ekuiper-new/docs/rules/overview.md

Rules

Rules are defined by JSON, below is an example.

{
  "id": "rule1",
  "sql": "SELECT demo.temperature, demo1.temp FROM demo left join demo1 on demo.timestamp = demo1.timestamp where demo.temperature > demo1.temp GROUP BY demo.temperature, HOPPINGWINDOW(ss, 20, 10)",
  "actions": [
    {
      "log": {}
    },
    {
      "mqtt": {
        "server": "tcp://47.52.67.87:1883",
        "topic": "demoSink"
      }
    }
  ]
}

The following 3 parameters are required for creating a rule.

Parameters

Parameter name	Optional	Description
id	false	The id of the rule
sql	false	The sql query to run for the rule
actions	false	An array of sink actions
options	true	A map of options

id

The identification of the rule. The rule name cannot be duplicated in the same XStream instance.

sql

The sql query to run for the rule.

• XStream provides embeded support MQTT source, see MQTT source stream for more detailed info.
• See SQL for more info of XStream SQL.
• Sources can be customized, see extension for more detailed info.

actions

Currently, 2 kinds of actions are supported: log and mqtt. Each action can define its own properties.

Actions could be customized to support different kinds of outputs, see extension for more detailed info.

options

The current options includes:

Option name	Type & Default Value	Description
isEventTime	boolean: false	Whether to use event time or processing time as the timestamp for an event. If event time is used, the timestamp will be extracted from the payload. The timestamp filed must be specified by the stream definition.
lateTolerance	int64:0	When working with event-time windowing, it can happen that elements arrive late. LateTolerance can specify by how much time(unit is millisecond) elements can be late before they are dropped. By default, the value is 0 which means late elements are dropped.