describeInputs

JSON hub "describeInputs" action returns all available information about each specified FairCom Edge input

The "describeInputs" action returns all available information about each specified input. Inputs collect tags from a data source and insert them into an integration table.

Note A tag is a piece of named data with an associated value. For example, the tag temperature 70 includes both the named data temperature and the value 70. In JSON, a tag is a JSON property, such as "temperature": 70. In a SQL table, a tag is a data field, such as a field named temperature with a value of 70.

 

Request examples

Minimal

{
    "apiVersion": "1.0",
    "requestId": "00000027",
    "action": "describeInputs",
    "params": {
        "inputNames": [
            "modbusTCP"
        ]
    },
    "authToken": "replaceWithAuthTokenFromCreateSession"
}
 
 

 

Response examples

Minimal

{
    "result": {
        "data": [
            {
                "inputName": "modbusTCP",
                "serviceName": "modbus",
                "thingName": "PLC 74",
                "enabled": true,
                "running": false,
                "stopCode": 138,
                "disconnectReason": "Modbus timeout(138)",
                "dataCollectionIntervalMilliseconds": 1000,
                "settings": {
                    "modbusProtocol": "TCP",
                    "modbusServer": "127.0.0.1",
                    "modbusServerPort": 502,
                    "propertyMapList": [
                        {
                            "propertyPath": "temperature",
                            "modbusDataAddress": 1199,
                            "modbusDataAccess": "register",
                            "modbusUnitId": 5,
                            "modbusDataLen": 1
                        },
                        {
                            "propertyPath": "volume",
                            "modbusDataAddress": 1299,
                            "modbusDataAccess": "register",
                            "modbusUnitId": 5,
                            "modbusByteOrder": "ABCD",
                            "modbusDataLen": 2
                        },
                        {
                            "propertyPath": "status",
                            "modbusDataAddress": 1199,
                            "modbusDataAccess": "coil",
                            "modbusUnitId": 5,
                            "modbusDataLen": 1
                        }
                    ]
                },
                "databaseName": "ctreeSQL",
                "ownerName": "admin",
                "tableName": "modbustabletcp",
                "metadata": {},
                "retentionPolicy": "autoPurge",
                "retentionPeriod": 30,
                "retentionUnit": "day"
            }
        ]
    },
    "requestId": "00000027",
    "errorCode": 0,
    "errorMessage": ""
}
 
 

Maximal

{
  "result": {
    "data": [
      {
        "id": 18,
        "inputName": "modbusTCP",
        "serviceName": "modbus",
        "databaseName": "faircom",
        "ownerName": "admin",
        "tableName": "modbustabletcp",


        "status": "userError",
        "stopCode": 16384,
        "stopReason": "Putting device in an uncertain error state while verifying data collection.",


        "purpose": "Track Celsius Temperatures from devices",
        "description": "My input connector's description",
        "labels": ["temperature", "celsius"],
        "metadata": { "myProperty": "myValue" },
        
        "createdTimestamp": "2025-08-28T10:47:13.041",
        "updatedTimestamp": "2025-08-28T10:47:13.041",
        "inactiveTimestamp": null,
        "lastCollectedTimestamp": null,
        "lastConnectedTimestamp": null,
        "lastDisconnectedTimestamp": null,
        
        "dataPersistenceStrategy": "onChange", 
        "dataCollectionIntervalMilliseconds": 5000,
        "immediatelyCollectDataOnStart": true,
        "dataCollectionBufferCount": 2,    
    
        "settings": {
          "modbusProtocol": "TCP",
          "modbusServer": "127.0.0.1",
          "modbusServerPort": 502,
          "propertyMapList": [
            {
              "propertyPath": "temperature",
              "modbusDataAccess": "holdingregister",
              "modbusDataAddress": 1199,
              "modbusUnitId": 5,
              "modbusDataLen": 1
            }
          ]
        },
        
        "fields": [],
        "retentionPolicy": "autoPurge",
        "retentionPeriod": 4,
        "retentionUnit": "week",
        "disableTransformSteps": false,
        "logTransformOverwrites": false
      }
    ]
  },
  "authToken": "replaceWithAuthTokenFromCreateSession",
  "errorCode": 0,
  "errorMessage": ""
}
 
 

 

Properties

Request properties ("params")

Property Description Default Type Limits (inclusive)

inputNames

 The "inputNames" property specifies the names of the inputs you want to be described in the result. Optional with default of [] array 0 or more strings

 

Response properties ("result")

Property Description Type Limits (inclusive)

data

The "data" property contains a response message. Its contents are defined by the action. It is an empty array when no results are available. 

 array of objects The action determines its contents.

data

.createdTimestamp

 The "createdTimestamp" property is the date and time when the connector was originally created in ISO 8601 format, such as "2025-08-28T10:47:13.041". It is never null. timestamp An ISO 8601 timestamp

data

.databaseName

The "databaseName" property specifies the database that contains the tables. 

Note In the API Explorer, "defaultDatabaseName" is set to "ctreeSQL" in the "createSession" action that happens at login.

  • If the "databaseName" property is omitted or set to null, the server will use the default database name specified at login.
  • If no default database is specified during "createSession", "databaseName" will be set to the "defaultDatabaseName" value that is specified in the services.json file.
  • This property's value is case insensitive. 
 string 1 to 64 bytes

data

.dataCollectionBufferCount

The "dataCollectionBufferCount" property specifies the number of times the collector retrieves and caches data from the device before writing the data to the integration table.

This option combines multiple data collection events and inserts them into the integration table as one MQTT message.

If this value is more than 1, the connector converts each set of collected data into a JSON object and adds the object to an array inside a JSON document. When the count is reached, the connector writes the JSON document to the source_payload field of a record it inserts into the integration table.

 integer 1 to 65535

data

.dataCollectionIntervalMilliseconds

The "dataCollectionIntervalMilliseconds" property schedules the connector to collect data periodically using the specified number of milliseconds. 

 integer 0 and negative values are invalid.

data

.dataPersistenceStrategy

The "dataPersistenceStrategy" property controls when a connector writes collected data to a record in the input table specified by "tableName". 

  • The "onSchedule" setting causes the connector to persist each collected value, which occurs on the schedule set by the "dataCollectionIntervalMilliseconds" property. This setting is useful for continuously collecting device data for trend analysis and machine learning.
  • The "onChange" setting causes the connector to collect data on the schedule set by the "dataCollectionIntervalMilliseconds" property, but it only persists data when it changes. This allows the connector to detect and store data changes as events, such as alerts and status updates. This setting greatly reduces data storage for infrequently changing telemetry, such as changes to a temperature sensor.

Note The connector misses events when its data collection schedule is not frequent enough to see data changes. Thus, the "onChange" setting makes a polling protocol, such as Modbus, behave like a push protocol, but it is not a push protocol like MQTT.

 string

"onSchedule"

"onChange"

data

.description

 The "description" property assigns a description to a connector. string 1 to 512 bytes

data

.disableTransformSteps

The "disableTransformSteps" property determines if the transform steps are active without removing them from the integration table. When true, it prevents the server from running an integration table's transform steps on newly inserted records. When false, the transform steps run normally. It is useful to quickly stop a broken transform process.

 Boolelan

true

false

data

.disconnectReason

 The "disconnectReason" property details the reason why the connector disconnected. string No limit

data

.enabled


The "enabled" property is true when a connector is allowed to connect to a device. It is false when a connector will not attempt to connect to the device.

 

 boolean true
false

data

.fields

The "fields" property is an array of objects. Each object in the array defines a field by specifying its properties.

 

"fields": [
  {
    "autoValue": "none",
    "name": "name",
    "type": "varchar",
    "length": 50,
    "scale": null,
    "defaultValue": null,
    "nullable": false,
    "primaryKey": 0, 
    "autoValue": "none"
  }
]
 array

"autoTimestamp"

"autoValue"

"primaryKey"
"name"
"type"
"length"
"scale"
"defaultValue"
"nullable"

"primaryKey"

"autoValue"

data

.immediatelyCollectDataOnStart

The "immediatelyCollectDataOnStart" property controls how a connector first collects data after being started.

  • When true, it immediately collects and stores data and thereafter collects data according to the strategy specified in "dataPersistenceStrategy". In other words, it ignores the "dataPersistenceStrategy" for the initial data collection event and unconditionally stores the first set of data it collects. This setting allows subscribers to receive an initial data collection message each time the server or connector starts, which is useful for systems that display live status information.
  • When false, which is the default, it collects data according to the strategy specified in "dataPersistenceStrategy". For example, when the "dataPersistenceStrategy" is "onChange", the connector collects data on a schedule and persists it only when the data changes - even after a restart.
 Boolean

true

false

data

.inactiveTimestamp

 The "inactiveTimestamp" property is the date and time when the connector was last made inactive. It is null when the connector is active. It is returned in ISO 8601 format, such as "2025-08-28T10:47:13.041". timestamp ISO 8601 timestamp

data

.inputName

 The "inputName" property specifies the unique name of an input. string 1 to 64 bytes

data

.labels

 The "labels" property assigns zero or more labels to a connector. You can use it to do lookups and filtering. You can display a list of existing labels, add new ones, rename them, and deprecate them.
When you use the "alterInput" or "alterOutput" actions, omit the "labels" property to leave existing labels unchanged, or specify a complete set of new labels. These actions do not allow you to change one label at a time.
You can use the "labelsFilter" property to lookup and filter connectors. 
The input and output connector actions implement the "labels" property using the Label API. 
The API stores and manages labels in the label group, "faircom/edge/labels", which allows labels to be used through FairCom Edge's APIs.
An API client can retrieve a list of all lifecycle labels by using the "listLabels" action with "partialGroupFilter": "faircom/edge/labels".
An API client should use the connector API's "labels" property to manage the labels assigned to a connector. It should not use the Label API to rename, link, or unlink connectors.		 string 1 to 64 bytes

data

.lastCollectedTimestamp

 The "lastCollectedTimestamp" property is optionally returned from the "describeInputs", "alterInput" actions. 
It returns the ISO 8601 date and time of the last data collected by the input connector. If no data has been collected, the value is null. The following string is an example of an ISO 8601 timestamp: "2025-08-28T10:47:13.041".		 ISO 8601 timestamp The ISO 8601 date and time of the last data collected by the input connector.

data

.lastConnectedTimestamp

 The "lastConnectedTimestamp" property is optionally returned from the "describeInputs", "alterInput", "describeOutputs", "alterOutput" actions. 
It returns the ISO 8601 date and time of the last time the connector was connected to its device. If it has never been connected, the value is null. The following string is an example of an ISO 8601 timestamp: "2025-08-28T10:47:13.041".		 ISO 8601 timestamp The last ISO 8601 date and time the input connector was connected to its device.

data

.lastDisconnectedTimestamp

 The "lastDisconnectedTimestamp" property is optionally returned from the "describeInputs", "alterInput", "describeOutputs", "alterOutput" actions. 
It returns the ISO 8601 date and time of the last time the connector disconnected from a device or software. If it has never disconnected, the value is null. The following string is an example of an ISO 8601 timestamp: "2025-08-28T10:47:13.041".		 ISO 8601 timestamp The last ISO 8601 date and time the input connector was disconnected from its device.

data

.logTransformOverwrites

The "logTransformOverwrites" property specifies whether or not the server will add a log entry to the log field when a transform step overwrites a field. When true and a record is inserted into the integration table, the server adds log entries to the log field when a transform step overwrites a field that already contains a value. When true, it protects fields, such as source_payload, from being overwritten accidentally. 

You typically set "logTransformOverwrites" to true when testing transform steps. Once they are working as expected, you can set it to false.

If multiple "recordPath" properties write to the same JSON properties in a "tableFieldsToJson" transform, the server will return an error because "recordPath" cannot overwrite. Multiple occurrences of the "recordPath" property may reference the same property as long as the property is in different fields/tables.

Additionally, non-JavaScript transform steps cannot overwrite protected fields or the source_payload field. The only exception is that a single "tableFieldsToJson" transform step may write to the source_payload field.

You may create transform steps to take the value of one JSON property and store it in multiple fields as long as no previous transform steps have already put values in these fields. Conversely, you may take the value of one field and store it in multiple JSON properties.

Tip Ensure JavaScript transform steps do not overwrite fields updated by other transform steps. 

Do not use the "tableFieldsToJson" transform method to overwrite the source_payload field; instead, use "tableFieldsToJson" to write to a different field and use the "configureTopic" action with the "outputPayloadField" property to configure the MQTT topic to deliver that field's value to subscribers. 

Ensure SQL, JSON DB, and other APIs set the value of the source_payload field and do not set field values that transform steps update.

 Boolean

true

false

data

.metadata

The "metadata" field allows a customer to add a JSON value to an object such as a label or thing. It is typically a JSON object, but may be any JSON value. Its purpose is to provide additional metadata about the label, such as translations in multiple languages, historical value changes, etc. The "alterLabel" action can only replace this value with a new JSON value.

 JSON 0 to 65,500 bytes

data

.ownerName

 The "ownerName" property identifies the user who owns an object (see Object owner).  string 0 to 64 bytes

data

.purpose

The "purpose" property specifies the purpose of the thing. You can use it for fast partial lookups and filtering. This API uses the Label API to manage purposes.

  • An API client can use the "listLabels" action to retrieve the purpose list. 
  • An API client can use the "alterLabel" action to rename a purpose label.
  • An API client can use the "createLabel" action to create a purpose label.
  • An API client can use the "changeLabel" action to delete a purpose label, but the API client must first use the "listInputs" or "listOutputs" actions with the "purposeFilter" property to ensure the label is unused.
 string

1 to 64 bytes

Values are managed in the Label API with the group "faircom/edge/purpose".

data

.retentionPeriod

The "retentionPeriod" property specifies how many units of data to retain. It refers to the unit of time specified by the "retentionUnit" property. For more details, see "retentionPeriod".

 integer 1 to 100

data

.retentionPolicy

The "retentionPolicy" property controls how messages are persisted. 

If not specified, the default found in the services.json file is used. Initially, it is "autoPurge".

 

retentionPolicy values:
  • "autoPurge"
    • This is the default. It is automatically applied when a new topic is created. It is preferred because it allows FairCom's servers to automatically remove messages that are older than the retention time. This helps ensure message data does not consume all storage space. It also minimizes storage costs and speeds up data access. The server partitions a table into multiple files so it can efficiently delete expired files.
  • "neverPurge"
    • This stores messages on disk and never removes them. This is useful when you need the entire history of the message stream. If message velocity is high, this can consume all storage space and cause an outage. The server creates a non-partitioned table, which is slightly faster than a partitioned table because it stores all records in one file.
 string

"autoPurge"

"neverPurge"

data

.retentionUnit

The "retentionUnit" property specifies a unit of time that the server will use to purge expired messages. For example, if you want a week's worth of messages to be purged once a week, set "retentionUnit" to "week". This property is optional.

If not specified, the default found in the services.json file is used. Initially, it is "week". 

  • This property is used in concert with "retentionPeriod" to determine retention time.
  • "retentionUnit" values:
    • "minute"
    • "hour"
    • "day"
    • "week"
    • "month"
    • "year"
    • "forever"

Note 

  • For best performance, set the "retentionUnit" to a value that keeps "retentionPeriod" between 5 and 30. 
  • When you set "retentionUnit" property to "forever" the server will not purge messages. This setting is the same as setting "retentionPolicy" to "neverPurge".
  • The "retentionUnit" and "retentionPeriod" properties are used only when the "retentionPolicy" is set to "autoPurge".

string

"minute"

"hour"

"day"

"week"

"month"

"year"

data

.running

 The "running" property is true when an input connector is collecting data or an output connector is delivering data; otherwise, it is false. A disabled connector will never be running. An enabled connector may or may not be running. Boolean

true

false

data

.serviceName

The "serviceName" property contains the name of a FairCom input or output service. 

See the "params" topic of each specific service for the requirements of this property.

The following services are available as of the V5 release:
  • "MODBUS"
  • "SIEMENSUDT2JSON"
  • "OPCUA"

Note The SQL, JSON RPC, and REST services can automatically query any integration table in FairCom's servers without requiring configuration.

Note MQTT always represents both input and output services. This is because once a topic is created and assigned to an integration table, any MQTT client can publish messages to it and subscribe to those messages.

 string A service name between 1 and 64 bytes.

data

.settings

The "settings" property contains properties that are specific for each connector type. Settings for Modbus are different than settings for OPC UA, and so forth. See the API reference "params" property of each connector for details of the "settings" property for that connector.

 object

See these pages for connector specific properties:

Allen-Bradley "params"

Modbus "params"

OPC UA "settings"

Siemens S7 "params"

data

settings

.propertyMapList

 The "propertyMapList" property specifies which data the connector requests and where to put it in the generated JSON. array of objects

See these pages for connector specific properties:

Allen-Bradley "params"

Modbus "params"

OPC UA "settings"

Siemens S7 "params"

data

settings

propertyMapList

.propertyPath

 The "propertyPath" property specifies the JSON path in the JSON document where the connector puts the data it collects. It is mutually exclusive with the "tagName" and "tagId" properties. string JSON path

data

settings

propertyMapList

.tagId

 The "tagId" property associates a tag with a value being collected by a connector. It is mutually exclusive with the "tagName" and "propertyPath" properties. See tagId for more details.
 		 integer If present, it must contain the ID of an existing tag, which is an integer from 0 to 9223372036854770000.
Note FairCom recommends using this property instead of "propertyPath".

data

settings

propertyMapList

.tagName

 The "tagName" property associates a tag with a value being collected by a connector. It is mutually exclusive with the "tagId" and "propertyPath" properties. See tagName for more details. 
 		 string

If present, it must contain the name of an existing tag. 

Note FairCom recommends using this property instead of "propertyPath".

data

.status

 The "status" property assigns an active or inactive status to a thing. An inactive status is like a soft delete. See "status" for more information.   string enum

"active"

"connectorError"

"deviceError"

"userError"

"paused"

"inactive"

data

.stopCode

 The "stopCode" property is 0 when the connector is successfully connected to its device or software; otherwise, it is non-zero. integer -2147483648 to 2147483647

data

.stopReason

 The "stopReason" property is "" when the input connector is collecting data; otherwise, it is a non-empty string. string 0 to 256 bytes

data

.tableName

The "tableName" property is a string containing the name of a table.

The table name must start with an upper or lowercase letter, must not contain special characters other than underscore "_", and can include a mix of upper-lower case characters, but are treated as case-insensitive.

 string 1 to 64 bytes

data

.thingId

 The "thingId" property associates a connector with a device or software application. It is mutually exclusive with the "thingName" property. See thingId for more details. integer If present, it must contain the ID of an existing thing, which is an integer form 0 to 9223372036854770000.

data

.thingName

 The "thingName" property associates a connector with a device or software application. It is mutually exclusive with the "thingId" property. See thingName for more details. string 1 to 64 bytes

data

.updatedTimestamp

 The "updatedTimestamp" property is the date and time when the connector was last updated. It is the same as the "createdTimestamp" property when the connector has never been updated. It is returned in ISO 8601 format, such as "2025-08-28T10:47:13.041". timestamp ISO 8601 timestamp

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