Unable to create top-level subsegment in image Lambda

[jamesohortle]

I have a Lambda deployed as a Docker image that instantiates a class in the global context. This class is used in various other functions.

I wanted to see how much of the time during instantiation (cold start) was taken up by this class instantiation. However, I can't seem to make a (sub)segment that shows me this in the console.

Minimal reproducible code:

from aws_xray_sdk.core import xray_recorder
from my_classes import BigClass

# Instantiate big class up-front.
xray_recorder.configure(sampling=False)
with xray_recorder.in_segment("instantiate class") as segment: # Have also tried without this line.
    with xray_recorder.in_subsegment("instantiate class") as subsegment:
        subsegment.put_annotation("key", "value")
        big_class = BigClass()

The X-Ray decorators work in other parts of my code so it's not an issue with requirements.txt or my Dockerfile.

Here's the Dockerfile anyway.

FROM public.ecr.aws/lambda/python:3.8

# Install dependencies.
COPY requirements.txt ./
RUN python3.8 -m pip --no-cache-dir install --upgrade pip && python3.8 -m pip --no-cache-dir install -r requirements.txt

# Copy application code and provide entrypoint.
COPY src/index.py   ./
CMD ["index.handler"]      

How should I trace the instantiation of global objects (top level of a script)?

[wangzlei]

It works as design that in AWS Lambda environment, XRay SDK cannot create any segment, refer code. Either beginning segment out of handler function or inside of handler function will get error "Cannot create segments inside Lambda function. Discarded."

That limits user is only able to add subsegments under an immutable Lambda function Invocation subsegment, which actually represents lambda handler function. So, it is not able to get a cold start segment/subsegment in Lambda even you begin segment/subsegment in the right place.

[stale]

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