DEV Community

Cover image for Opentelemetry for python
prumand
prumand

Posted on

Opentelemetry for python

I have a cli-app (see my previous post) and I want to collect some usage stats. Of course opentelemetry is the way to go and python support is pretty far.

I’m using jaeger for my traces. I don’t need live observability, but just some analytics from time to time. So I’d prefer starting a container and ingesting traces which are stored on disk on demand.

Unfortunately there is no to-disk exporter for traces out of the box, but it’s easy to set up. First for writing to files, I’ll just use the standard python logging:

import logging
from logging import LogRecord, Logger
from logging.handlers import RotatingFileHandler


handler = RotatingFileHandler(LOG_FILE_PATH, maxBytes=1024 * 1024, backupCount=5)
logging.basicConfig(
    level=logging.INFO,
    handlers=[handler],
    format='%(message)s',   
)
Enter fullscreen mode Exit fullscreen mode

It's ok to rotate logs from time to time. I can alway crank up the backupCount, if I think it’s important.

I’m using the standard otel-ConsoleExporter and change the formatter, since I want all traces to be written on one line. That makes it easier to ingest the file later. Further I change the output of the Exporter to my customer implementation.

class LogOut:
    def __init__(self, logger: Logger) -> None:
        self._logger = logger

    def write(self, msg):
        self._logger.info(msg)

    def flush(self):
        pass

provider = TracerProvider(resource=resource)
processor = BatchSpanProcessor(ConsoleSpanExporter(
    formatter=lambda span: span.to_json(None),
    out=LogOut(logging.getLogger('makit.cli'))
))

provider.add_span_processor(processor)
trace.set_tracer_provider(provider)
tracer = trace.get_tracer('makit.cli')

Enter fullscreen mode Exit fullscreen mode

So basically I just need to add the traces to my action-functions and I’ve all I need to know:

if __name__ == "__main__":
    with tracer.start_as_current_span("main") as span:
        get_app()()

Enter fullscreen mode Exit fullscreen mode

Sidenote

For me it’s fine to use span events as logging. Unfortunately those don’t show up in the jaeger-ui. But I tried something like the following:

class OtelLogger(logging.Logger):
    def handle(self, record: LogRecord) -> None:
        span = trace.get_current_span()
        span.add_event(record.msg)

Enter fullscreen mode Exit fullscreen mode

It gives me all the information I need and I thought about setting the span status based on the log-level.

Image of Timescale

🚀 pgai Vectorizer: SQLAlchemy and LiteLLM Make Vector Search Simple

We built pgai Vectorizer to simplify embedding management for AI applications—without needing a separate database or complex infrastructure. Since launch, developers have created over 3,000 vectorizers on Timescale Cloud, with many more self-hosted.

Read full post →

Top comments (0)

Image of Docusign

🛠️ Bring your solution into Docusign. Reach over 1.6M customers.

Docusign is now extensible. Overcome challenges with disconnected products and inaccessible data by bringing your solutions into Docusign and publishing to 1.6M customers in the App Center.

Learn more