Actions are executable logic blocks triggered by events such as timed intervals, topic updates, or explicit calls. They are the primary way to implement automation in LoT.
Actions run inside the MQTT broker itself, eliminating the need for external middleware or application servers.
In This Page
| Section | Description |
|---|
| Basic Syntax | DEFINE ACTION structure and components |
| Trigger Types | Time-based, topic-based, and callable actions |
| Variable Operations | SET, GET TOPIC, GET JSON |
| Topic Operations | PUBLISH and KEEP |
| Control Flow | IF/THEN/ELSE conditionals |
| Type Casting | Converting between data types |
| Complete Example | Full working action |
Basic Syntax
DEFINE ACTION <action_name>
ON <EVENT_TRIGGER>
DO
<action_logic>
Components
A unique identifier for the action. Use descriptive names that indicate the action’s purpose (e.g., SensorDataProcessor, HeartbeatMonitor).
Specifies when the action executes. Can be time-based (ON EVERY), topic-based (ON TOPIC), or omitted for callable actions.
One or more LoT statements that execute when the action triggers. These can include publishing, variable assignment, conditionals, and Python calls.
Action Structure
Every action follows this general structure:
DEFINE ACTION ActionName
ON <trigger_type> DO
// Variable assignment
SET "variable" WITH <value>
// Conditional logic
IF <condition> THEN
// Statements
ELSE
// Alternative statements
// Topic operations
PUBLISH TOPIC "output/topic" WITH <payload>
KEEP TOPIC "internal/topic" WITH <payload>
Trigger Types
Time-Based
Topic-Based
Callable
Execute at regular intervals:DEFINE ACTION PeriodicTask
ON EVERY 5 SECONDS DO
PUBLISH TOPIC "system/heartbeat" WITH "alive"
SECOND(S), MINUTE(S), HOUR(S), DAY(S), WEEK(S) Execute when a topic receives data:DEFINE ACTION MessageProcessor
ON TOPIC "sensors/temperature" DO
PUBLISH TOPIC "processed/temp" WITH PAYLOAD
+ (single level), # (multi-level) No trigger - called manually or by other actions:DEFINE ACTION UtilityFunction
DO
KEEP TOPIC "cache/data" WITH (GET TOPIC "source/data")
$SYS/Coreflux/Command with payload -runAction ActionName Compatible Keywords
Keywords that can be used within action logic:
Variable Operations
| Keyword | Description |
|---|
SET | Create or assign a variable |
GET TOPIC | Retrieve data from a topic |
GET JSON | Extract fields from JSON payloads |
// For topic "sensors/temp001/data": POSITION 1="sensors", POSITION 2="temp001", POSITION 3="data"
SET "sensor_id" WITH TOPIC POSITION 2
SET "temperature" WITH (GET TOPIC "sensors/temp" AS DOUBLE)
SET "humidity" WITH (GET JSON "humidity" IN PAYLOAD AS DOUBLE)
Topic Operations
| Keyword | Description |
|---|
PUBLISH TOPIC | Broadcast data to all subscribers |
KEEP TOPIC | Store data internally (not broadcast) |
PUBLISH TOPIC "output/data" WITH {temperature}
PUBLISH TOPIC "devices/" + {device_id} + "/status" WITH "online"
KEEP TOPIC "cache/last_reading" WITH PAYLOAD
Control Flow
| Keyword | Description |
|---|
IF ... THEN ... ELSE | Conditional execution |
IF {temperature} > 80 THEN
PUBLISH TOPIC "alerts/high_temp" WITH {temperature}
ELSE
PUBLISH TOPIC "status/normal" WITH "OK"
Entities
| Entity | Description |
|---|
PAYLOAD | The data that triggered the action |
TOPIC POSITION n | Extract segment from topic path |
TIMESTAMP | Generate timestamps (UTC, UNIX) |
EMPTY | Check if a topic has no data |
Python Integration
| Keyword | Description |
|---|
CALL PYTHON | Execute Python functions |
Extend LoT with Python: Use CALL PYTHON to execute complex calculations, data validation, or integrate external libraries. See the Python Integration guide for complete syntax and examples.
Type Casting
Use AS to cast values when performing comparisons or calculations:
GET TOPIC "sensors/value" AS DOUBLE
GET TOPIC "config/enabled" AS BOOL
GET TOPIC "settings/count" AS INT
GET JSON "temperature" IN PAYLOAD AS DOUBLE
STRING, INT, DOUBLE, BOOL, TIMESTAMP
Complete Example
Putting It All Together: This example demonstrates topic extraction, JSON parsing, conditional logic, and publishing - the core patterns you’ll use in most actions.
DEFINE ACTION SensorDataProcessor
ON TOPIC "sensors/+/raw" DO
// Extract sensor ID from topic (position 2 = the wildcard)
// Topic: sensors/temp001/raw → POSITION 1="sensors", POSITION 2="temp001", POSITION 3="raw"
SET "sensor_id" WITH TOPIC POSITION 2
// Get the temperature value
SET "temp_value" WITH (GET JSON "temperature" IN PAYLOAD AS DOUBLE)
// Check thresholds
IF {temp_value} > 80 THEN
PUBLISH TOPIC "alerts/high_temp/" + {sensor_id} WITH PAYLOAD
ELSE
PUBLISH TOPIC "sensors/processed/" + {sensor_id} WITH PAYLOAD
// Always update the last reading timestamp
PUBLISH TOPIC "sensors/" + {sensor_id} + "/last_update" WITH TIMESTAMP "UTC"
Next Steps
