Use HTTP/1.1 when ALPN protocol is not specified

[3dgiordano]

This pull request introduces robust handling for servers that do not support HTTP/2, particularly when TLS ALPN negotiation fails and the server responds with HTTP/1.1. The changes ensure that such origins are remembered and future requests avoid attempting HTTP/2, improving efficiency and reliability, especially in multi-address scenarios. Additionally, the implementation prevents repeated failed HTTP/2 attempts for the same origin and adds comprehensive tests to validate the new behavior.

HTTP/2 Rejection Detection and Caching:

• Added logic to detect when an origin rejects the HTTP/2 preface (e.g., due to missing ALPN negotiation) and remember that the origin should be accessed via HTTP/1.1 in the future (HTTP2JettyClient.java, CustomHttpSessionListenerPromise.java). [1] [2] [3]
• Updated the HTTP/2 connection factory to accept a callback for HTTP/2 rejection, propagating this information through the connection setup process (CustomClientConnectionFactoryOverHTTP2.java). [1] [2] [3]

Connection Handling Improvements:

• Modified the connection logic to immediately fallback to HTTP/1.1 for all addresses of an origin known to reject HTTP/2, preventing repeated failed connection attempts for each address (HTTP2JettyClient.java, RecordingHttpClientTransportDynamic).

Fallback Logic Enhancements:

• Enhanced the fallback mechanism in request sending to trigger on both transport failures and HTTP/2 rejection, ensuring samples succeed whenever possible (HTTP2JettyClient.java).

Testing:

• Added AlpnAbsentHttp2RejectedTest to reproduce and verify the handling of origins that do not negotiate ALPN, including scenarios with multiple resolved addresses and ensuring that repeated HTTP/2 attempts are avoided (AlpnAbsentHttp2RejectedTest.java).

Dependency and Import Updates:

• Added necessary imports for new classes and interfaces used in the implementation (HTTP2JettyClient.java, CustomClientConnectionFactoryOverHTTP2.java, CustomHttpSessionListenerPromise.java). [1] [2] [3] [4]

These changes significantly improve the client's resilience and performance when interacting with servers that do not support HTTP/2, especially in complex network environments.

[3dgiordano]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Merge conflicts resolved in commit 30a0ec4. The conflicts in HTTP2JettyClient.java were resolved by accepting the connectors/dnsResolver field declarations and setSourceAddress method from development, while preserving the infos field and newConnection override from this branch.