Ensure tasks preserve versions in MasterService
#109900
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`ClusterState#version`, `Metadata#version` and `RoutingTable#version` are all managed solely by the `MasterService`, in the sense that it's a definite bug for the cluster state update task executor to meddle with them. Today if we encounter such a bug then we try and publish the resulting state anyway, which hopefully fails (triggering a master election) but it may in theory succeed (potentially reverting older cluster state updates). Neither is a particularly good outcome. With this commit we add a check for consistency of these version numbers during the cluster state computation and fail the state update without a master failover if a discrepancy is found. It also fixes a super-subtle bug in `TransportMigrateToDataTiersAction` that can muck up these version numbers.
DaveCTurner
added
>bug
:Distributed/Cluster Coordination
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ClusterState#version,Metadata#versionandRoutingTable#versionare all managed solely by the
MasterService, in the sense that it's adefinite bug for the cluster state update task executor to meddle with
them. Today if we encounter such a bug then we try and publish the
resulting state anyway, which hopefully fails (triggering a master
election) but it may in theory succeed (potentially reverting older
cluster state updates). Neither is a particularly good outcome.
With this commit we add a check for consistency of these version numbers
during the cluster state computation and fail the state update without a
master failover if a discrepancy is found.
It also fixes a super-subtle bug in
TransportMigrateToDataTiersActionthat can muck up these version numbers.
Backport of #109850 to 8.14