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EMQ X Rule Engine

This is the design guide of message routing rule engine for the EMQ X Broker.

Concept

A rule is:

when
    Match <conditions> | <predicates>
then
    Select <data> and Take <action>;

or:

rule "Rule Name"
  when
    rule match
  select
    para1 = val1
    para2 = val2
  then
    action(#{para2 => val1, #para2 => val2})

Architecture

          |-----------------|
   P ---->| Message Routing |----> S
          |-----------------|
               |     /|\
              \|/     |
          |-----------------|
          |   Rule Engine   |
          |-----------------|
               |      |
        Backends Services Bridges

Design

Event | Message -> Rules -> Actions -> Resources

   P -> |--------------------|    |---------------------------------------|
        | Messages (Routing) | -> | Rules (Select Data, Match Conditions) |
   S <- |--------------------|    |---------------------------------------|
          |---------|    |-----------|    |-------------------------------|
        ->| Actions | -> | Resources | -> | (Backends, Bridges, WebHooks) |
          |---------|    |-----------|    |-------------------------------|

Rule

A rule consists of a SELECT statement, a topic filter, and a rule action

Rules consist of the following:

Id
Name
Topic
Description
Action
Enabled

The operations on a rule:

Create
Enable
Disable
Delete

Action

Actions consist of the following:

Id
Name
For
App
Module
Func
Args
Descr

Define a rule action in ADT:

action :: Application -> Resource -> Params -> IO ()

A rule action:

Module:function(Args)

Resource

Resource Name

backend:mysql:localhost:port:db
backend:redis:localhost:
webhook:url
bridge:kafka:
bridge:rabbit:localhost

Resource Properties

Name
Descr or Description
Config #{}
Instances
State: Running | Stopped

Resource Management

Create Resource
List Resources
Lookup Resource
Delete Resource
Test Resource

Resource State (Lifecircle)

Create Resource and Validate a Resource
Start/Connect Resource
Bind resource name to instance
Stop/Disconnect Resource
Unbind resource name with instance
Is Resource Alive?

Resource Type

The properties and behaviors of resources is defined by resource types. A resoure type is provided(contributed) by a plugin.

Resource Type Provider

Provider of resource type is a EMQ X Plugin.

Resource Manager

              Supervisor
                   |
                  \|/
Action ----> Proxy(Batch|Write) ----> Connection -----> ExternalResource
  |                                      /|\
  |------------------Fetch----------------|

REST API

Rules API Actions API Resources API

CLI

rules list
rules show <RuleId>

rule-actions list
rule-actions show <ActionId>

resources list
resources show <ResourceId>

resource_templates list
resource_templates show <ResourceType>

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