Joseph Doherty
57 lines
2.6 KiB
C#
57 lines
2.6 KiB
C#
using Akka.Cluster;
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using Microsoft.Extensions.Diagnostics.HealthChecks;
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namespace ZB.MOM.WW.Health.Akka;
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/// <summary>
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/// Pure mapping from an Akka <see cref="MemberStatus"/> to a <see cref="HealthStatus"/>.
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/// </summary>
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/// <remarks>
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/// <para>
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/// Wraps a <see cref="Func{MemberStatus, HealthStatus}"/> so the decision logic is a deterministic,
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/// table-testable function — <see cref="AkkaClusterHealthCheck"/> only supplies the live cluster
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/// status. Two named presets reconcile the divergence between the existing ScadaBridge and OtOpcUa
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/// implementations; construct a custom instance for project-specific overrides.
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/// </para>
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/// </remarks>
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public sealed class AkkaClusterStatusPolicy
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{
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private readonly Func<MemberStatus, HealthStatus> _evaluate;
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/// <summary>Initializes a new <see cref="AkkaClusterStatusPolicy"/>.</summary>
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/// <param name="evaluate">The pure status-to-health mapping function.</param>
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public AkkaClusterStatusPolicy(Func<MemberStatus, HealthStatus> evaluate)
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{
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_evaluate = evaluate ?? throw new ArgumentNullException(nameof(evaluate));
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}
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/// <summary>Applies the policy to the given member status.</summary>
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/// <param name="status">The local node's Akka cluster member status.</param>
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/// <returns>The mapped <see cref="HealthStatus"/>.</returns>
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public HealthStatus Evaluate(MemberStatus status) => _evaluate(status);
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/// <summary>
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/// ScadaBridge origin: <c>Up</c>/<c>Joining</c> → Healthy, <c>Leaving</c>/<c>Exiting</c> →
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/// Degraded, everything else → Unhealthy. The convergence target for all projects.
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/// </summary>
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public static AkkaClusterStatusPolicy Default { get; } = new(static status => status switch
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{
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MemberStatus.Up or MemberStatus.Joining => HealthStatus.Healthy,
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MemberStatus.Leaving or MemberStatus.Exiting => HealthStatus.Degraded,
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_ => HealthStatus.Unhealthy,
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});
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/// <summary>
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/// OtOpcUa origin: self-<c>Up</c>-among-reachable-members → Healthy, any non-<c>Up</c> state
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/// (including <c>Leaving</c>/<c>Exiting</c>/<c>Down</c>) → Degraded. Provided for backward
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/// compatibility during OtOpcUa's migration.
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/// </summary>
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/// <remarks>
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/// The original OtOpcUa check scanned the reachable member set for self with
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/// <c>Status == Up</c>; any other state caused the scan to miss self and collapse to Degraded.
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/// This preset reproduces that behavior: only <see cref="MemberStatus.Up"/> is Healthy.
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/// </remarks>
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public static AkkaClusterStatusPolicy OtOpcUaCompat { get; } = new(static status =>
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status == MemberStatus.Up ? HealthStatus.Healthy : HealthStatus.Degraded);
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}
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