delay

Overview

The delay node delays messages or limits message rate. Essential for rate limiting API calls, debouncing sensor readings, implementing timeouts, and controlling message flow to prevent overwhelming downstream systems.

Properties

Delay Modes

Input:  msg1 ─┬─ msg2 ─┬─ msg3
              │        │
Output: ──────msg1────msg2────msg3
        (5s delay for each)

// Between 1-5 seconds
Input:  msg1 ─┬─ msg2 ─┬─ msg3
Output: ──msg1────────msg2──msg3
        (varies each time)

// 1 message per second
Input:  msg1,msg2,msg3,msg4 (burst)
Output: msg1──msg2──msg3──msg4
        (evenly spaced)

// 1 msg/sec, drop excess
Input:  msg1,msg2,msg3,msg4 (burst)
Output: msg1──────────────msg4
        (only latest kept)

Example: API Rate Limiting

Limit API calls to 10 per minute to avoid throttling.

// Delay node configuration
{
  "pauseType": "rate",
  "rate": 10,
  "rateUnits": "minute",
  "drop": false
}

// Flow: sensor readings → delay (rate limit) → HTTP API
// Ensures max 10 calls per minute regardless of sensor frequency

Example: Button Debounce

Debounce button presses to ignore rapid repeated clicks.

// Delay node configuration (drop mode)
{
  "pauseType": "rate",
  "rate": 1,
  "rateUnits": "second",
  "drop": true  // Drop intermediate messages
}

// User presses button rapidly: click click click click
// Output: Only first click passes
// Next click allowed after 1 second

Example: Dynamic Delay

Set delay time dynamically based on message properties.

// Delay node configuration
{
  "pauseType": "delayv",
  "timeoutUnits": "seconds"
}

// Function node before delay:
msg.delay = msg.payload.priority === "low" ? 10000 : 1000; // ms
return msg;

// Low priority: 10 second delay
// High priority: 1 second delay

Control Messages

msg.flush = true;
// or
msg.payload = "flush";

msg.reset = true;
// Clears queue without sending

msg.toFront = true;
// Message goes to front of queue

// Status shows: "X queued"
// Use inject to trigger status check

Common Use Cases