EdgeX rule engine tutorial

    • Source: The data source of streaming data, such as data from MQTT broker. In EdgeX scenario, the data source is EdgeX message bus, which could be ZeroMQ or MQTT broker.
    • SQL: SQL is where you specify the business logic of streaming data processing. eKuiper provides SQL-like statements to allow you to extract, filter & transform data.
    • Sink: Sink is used for sending analysis result to a specified target. For example, send analysis result to another MQTT broker, or an HTTP rest address.

    Following three steps are required for using eKuiper.

    • Create a stream, where you specify the data source.
    • Write a rule.
      • Write a SQL for data analysis
      • Specify a sink target for saving analysis result
    • Deploy and run rule.

    The tutorial demonstrates how to use eKuiper to process the data from EdgeX message bus.

    EdgeX uses message bus to exchange information between different micro services. It contains the abstract message bus interface and implementations for ZeroMQ & MQTT. The integration work for eKuiper & EdgeX includes following 3 parts.

    • An EdgeX message bus source is extended to support consuming data from EdgeX message bus.

    • To analyze the data, eKuiper need to know data types that passed through it. Generally, user would be better to specify data schema for analysis data when a stream is created. Such as in below, a demo stream has a field named temperature field. It is very similar to create table schema in relational database system. After creating the stream definition, eKuiper can perform type checking during compilation or runtime, and invalid SQLs or data will be reported to user.

      However, data type definitions are already specified in the EdgeX events/readings and to improve the using experience, user are NOT necessary to specify data types when creating stream. For any data sending from message bus, it will be converted into .

    • An EdgeX message bus sink is extended to support send analysis result back to EdgeX Message Bus. User can also choose to send analysis result to RestAPI, eKuiper already supported it.

    EdgeX Foundry installation - 图2

    Since eKuiper v1.2.1, we will only support EdgeX v2(Ireland and later). There are several breaking changes to migrate to the new combintion.

    1. EdgeX source does not rely on Core contract Service anymore. Users can remove the serviceServer property in the edgex.yaml configuration.
    2. Breaking changes in metadata. For example, metadata Device is now renamed to DeviceName.

    In out tutorial, we will use which is shipped in official EdgeX release, and run rules against the data generated by this sample device service.

    Go to EdgeX-compose project, and download related Docker compose file for Ireland release, then bring up EdgeX Docker instances. 

    1. $ docker-compose -f ./docker-compose-no-secty.yml up -d --build

    After all of the Docker instances are started, you can use docker ps command to verify all services are running correctly.

    1. $ docker ps
    2. CONTAINER ID   IMAGE                                                           COMMAND                  CREATED
    3.  STATUS          PORTS                                                                                  NAMES
    4. c7cb2c07dc4f   nexus3.edgexfoundry.org:10004/device-virtual:latest             "/device-virtual --c…"   13 minutes ago   Up 13 minutes   127.0.0.1:59900->59900/tcp                                                             edgex-device-virtual
    5. d7089087c301   nexus3.edgexfoundry.org:10004/device-rest:latest                "/device-rest --cp=c…"   13 minutes ago   Up 13 minutes   127.0.0.1:59986->59986/tcp                                                             edgex-device-rest
    6. 32cd339157e2   nexus3.edgexfoundry.org:10004/app-service-configurable:latest   "/app-service-config…"   13 minutes ago   Up 13 minutes   48095/tcp, 127.0.0.1:59701->59701/tcp                                                  edgex-app-rules-engine
    7. 62c2174d4b45   nexus3.edgexfoundry.org:10004/sys-mgmt-agent:latest             "/sys-mgmt-agent -cp…"   13 minutes ago   Up 13 minutes   127.0.0.1:58890->58890/tcp                                                             edgex-sys-mgmt-agent
    8. 5b9f9cfb4307   nexus3.edgexfoundry.org:10004/core-data:latest                  "/core-data -cp=cons…"   13 minutes ago   Up 13 minutes   127.0.0.1:5563->5563/tcp, 127.0.0.1:59880->59880/tcp                                   edgex-core-data
    9. b455b06e2e7c   nexus3.edgexfoundry.org:10004/core-command:latest               "/core-command -cp=c…"   13 minutes ago   Up 13 minutes   127.0.0.1:59882->59882/tcp                                                             edgex-core-command
    10. 6de994ce09d6   nexus3.edgexfoundry.org:10004/core-metadata:latest              "/core-metadata -cp=…"   13 minutes ago   Up 13 minutes   127.0.0.1:59881->59881/tcp                                                             edgex-core-metadata
    11. 1b62bf57dd34   nexus3.edgexfoundry.org:10004/support-notifications:latest      "/support-notificati…"   13 minutes ago   Up 13 minutes   127.0.0.1:59860->59860/tcp                                                             edgex-support-notifications
    12. 38776815a286   nexus3.edgexfoundry.org:10004/support-scheduler:latest          "/support-scheduler …"   13 minutes ago   Up 13 minutes   127.0.0.1:59861->59861/tcp                                                             edgex-support-scheduler
    13. c78419bc5096   consul:1.9.5                                                    "docker-entrypoint.s…"   13 minutes ago   Up 13 minutes   8300-8302/tcp, 8301-8302/udp, 8600/tcp, 8600/udp, 127.0.0.1:8500->8500/tcp             edgex-core-consul
    14. d4b236a7b561   redis:6.2.4-alpine                                              "docker-entrypoint.s…"   13 minutes ago   Up 13 minutes   127.0.0.1:6379->6379/tcp                                                               edgex-redis

    Connection reuse

    • redis messageBus: this is especially useful when EdgeX use secure mode, in which case the client credentials will be injected into that share place automatically when services bootstrap. In order to use this feature, users need do some modifications on the target docker-compose file’s rulesengine service part add these in environment part and make sure the image is 1.4.0 or later. 

      1. environment:
      2.     CONNECTION__EDGEX__REDISMSGBUS__PORT: 6379
      3.     CONNECTION__EDGEX__REDISMSGBUS__PROTOCOL: redis
      4.     CONNECTION__EDGEX__REDISMSGBUS__SERVER: edgex-redis
      5.     CONNECTION__EDGEX__REDISMSGBUS__TYPE: redis
      6.     EDGEX__DEFAULT__CONNECTIONSELECTOR: edgex.redisMsgBus

    • mqtt/zeromq messageBus: adjust the parameters accordingly and specify the client credentials if have. There is a mqtt message bus example, make sure the connection info exists in etc/connections/connection.yaml, for more info please check this. 

      1. environment:
      2.     CONNECTION__EDGEX__MQTTMSGBUS__PORT: 1883
      3.     CONNECTION__EDGEX__MQTTMSGBUS__PROTOCOL: tcp
      5.     CONNECTION__EDGEX__MQTTMSGBUS__TYPE: mqtt
      6.     CONNECTION__EDGEX__MQTTMSGBUS__OPTIONAL__USERNAME: username
      7.     CONNECTION__EDGEX__MQTTMSGBUS__OPTIONAL__PASSWORD: password
      8.     EDGEX__DEFAULT__CONNECTIONSELECTOR: edgex.mqttMsgBus

      After these modifications and eKuiper starts up, please read to learn how to refer to the connection info

    Use Redis as KV storage

    Since 1.4.0, eKuiper supports redis to store the KV metadata, user can make some modifications on the target docker-compose file’s rulesengine service part to apply this change. Users can add these in environment part and make sure the image is 1.4.0 or later.

    Note: This feature only works when redis in no-secty mode

    Run with native

    For performance reason, reader probably wants to run eKuiper with native approach. But you may find that EdgeX cannot be used with the downloaded eKuiper binary packages. It’s because that EdgeX message bus relies on zeromq library. If zeromq library cannot be found in the library search path, it cannot be started. So it will have those eKuiper users who do not want to use EdgeX install the zeromq library as well. For this reason, the default downloaded eKuiper package does NOT have embedded support for EdgeX. If reader wants to support EdgeX in native packages, you can either make a native package by running command make pkg_with_edgex, or just copy the binary package from docker container.

    Create a stream

    There are two approaches to manage stream, you can use your preferred approach.

    Option 1: Use Rest API

    Notice: Rest API of eKuiper in EdgeX uses 59720 instead of default 9081. So please change 9081 to 59720 in all of documents when you use EdgeX eKuiper Rest API.

    The next step is to create a stream that can consume data from EdgeX message bus. Please change $kuiper_docker to eKuiper docker instance IP address.

    1. curl -X POST \
    2.   http://$kuiper_docker:59720/streams \
    3.   -H 'Content-Type: application/json' \
    4.   -d '{
    5.   "sql": "create stream demo() WITH (FORMAT=\"JSON\", TYPE=\"edgex\")"
    6. }'

    For other Rest APIs, please refer to .

    Option 2: Use eKuiper CLI

    Run following command to enter the running eKuiper docker instance.

    1. docker exec -it edgex-kuiper /bin/sh

    Use following command to create a stream named demo.

    1. bin/kuiper create stream demo'() WITH (FORMAT="JSON", TYPE="edgex")'

    For other command line tools, please refer to .

    1. #Global Edgex configurations
    2. default:
    3.   protocol: tcp
    4.   server: localhost
    5.   port: 5566
    6.   topic: events
    7. .....

    For more detailed information of configuration file, please refer to this doc.

    Let’s create a rule that send result data to an MQTT broker, for detailed information of MQTT sink, please refer to . Similar to create a stream, you can also choose REST or CLI to manage rules.

    So the below rule will get all of values from event topic. The sink result will

    • Published to topic result of public MQTT broker broker.emqx.io.
    • Print to log file.

    Option 1: Use Rest API

    Option 2: Use eKuiper CLI

    You can create a rule file with any text editor, and copy following contents into it. Let’s say the file name is rule.txt. 

    1. {
    2.   "sql": "SELECT * from demo",
    3.   "actions": [
    4.     {
    6.         "server": "tcp://broker.emqx.io:1883",
    7.         "topic": "result",
    8.         "clientId": "demo_001"
    9.       }
    10.     {
    11.       "log":{}
    12.     }
    13.   ]
    14. }

    In the running eKuiper instance, and execute following command.

    1. $ bin/kuiper create rule rule1 -f rule.txt
    2. Connecting to 127.0.0.1:20498...
    3. Creating a new rule from file rule.txt.
    4. Rule rule1 was created successfully, please use 'cli getstatus rule rule1' command to get rule status.

    If you want to send analysis result to another sink, please refer to other sinks that supported in eKuiper.

    Now you can also take a look at the log file under log/stream.log, or through command docker logs edgex-kuiper to see detailed info of rule.

    1. time="2021-07-08 01:03:08" level=info msg="Serving kuiper (version - 1.2.1) on port 20498, and restful api on http://0.0.0.0:59720. \n" file="server/server.go:144"
    2. Serving kuiper (version - 1.2.1) on port 20498, and restful api on http://0.0.0.0:59720. 
    3. time="2021-07-08 01:08:14" level=info msg="Successfully subscribed to edgex messagebus topic rules-events." file="extensions/edgex_source.go:111" rule=rule1
    4. time="2021-07-08 01:08:14" level=info msg="The connection to server tcp://broker.emqx.io:1883 was established successfully" file="sinks/mqtt_sink.go:182" rule=rule1
    5. time="2021-07-08 01:08:20" level=info msg="sink result for rule rule1: [{\"Float32\":-2.4369560555943686e+38}]" file="sinks/log_sink.go:16" rule=rule1
    6. time="2021-07-08 01:08:20" level=info msg="sink result for rule rule1: [{\"Float64\":-1.488582e+308}]" file="sinks/log_sink.go:16" rule=rule1
    7. time="2021-07-08 01:08:20" level=info msg="sink result for rule rule1: [{\"Uint64\":9544048735510870974}]" file="sinks/log_sink.go:16" rule=rule1
    8. time="2021-07-08 01:08:20" level=info msg="sink result for rule rule1: [{\"Uint16\":33714}]" file="sinks/log_sink.go:16" rule=rule1
    9. time="2021-07-08 01:08:20" level=info msg="sink result for rule rule1: [{\"Uint8\":57}]" file="sinks/log_sink.go:16" rule=rule1
    10. time="2021-07-08 01:08:20" level=info msg="sink result for rule rule1: [{\"Uint32\":3860684797}]" file="sinks/log_sink.go:16" rule=rule1
    11. ...

    Monitor analysis result

    Since all of the analysis result are published to tcp://broker.emqx.io:1883, so you can just use below mosquitto_sub command to monitor the result. You can also use other MQTT client tools.

    1. $ mosquitto_sub -h broker.emqx.io -t result
    2. [{"Bool":false}]
    3. [{"Int64":228212448717749920}]
    4. [{"Int8":-70}]
    5. [{"Int16":16748}]
    6. [{"Int32":728167766}]
    7. [{"Uint16":32311}]
    8. [{"Uint8":133}]
    9. [{"Uint64":16707883778643919729}]
    10. [{"Uint32":1453300043}]
    11. [{"Bool":false}]
    12. [{"Float32":1.3364580409833176e+37}]
    13. [{"Float64":8.638344e+306}]
    14. [{"Int64":-2517790659681968229}]
    15. [{"Int16":-31683}]
    16. [{"Int8":96}]
    17. [{"Int32":-1245869667}]

    You can also type below command to look at the rule execution status. The corresponding REST API is also available for getting rule status, please check .

    In this tutorial, we introduce a very simple use of EdgeX eKuiper rule engine. If having any issues regarding to use of eKuiper rule engine, you can open issues in EdgeX or eKuiper Github respository.

    More Excecise

    Current rule does not filter any data that are sent to eKuiper, so how to filter data? Please and change the SQL in previous rule accordingly. After update the rule file, and then deploy the rule again. Please monitor the result topic of MQTT broker, and please verify see if the rule works or not.

    Extended Reading

    • Starting from eKuiper 0.9.1 version, is released with a separated Docker image. You can manage the streams, rules and plugins through web page.
    • Read EdgeX source for more detailed information of configurations and data type conversion.
    • There are some other information are sent along with device service, such as event created time, event id etc. If you want to use such metadata information in your SQL statements, please refer to this doc.
    • Use Golang template to customize analaysis result in eKuiper Before the analysis result is sent to different sinks, the data template can be used to make more processing. You can refer to this doc for more scenarios of using data templates.
    • . The document describes how to use EdgeX message bus sink. If you’d like to have your analysis result be consumed by other EdgeX services, you can send analysis data with EdgeX data format through this sink, and other EdgeX services can subscribe new message bus exposed by eKuiper sink.

    • eKuiper plugin development tutorial: eKuiper plugin is based on the plugin mechanism of Golang, users can build loosely-coupled plugin applications, dynamic loading and binding when it is running. You can refer to this article if you’re interested in eKuiper plugin development.

      If you want to explore more features of eKuiper, please refer to below resources.