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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
55 lines
1.8 KiB
Plaintext
55 lines
1.8 KiB
Plaintext
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#
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# The default sanlock configuration requires the management
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# application to manually define <lease> elements in the
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# guest configuration, typically one lease per disk. An
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# alternative is to enable "auto disk lease" mode. In this
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# usage, libvirt will automatically create a lockspace and
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# lease for each fully qualified disk path. This works if
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# you are able to ensure stable, unique disk paths across
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# all hosts in a network.
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#
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# Uncomment this to enable automatic lease creation.
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#
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# NB: the 'host_id' parameter must be set if enabling this
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#
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#auto_disk_leases = 1
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#
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# The default location in which lockspaces are created when
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# automatic lease creation is enabled. For each unique disk
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# path, a file $LEASE_DIR/NNNNNNNNNNNNNN will be created
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# where 'NNNNNNNNNNNNNN' is the MD5 checkout of the disk path.
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#
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# If this directory is on local storage, it will only protect
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# against a VM being started twice on the same host, or two
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# guests on the same host using the same disk path. If the
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# directory is on NFS, then it can protect against concurrent
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# usage across all hosts which have the share mounted.
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#
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# Recommendation is to just mount this default location as
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# an NFS volume. Uncomment this, if you would prefer the mount
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# point to be somewhere else.
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#
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#disk_lease_dir = "/var/lib/libvirt/sanlock"
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#
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# The unique ID for this host.
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#
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# IMPORTANT: *EVERY* host which can access the filesystem mounted
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# at 'disk_lease_dir' *MUST* be given a different host ID.
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#
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# This parameter has no default and must be manually set if
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# 'auto_disk_leases' is enabled
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#host_id = 1
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#
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# Flag to determine whether we allow starting of guests
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# which do not have any <lease> elements defined in their
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# configuration.
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#
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# If 'auto_disk_leases' is disabled, this setting defaults
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# to enabled, otherwise it defaults to disabled.
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#
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#require_lease_for_disks = 1
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