Difference between revisions of "SensiNact/Bridge MQTT"

Revision as of 12:54, 15 March 2018

Description

This bridge allows sensinact to subscribe to a topic, and materialize a sensinact device based on this topic messages. The devices will be display just after its configuration (once the .cfg file is deployed, check below) but the value will be update upon the message arrivals.

Sensinact version

This bridge is available in version 1.5-SNAPSHOT

Requirements

• mqtt-sb bridge activated (via sensinact -c)
• A mosquitto server running

Capability

• Create a sensinact provider from a message receveid from a MQTT broker topic.
• Instantiate multiple providers, as many as there are configuration files respecting the pattern "mosquitto-*.cfg", the content format example can be seen below
• Pre-process the message content from the MQTT topic, check the section about processors

How to instantiate

Declarative file

The declarative file allow you to create at runtime a device mapped to a mosquitto topic. According to the topic information added in the file (that will be explained below) you will have a device connected directly to your MQTT broker topic.

In order to create the instance of your device inside sensinact platform you have to create a file that respect the certain pattern mqtt-*.cfg where * can be any string that identify your rule, this will be assigned as your OSGi service PID (for more details check felix Configuration Manager). This configuration file MUST be deployed in the directory $SENSINACTHOME/cfgs_.

The fields in this file are define as in a regular property file, that by definition contains a list of key and values pairs separated by =. The allowed fields are specified in the list in BNF extended format below .

id=ALPHA; mandatory
host=ALPHA;default=127.0.0.1
port=ALPHA;default=1883
protocol=["ssl"|"tcp"];default=tcp
topic=ALPHA; mandatory
topic.type=["mqtt"|"smarttopic"];default=mqtt
processor=([PROCESSOR["$"[PROCESSOR_EXPRESSION]][","])*
location.latitude=DIGIT
location.longitude=DIGIT
auth.username=ALPHA
auth.password=ALPHA
discovery.firstMessage=["false"|"true"];default=false

Some processors do not require a PROCESSOR_EXPRESSION, refer to the processor specific topic to get more details

One example of file (named mqtt-1.cfg) content is shown below:

id=counter
topic=/camera

SmartTopic

Using regular topic you can only attach one device to one topic and you cannot define the service and resource name in which this information will be attached. For this reason the smarttopic was created, its is an language inside a regular MQTT topic that allows the user to specify which portion of the topic will be considered as provider, which as service and so on.

In smarttopic only the {provider}tag is mandatory, case service or resource are not specified the values info and value will be adopted. You can also indicate the value defined for your sensinact devices in the topic using the tag {value}, case this tag is not present the MQTT message will be used as the value of your device.

The supported tags for a smarttopic are:

{provider}
{service}
{resource}
{value}

One example of smarttopic declaration is:

id=thingsnetworkdevicediscovery
topic.type=smarttopic
topic=+/devices/{provider}/up
host=eu.thethings.network
auth.username=cea-wise-iot
auth.password=ttn-account-xxxIGBKAJtVg_Q1LyMOOqNQPjxxxx4

You can use the same mechanism of processor by declaring processor= property in this very same file.

MQTTRuntime service

Allow during the gateway runtime to publish the configuration necessary to create a device attached to a topic by passing the file configuration deployment.

TBD

Annotation

TBD

Processors

Processors are functions that can be chained one after another, each processor receive an input and produces an output; and an output of a processor can serve as an input of another; this chaining can be performed as many time as you need.

Notice that the execution of each processor is performed according to the order in which it appears in the declaration.

json

This file receive as input a content in JSON format, and it can output one of the items present in any level of this JSON, and to identify which element of the JSON formmated input should be selected you use a selector. Selector is how you specify the element you want to select.

For instance assume the input ex-01 as example, you can select the the name of the library with the expression json$store.name thus the result will be mylibrary, and this can be performed in several levels.

INPUT {"store":{"name":"mylibrary","address":"rue des martyrs","bestseller":["Book1","Book2", "Book3"]}}

PROCESSOR json

PROCESSOR_EXPRESSION store.name (if you use this with configuration file you add processor=json$store.name)

OUTPUT mylibrary

array

INPUT ["one","two","three"](json array string)

PROCESSOR array

PROCESSOR_EXPRESSION 1 (the item index)

OUTPUT two

base64

INPUT c3VycHJpc2Uh(base64 encoded string)

PROCESSOR base64

PROCESSOR_EXPRESSION ` ` (empty)

OUTPUT surprise!

urlencode

INPUT http%3A%2F%2Fcea.fr%3Fname%3DFeuer%20Bach%26theme%3DPhilosophie(url encoded string)

PROCESSOR urlencode

PROCESSOR_EXPRESSION ` `(empty)

OUTPUT http://cea.fr?name=Feuer Bach&theme=Philosophie

toString

Default filter, that display the string representation of the Object used in the backend

toInteger

TBC

toFloat

TBC

plus

TBC

minus

TBC

multiply

TBC

divide

TBC

Limitations

• The topic message is considered as String value, although the SNA generic will perform automatic convertion to numeric types in SNA. Meaning that even String values can use numeric operators as more than, less then, etc. The conversion will be performed automatically in SNA