Joseph Doherty
41 lines
2.2 KiB
C#
41 lines
2.2 KiB
C#
using Akka.Cluster;
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namespace ZB.MOM.WW.ScadaBridge.Host.Health;
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/// <summary>
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/// THE single definition of "active node" (review 01 [High]): a node is active
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/// when it is the OLDEST Up member (optionally within a role scope) — i.e. the
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/// member the ClusterSingletonManager places singletons on. Cluster LEADERSHIP
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/// (lowest address) is an Akka-internal concept that diverges from singleton
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/// placement permanently once the original first node restarts and rejoins;
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/// every product-level active/standby decision must use this evaluator, never
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/// cluster.State.Leader.
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/// </summary>
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public static class ClusterActivityEvaluator
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{
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/// <summary>True when self is Up and no other Up member (in the role scope) is older.
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/// Delegates to the shared <see cref="Communication.ClusterState.ActiveNodeEvaluator"/> —
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/// one implementation for the delivery gate, the resync authority checks, and the
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/// heartbeat IsActive stamp (review 02 round 2, N1).</summary>
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/// <param name="cluster">The Akka cluster to evaluate.</param>
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/// <param name="role">Optional role scope; when set, only members with this role are considered.</param>
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/// <returns><c>true</c> when self is Up and the oldest Up member in the role scope.</returns>
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public static bool SelfIsOldest(Cluster cluster, string? role = null) =>
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Communication.ClusterState.ActiveNodeEvaluator.SelfIsOldestUp(cluster, role);
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/// <summary>The oldest Up member in the role scope, or null while none is Up. Used for Primary/Standby labelling.</summary>
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/// <param name="cluster">The Akka cluster to evaluate.</param>
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/// <param name="role">Optional role scope; when set, only members with this role are considered.</param>
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/// <returns>The oldest Up member in the role scope, or null when none is Up.</returns>
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public static Member? OldestUpMember(Cluster cluster, string? role = null)
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{
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Member? oldest = null;
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foreach (var m in cluster.State.Members.Where(m => m.Status == MemberStatus.Up))
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{
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if (role != null && !m.HasRole(role)) continue;
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if (oldest == null || m.IsOlderThan(oldest)) oldest = m;
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}
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return oldest;
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}
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}
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