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The current sanlock plugin requires a central management application to manually add <lease> elements to each guest, to protect resources that are assigned to it (eg writable disks). This makes the sanlock plugin useless for usage in more ad hoc deployment environments where there is no central authority to associate disks with leases. This patch adds a mode where the sanlock plugin will automatically create leases for each assigned read-write disk, using a md5 checksum of the fully qualified disk path. This can work pretty well if guests are using stable disk paths for block devices eg /dev/disk/by-path/XXXX symlinks, or if all hosts have NFS volumes mounted in a consistent pattern. The plugin will create one lockspace for managing disks with filename /var/lib/libvirt/sanlock/__LIBVIRT__DISKS__. For each VM disks, there will be another file to hold a lease /var/lib/libvirt/sanlock/5903e5d25e087e60a20fe4566fab41fd Each VM disk lease is usually 1 MB in size. The script virt-sanlock-cleanup should be run periodically to remove unused lease files from the lockspace directory. To make use of this capability the admin will need to do several tasks: - Mount an NFS volume (or other shared filesystem) on /var/lib/libvirt/sanlock - Configure 'host_id' in /etc/libvirt/qemu-sanlock.conf with a unique value for each host with the same NFS mount - Toggle the 'auto_disk_leases' parameter in qemu-sanlock.conf Technically the first step can be skipped, in which case sanlock will only protect against 2 vms on the same host using the same disk (or the same VM being started twice due to error by libvirt). * src/locking/libvirt_sanlock.aug, src/locking/sanlock.conf, src/locking/test_libvirt_sanlock.aug: Add config params for configuring auto lease setup * libvirt.spec.in: Add virt-sanlock-cleanup program, man page * tools/virt-sanlock-cleanup.in: Script to purge unused disk resource lease files |
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|---|---|---|
| .. | ||
| domain_lock.c | ||
| domain_lock.h | ||
| libvirt_sanlock.aug | ||
| lock_driver_nop.c | ||
| lock_driver_nop.h | ||
| lock_driver_sanlock.c | ||
| lock_driver.h | ||
| lock_manager.c | ||
| lock_manager.h | ||
| README | ||
| sanlock.conf | ||
| test_libvirt_sanlock.aug | ||
Using the Lock Manager APIs
===========================
This file describes how to use the lock manager APIs.
All the guest lifecycle sequences here have higher
level wrappers provided by the 'domain_lock.h' API,
which simplify thue usage
At libvirtd startup:
plugin = virLockManagerPluginLoad("sync-manager");
At libvirtd shtudown:
virLockManagerPluginUnload(plugin)
At guest startup:
manager = virLockManagerNew(plugin,
VIR_LOCK_MANAGER_OBJECT_DOMAIN,
0);
virLockManagerSetParameter(manager, "id", id);
virLockManagerSetParameter(manager, "uuid", uuid);
virLockManagerSetParameter(manager, "name", name);
foreach disk
virLockManagerRegisterResource(manager,
VIR_LOCK_MANAGER_RESOURCE_TYPE_DISK,
disk.path,
..flags...);
if (!virLockManagerAcquireObject(manager))
abort..
run QEMU
At guest shutdown:
...send QEMU 'quit' monitor command, and/or kill(qemupid)...
if (!virLockManagerShutdown(manager))
kill(supervisorpid); /* XXX or leave it running ??? */
virLockManagerFree(manager);
At libvirtd restart with running guests:
foreach still running guest
manager = virLockManagerNew(driver,
VIR_LOCK_MANAGER_START_DOMAIN,
VIR_LOCK_MANAGER_NEW_ATTACH);
virLockManagerSetParameter(manager, "id", id);
virLockManagerSetParameter(manager, "uuid", uuid);
virLockManagerSetParameter(manager, "name", name);
if (!virLockManagerGetChild(manager, &qemupid))
kill(supervisorpid); /* XXX or leave it running ??? */
With disk hotplug:
if (virLockManagerAcquireResource(manager,
VIR_LOCK_MANAGER_RESOURCE_TYPE_DISK,
disk.path
..flags..))
...abort hotplug attempt ...
...hotplug the device...
With disk unhotplug:
...hotunplug the device...
if (virLockManagerReleaseResource(manager,
VIR_LOCK_MANAGER_RESOURCE_TYPE_DISK,
disk.path
..flags..))
...log warning ...
During migration:
1. On source host
if (!virLockManagerPrepareMigrate(manager, hosturi))
..don't start migration..
2. On dest host
manager = virLockManagerNew(driver,
VIR_LOCK_MANAGER_START_DOMAIN,
VIR_LOCK_MANAGER_NEW_MIGRATE);
virLockManagerSetParameter(manager, "id", id);
virLockManagerSetParameter(manager, "uuid", uuid);
virLockManagerSetParameter(manager, "name", name);
foreach disk
virLockManagerRegisterResource(manager,
VIR_LOCK_MANAGER_RESOURCE_TYPE_DISK,
disk.path,
..flags...);
char **supervisorargv;
int supervisorargc;
supervisor = virLockManagerGetSupervisorPath(manager);
virLockManagerGetSupervisorArgs(&argv, &argc);
cmd = qemuBuildCommandLine(supervisor, supervisorargv, supervisorargv);
supervisorpid = virCommandExec(cmd);
if (!virLockManagerGetChild(manager, &qemupid))
kill(supervisorpid); /* XXX or leave it running ??? */
3. Initiate migration in QEMU on source and wait for completion
4a. On failure
4a1 On target
virLockManagerCompleteMigrateIn(manager,
VIR_LOCK_MANAGER_MIGRATE_CANCEL);
virLockManagerShutdown(manager);
virLockManagerFree(manager);
4a2 On source
virLockManagerCompleteMigrateIn(manager,
VIR_LOCK_MANAGER_MIGRATE_CANCEL);
4b. On succcess
4b1 On target
virLockManagerCompleteMigrateIn(manager, 0);
42 On source
virLockManagerCompleteMigrateIn(manager, 0);
virLockManagerShutdown(manager);
virLockManagerFree(manager);
Notes:
- If a lock manager impl does just VM level leases, it can
ignore all the resource paths at startup.
- If a lock manager impl does not support migrate
it can return an error from all migrate calls
- If a lock manger impl does not support hotplug
it can return an error from all resource acquire/release calls