Loop

Type: loop • Category: flow • Tags: loop, iteration, control, flow, cycle

Description

Execute iterations with continue/exit branches

Parameters

Name	Type	Description	Required	Default
max_iterations	number	Maximum number of iterations	no	10
exit_condition	string	Expression for early exit (optional, e.g., 'vars.counter > 5')	no
check_after	boolean	If true, evaluate exit_condition after running the loop body (continue branch)	no	false
loop_var	string	Variable name to store iteration counter in workflow vars	no	"loop_iteration"

Help

Loop Worker

This worker implements loop control flow with two output branches for workflow routing.

How it works:

1. Initialize: Set maximum iterations and optional exit condition
2. Check conditions: Evaluate exit condition (pre- or post-body based on check_after) and iteration count
3. Route execution:
   • continue branch: When loop should proceed to next iteration (loops back)
   • exit branch: When loop should terminate (exits loop)

Setting up the Loop:

1. Connect previous workers → to Loop worker (entry point)
2. Connect Loop worker "continue" → back to the beginning of loop tasks
3. Connect Loop worker "exit" → to post-loop processing

Workflow Structure:

[Entry Tasks] → [Loop Worker] → continue → [Loop Tasks] → [Loop Worker]
                        ↓ exit
                   [Exit Tasks]

Parameters:

• max_iterations: Maximum number of loop iterations (default: 10)
• exit_condition: Expression for early exit (optional, e.g., 'vars.counter > 5')
• check_after: If true, evaluate exit_condition after running the loop body (default: false)
• loop_var: Variable name to store iteration counter (default: "loop_iteration")

Branch Logic:

• continue: Returns {"action": "continue", "next_iteration": N+1} - loops back
• exit: Returns {"action": "exit", "exit_reason": "..."} - exits loop

Example: Create a loop that processes items until condition met:

1. Set max_iterations: 100
2. Set exit_condition: 'vars.items_processed >= vars.total_items'
3. Connect continue → back to data processing workers
4. Connect exit → to final reporting worker

The workflow will cycle through the loop tasks until exit condition is met or max iterations reached.

Notes:

• exit_condition supports template braces: "{{ expr }}" (the braces are stripped before evaluation).
• The expression must evaluate to a boolean; prefer comparisons (>, >=, ==) rather than returning strings.
• Use safe accessors to avoid KeyError, e.g., vars.get('redis_n_ijnr', {}).get('result', 0) > 100.
• Use check_after=true to evaluate the condition after executing the continue branch (useful when the loop body computes the condition).

Examples:

• Pre-check (default): exit when counter reached total exit_condition: vars.get('items_processed', 0) >= vars.get('total_items', 0)
• Post-check: exit when Redis counter exceeds 100 after body exit_condition: vars.get('redis_n_ijnr', {}).get('result', 0) > 100 check_after: true