TahUtils

A small wrapper package for using Tahu for Sparkplug B in Python. Comes with an unmodified (barring import structure) Tahu included, hence the use of the Eclipse license.

Examples

See the examples directory in the project repository.

Current Support

• Generating Sparkplug B topics
• Generating birth, death, and data payloads for nodes and devices
• Managing aliases
• Using enums for metric names
• Using dataclasses to manage metric names and metric states
• Parsing sparkplug b messages

Changes to the tahu library

Updating compiled Protobuf files

Assuming no major refactoring to the tahu library, updating the included tahu consists of the following steps:

1. Download the latest release from the repository: https://github.com/eclipse/tahu/tags

2. Extract the source code.

3. Regenerate the sparkplug_b_pb2.py file per the instructions in tahu-<version>/python/core/README.md. Use tahu-<version>/python/core as your working directory when executing the command, and you'll need the protobuf compiler.

4. Copy the contents of the tahu-<version>/python/core directory to the tahutils/tahu directory.

5. Overwrite the tahutils/tahu/__init__.py file with the appropriate imports, typically:

   from . import sparkplug_b_pb2
   from . import array_packer
   from . import sparkplug_b

6. Modify the imports in tahutils/tahu/sparkplug_b.py to include the tahu package name:

   import tahutils.tahu.sparkplug_b_pb2 as sparkplug_b_pb2
   import time
   from tahutils.tahu.sparkplug_b_pb2 import Payload
   from tahutils.tahu.array_packer import *

Fixing metric timestamps

As of this version, there is a bug in the tahu library relating to metric timestamps. See this pull request for more details.

This is patched by updating sparkplug_b.py.

def addMetric(container, name, alias, type, value, timestamp=None):
    if timestamp is None:
        timestamp = int(round(time.time() * 1000))
	...

def addNullMetric(container, name, alias, type, timestamp=None):
    if timestamp is None:
        timestamp = int(round(time.time() * 1000))
    metric = container.metrics.add()
    if name is not None:
        metric.name = name
    if alias is not None:
        metric.alias = alias
    metric.timestamp = timestamp
    metric.is_null = True
	...