...

MQTT Transmission provides a configuration section to the Ignition Gateway.  These can be seen in the Configure section of the Ignition Gateway web UI. There are two configuration pages "History" and "Settings".                                                                  

Settings

Once in the "Settings" configuration section there are four tabs: General, Servers, Sets, and Transmitters.  Each of these tabs is described in detail in the following sections.  

General

The General Settings tab contains advanced configuration options for the default MQTT Server settings created in the Servers tab.  These are described below.

• Enabled
  • Whether or not to enable or disable MQTT Transmission from connecting to the configured MQTT Servers.
    
• Primary Host ID
  • The primary host ID to use for 'state' notifications.  These notifications are used to notify MQTT Transmission if the primary backend application loses connection with the MQTT Server, meaning it has gone 'offline'.  If MQTT Transmission is notified that the primary backend application has gone 'offline', it will close it's client connection with the MQTT server and walk to the next MQTT server defined in the set.  If the primary host ID is not set, MQTT Transmission will not subscribe on the notification topics and not receive any 'state' notifications.

Servers

The first tab is a list of MQTT Servers that MQTT Transmission should connect to.  By default, MQTT Transmission is configured to connect to a local MQTT Distributor based MQTT Server.  It is set up to connect to localhost, port 1883, using the default username/password pair of admin/changeme.  Out of the box MQTT Transmission will work with MQTT Distributor and its default configuration.

...

Clicking on the 'Create new MQTT Server...' link will bring up the following form to add a new Server.

Sets

The Sets tab contains a list of server sets.  Each set represents a logical grouping of MQTT servers.  When a set is referenced by a Transmitter configuration a single connection to one of the servers in the set will be maintained. The other servers will act as failover in the case that a connection with the first is lost.  Server sets are disjoint, meaning that a single MQTT server cannot be in more than one set.

...

• Name
  • This is the friendly name of the set used to easily identify it.
• Description
  
  • This is a friendly description of the set.

Transmitters

Transmitters are the agents within MQTT Transmission that monitor tags, convert them to Sparkplug Messages, and publish them to an MQTT Server. Each transmitter is configured with a server Set and will attempt to maintain an MQTT client connection with one server in that Set at all times.

There are two types of Transmitters: Default and Custom.  These types are explained in more detail below.

Default Transmitter

MQTT Transmission provides a single Default Transmitter. The Tags that this Transmitter monitors must be placed in the "Edge Nodes" folder within the configured Tag Provider.  Their Tag paths must conform to the strict structure of:

...

• Tag Provider Name
  
  • The name of the tag provider that Transmission will monitor.  By default this is the Ignition 'default' provider.
• Tag Pacing Period
  
  • The buffer period for outgoing Transmission messages in milliseconds.  The default is 1000ms.  This means when a tag change event is detected 1000ms will elapse before an MQTT message is sent.  This allows additional tag change events to be buffered and put into the message and in turn reduce the number of generated MQTT messages.
• Set
  • The Set that the default MQTT Transmission client will connect to.
• History Store
  • The MQTT Transmission History Store to use with the Default Transmitter.
• Aliased Tags
  • Whether to use aliases for tag names when published data messages as tag values change.  This is used to optimize payload size when publishing data.
• Compression
  • The algorithm to use to compress payloads before they are published to the MQTT Server.  If 'NONE' is selected then compression is disabled.
• Block Commands
  
  • Whether to block commands and tag writes received as messages from the MQTT server.
• Convert UDTs
  • Whether to convert UDT members to normal Tags before publishing.  If enabled the Tags representing the UDT member will retain their member path prefixed by the UDT Instance name.

Custom Transmitters

Custom Transmitters behave in much the same way as the Default Transmitter.  However, unlike the Default Transmitter, Custom Transmitters are not bound to a specific "Edge Nodes" folder and do not have any required folder path structure.  The Group ID, Edge Node ID and Device ID are explicitly defined in a Custom Transmitter configuration instead of inferred from the tag path, as in the Default Transmitter.  This allows Custom Transmitters to point at any folder in any provider and monitor the contained tags and/or tag folders.

...

Clicking on the 'Create new Custom Settings..' link will bring up the following form to add a new Server.

History

The "History" page allows for the configuration of MQTT Transmission History Stores.  In the event that a Transmitter loses it's connection with the MQTT Server and is unable to reconnect, a History Store (if enabled) will store all messages corresponding to change events on the monitored tags.  Once a connection with an MQTT server is reestablished the History Store will publish the stored messages with a flag set to indicate that the messages are "historical" to prevent confusion with live data values.

...