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

Type 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.
Learn more about Error handling.

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

 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
Minimum loop duration Integer/Expression Specify the minimum time in seconds that each loop iteration should take, measured from the iteration start time.
  • If the child pipeline execution completes in less than the configured duration, the Snap waits the remaining time before starting the next iteration.
  • If the iteration exceeds the configured duration, the Snap starts the next iteration immediately with no additional delay.

Unlike Loop interval (which adds a fixed wait in milliseconds after each iteration completes), Minimum loop duration enforces a minimum wall-clock time in seconds per iteration measured from its start. When using this field, set Loop interval to 0 to avoid timing conflicts.

Accepts expressions, enabling dynamic values via pipeline parameters for per-environment configuration.

CAUTION: A Lint warning is displayed when both Loop interval and Minimum loop duration are set to non-zero values, as this may cause inconsistent timing. Consider setting one of the values to 0.
Note: The Snap validates this field before execution and returns an error if the value is non-numeric or negative.

Common use cases:

  • Sub-minute polling: Set to 3 to poll a system such as an AS400/DB2 database no more frequently than every 3 seconds, without requiring a Poller workaround.
  • API rate-limit compliance: Set to 1 to ensure at least 1 second elapses between API call iterations, preventing rate-limit errors.
  • Dynamic interval: Use an expression such as $min_loop_duration to configure different polling frequencies per environment via a pipeline parameter.

Default value: 0 (no minimum duration; preserves existing behavior)

Example: 3
Snap execution

Dropdown list

 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: