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Distributed tracing not possible when using Google Cloud Load Balancer

2025/4/22 20:552025/4/22 21:14

This is Hasegawa (@rarirureluis) from the Service Reliability Group (SRG) of the Media Headquarters.

#SRG(Service Reliability Group) mainly provides cross-sectional support for the infrastructure of our media services, improving existing services, launching new ones, contributing to OSS, etc.

This article explains an issue where distributed tracing does not work as expected in an environment using Google Cloud Load Balancer.

Introduction Symptoms of the issue: The flag in the traceparent header changes Cause: Known bug in Load Balancer Workaround: Rewrite the headers at the CDN Conclusion

Introduction

In environments that use Google Cloud Load Balancer, you may encounter issues with distributed tracing not working as expected.

traceparent

This article explains the cause of this issue and provides specific workarounds.

Symptoms of the issue: The flag in the traceparent header changes

traceparent

This header is defined by the W3C Trace Context standard and contains information such as the trace ID, span ID, and sampling flag.

traceparent

-00

This causes problems as requests that you want to trace are not sampled and cannot be tracked by the distributed tracing system.

Cause: Known bug in Load Balancer

This issue is caused by a known bug in the Google Cloud Load Balancer.

This issue has been filed in Google's issue tracker and is currently being worked on to resolve.

Google Issue Tracker

https://issuetracker.google.com/issues/401141843

X-Cloud-Trace-Context

o=0

-00

o=1

-01

Workaround: Rewrite the headers at the CDN

As an effective workaround for this issue, if you have a CDN in front of the Google Cloud Load Balancer, you can use the CDN's functionality to rewrite the HTTP header.

Specifically, add the following rules to your CDN settings: