Re: [libvirt] [PATCH v3] blockjob: use stable disk string in job event

When the block job event was first added, it was for block pull, where the active layer of the disk remains the same name. It was also in a day where we only cared about local files, and so we always had a canonical absolute file name. But two things have changed since then: we now have network disks, where determining a single absolute string does not really make sense; and we have two-phase jobs (copy and active commit) where the name of the active layer changes between the first event (ready, on the old name) and second (complete, on the pivoted name). Adam Litke reported that having an unstable string between events makes life harder for clients. Furthermore, all of our API that operate on a particular disk of a domain accept multiple strings: not only the absolute name of the active layer, but also the destination device name (such as 'vda'). As this latter name is stable, even for network sources, it serves as a better string to supply in block job events. But backwards-compatibility demands that we should not change the name handed to users unless they explicitly request it. Therefore, this patch adds a new event, BLOCK_JOB_2 (alas, I couldn't think of any nicer name - but at least Migrate2 and Migrate3 are precedent for a number suffix). We must double up on emitting both old-style and new-style events according to what clients have registered for (see also how IOError and IOErrorReason emits double events, but there the difference was a larger struct rather than changed meaning of one of the struct members). Unfortunately, adding a new event isn't something that can easily be broken into pieces, so the commit is rather large. * include/libvirt/libvirt.h.in (virDomainEventID): Add a new id for VIR_DOMAIN_EVENT_ID_BLOCK_JOB_2. (virConnectDomainEventBlockJobCallback): Document new semantics. * src/conf/domain_event.c (_virDomainEventBlockJob): Rename field, to ensure we catch all clients. (virDomainEventBlockJobNew): Add parameter. (virDomainEventBlockJobDispose) (virDomainEventBlockJobNewFromObj) (virDomainEventBlockJobNewFromDom) (virDomainEventDispatchDefaultFunc): Adjust clients. (virDomainEventBlockJob2NewFromObj) (virDomainEventBlockJob2NewFromDom): New functions. * src/conf/domain_event.h: Add new prototypes. * src/libvirt_private.syms (domain_event.h): Export new functions. * src/qemu/qemu_driver.c (qemuDomainBlockJobImpl): Generate two different events. * src/qemu/qemu_process.c (qemuProcessHandleBlockJob): Likewise. * src/remote/remote_protocol.x (remote_domain_event_block_job_2_msg): New struct. (REMOTE_PROC_DOMAIN_EVENT_BLOCK_JOB_2): New RPC. * src/remote/remote_driver.c (remoteDomainBuildEventBlockJob2): New handler. (remoteEvents): Register new event. * daemon/remote.c (remoteRelayDomainEventBlockJob2): New handler. (domainEventCallbacks): Register new event. * tools/virsh-domain.c (vshEventCallbacks): Likewise. (vshEventBlockJobPrint): Adjust client. * src/remote_protocol-structs: Regenerate. Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- v3: don't do s/path/disk/ on code that is not shared; s/disk/dst/ on new code that is not shared; touch up libvirt.c docs, actually test with python bindings daemon/remote.c | 39 +++++++++++++++++++++++++++++++++++++++ include/libvirt/libvirt.h.in | 19 ++++++++++++++++--- src/conf/domain_event.c | 44 +++++++++++++++++++++++++++++++++++--------- src/conf/domain_event.h | 11 +++++++++++ src/libvirt_private.syms | 2 ++ src/qemu/qemu_driver.c | 8 +++++++- src/qemu/qemu_process.c | 7 +++++++ src/remote/remote_driver.c | 31 +++++++++++++++++++++++++++++++ src/remote/remote_protocol.x | 16 +++++++++++++++- src/remote_protocol-structs | 8 ++++++++ tools/virsh-domain.c | 7 +++++-- 11 files changed, 176 insertions(+), 16 deletions(-)