NiFi Flow Layout

Use this universal skill when any Apache NiFi flow must be readable a year later: clear names, useful comments, compact vertical flow, and connections that do not cross blocks. The skill has no environment-specific defaults: pass the NiFi URL, credentials/certificates, and target process group explicitly.

Workflow

1. Inspect first

   • Read the target process group through NiFi REST.
   • Save a JSON snapshot before changing anything.
   • Run audit/dry-run before apply.

2. Apply the house style

   • Main route goes top-to-bottom.
   • Input/source nodes go to the top boundary; output/terminal sinks go to the bottom boundary.
   • Errors/logs/fallback/notification branches go to a side lane.
   • Connections are orthogonal: vertical/horizontal, no diagonals.
   • Connection names stay empty. Connections do not support comments in NiFi.
   • Every commentable object gets a useful human comment: processor, process group, input port, output port.
   • Names use hierarchical numbering: 10, 20, 30, then 30.10, 30.20, then 30.20.10. Never use .00.
   • Move processors/ports before drawing long detours. A cleaner node position is better than a giant route rectangle.

3. Verify visually

   • Use Playwright when available to capture real DOM bounding boxes and a screenshot.
   • Treat route/label overlap with processors, process groups, ports, or queued boxes as a defect.

Scripts

• scripts/nifi_layout.py — REST audit, dry-run, apply, geometry tests.
• scripts/nifi_visual_check.cjs — Playwright screenshot and DOM bounding-box capture.
• references/layout-rules.md — detailed rules and routing decisions.

Typical commands

python3 scripts/nifi_layout.py \
  --base-url https://nifi.example.com/nifi-api \
  --group-id <process-group-id> \
  --cert /path/client.crt --key /path/client.key \
  --mode audit --recursive

python3 scripts/nifi_layout.py \
  --base-url https://nifi.example.com/nifi-api \
  --group-id <process-group-id> \
  --cert /path/client.crt --key /path/client.key \
  --mode dry-run --recursive --backup-dir ./nifi-backups

python3 scripts/nifi_layout.py \
  --base-url https://nifi.example.com/nifi-api \
  --group-id <process-group-id> \
  --cert /path/client.crt --key /path/client.key \
  --mode apply --recursive --backup-dir ./nifi-backups

Non-negotiable visual rules from real reviews

• Verify with Playwright screenshots after changes; REST geometry is not enough.
• Use boundary-aware layers: sources at top, business processors in middle, terminal outputs at bottom.
• Before adding bends, try moving the source/destination into a cleaner layer or closer side lane.
• Do not leave a huge empty left/right canvas area while another side is overloaded with route loops.
• For dense fan-in, evaluate all useful target sides. Do not force every branch into one side or one shared point.
• Dense fan-in must stay local and comb-shaped. Do not move a sink far away just to make route scoring pass.
• If a lower source crosses the central bus/labels when entering from the left, try right-side entry, but only after checking the full candidate route for component and label blockers.
• Treat connection labels as real obstacles. Lines must not pass through Name/Queued boxes, even if they do not touch processors.
• Side handler returns should avoid queue labels between main-lane processors. Use a clear side/bottom lane instead of a short route that hides under labels.
• Side handler → output port should not add tiny doglegs when the output centerline is clear; prefer the compact side route.
• Always inspect screenshots for the whole affected area, not only one cropped defect. If the flow is larger than a viewport, pan/scroll and capture more screenshots.

Safety rules

• Do not print secrets or certificate passphrases.
• Do not edit processor business properties unless the user explicitly asked.
• Default to audit/dry-run; use apply only when implementation is requested.
• Preserve revisions and current processor state; only update names, comments, positions, connection bends, labelIndex, and empty connection names.
• Before apply, always write a backup flow JSON using --backup-dir.

Review hardening additions

• scripts/nifi_layout.py supports --single-group, --group-order top-down, --report-dir, --screenshots-dir, --visual-gate, and PKCS#12 auth via --p12.
• Apply mode is state-preserving by default: processor/port metadata updates do not stop running components; connection updates first try without stopping and only retry by stopping the two endpoint components when the connection queue is empty.
• scripts/nifi_visual_check.cjs supports --tile-grid CxR and --tile-dir for large-canvas evidence.
• Dense fan-in, same-column side chains, side-column handler returns, hard label packing, 12px visual label/component clearance, and 32px visual line spacing are handled to prevent merged wires, processor overlaps, queued-label overlaps, and near-touching lines.
• Treat visual X/T line crossings as hard defects; use wider bus lanes instead of ambiguous intersections.
• Non-adjacent segments of the same connection must also keep wide spacing; self-overlapping U-turns are defects.
• Reports include topology_blockers when a clean visual layout likely requires a graph decision, such as adding a funnel, collector processor, split sink, or separate process group.