snap7-to-prometheus

Getting PLC tags out of Siemens PLCs and presenting them as a plaintext metrics file that can be read by prometheus.

For Siemens S7-1200/1500, see the notes

Build and run

• Either use docker to build and run the application (best for deployment on a server)
• Use Visual Studio debugging (easiest for testing)
• Build an exe using Visual Studio

Using docker

• copy example.docker-compose.yml to docker-compose.yml and adjust for your purposes
• copy ./snap7-to-prometheus/config.yml to ./config.yml fill in your tags
• execute sudo docker-compose up --build

Configure prometheus to use the metrics file that is available on http://<host>:5489/metrics

Config file

The config file ./snap7-to-prometheus/config.yml has the connection details of the PLC and a list of tags that will be exposed in the metrics file. This config file is automatically reloaded when changes are detected. Automatic config file reload does not work with docker, restart the container after changing config.

Labels

Tags can have labels. This is used in the prometheus metric file as {labelname1="labelvalue1", labelname2="labelvalue2"}. Labels can have a static value by specifying the Value or a reference to a tagname which has the value.

Tag with a label that has a static value and another label with a dynamic value:

- Name: MeterStatus1
  OffsetByte: 1004
  Type: String
  StringLength: 254
- MetricsName: mytags_power
  Labels:
  - Name: meter
    Value: Appartment1
  - Name: status
    ValueTagName: MeterStatus1
# Result: mytags_power{meter="Appartment1", status="Status read from PLC"}

Types

• Bool (Bit, OffsetBit must be supplied (default 0))
• Int8 (Byte)
• Int16 (Int)
• Int32 (DInt)
• Int64 (LInt)
• Float (Real)
• Double (LReal)
• String (StringLength must be supplied, this is the number of characters, not the byte length)

A string cannot have a MetricsName as a string cannot be read by Prometheus, only as a Label.

Acknowledgements

Uses the Snap7 library available on http://snap7.sourceforge.net/