EGD Dynamic Binding Protocol Adapter

EGD Configuration

EGD configuration details need to be distributed to a large audience. EGD configurations support XML format for extensibility and flexibility. The configuration description supports the inherent hierarchy of nodes, exchanges, variables and variable attributes of an EGD producer.

The EGD protocol uses HTTP 1.1 over TCP/IP as the transport mechanism for configuration messages. The profile of the HTTP protocol required by this specification requires servers that are at least conditionally compliant with HTTP 1.1 to be used. Although implementations are not required to support the configuration port (7937), it is encouraged.

Overview of Capabilities

The EGD dynamic binding protocol adapter enables data transfer from any controller that supports EGD protocol to MQTT or Predix cloud. Currently only Class 2 Dynamic Read is supported. The adapter is able to determine when the configuration of the EGD producer it is listening on has changed and adapt in real time by querying for a new configuration via HTTP 1.1 over TCP/IP REST calls. Events that would trigger a configuration include moving a variable from one EGD exchange to another, causing the signature and timestamp of the exchange to update.

Data Format

Once data has been sourced from an EGD producer exchange via UDP Data Production Packet, the binary format of the desired EGD variables are extracted and transformed into a flat json format.

Example:

{
    "timestamp": "1504739531776",
    "data": {
        "temperature": {
            "val": 15,
            "type": "int16"
        },
        "pressure": {
            "val": 16.2,
            "type": "float"
        }
    }
}

Configuration Resources

The EGD dynamic binding protocol adapter supports the following configuration options:


Type	Name
type	egddynamicflat


Name	Type	Required
transport_addr	String	Yes
log_level	String	No
log_name	String	No
subscriptions	Array	Yes
egress	Object	No

Transport Address (transport_addr)

The host address where EGD messages are expected to be received. It is recommended to keep this field as "127.0.0.1" unless multicast is used. The transport_addr can be specified as either of the following:

"transport_addr":"egd://<ip address>"
"transport_addr":"egd://<FQDN>"

Log Level (log_level)

Configures the logger for the EGD client used internally to the block, can be any of the following (case insensitive):

off (default)
critical
err
warn
info
debug

Log Name (log_name): Used in the log file to associate statements with the block. If omitted, the block name is used for the log name.

Subscriptions (subscriptions)

An array that contains JSON objects that describe a particular producer and its associated configuration server. Within each subscription, the following configuration options are supported:


Name	Type	Required
port	Integer	No
producer_id	Integer	Yes
config_url	String	Yes
variables	Array	No

Port (port): The port on which EGD messages are expected to be received. The default is port 18246.
Producer ID (producer_id): Producer ID of the EGD producer whose values you want to listen for.
Config URL (config_url): URL of the EGD configuration server to request new producer configurations from.
Variables (variables): An array containing objects with the names of variables you want to read from the EGD producer and optional aliases.
Note: If variables is not included in config, all variables from the producer will be returned to the user.

Egress

Used to change the EGD output or egress formats.


Field	Type	Applicable to	Default	Description
Output Format	String		`flat_json`	Format of the JSON file output by the adapter into other blocks. Valid entries: `flat_json` `time_series`
Batch Interval	Integer		30 seconds	Amount of time (in milliseconds) the batcher will hold or accumulate data before generating a message. Upon sending data, the internal state is reset and emptied.
Maximum Number of Datapoints	Integer		1	The maximum number of data values the batcher will hold, per tag, over a batching interval. This functions as a very simple filtering step that helps control CPU usage.
Attributes	Object	time_series	empty block	Attributes are dependent on the Output Format value.
Timestamp From	String		`source`	Configures how the output timestamp values are set. Valid entries: host (the adapter will use the local time in its output) source (the adapter will use the timestamp from the EGDsource in its output, unless that time is 0, in which case it will use the local time)

Flat_json Output Example:

"egress": {
        "output_format": "flat_json",
        "timestamp_from": 1
    }

Time_series Output Example:

"egress": {
        "output_format": "time_series",
        "batch_interval": 30000,
        "max_num_datapoints": 1,
        "attributes": {},
        "timestamp_from": 1
    }

Example

{
            "type": "egddynamicflat",
            "config": {
                "log_level": "debug",
                "log_name": "egddynamicflat",
                "transport_addr": "egd://127.0.0.1",
                "subscriptions": [
                    {
                        "port": 18246,
                        "producer_id": 1234,
                        "config_url": "http://192.168.1.8:8080",
                        "variables": [
                            {
                                "name": "01_BOOL",
                                "alias": "EGD.01_BOOL"
                            }
                        ]
                    },
                    {
                        "port": 18246,
                        "producer_id": 1235,
                        "config_url": "http://192.168.1.8:8080",
                        "variables": [
                            {
                                "name": "02_BOOL",
                                "alias": "EGD.02_BOOL"
                            }
                        ]
                    }
                ]
            }
        }