EMQ <-> APInf architecture

This document describes architecture and the way how EMQ is being integrated to work with APInf.

Components

APInf - App

API Management Platform

API-Umbrella - Proxy

API Management Proxy

EMQ - Proxy

Erlang MQTT Broker. Uses emq-auth-pgsql plugin for Authentication and ACL with PostgreSQL DB.

EMQ-REST-API - REST APi

SailsJS REST API server, is a middleware that can handle map and route data from EMQ's data store which is PostgreSQL. It was created due to lack of REST API on EMQ side. Uses sails-postgresql adapter to communicate with PostgreSQL DB.

Schemas

DB schemas in EMQ-REST0-API pretty much replicate initial schemas provided in emq-auth-pgsql with certain additions.

emq-user

module.exports = {
  attributes: {
    username: {
      type: 'string',
      unique: true,
    },
    password: {
      type: 'string',
    },
    is_superuser: {
      type: 'boolean',
      defaultsTo: false
    },
    salt: {
      type: 'string'
    }
  }
}

emq-acl

module.exports = {
  attributes: {
    id: {
      type: 'string',
    },
    allow: {
      type: 'integer',
    },
    ipaddr: {
      type: 'string',
      size: 60
    },
    username: {
      type: 'string',
      size: 100
    },
    clientid: {
      type: 'string',
      size: 1024
    },
    access: {
      type: 'integer'
    },
    topic: {
      type: 'string',
      size: 100
    },
    proxyId: {
      type: 'string',
      size: 100
    }
  }
};

PostgreSQL - Database

Database for storing ACL and Auth data.

Overview

   +---------+
   |         |
   |  APInf  |<----------------------------------------+
   |         |                                         |
   +---------+                                         |
       ^                                               |
       |                                               |
       |                                               |
       |                                               |
       |        +--------------+                       |
       +------->| API Umbrella |                       |
                +--------------+                       |
                        ^                              |
---+        HTTP        |                              |
 A |--------------------+                              |
 P |                                                   |
 I |                                                   |
 s |--------------------+                              |
---+        MQTT        |                              |
                        V                              V
                +--------------+                +--------------+
                | EMQ (EMQTTD) |                | EMQ-REST-API |
                +--------------+                +--------------+
                       ^                               ^
                       |                               |
                       |       +---------------+       |
                       +------>| PostgreSQL DB |<------+
                               +---------------+

Data flow between EMQ and APInf

APInf stores ACL data (including API proxy backend) in Meteor MongoDB collection proxyBackends when ACL rules added for the first time. APInf uses a package for dynamic HTML form construction called aldeed:autoform. It takes care of INSERT, UPDATE and DELETE of items in Meteor collection.

aldeed:autoform has a number of pre-defined hooks which are called when certain event occurs. Those hooks which are used by proxyBackendsForm collection are: before insert, before update, onSuccess and onError.

before insert

If EMQ is selected as a proxy backends for an API, we iterate though all ACL rules to be added and attach unique identifier (id) & proxy id related to it (proxyId).

before update

Almost the similar pattern as in before insert hook, but additional check is needed before attaching id and proxyId in order to make sure either new ACL rule was added in addition to existing ones (in that case attaching id and proxyId is needed) or only edit already exiting rules.

onSuccess

When before insert and before update passed, we can push ACL rules to EMQ-REST-API via POST request. emqAclRequest meteor method is called which handles EMQ-APInf talking.

Meteor.call('emqAclRequest', method, proxyId, rules)

• method - String - HTTP method, either POST or PUT
• proxyId - String - related API proxy backend - String
• rules - Array - list of ACL rules to update or insert

onError

Throws an error when any submit operation fails.