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HTTP_STATUS_VERSION_NOT_SUPPORTED
The response concerns protocol version support, not the version of the resource or API. It is rare with modern clients but can appear with custom proxies, protocol tests, or incorrect transport negotiation.
Inspect the actual request line and ALPN or upgrade negotiation. Confirm that the front-end and upstream agree on supported HTTP versions.
Operational meaning of HTTP 505 for HTTP_STATUS_VERSION_NOT_SUPPORTED
HTTP 505 (HTTP_STATUS_VERSION_NOT_SUPPORTED) is a server-error response. AllStat records its meaning as “505 HTTP Version Not Supported”. For HTTP_STATUS_VERSION_NOT_SUPPORTED, interpret it with the request method, selected representation, response headers, and the specification or product that defines the code; the number alone does not prove that application work completed.
Client and server handling for HTTP_STATUS_VERSION_NOT_SUPPORTED
- Correlate HTTP_STATUS_VERSION_NOT_SUPPORTED with origin, gateway, load-balancer, and dependency logs to locate which hop generated it.
- For HTTP_STATUS_VERSION_NOT_SUPPORTED, record request and trace identifiers, upstream timing, retry count, and the health of the selected backend.
- For HTTP_STATUS_VERSION_NOT_SUPPORTED, use bounded retries with backoff only for idempotent work and only when the service policy permits them.
For telemetry, record HTTP 505, method, authority, route template rather than secrets, response headers relevant to caching or retry, latency, upstream identity, and whether the response originated at the application or an intermediary.
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