2010/3/23 Chris Lalancette <clalance@redhat.com>:
Hello, As some of you know, I've been working on a new snapshot API. This API is heavily based on DanB's earlier API proposed here:
https://www.redhat.com/archives/libvir-list/2010-January/msg00626.html
I've made some modifications to make it more libvirt-ish, and to add a couple of features I think it lacked. The full documentation is below. Any comments are appreciated.
/* NOTE: struct _virDomainSnapshot is a private structure, ala * struct _virDomain. */ typedef struct _virDomainSnapshot virDomainSnapshot;
/* Take a snapshot of the current VM state */ virDomainSnapshotPtr virDomainSnapshotCreateXML(virDomainPtr domain, const char *xmlDesc, unsigned int flags);
/* Dump the XML of a snapshot */ /* NOTE: see below for proposed XML */ char *virDomainSnapshotGetXMLDesc(virDomainSnapshotPtr snapshot, unsigned int flags);
/* Return the number of snapshots for this domain */ int virDomainSnapshotNum(virDomainPtr domain, unsigned int flags);
Shouldn't this be called virDomainNumOfSnapshots to be consistent with the naming or other num-of functions?
/* Get the names of all snapshots for this domain */ int virDomainListSnapshotNames(virDomainPtr domain, char **names, int nameslen, unsigned int flags);
/* Get a handle to a named snapshot */ virDomainSnapshotPtr virDomainSnapshotLookupByName(virDomainPtr domain, const char *name, unsigned int flags);
/* Set this snapshot as the current one for a domain, to be * used next time domain is started */ int virDomainSnapshotActivate(virDomainSnapshotPtr snapshot, unsigned int flags);
This delayed semantic cannot be implemented for ESX. ESX can revert to a snapshot immediately only. I think the same holds true for VirtualBox. Maybe I misunterstand this. What should happen if you call activate on a running domain?
/* Deactivate a snapshot - with no flags, the snapshot is not used anymore, * but also not removed. With a MERGE flag, it merges the snapshot into * the base image. With a DISCARD flag, it deletes the snapshot. MERGE * and DISCARD are mutually-exclusive. Note that this operation can * generally only happen when the domain is shut down, though this is * hypervisor-specific */ typedef enum { VIR_DOMAIN_SNAPSHOT_DEACTIVATE_MERGE, VIR_DOMAIN_SNAPSHOT_DEACTIVATE_DISCARD, } virDomainSnapshotDeactivate; int virDomainSnapshotDeactivate(virDomainSnapshotPtr snapshot, unsigned int flags);
I'm not sure if virDomainSnapshotDeactivate is a good name. Why would I deactivate a snapshot, but not merge/discard it? What's the use case for this?
int virDomainSnapshotFree(virDomainSnapshotPtr snapshot);
NOTE: During snapshot creation, *none* of the fields are required. That is, you can call virDomainSnapshotCreateXML() with an XML of "<domainsnapshot/>". In this case, the individual driver will make up a <name> for you, the <creationdate> will be set to the current time+date, <description> will be empty, <state> will be "off", <compression> will be empty, and <parent> will be empty. If you do want to specify some fields during virDomainSnapshotCreateXML(), note that the only ones that are settable are <name>, <description>, <compression>, and <parent>; the rest are ignored,
How can <parent> be settable? If I have snapshots A and B A -> B -> current state and I create a new snapshot C, then B will be the parent of C. A -> B -> C -> current state If I create another snapshot D now and specify A to be its parent, what's supposed to happen then? Matthias