45 lines
1.7 KiB
C#
45 lines
1.7 KiB
C#
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using StackExchange.Redis;
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namespace w4c_workflows.Services;
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/// <summary>Distributed lease over Redis for in-flight run state.</summary>
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public interface ILeaseService
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{
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Task<bool> AcquireAsync(string tenantId, string runId, string owner, TimeSpan ttl);
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Task<bool> ReleaseAsync(string tenantId, string runId, string owner);
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}
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/// <summary>
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/// Lease / distributed lock over Redis for in-flight run state:
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/// wf:{tenant}:leases:{runId} → owner id, with a TTL.
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/// Acquire is atomic (SET NX PX); release compares the owner before deleting so
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/// a stale owner can never release someone else's lease.
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/// </summary>
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public class LeaseService : ILeaseService
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{
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// Compare-and-delete: only delete if the value still matches the owner.
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private const string ReleaseScript =
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"if redis.call('GET', KEYS[1]) == ARGV[1] then return redis.call('DEL', KEYS[1]) else return 0 end";
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private readonly IDatabase _db;
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public LeaseService(IConnectionMultiplexer redis)
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{
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_db = redis.GetDatabase();
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}
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private static RedisKey KeyFor(string tenantId, string runId) => $"wf:{tenantId}:leases:{runId}";
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/// <summary>Atomically acquires the lease; returns false if already held.</summary>
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public Task<bool> AcquireAsync(string tenantId, string runId, string owner, TimeSpan ttl)
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=> _db.StringSetAsync(KeyFor(tenantId, runId), owner, ttl, When.NotExists);
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/// <summary>Releases the lease only if the caller owns it.</summary>
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public async Task<bool> ReleaseAsync(string tenantId, string runId, string owner)
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{
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var result = await _db.ScriptEvaluateAsync(
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ReleaseScript, new RedisKey[] { KeyFor(tenantId, runId) }, new RedisValue[] { owner });
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return (long)result == 1;
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}
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}
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