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Rules

생성일
2021/02/24 02:29
Rules are defined by JSON, below is an example.
The following 3 parameters are required for creating a rule.

Parameters

id

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

sql

The sql query to run for the rule.

options

The current options includes:
Search
Option name
Type & Default Value
Description
isEventTime
Open
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
Open
int64:0
When working with event-time windowing, it can happen that elements arrive late. LateTolerance can specifiy by how much time(unit is millisecond) elements can be late before they are dropped. By default, the value is 0 wich means late elements are dropped.
concurrency
Open
int: 1
A rule is processed by several phases of plans according to the sql statement. This option wil specify how many instances will be run for each plan. If the value is bigger than 1, the order of the messages may no be retained.
bufferLength
Open
int: 1024
Specify how many messages can be buffered in memor for each plan. If the buffered messages exceed the limit, the plan will block message receiving until the buffered messages have been sent out so that the buffered size is less than the limit. A bigger value will accommodate more throughput but will also take up more memory footprint.
sendMetaToSink
Open
bool: false
Specify whether the meta data of an event will be sent to the sink. If true, the sink can get meta data information.
qos
Open
int: 0
Specify the qos of the stream. The options are 0: At most once; 1: At least once and 2: Exactly once. If qos is bigger than 0, the checkpoint mechanism will be activated to save states periodically so that the rule can be resumed from errors.
checkpointInterval
Open
int: 300000
Specify the time interval in milliseconds to trigger a checkpoint. This is only effective when qos is bigger than 0.
COUNT7
For detail about qos and checkpointInterval, please check state and fault tolerance.
The rule options can be defined globally in etc/kuiper.yaml under the rules section. The options defined in the rule json will override the global setting.

Sources

•
Kuiper provides embedded following 3 sources,
◦
MQTT source, see MQTT source stream for more detailed info.
◦
EdgeX source by default is shipped in docker images, but NOT included in single download binary files, you use make pkg_with_edgex command to build a binary package that supports EdgeX source. Please see EdgeX source stream for more datailed info.
◦
HTTP pull source, regularly pull the contents at user's specified interval time, see here for more detailed info.
•
See SQL for more info of Kuiper SQL.
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Sources can be customized, see extension for more detailed info.

sinks/actions

Currently, below kinds of sinks/actions are supported:
•
log: Send the result to log file.
•
mqtt: Send the result to an MQTT broker.
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edgex: Send the result to EdgeX message bus.
•
rest: Send the result to a Rest HTTP server.
•
nop: Send the result to a nop operation.
Each action can define its own properties. There are several common properties:
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Property name
Type & Default Value
Description
비고
concurrency *
Open
int: 1
Specify how many instances of the sink will be run. If the value is bigger than 1, the order of the messages may not be retained.
bufferLength
Open
int: 1024
Specify how many messages can be buffered in memory. If the buffered messages exceed the limit, the sink will block message receiving until the buffered messages have been sent out so that the buffered size is less than the limit.
runAsync *
Open
bool: false
Wherther the sink will run asynchronously for better performance. If it is true, the sink result order is not promised.
retryInterval *
Open
int: 1000
Specify how many milliseconds will the sink retry to send data out if the previous send failed. If the specified value <= 0, then it will not retry.
retryCount *
Open
int: 3
Specify how many will the sink retry to send data out if the previous send failed. If the specified value <= 0, then it will not retry.
cacheLength
Open
int: 1024
Specify how many messages can be cached. The cached messages will be resent to external system until the data sent out succesfully. The cached message will be sent in order except in runAsync or concurrent mode. The cached message will be saved to disk in fixed intervals.
cacheSaveInterval
Open
int:1000
Specify the interval to save cached message to the disk. Notice that, if the rule is closed in plan, all the cached messages will be saved at close. A larger value can reduce the saving overhead but may lose more cache messages when the system is interrupted in error.
omitIfEmpty *
Open
bool: false
If the configuration item is set to true, when SELECT result is empty, then the result will not feed to sink operator.
경고 메시지에 사용될 수 있을듯
sendSingle
Open
??
The output messages are received as an array. This is indicate whether to send the results one by one. If false, the output message will be {"result":"${the string of received message}"}. For example, {"result":"[{\"count\":30},"\"count\":20}]"}. Otherwise, the result message will be sent one by one with the actual field name. For the same example as above, it will send {"count":30}, then send {"count":20} to the RESTful endpoint. Defualt to false.
dataTemplate
Open
??
The golang template (opens new window) format string to specify the output data format. The input of the template is the sink message which is always an array of map. If no data template is specified, the raw input will be the data.
COUNT10

Data Template

EMQ Docs
Rules are defined by JSON, below is an example. The following 3 parameters are required for creating a rule. The identification of the rule. The rule name cannot be duplicated in the same Kuiper instance. The sql query to run for the rule.
https://docs.emqx.io/en/kuiper/latest/rules/overview.html#data-template

Functions supported in template

EMQ Docs
Rules are defined by JSON, below is an example. The following 3 parameters are required for creating a rule. The identification of the rule. The rule name cannot be duplicated in the same Kuiper instance. The sql query to run for the rule.
https://docs.emqx.io/en/kuiper/latest/rules/overview.html#functions-supported-in-template
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