Generic CDP Blocks

transport_addr

The transport_addr field determines the protocol and location of the endpoint the block will communicate with.

The prefix to the URI (for example, the "mqtt-tcp" in mqtt-tcp://localhost:1883 determines what protocol to use:

node_ref

The node_ref field means a slightly different thing for each protocol but is essentially the specific node that is to be communicated with in the protocol specified by the transport_addr. For MQTT, this means the topic to publish to or subscribe from.

method

The method field determines the method of the communication (synch/asynch, send/receive). This field’s possible values are dependent on both the block type and protocol used, for example, some protocols support only the publish/subscribe or get/set type of communication.

interval

The interval field is only relevant (and required) if the block is of type cdpin and the method field is get. This determines the interval (in milliseconds) at which the block will poll its endpoint for data.

For example, if this is set to 1000, the block will attempt to get data every second.

log_level

The log_level field determines which level of logs to output. If the field is not set to one of the following values, the block will not log anything.

log_name

The log_name field defines a name to identify the block’s logs. This is typically prepended to the log output. If unset, it defaults to the block name.

options

The options field is a JSON object whose contents are specific to the protocol specified in the transport_addr field.

This is not considered a required field, but some protocols may require it to function properly. For example, if the Time Series protocol ('pxtss') is specified in the transport_addr field and the options field does not contain the token_file and predix_zone_id, the block will be unable to connect to the Time Series endpoint.

directory

The directory field is only used in the CDP Out Queue block. This field determines the directory where the block’s store-and-forward files (a disk-backed queue of data to be sent) will be created and updated. If the directory does not exist, it will be created, but if its parent directory does not exist, an error will be thrown.

max_cache_size

The max_cache_size field determines the maximum amount of disk space allowed for this block to use for one of its disk-backed queues (store-and-forward file).

If left unset, this field’s value will default to 90 and the max_cache_size_units field will default to %.

max_cache_size_units

The max_cache_size_units field determines the units to use for the max_cache_size field.

This field’s default value is %.

CDP In

This block is used to receive data from any transport on the CDP. Its configuration fields are as follows:

For more specific information on these fields, see the high level description of generic CDP blocks above.

Example CDP In Block:

"example_cdpin_mqtt_source_block": {
    "type": "cdpin",
    "config": {
        "transport_addr": "mqtt-tcp://predix-edge-broker",
        "node_ref": "predix_historian",
        "method": "sub",
        "log_name": "mqtt_source_block",
        "log_level": "err"
    }
}

CDP Out

This block is used to send data to any transport on the CDP. Its configuration fields are as follows:

For more specific information on these fields see the high level description of generic CDP blocks above.

Example CDP Out Block:

"example_cdpout_mqtt_sink_block": {
    "type": "cdpout",
    "config": {
        "transport_addr": "mqtt-tcp://predix-edge-broker",
        "node_ref": "data/pressure",
        "method": "pub",
        "log_name": "mqtt_sink",
        "log_level": "err",
        "options": {
            "qos": 1
        }
    }
}

CDP Out Queue

This block is used to send data to any transport on the CDP. It is identical to the CDP Out block above, except that this block will also queue messages on a disk-backed queue (store-and-forward) if it is unable to deliver them. Its configuration fields are as follows:

Example CDP Out Queue Block:

"example_cdpoutqueue_timeseries_sink_block": {
    "type": "cdpoutqueue",
    "config": {
        "transport_addr": "pxtss://timeseries-instance.run.aws-usw02-pr.ice.predix.io/v1/stream/messages",
        "node_ref": "doesn't_matter_for_timeseries",
        "method": "set",
        "log_name": "timeseries_sink",
        "log_level": "err",
        "directory": "/data/container_name/timeseries_sink/dbq/",
        "max_cache_size": 100,
        "max_cache_size_units": "MB",
        "options": {
            "token_file": "/edge-agent/access_token",
            "predix_zone_id": "01234567-8987-6543-2101-234567898765",
            "proxy_url": "https://proxy.proxy.proxy.com:8080"
        }
    }
}