IoT Plugin Configuration

Overview

The IoT plugin is the bridge between the Alemca Agent and physical equipment—sensors, actuators, PLCs, gateways, and more.
It handles the following:

Function	Description	Opinion
Acquisition	Regular reading of field registers/frames	Run it at the cadence dictated by your business requirements; triggering “every second” never saved a project.
Automation	Execution of embedded Lua scripts	Lua is the right choice: lightweight and easy to sandbox. Avoid shell scripts in this context.
Remote control	Launch of commands pushed from the central console	Limit the number of concurrent scripts; embedded devices dislike fork bombs.
Data publishing	Push to the platform via AMQP (RabbitMQ)	Enable caching—industrial networks fail more often than we like to admit.

Typical Use Cases

1. Continuous telemetry: collect temperature, pressure, and I/O states every 30 s and feed them almost in real-time to SCADA.
2. Conditional command: trigger a relay output via Lua if the temperature > 50 °C and an operator has approved the procedure in the UI.
3. Preventive maintenance: inject a remote Lua script that measures cycle times and alerts if drift > 5 %.

Configuration Details

/etc/alemca/config.yaml

iot:
  enabled: true                     # Fully enable/disable the plugin

  lua:                              # Embedded automation
    path: "/etc/alemca/agent.lua"   # Main script
    trigger: 5                      # Execution period in seconds
    timeout: 0                      # 0 = no limit
    kill_on_trigger: false          # true = kill previous instance if it is still running

  commands:                         # Remote scripts pushed via the UI
    max_concurrent: 1               # Maximum number of concurrent remote scripts
    folder_path: "/etc/alemca/commands"

  alemca:                           # AMQP link to the central platform
    max_cache_size: 1024            # Max messages queued if the network is down
    stay_connected: false           # true = permanent AMQP socket (consumes a file descriptor)
    destinations:
      - name: "example_destination"
        exchange: "example_exchange"
        routing_key: "example_routing_key"
        queue_not_durable: false
        exchange_type: "direct"

  modules:
    modbus:
      - name: "modbus1"
        transmissionmode: "TCP"
        controller: "tcp://127.0.0.1:502"
        slaveid: 1
    ping:
      - name: "ping1"
        timeout: 10
        count: 5

Section Breakdown

• enabled – Toggles the IoT plugin on or off.

lua (legacy)

• path – Path to the locally executed Lua script.
• trigger – Interval (seconds) between two executions.
• timeout – Maximum runtime (0 = unlimited).
• kill_on_trigger – If true, interrupts the previous script when a new one starts.

lua_scripts

• name – Lua script name.
• path – Path to the script executed locally.
• trigger – Interval (seconds) between two executions.
• timeout – Maximum runtime (0 = unlimited).
• kill_on_trigger – If true, interrupts the previous script when a new one starts.

commands

• max_concurrent – Maximum number of remote Lua scripts that can run in parallel.
• folder_path – Folder where queued command scripts are stored.

alemca

• max_cache_size – Maximum local cache size before sending.
• stay_connected – If enabled, the connection stays open permanently.
• destinations – AMQP connection parameters (name, exchange, routing key, exchange type, etc.).

modules

This section configures the modules available from Lua. Settings are module-specific and are documented in each module’s guide.
See here for a list of available modules.