docs(design): async runtime evaluation for SSH transport (#1411)#4194
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Add docs/design/async-ssh-evaluation.md, the focused evaluation that backs the Phase 3 SSH-transport recommendation in the async migration plan. Documents the current subprocess-pipe path, what async overlap actually buys, the integration boundary and spawn_blocking surfaces, and the embedded-russh-vs-subprocess tradeoff. Recommends embedded russh as the first async SSH target since the internal futures already exist and it eliminates fork+execve per connection; defers async subprocess until embedded is proven.
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This was referenced May 17, 2026
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Add docs/design/async-ssh-evaluation.md, the focused evaluation that backs the Phase 3 SSH-transport recommendation in the async migration plan. Documents the current subprocess-pipe path, what async overlap actually buys, the integration boundary and spawn_blocking surfaces, and the embedded-russh-vs-subprocess tradeoff. Recommends embedded russh as the first async SSH target since the internal futures already exist and it eliminates fork+execve per connection; defers async subprocess until embedded is proven.
oferchen
added a commit
that referenced
this pull request
May 18, 2026
Add docs/design/async-ssh-evaluation.md, the focused evaluation that backs the Phase 3 SSH-transport recommendation in the async migration plan. Documents the current subprocess-pipe path, what async overlap actually buys, the integration boundary and spawn_blocking surfaces, and the embedded-russh-vs-subprocess tradeoff. Recommends embedded russh as the first async SSH target since the internal futures already exist and it eliminates fork+execve per connection; defers async subprocess until embedded is proven.
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Summary
docs/design/async-ssh-evaluation.md, the focused evaluation for Allow workspace brand metadata aliases #1411 that supports the Phase 3 SSH-transport recommendation indocs/design/async-migration-plan.md(Add safe Apple special-file helpers #1594).crates/rsync_io/src/ssh/subprocess path - blocking pipe I/O, stderr drain thread, connect watchdog - and quantifies what async overlap actually buys (per-transfer read/write overlap, one-loop-many-transfers fan-out, helper-thread elimination).docs/design/async-runtime-ssh-eval.md(Allow workspace brand metadata aliases #1411 runtime survey),docs/design/async-ssh-transport.md(CI: remove unsupported windows aarch64 target #1593), anddocs/design/tokio-spawn-blocking-rayon.md(Refactor local copy options into dedicated module #1751) for the rayon bridge.crates/rsync_io/src/ssh/embedded/; eliminates per-connectionfork+execve; drops the two helper threads) and defers async subprocess until embedded is proven. Both backends sit behind the same--features async-sshflag, default off, with the syncstd::processtransport remaining default throughout Phase 3.tokio::io::copy_bidirectional), Enforce unique cross-compile metadata entries #1805 (cancellation, exit-code mapping, panic isolation), Handle forced missing cargo tools in packaging tests #1806 (async subprocess backend with bench-gated promotion).Test plan
docs/design/.