Java Captain
Jul 7, 2019 · Backend Development
Root Cause Analysis of HTTP 400 Errors After Spring Boot and Tomcat Upgrade Due to Nginx Host Header Handling
The article investigates why upgrading Spring Boot (and Tomcat) caused massive HTTP 400 errors in production, traces the issue to Nginx forwarding a Host header with an underscore, explains Tomcat's stricter RFC‑compliant validation introduced in version 8.5.31, and provides reproducible steps and remediation guidance.
BackendDistributed TracingJaeger
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