Issue #12: implement session manager and registry
This commit is contained in:
Joseph Doherty
@@ -0,0 +1,287 @@
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using System.Security.Cryptography;
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using Google.Protobuf.WellKnownTypes;
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using Microsoft.Extensions.Logging;
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using Microsoft.Extensions.Logging.Abstractions;
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using Microsoft.Extensions.Options;
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using MxGateway.Contracts;
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using MxGateway.Contracts.Proto;
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using MxGateway.Server.Configuration;
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using MxGateway.Server.Metrics;
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using MxGateway.Server.Workers;
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namespace MxGateway.Server.Sessions;
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public sealed class SessionManager : ISessionManager
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{
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public const string DefaultCloseReason = "client-close";
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public const string GatewayShutdownReason = "gateway-shutdown";
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public const string LeaseExpiredReason = "lease-expired";
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private readonly ISessionRegistry _registry;
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private readonly ISessionWorkerClientFactory _workerClientFactory;
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private readonly GatewayMetrics _metrics;
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private readonly TimeProvider _timeProvider;
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private readonly ILogger<SessionManager> _logger;
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private readonly GatewayOptions _options;
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public SessionManager(
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ISessionRegistry registry,
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ISessionWorkerClientFactory workerClientFactory,
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IOptions<GatewayOptions> options,
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GatewayMetrics metrics,
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TimeProvider? timeProvider = null,
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ILogger<SessionManager>? logger = null)
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{
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_registry = registry ?? throw new ArgumentNullException(nameof(registry));
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_workerClientFactory = workerClientFactory ?? throw new ArgumentNullException(nameof(workerClientFactory));
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ArgumentNullException.ThrowIfNull(options);
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_metrics = metrics ?? throw new ArgumentNullException(nameof(metrics));
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_timeProvider = timeProvider ?? TimeProvider.System;
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_logger = logger ?? NullLogger<SessionManager>.Instance;
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_options = options.Value;
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}
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public async Task<GatewaySession> OpenSessionAsync(
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SessionOpenRequest request,
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string? clientIdentity,
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CancellationToken cancellationToken)
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{
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ArgumentNullException.ThrowIfNull(request);
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EnsureSessionCapacity();
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GatewaySession session = CreateSession(request, clientIdentity);
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if (!_registry.TryAdd(session))
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{
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throw new SessionManagerException(
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SessionManagerErrorCode.OpenFailed,
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$"Session id collision while opening session {session.SessionId}.");
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}
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try
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{
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session.TransitionTo(SessionState.StartingWorker);
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IWorkerClient workerClient = await _workerClientFactory
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.CreateAsync(session, cancellationToken)
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.ConfigureAwait(false);
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session.AttachWorkerClient(workerClient);
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session.MarkReady();
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_metrics.SessionOpened();
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return session;
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}
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catch (Exception exception)
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{
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session.MarkFaulted(exception.Message);
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_registry.TryRemove(session.SessionId, out _);
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await session.DisposeAsync().ConfigureAwait(false);
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_metrics.Fault(SessionManagerErrorCode.OpenFailed.ToString());
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_logger.LogWarning(
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exception,
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"Failed to open gateway session {SessionId}.",
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session.SessionId);
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throw new SessionManagerException(
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SessionManagerErrorCode.OpenFailed,
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$"Failed to open session {session.SessionId}.",
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exception);
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}
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}
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public bool TryGetSession(
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string sessionId,
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out GatewaySession session)
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{
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return _registry.TryGet(sessionId, out session);
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}
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public async Task<WorkerCommandReply> InvokeAsync(
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string sessionId,
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WorkerCommand command,
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CancellationToken cancellationToken)
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{
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GatewaySession session = GetRequiredSession(sessionId);
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try
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{
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return await session.InvokeAsync(command, cancellationToken).ConfigureAwait(false);
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}
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catch (SessionManagerException)
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{
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throw;
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}
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catch (Exception exception)
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{
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if (session.WorkerClient?.State == WorkerClientState.Faulted)
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{
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session.MarkFaulted(exception.Message);
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}
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throw;
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}
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}
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public IAsyncEnumerable<WorkerEvent> ReadEventsAsync(
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string sessionId,
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CancellationToken cancellationToken)
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{
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GatewaySession session = GetRequiredSession(sessionId);
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return session.ReadEventsAsync(cancellationToken);
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}
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public async Task<SessionCloseResult> CloseSessionAsync(
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string sessionId,
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CancellationToken cancellationToken)
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{
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GatewaySession session = GetRequiredSession(sessionId);
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SessionCloseResult result = await CloseSessionCoreAsync(
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session,
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DefaultCloseReason,
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cancellationToken).ConfigureAwait(false);
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return result;
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}
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public async Task<int> CloseExpiredLeasesAsync(
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DateTimeOffset now,
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CancellationToken cancellationToken)
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{
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int closedCount = 0;
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foreach (GatewaySession session in _registry.Snapshot())
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{
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if (!session.IsLeaseExpired(now))
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{
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continue;
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}
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await CloseSessionCoreAsync(session, LeaseExpiredReason, cancellationToken).ConfigureAwait(false);
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closedCount++;
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}
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return closedCount;
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}
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public async Task ShutdownAsync(CancellationToken cancellationToken)
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{
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foreach (GatewaySession session in _registry.Snapshot())
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{
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try
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{
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await CloseSessionCoreAsync(session, GatewayShutdownReason, cancellationToken).ConfigureAwait(false);
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}
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catch (Exception exception)
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{
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_logger.LogWarning(
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exception,
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"Graceful shutdown failed for session {SessionId}; killing worker.",
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session.SessionId);
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session.KillWorker(GatewayShutdownReason);
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}
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}
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}
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private async Task<SessionCloseResult> CloseSessionCoreAsync(
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GatewaySession session,
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string reason,
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CancellationToken cancellationToken)
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{
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bool wasClosed = session.State == SessionState.Closed;
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try
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{
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SessionCloseResult result = await session.CloseAsync(reason, cancellationToken).ConfigureAwait(false);
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if (!wasClosed && !result.AlreadyClosed)
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{
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_metrics.SessionClosed();
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}
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return result;
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}
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catch (Exception exception)
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{
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session.MarkFaulted(exception.Message);
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_metrics.Fault(SessionManagerErrorCode.CloseFailed.ToString());
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throw new SessionManagerException(
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SessionManagerErrorCode.CloseFailed,
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$"Failed to close session {session.SessionId}.",
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exception);
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}
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}
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private GatewaySession GetRequiredSession(string sessionId)
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{
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if (!_registry.TryGet(sessionId, out GatewaySession session))
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{
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throw new SessionManagerException(
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SessionManagerErrorCode.SessionNotFound,
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$"Session {sessionId} was not found.");
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}
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return session;
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}
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private void EnsureSessionCapacity()
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{
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if (_registry.ActiveCount >= _options.Sessions.MaxSessions)
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{
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throw new SessionManagerException(
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SessionManagerErrorCode.SessionLimitExceeded,
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$"Gateway session limit {_options.Sessions.MaxSessions} has been reached.");
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}
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}
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private GatewaySession CreateSession(
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SessionOpenRequest request,
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string? clientIdentity)
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{
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string sessionId = CreateSessionId();
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string backendName = string.IsNullOrWhiteSpace(request.RequestedBackend)
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? GatewayContractInfo.DefaultBackendName
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: request.RequestedBackend!;
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TimeSpan commandTimeout = ResolveCommandTimeout(request.CommandTimeout);
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TimeSpan startupTimeout = TimeSpan.FromSeconds(_options.Worker.StartupTimeoutSeconds);
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TimeSpan shutdownTimeout = TimeSpan.FromSeconds(_options.Worker.ShutdownTimeoutSeconds);
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string pipeName = $"mxaccess-gateway-{Environment.ProcessId}-{sessionId}";
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string nonce = CreateNonce();
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DateTimeOffset openedAt = _timeProvider.GetUtcNow();
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return new GatewaySession(
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sessionId,
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backendName,
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pipeName,
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nonce,
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clientIdentity,
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request.ClientSessionName,
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request.ClientCorrelationId,
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commandTimeout,
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startupTimeout,
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shutdownTimeout,
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openedAt);
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}
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private TimeSpan ResolveCommandTimeout(Duration? requestedTimeout)
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{
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if (requestedTimeout is null)
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{
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return TimeSpan.FromSeconds(_options.Sessions.DefaultCommandTimeoutSeconds);
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}
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TimeSpan timeout = requestedTimeout.ToTimeSpan();
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return timeout <= TimeSpan.Zero
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? TimeSpan.FromSeconds(_options.Sessions.DefaultCommandTimeoutSeconds)
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: timeout;
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}
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private static string CreateSessionId()
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{
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return $"session-{Guid.NewGuid():N}";
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}
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private static string CreateNonce()
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{
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Span<byte> bytes = stackalloc byte[32];
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RandomNumberGenerator.Fill(bytes);
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return Convert.ToBase64String(bytes);
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}
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}
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