Collector MQTT

Updated on 19 Apr 2024
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The purpose of this article is to be a reference for the MQTT collector part of the full Data Collection Module documentation.

The MQTT collector can operate in two modes. Client mode; where it acts as a subscriber to an external MQTT broker, and broker mode; where it acts as broker which external publishers can publish to.

NOTE: Broker mode cannot be used as a general-purpose broker, it allows publishers to connect but does not allow subscriptions.

Example configuration can be found here

MQTT Collector main

The Collectors list (mandatory array of objects) contains the following fields

Function	Type	Importance	Description
CollectorName	string	mandatory	Unique name (within this configuration file) of a device to collect data from. (This is the name used in the agent configuration.) Follows the normal rules for names.
CollectorDescription	string	optional	Description of this collector. (For your use, no system function)
CollectorIPAddr	string	optional	Default IP address (or DNS name) for the device to be polled. The agent Target IP address will take precedence over this. If MQTTCollectorMode is set to broker, this is ignored.
CollectorPortno	integer >0 and <65535	optional	Default port number for the device to be polled. The agent Target Port number will take precedence over this. If neither CollectorPortno nor agent Target Port Number is specified, the appropriate port will be used, depending on the Protocol parameter value. If MQTTCollectorMode is set to broker, this is ignored.
Alias	string	optional	This is the CollectorName of another collector, from which all the parameters (except CollectorName , CollectorDescription , CollectorIPAddr and CollectorPortno ) are copied. An alias cannot refer to another alias.
Protocol	string-enum	mandatory	The protocol used to collect data. Currently only “MQTT” is available.
ConnectRetryMin	integer >0	mandatory	The minimum number of seconds before trying to re-establish a connection to the device being sampled. An exponential backoff algorithm is used to retry connection establishment, starting after ConnectRetryMin and increasing to ConnectRetryMax.
ConnectRetryMax	integer >0	mandatory	The maximum number of seconds before trying to re-establish a connection to the device being sampled.
MQTTAccess	Object	mandatory	Collection of parameters needed to collect MQTT messages.
SamplePoints	Array of objects	mandatory	List of samples to be collected, possibly aggregated and stored in the Store'n'Forward database.

MQTT Access object

The MQTTAccess objects contains the following elements:

Function	Type	Importance	Description
MQTTCollectorMode	string-enum	mandatory	The collector mode. It can be either “client” or “broker”.
MQTTBrokerConfig	object	maybe-optional	The broker mode config object containing parameters needed to configure DCM to collect as a broker by allowing external clients/publishers to publish to DCM. Becomes mandatory when “MQTTCollectorMode” is set to “broker”.
MQTTClientConfig	object	maybe-optional	The client mode config object containing parameters needed to configure DCM to collect as a client/subscriber to an external broker. Becomes mandatory when “MQTTCollectorMode” is set to “client”.

MQTTClientConfig object

The MQTTClientConfig objects contains the following elements:

Function	Type	Importance	Description
ClientProtocolVersion	string-enum	optional	The MQTT protocol version (v3.1, v3.1.1 or v5.0) to use for the client connection. The possible values are: "MQTT_V31", "MQTT_V311", "MQTT_V5".Default: MQTT_V5
ClientKeepAlive	string	optional	Keep-alive interval to use for the client connection.
ClientPasswordFile	string	optional	Password file in the format username:password. One entry per line.
ClientTLSMode	string-enum	optional	The possible values are: "TLS-DISABLED", "TLS-CERT", "TLS-PSK".
ClientSSLSecure	boolean	optional	Whether TLS certificates should be verified. Default: true.
ClientCACertificate	string	maybe-optional	Certificate of the CA who signs the broker to collect from. Required if ClientTLSMode is TLS-CERT.
ClientCertificate	string	maybe-optional	Certificate with public key to use for DCM as client. Required if ClientTLSMode is TLS-CERT
ClientPrivateKey	string	maybe-optional	Private key to use for DCM as client. Required if ClientTLSMode is TLS-CERT.
ClientPSKFile	string	maybe-optional	File with pre-shared key in the format identity:key. Required if ClientTLSMode is TLS-PSK.

MQTTBrokerConfig object

The MQTTBrokerConfig objects contains the following elements:

Function	Type	Importance	Description
BrokerIPAddr	string	mandatory	The IP address on the SiteManager to bind the broker to.
BrokerPortno	integer	mandatory	Network portnumber to use for the broker.
BrokerSourceFilteringMode	string-enum	mandatory	The possible values are: "ALLOW-ANY", "IP-WHITELIST", "MAC-WHITELIST".
BrokerSourceFilteringFile	string	maybe-optional	File with white-listed (allowed to connect) clients. Must be a list of either IPv4 or MAC addresses, one per line. Required if BrokerSourceFilteringMode is different from "ALLOW-ANY".
BrokerAuthenticationMode	string-enum	mandatory	Select the authentication mode to use for the broker connection. The possible values are: "ALLOW-ANONYMOUS", "PASSWORDFILE".
BrokerPasswordFile	string	maybe-optional	Password file credentials in the format username:password - one line per. Required if BrokerAuthenticationMode is PASSWORDFILE.
BrokerTLSMode	string-enum	mandatory	Select the security type (if any) to use for the transport layer. The possible values are: "TLS-DISABLED", "TLS-CERT", "TLS-PSK".
BrokerSSLSecure	boolean	optional	Whether TLS certificates should be verified (Default: true).
BrokerCACertificate	string	maybe-optional	Certificate of the CA who signs the clients which will be connecting to the broker. Required if BrokerTLSMode is TLS-CERT.
BrokerCertificate	string	maybe-optional	Certificate public key file. Required if BrokerTLSMode is TLS-CERT.
BrokerPrivateKey	string	maybe-optional	Private key file. Required if BrokerTLSMode is TLS-CERT.
BrokerPSKHint	string	maybe-optional	String to send to clients to aid in authentication. Required if BrokerTLSMode is TLS-PSK.
BrokerPSKFile	string	maybe-optional	File with pre-shared keys in the format identity:key - one identity per line. Required if BrokerTLSMode is TLS-PSK.

Samplepoint object

The SamplePoints objects contains the following elements:

Function	Type	Importance	Description
SampleName	string	mandatory	Name of this sampled value (sometimes called a tagname). Follows the normal rules for names.
SampleDescription	string	optional	A text description of this sample value.
SampleUnit	string	optional	A description of the unit measurement for this sample.
SampleGroup	string	optional	Group affiliation. All sample points in the same group (in some datasrvs) should be handled (displayed) together. The DCM system itself places no meaning on this group affiliation
SamplesSaved	integer > 0	optional	The number of collected values that are saved in the Store'n'Forward database even after the values have been sent to all dataservers. When 0 is specified, the value can be used in aggregators. but nothing will be sent via dataservers. If left unspecified, values are only saved in the Store'n'Forward database until they have been delivered to all dataservers
OnlySaveOnChanged	bool	optional	Specifies if new sample values should be saved to the store-and-forward database only when the value is different from the last sample value. Default: false.
ChangeLimit	Integer/double	optional	Used if OnlySaveOnChanged is true. Specifies an amount which a sample must be greater than, to count as a changed value. This is a simple hysteresis to filter out inaccurate (jitter) measurements. Default: 0
SampleDataType	string -enum	mandatory	The type of data collected. The possible values are: "bool" (1 bit), "sbyte" (8 bit signed), "byte" (8 bit unsigned), "int16" (16 bit signed), "uint16" (16 bit unsigned), "int32" (32 signed), "uint32" (32 bit unsigned), "int64" (64 bit signed), "uint64" (64 bit unsigned), "float" (32 bit), "double" (64 bit), "string" (variable text up to 24575 bytes. Includes terminating NUL), "data" (variable data up to 24575 bytes).
SampleMaxVDataSize	integer > 0 and <= 24575	optional	The max size of variable data allowed for this sample. This is only relevant for SampleDataType "string" or "data". If not specified, the value is 1024.
SampleLowerLimit	integer/double	optional	The lower limit for the collected data. If the collected data value is less than SampleLowerLimit it is evaluated in accordance with SampleLimitDiscard and SampleLimitAlarm
SampleUpperLimit	integer/double	optional	The upper limit for the collected data. If the collected data value is more than SampleUpperLimit it is evaluated in accordance with SampleLimitDiscard and SampleLimitAlarm.
SampleLimitDiscard	bool	maybe-optional	Specifies whether samples that violates the sample limit should be discarded. Mandatory if either SampleLowerLimit or SampleUpperLimit is present.
SampleLimitAlarm	bool	maybe-optional	Specifies whether samples that violates the sample limits should generate an alarm. Mandatory if either SampleLowerLimit or SampleUpperLimit is present
MQTTTopic	object	mandatory	Specification of the MQTT topic containing this sample value.

MQTT Topic object

The MQTT Topic object contains the following elements:

Function	Type	Importance	Description
TopicString	string	mandatory	The MQTT topic to subscribe to. Wildcards ('#', '+') are not allowed.
TopicSubscribeQos	string-enum	optional	QoS (Quality of Service) to use when subscribing to this topic. Possible values are “qos0”, “qos1”, and “qos2”
PayloadEndianness	string-enum	optional	Endianness to use when interpreting binary data in message payload. The possible values are: "big" and "little". If not specified the default value "big", corresponding to network byte order, is assumed.
NumberAsString	boolean	optional	Indicate if numeric data is formatted as a string in the payload - use with appropriate SampleDataType to get correct conversion.

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