Re: [PATCH v1] chardev: introduce 'reconnect-ms' and deprecate 'reconnect'

Daniil Tatianin <d-tatianin(a)yandex-team.ru&gt; writes: > The 'reconnect' option only allows to specify the time in seconds, > which is way too long for certain workflows. > > We have a lightweight disk backend server, which takes about 20ms to > live update, but due to this limitation in QEMU, previously the guest > disk controller would hang for one second because it would take this > long for QEMU to reinitialize the socket connection. > > Introduce a new option called 'reconnect-ms', which is the same as > 'reconnect', except the value is treated as milliseconds. These are > mutually exclusive and specifying both results in an error. Good: $ upstream-qemu -nodefaults -chardev socket,id=chr0,path=test-hmp,server=off,reconnect=1,reconnect-ms=2 upstream-qemu: -chardev socket,id=chr0,path=test-hmp,server=off,reconnect=1,reconnect-ms=2: 'reconnect' and 'reconnect-ms' are mutually exclusive Bad: $ upstream-qemu -nodefaults -S -display none -qmp stdio {"QMP": {"version": {"qemu": {"micro": 50, "minor": 1, "major": 9}, "package": "v9.1.0-211-ga0866249bd"}, "capabilities": ["oob"]}} {"execute": "qmp_capabilities", "arguments": {"enable": ["oob"]}} {"return": {}} {"execute":"chardev-add", "arguments": {"id":"chr0", "backend": {"type": "socket", "data": {"server": false, "addr": {"type": "unix", "data": {"path": "xyz"}}, "reconnect": 1, "reconnect-ms": 2}}}} {"return": {}} upstream-qemu: Unable to connect character device chr0: Failed to connect to 'xyz': No such file or directory We're not rejecting simultaneous use of @reconnect and @reconnect-ms here. Moreover, you somehow regressed the handling of the "unable to connect" error. Before the patch, behavior is correct: $ upstream-qemu -nodefaults -S -display none -qmp stdio {"QMP": {"version": {"qemu": {"micro": 50, "minor": 1, "major": 9}, "package": "v9.1.0-210-g4b7ea33074"}, "capabilities": ["oob"]}} {"execute": "qmp_capabilities", "arguments": {"enable": ["oob"]}} {"return": {}} {"execute":"chardev-add", "arguments": {"id":"chr0", "backend": {"type": "socket", "data": {"server": false, "addr": {"type": "unix", "data": {"path": "xyz"}}}}}} {"error": {"class": "GenericError", "desc": "Failed to add chardev 'chr0': Failed to connect to 'xyz': No such file or directory"}}