Fix SSHAttach.detach() #3306
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Fix SSHAttach.detach() #3306
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When error logging was added to SSHTunnel.close()[1], it was discovered that SSHAttach.detach() is called multiple times on detach. Although this is harmless as long as this method is idempotent (and it is), this patch ensures that detach() is no-op when called more than one time, removing ERROR level log noise. As a side-effect, detaching SSHAttach that reuses SSHTunnel no longer kills "master" SSHAttach, meaning that one can `dstack attach` multiple times and detach independently (detaching from the "master" attach still kicks out all other attaches). [1]: #3296
start_new_session is POSIX-only (ignored on Windows), and Windows-specific CREATE_NEW_PROCESS_GROUP flag doesn't work as expected (it seems that ssh still receives CTRL_C_EVENT, at least it exits immediately on Ctrl+C event).
r4victor
approved these changes
Nov 21, 2025
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When error logging was added to SSHTunnel.close()1, it was discovered that SSHAttach.detach() is called multiple times on detach. Although this is harmless as long as this method is idempotent (and it is), this patch ensures that detach() is no-op when called more than one time, removing ERROR level log noise.
As a side-effect, detaching SSHAttach that reuses SSHTunnel no longer kills "master" SSHAttach, meaning that one can
dstack attachmultiple times and detach independently (detaching from the "master" attach still kicks out all other attaches).