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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id g23-20020ac84dd7000000b00436e0eb2346sm804146qtw.55.2024.04.18.09.43.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Apr 2024 09:43:45 -0700 (PDT) Date: Thu, 18 Apr 2024 12:43:42 -0400 From: Peter Xu To: Vladimir Sementsov-Ogievskiy Cc: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= , farosas@suse.de, yc-core@yandex-team.ru, thuth@redhat.com, lvivier@redhat.com, pbonzini@redhat.com, qemu-devel@nongnu.org, pkrempa@redhat.com Subject: Re: [PATCH] migration: do not exit on incoming failure Message-ID: References: <20240417221329.248803-1-vsementsov@yandex-team.ru> <0a1d8984-bc01-41bf-9099-0ef426e848ca@yandex-team.ru> <985d47bb-3c14-4576-95fa-28649710686b@yandex-team.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <985d47bb-3c14-4576-95fa-28649710686b@yandex-team.ru> Received-SPF: pass client-ip=170.10.129.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-2.067, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Thu, Apr 18, 2024 at 06:47:31PM +0300, Vladimir Sementsov-Ogievskiy wrote: > On 18.04.24 18:43, Daniel P. Berrangé wrote: > > On Thu, Apr 18, 2024 at 06:40:38PM +0300, Vladimir Sementsov-Ogievskiy wrote: > > > On 18.04.24 17:37, Daniel P. Berrangé wrote: > > > > On Thu, Apr 18, 2024 at 01:13:29AM +0300, Vladimir Sementsov-Ogievskiy wrote: > > > > > We do set MIGRATION_FAILED state, but don't give a chance to > > > > > orchestrator to query migration state and get the error. > > > > > > > > > > Let's report an error through QAPI like we do on outgoing migration. > > > > > > > > > > migration-test is updated correspondingly. > > > > > > > > > > Signed-off-by: Vladimir Sementsov-Ogievskiy > > > > > --- > > > > > > > > > > Doubt: is exiting on failure a contract? Will this commit break > > > > > something in Libvirt? Finally, could we just change the logic, or I need > > > > > and additional migration-parameter for new behavior? > > > > > > > > There's a decent risk that this could break apps, whether > > > > libvirt or something else, especially if the app is just > > > > launching QEMU with '-incoming URI', rather than using > > > > '-incoming defer' and then explicitly using QMP to start the > > > > incoming migration. > > > > > > > > I'd say that with '-incoming defer' we should *not* exit on > > > > migration error, because that arg implies the app explicitly > > > > wants to be using QMP to control migration. > > > > > > > > With the legacy '-incoming URI' it is probably best to keep > > > > exit on error, as that's comparatively more likely to be used > > > > in adhoc scenarios where the app/user is ignoring QMP on the > > > > dst side. > > > > > > > > None the less, I think we need to check how libvirt behaves > > > > with this patch to be sure of no surprises. > > > > > > > > > > Sounds reasonable, thanks! I'll rework it to behave the new > > > way only with "-incoming defer", and check how libvirt behave with it. > > > > If there are problems and/or we want to be super safe wrt > > backcompat, we could add a new '-incoming managed' as > > being equivalent to '-incoming defer' but without the > > implicit exit. > > > > Probably, that's the best variant. As I can check libvirt in some case, but not at all cases. And libvirt is not the only vm manager finally. > And we can in the same time deprecate "-incoming defer" in favor of new behavior. Or just make it a new migration parameter? Then we keep all existing interfaces untouched, no risk of breaking anyone, and then it'll also apply to anyone who uses things like -incoming tcp but still wants to keep the qemu instance alive? Thanks, -- Peter Xu