Joseph Doherty
43 lines
1.7 KiB
C#
43 lines
1.7 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.</summary>
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public static bool SelfIsOldest(Cluster cluster, string? role = null)
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{
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var self = cluster.SelfMember;
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if (self.Status != MemberStatus.Up)
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return false;
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if (role != null && !self.HasRole(role))
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return false;
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return cluster.State.Members
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.Where(m => m.Status == MemberStatus.Up)
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.Where(m => role == null || m.HasRole(role))
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.All(m => m.UniqueAddress.Equals(self.UniqueAddress) || self.IsOlderThan(m));
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}
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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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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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