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authorKaushal M <kaushal@redhat.com>2013-08-12 10:43:52 +0530
committerAnand Avati <avati@redhat.com>2013-09-29 21:39:38 -0700
commit9b286d5937e7c78fd17185e9afe25e809153a265 (patch)
tree3495dc5594d43d677555cb292d722a9790de55e2 /xlators/cluster
parent623d232d29bbed71349334988054a5bd205b1a39 (diff)
glusterd: Calculate volume op-versions only on set/reset
The volume op-versions are calculated during a volume set/reset, reading a volume from disk and importing a volume during probe or volume sync. The calculation of the volume op-version depends on the clusters op-version as some features are enabled automatically depending on the clusters op-version. We also don't store the volume op-versions persistently and don't export the volume op-versions during sync. Due to this, there can occur cases which will lead to inconsistencies in volumes in different peers. One such case is below, Consider, a cluster made up 3 peers P1, P2 and P3, operating at op-version N. The cluster has two volumes V1 and V2, which have volume op-versions N (since volume op-version cannot be greater than cluster op-version). We have, Cluster-op-version = N V1 op-version = N V2 op-version = N A set operation on V1 causes the clusters op-version to be bumped up to N+1. Assume that there exist some features that are automatically enabled on op-version N+1. The op-version of V2 remains at N as no operation has been performed on it. So, Cluster op-version = N+1 V1 op-version = N+1 V2 op-version = N Now, we probe a new peer P4. On the new peer we will have the following op-versions, Cluster op-version = N+1 V1 op-version = N+1 V2 op-version = N+1 This happens because we don't send volume op-versions during the sync after probe. P4 will freshly calculate the op-version of V2 (assuming features have been auto enabled due to the cluster op-version being N+1) as N+1. Another case is when glusterd on a peer restarts. Assume P3 was restarted, glusterd will recalculate the volume op-versions during the restore state. Again, op-version of V2 will be calculated as N+1 assuming auto enabled features. This will lead to inconsistency in the volume representation in memory and on disk, as glusterd will assume the volume contains auto enabled features, but the volfiles don't contain them as they were not regenrated. These kind of issues can be solved by calculating the volume op-version only when features are enabled and disabled (ie. during volume set/reset), persisting the volume-op-versions and exporting/importing them. Change-Id: I52de0668c92628622e85f4588fb28829a7231132 BUG: 1005043 Signed-off-by: Kaushal M <kaushal@redhat.com> Reviewed-on: http://review.gluster.org/5568 Reviewed-by: Amar Tumballi <amarts@redhat.com> Tested-by: Gluster Build System <jenkins@build.gluster.com> Reviewed-by: Anand Avati <avati@redhat.com>
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