APMConfig SamplingRate binary float formatting breaks apm-agent-go tracer instrumentation

[1pkg]

Description

The changes to support configurable sampling rate for APMConfig in elastic/elastic-agent-client#123 seem to now work as expected. During the course of integrating the change to APM Server in PR, I discovered that sampling_rate is formatted as a binary (hex) with exponent instead of decimal literal without exponent, this breaks subsequent call in apm-agent-go when tracer is initialized via ELASTIC_APM_TRANSACTION_SAMPLE_RATE with a custom sampling rate.

A quick stripped down go playground snippet with the problem.

Steps to Reproduce

On the latest agent build set non empty value to agent.monitoring.apm.sampling_rate for example "0.1".

Related Issues

• Add missing tracing sampling APM config section #5211
• Add sampling rate to elastic APM config elastic-agent-client#123
• monitoring: enable tracing self instrumentation in APM Server apm-server#14231

[elasticmachine]

Pinging @elastic/elastic-agent-control-plane (Team:Elastic-Agent-Control-Plane)