opentelemetry.tracer crashes with TypeError in transaction with high number of spans

[kozako2]

Describe the bug:

Using opentelemetry bridge crashes with TypeError: 'NoneType' object does not support item assignment exception when number of spans in transaction is higher than ELASTIC_APM_TRANSACTION_MAX_SPANS

File ~/.pyenv/versions/3.11.11/envs/test/lib/python3.11/site-packages/elasticapm/contrib/opentelemetry/trace.py:169, in Tracer.start_span(self, name, context, kind, attributes, links, start_time, record_exception, set_status_on_exception)
    167     span.set_attributes(attributes)
    168 spankind = get_span_kind(kind)
--> 169 elastic_span.context["otel_spankind"] = spankind
    171 return span

.
Debugger shows that elastic_span inside is DroppedSpan. Increasing nr of ELASTIC_APM_TRANSACTION_MAX_SPANS "fixes" problem as shown in code below.

To Reproduce

from elasticapm.contrib.opentelemetry import trace
from elasticapm import Client, capture_span

import os

# Reduce number of spans required to reproduce the issue
ELASTIC_APM_TRANSACTION_MAX_SPANS = 10
STEPS_ABOVE = ELASTIC_APM_TRANSACTION_MAX_SPANS + 1 
STEPS_BELLOW = ELASTIC_APM_TRANSACTION_MAX_SPANS - 1 
os.environ["ELASTIC_APM_TRANSACTION_MAX_SPANS"] = str(ELASTIC_APM_TRANSACTION_MAX_SPANS)

apm_client = Client()
tracer = trace.get_tracer(__name__)

# Simulate deep nested spans
def capture_span_elasticapm(steps=10):
     if steps == 0:
        return
     
     with capture_span():
        capture_span_elasticapm(steps-1)

def capture_span_opentelemetry(steps=10):
     if steps == 0:
        return
     
     with tracer.start_as_current_span("test"):
        capture_span_opentelemetry(steps-1)


# TEST

# Works - Expected
transaction = apm_client.begin_transaction('processors')
capture_span_elasticapm(STEPS_BELLOW)
apm_client.end_transaction('myapp.billing_process')

# Works - Expected
transaction = apm_client.begin_transaction('processors')
capture_span_opentelemetry(STEPS_BELLOW)
apm_client.end_transaction('myapp.billing_process')

# Works - Expected
transaction = apm_client.begin_transaction('processors')
capture_span_elasticapm(STEPS_ABOVE)
apm_client.end_transaction('myapp.billing_process')

# Crashes - Unexpected 
# TypeError: 'NoneType' object does not support item assignment
transaction = apm_client.begin_transaction('processors')
capture_span_opentelemetry(STEPS_ABOVE)
apm_client.end_transaction('myapp.billing_process')

Environment (please complete the following information)

• OS: [e.g. Linux] Linux Mint 22.1 Cinnamon
• Python version: 3.11.11
• Framework and version [e.g. Django 2.1]: N/A
• APM Server version: N/A
• Agent version: elastic-apm==6.23.0

[xrmx]

Thanks for reporting, if you are interested in exporting Open Telemetry data I would suggest to checkout our Elastic Distribution of OpenTelemetry instead, we have a migration document with some information.

[kozako2]

Thx! i will for sure check. In that case would elastic-apm agent be still supported? Or is it better to completely switch to EDOT ?

[xrmx]

Thx! i will for sure check. In that case would elastic-apm agent be still supported? Or is it better to completely switch to EDOT ?

Sorry, missed this. If you are going to export OTLP I suggest to switch to EDOT so you get all the OTel support. elastic-apm-agent is still supported.