Remove the Witness DC role; collapse to Member and Arbiter#51
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The DC failover topology has exactly two kinds of data center: Member (holds data, votes, primary eligible) and Arbiter (no data, never primary, vote only for tie-breaking). The Witness role meant "a third DC that holds data but is never primary," and that case no longer exists: a third site is either a data-less Arbiter or a full Member, and MongoDB's third-site vote is a data-less arbiter placed in the Arbiter DC, not a data-bearing member. Witness was only just added and never shipped, so removing the enum value breaks nothing in use. - DCRole: drop the DCRoleWitness constant, the enum value, and the doc lines. - ClusterSpreadConstraint.Validate(): drop the witnesses counter and the Witness branch; TwoDC now requires exactly two Members and at least one Arbiter. - Webhook and FailoverMode/FailoverPolicy comments updated to Member/Arbiter. - Regenerate the PlacementPolicy CRD (controller-gen): role enum is Member;Arbiter. - Add Validate tests: TwoDC needs an Arbiter, and Witness is now an unknown role. Signed-off-by: Tamal Saha <tamal@appscode.com>
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The DC failover topology has exactly two kinds of data center:
replicaIndices, holds no data, never primary, votes for tie-breaking (runs thedr-controlplanefailover service, plus for geo-quorum engines a data-less engine voter the operator places there).The
Witnessrole meant "a third DC that holds data but is never primary," and that case no longer exists: a third site is either a data-lessArbiteror a fullMember, and MongoDB's third-site vote is a data-less arbiter in the Arbiter DC, not a data-bearing member.Witnesswas only just added (this branch) and has never shipped, so removing the enum value breaks nothing in use.Changes
DCRole: drop theDCRoleWitnessconstant, the+kubebuilder:validation:Enumvalue, and the doc lines (enum is nowMember;Arbiter).ClusterSpreadConstraint.Validate(): drop thewitnessescounter and theWitnessbranch;TwoDCnow requires exactly two Members and at least one Arbiter (error text updated).FailoverModeTwoDC/FailoverPolicy.Modecomments updated to Member/Arbiter.roleenum dropsWitness.Validatetests: TwoDC requires an Arbiter, and aWitnessrole is now rejected as an unknown role.Based on
dc-dr-failover-policy(where theRolefield was introduced; it is not yet on master).go build,go vet, andgo test ./apis/... ./pkg/webhooks/...pass. dr-controlplane and the db operators re-vendor afterward in their own PRs.