Re: [libvirt] [PATCH 3/3] gluster: Fix key attribute for gluster volumes
On 02/24/14 21:59, Eric Blake wrote: On 02/24/2014 08:21 AM, Peter Krempa wrote: According to our documentation the key value has the following meaning: Providing an identifier for the volume which is globally unique. This cannot be set when creating a volume: it is always generated. The currently used keys for gluster volumes consist of the gluster volume name and file path. This can't be considered unique as a different storage server can serve a volume with the same name. Use the full URI as the key for the volume to avoid ambiguity problems. The full URI cannot be considered unique, either, as both gluster://hosta/volume/file and gluster://hostb/volume/file may resolve to the same file. I think we are better off documenting that a key is This depends on what we consider as unique in this context: The problem you are describing here is that two different keys may map to a single volume. The issue I'm trying to solve is that one key may map to two distinct volumes. As a first step we should thus clarify which way the key should be unique. If we want to make sure the mapping is always just 1:1, we might want to choose the gluster volume UUID as the first part of the key instead of the name. unique for some pools, but best effort for others, and not change what we have already been outputting. But if we DO keep this patch, you also need to change the documentation that gives examples of gluster keys. Peter signature.asc Description: OpenPGP digital signature -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [PATCH 3/3] gluster: Fix key attribute for gluster volumes
On Mon, Feb 24, 2014 at 01:59:30PM -0700, Eric Blake wrote: On 02/24/2014 08:21 AM, Peter Krempa wrote: According to our documentation the key value has the following meaning: Providing an identifier for the volume which is globally unique. This cannot be set when creating a volume: it is always generated. The currently used keys for gluster volumes consist of the gluster volume name and file path. This can't be considered unique as a different storage server can serve a volume with the same name. Use the full URI as the key for the volume to avoid ambiguity problems. The full URI cannot be considered unique, either, as both gluster://hosta/volume/file and gluster://hostb/volume/file may resolve to the same file. You're talking about a different type of uniqueness here. The important aspect of key uniqueness is that a single 'key' must be unambigous about what volume it is associated with. ie a single 'key' must not be capable of refering to 2 completely different volumes. Your example is about whether each volume has precisely 1 unique key. In the context of the storage pools I believe only the former point is important. Regards, Daniel -- |: http://berrange.com -o-http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [PATCH 3/3] gluster: Fix key attribute for gluster volumes
On 02/25/2014 03:36 AM, Peter Krempa wrote: The problem you are describing here is that two different keys may map to a single volume. The issue I'm trying to solve is that one key may map to two distinct volumes. As a first step we should thus clarify which way the key should be unique. If we want to make sure the mapping is always just 1:1, we might want to choose the gluster volume UUID as the first part of the key instead of the name. That actually sounds like a reasonable idea - if we are trying to ensure that a key lookup will find exactly one volume across multiple pools, then encoding the pool UUID into the volume key name seems reasonable. unique for some pools, but best effort for others, and not change what we have already been outputting. But if we DO keep this patch, you also need to change the documentation that gives examples of gluster keys. This is still true - we'd need to document the choice, as well as mention that early implementations of gluster pools were buggy with regards to key generation. As it would be a bug fix, I think we can still try to get this done in time for 1.2.2. -- Eric Blake eblake redhat com+1-919-301-3266 Libvirt virtualization library http://libvirt.org signature.asc Description: OpenPGP digital signature -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
[libvirt] [PATCH 3/3] gluster: Fix key attribute for gluster volumes
According to our documentation the key value has the following
meaning: Providing an identifier for the volume which is globally
unique. This cannot be set when creating a volume: it is always
generated. The currently used keys for gluster volumes consist of the
gluster volume name and file path. This can't be considered unique as a
different storage server can serve a volume with the same name.
Use the full URI as the key for the volume to avoid ambiguity problems.
---
src/storage/storage_backend_gluster.c | 10 --
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/src/storage/storage_backend_gluster.c
b/src/storage/storage_backend_gluster.c
index 202a441..bb13463 100644
--- a/src/storage/storage_backend_gluster.c
+++ b/src/storage/storage_backend_gluster.c
@@ -185,6 +185,7 @@
virStorageBackendGlusterSetMetadata(virStorageBackendGlusterStatePtr state,
const char *name)
{
int ret = -1;
+char *path = NULL;
char *tmp;
VIR_FREE(vol-key);
@@ -199,12 +200,12 @@
virStorageBackendGlusterSetMetadata(virStorageBackendGlusterStatePtr state,
goto cleanup;
}
-if (virAsprintf(vol-key, %s%s%s, state-volname, state-dir,
+if (virAsprintf(path, %s%s%s, state-volname, state-dir,
vol-name) 0)
goto cleanup;
tmp = state-uri-path;
-if (virAsprintf(state-uri-path, /%s, vol-key) 0) {
+if (virAsprintf(state-uri-path, /%s, path) 0) {
state-uri-path = tmp;
goto cleanup;
}
@@ -216,9 +217,14 @@
virStorageBackendGlusterSetMetadata(virStorageBackendGlusterStatePtr state,
VIR_FREE(state-uri-path);
state-uri-path = tmp;
+/* the path is unique enough to serve as a volume key */
+if (VIR_STRDUP(vol-key, vol-target.path) 0)
+goto cleanup;
+
ret = 0;
cleanup:
+VIR_FREE(path);
return ret;
}
--
1.8.5.5
--
libvir-list mailing list
libvir-list@redhat.com
https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [PATCH 3/3] gluster: Fix key attribute for gluster volumes
On 02/24/2014 08:21 AM, Peter Krempa wrote: According to our documentation the key value has the following meaning: Providing an identifier for the volume which is globally unique. This cannot be set when creating a volume: it is always generated. The currently used keys for gluster volumes consist of the gluster volume name and file path. This can't be considered unique as a different storage server can serve a volume with the same name. Use the full URI as the key for the volume to avoid ambiguity problems. The full URI cannot be considered unique, either, as both gluster://hosta/volume/file and gluster://hostb/volume/file may resolve to the same file. I think we are better off documenting that a key is unique for some pools, but best effort for others, and not change what we have already been outputting. But if we DO keep this patch, you also need to change the documentation that gives examples of gluster keys. -- Eric Blake eblake redhat com+1-919-301-3266 Libvirt virtualization library http://libvirt.org signature.asc Description: OpenPGP digital signature -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
