separated list of values.
  • Upload : Uploads files. Learn more.
Learn more about the icons in the Snap settings dialog.
Field / Field set Type Description
Label String

Required. Specify a unique name for the Snap. Modify this to be more appropriate, especially if more than one of the same Snaps is in the pipeline.

Default value: PipeLoop

Example: SimpleLoop
Pipeline Dropdown list/Expression Required. Specify the path of the pipeline to execute.

Default value: N/A

Example: demo-child-pipeline
Pipeline Parameters Use this field set to define child pipeline parameters to use for executing the pipeline.
Parameter name String/Suggestion Specify the parameter's name. You can also select the Pipeline Parameters defined for the pipeline selected in the Pipeline field.

Default value: N/A

Example: tools
Parameter value Integer/Expression Specify the value for the pipeline parameter, which can be an expression based on incoming documents or a constant.

If you configure the value as an expression based on the input, then each incoming document or binary data is evaluated against that expression when invoking the pipeline. The result of the expression is JSON-encoded if it is not a string. The child pipeline then needs to use the JSON.parse() expression to decode the parameter value.

Default value: N/A

Example: $tools
Loop settings Define the iteration configuration.
Stop condition Dropdown list/Expression Specify the condition to be evaluated during execution that decides whether the execution should stop or continue. The iteration continues until the stop condition is met or the iteration limit is reached. The Snap errors out if the Stop condition cannot be evaluated at run time. The stop condition is evaluated on the output document from each iteration.

Default value: N/A

Example: $num >= 10
Iteration limit Integer/Expression Required. Specify the maximum limit for the number of iterations to run to avoid infinite loops.

Default value: 10

Example: 15
Debug iteration outputs Checkbox Select this checkbox to include the index, output document, and stop condition evaluation for each iteration as part of the output format.

Default status: Deselected
Execution settings Define the child pipeline execution configuration.
Execute on Dropdown list Required. Select one of the following Snaplex options to specify the target Snaplex for the child pipeline:

  • LOCAL_NODE: Runs the child pipeline on the same node as the parent pipeline.

  • LOCAL_SNAPLEX: Runs the child pipeline on one of the available nodes in the same Snaplex as the parent pipeline.

Default value: LOCAL_NODE

Example: LOCAL_SNAPLEX
Execution label String/Expression Specify the label to display in the Dashboard for the current execution.

Default value: N/A

Example: demo
Pre-spawned pipelines Integer/Expression Specify a value to maintain a pool of pre-initialized child pipelines. A pre-spawned pipeline is initialized only if the current Pool size is below the Iteration limit. For example, if the Iteration limit is 10 and 5 pipelines are pre-spawned, the process starts with 5 pipelines. Once there are only 4 iterations left, no new pipelines will be initialized.

Default value: 1

Example: 1
Parallel executions Integer/Expression Specify the number of parallel executions the Snap must perform.
Note:
  • The Snap supports Ultra tasks when Parallel execution is set to 1. When the value is greater than 1, the Snap displays a configuration error while processing Ultra tasks.

  • When you do not provide a value in this field, the Snap processes the docs individually and writes to the output immediately.

Default value: 1

Example: 2
Loop interval Integer/Expression Specify the loop interval between iterations in milliseconds.

  • After each child pipeline execution, the Snap checks the value of the Loop interval and waits for the specified time.

  • If the Loop interval is greater than 0, the Snap stops processing for the specified number of milliseconds before starting the next iteration.

Default value: 0

Example: 5
Snap execution Dropdown list
Choose one of the three modes in which the Snap executes. Available options are:
  • Validate & Execute: Performs limited execution of the Snap and generates a data preview during pipeline validation. Subsequently, performs full execution of the Snap (unlimited records) during pipeline runtime.
  • Execute only: Performs full execution of the Snap during pipeline execution without generating preview data.
  • Disabled: Disables the Snap and all Snaps that are downstream from it.

Default value: Validate and Execute

Example: Execute only

Example: