Improve Error Handling in Http2Transport for Graceful vs Abrupt Disconnections

[w1am]

This modification builds upon the changes made in #2563

Changed: Improved error handling in the Http2Transport class to differentiate between graceful and abrupt server disconnections. The handleDisconnect method has been updated to distinguish between a server's graceful shutdown, signaled by a GOAWAY frame, and abrupt terminations like socket errors.

The status of active calls is now set more appropriately - either to Cancelled or Unavailable. This addresses an inconsistency in a project, which previously led to confusion due to varying status codes from different server shutdown methods. It makes error handling clearer and more predictable.

[linux-foundation-easycla]

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• ✅ login: w1am / name: William Chong (05a7954)

[murgatroid99]

A graceful shutdown is indicated by a GOAWAY with code 0. When that happens, open streams should continue until they end on their own. In some versions of Node, that doesn't happen due to nodejs/node#42713, which has only recently been fixed in Node 20.10.0.

GOAWAYs with other codes cause requests to fail, but not through this code path. Instead, Node itself signals a RST_STREAM to each open stream on that connection, and that is handled by this code path.

As a result, handleDisconnect should already only be handling abrupt disconnects that don't have a corresponding GOAWAY, so I don't think this change is necessary. If there is a particular case where you are seeing an unexpected error code, I suggest opening an issue.