FetchPLC 2.4.0.4.11.0.0-352

Bundle
com.cloudera | nifi-cdf-plc4x-processors-nar
Description
Processor able to read data from industrial PLCs using Apache PLC4X
Tags
plc4x, read, source
Input Requirement
ALLOWED
Supports Sensitive Dynamic Properties
false
  • Additional Details for FetchPLC 2.4.0.4.11.0.0-352

    FetchPLC

    Purpose

    This processor is supposed to read specific register values from a PLC device, and to generate NiFi records from these readings.

    General Concept

    A minimum setup requires an enabled PLC4X Connection Pool, a Record Writer, and any number of registers defined in the Address Map (dynamic properties). During execution, it compiles the Address Map into an Avro schema, and connects to the device, specified by the Connection Pool. Then reads the addresses from the device, and converts the results into a NiFi record, on success. Failing to read any of the specified registers count as an error, and in this case no record is generated, even if there is a partial result.

    User can supply input FlowFile to this processor, by connecting it after another one. In this case, the attributes or the contents of the input can be referred in the Address Map, using Expression Language. Please note that, if Expression Language is present in the Address Map, the address syntax is not validated.

    Address Map

    Address Map is defined as Dynamic Properties in the processor settings. Validation fails, if there is none defined. The generated record consists of fields, and the mapping defines which field should contain which PLC register’s value. The name (key) defines the record field, the value defines the PLC register’s address. (Please refer to the Driver documentation, to find the required address format.) You can define any number of fields, all of these are fetched in a single pass.

    Schema Cache

    The processor needs to compile the Address Map into an Avro Schema, which uses noticeable amount of the system resources for a short duration (a spike). Normally this is done only once, when the processor starts up.

    With Expression Language, you can make the Address Map dynamic, that can require multiple schema versions to be generated, during execution. The Schema Cache stores these compilations in an associative FiFo array, so that the schemas are generated only once, if there are no more variations than the specified cache size.

    Input

    Providing input is not necessary. In case you do, the processor will only read data, when an input FlowFile is available, and you can refer to the attributes of this file, when specifying the Address Map.

    If input is not provided, the processor reads data as per Run Schedule.

    Output

    In case of a successful reading, the emitted FlowFile contain a single NiFi record, written by the specified Record Writer. In case of failure, there is no output, if the processor has no ingress connection.

    The failure relationship is only used, if the processor is driven by an input FlowFile, and was unable to read all the specified registers. In this case, the input FlowFile is forwarded as-is.

    Note: Partial read results are always dropped.

    Type Mapping

    Due to the limitations of Avro, some data types are translated into plain string value, and the correct type information is not carried over in the generated records. You can find the exact mapping below:

    Mapping of PLC4X data types to Avro field types

    PLC Type Name Numeric Code (HEX) Avro Type
    NULL 0x00 stringType
    BOOL 0x01 booleanType
    BYTE 0x02 intType
    WORD 0x03 intType
    DWORD 0x04 longType
    LWORD 0x05 stringType
    USINT 0x11 intType
    UINT 0x12 intType
    UDINT 0x13 longType
    ULINT 0x14 stringType
    SINT 0x21 intType
    INT 0x22 intType
    DINT 0x23 intType
    LINT 0x24 longType
    REAL 0x31 floatType
    LREAL 0x32 doubleType
    CHAR 0x41 stringType
    WCHAR 0x42 stringType
    STRING 0x43 stringType
    WSTRING 0x44 stringType
    TIME 0x51 stringType
    LTIME 0x52 stringType
    DATE 0x53 stringType
    LDATE 0x54 stringType
    TIME_OF_DAY 0x55 stringType
    LTIME_OF_DAY 0x56 stringType
    DATE_AND_TIME 0x57 stringType
    LDATE_AND_TIME 0x58 stringType
    Struct 0x61 stringType
    List 0x62 array (of first element type)
    RAW_BYTE_ARRAY 0x71 bytesType

    PLC4X Documentation

    PLC4X Support

Properties
Dynamic Properties
Relationships
Name Description
failure An error occurred while processing
success Successfully processed
Writes Attributes
Name Description
plc4x.read.row.count Number of rows written into the output FlowFile
See Also