natsdotnet/tests/NATS.E2E.Cluster.Tests/Infrastructure/ThreeNodeClusterFixture.cs

using System.Net.Http.Json;
using System.Text.Json.Serialization;
using NATS.Client.Core;

namespace NATS.E2E.Cluster.Tests.Infrastructure;

public sealed class ThreeNodeClusterFixture : IAsyncLifetime
{
    private readonly NatsServerProcess?[] _servers = new NatsServerProcess?[3];
    private readonly int[] _clientPorts = new int[3];
    private readonly int[] _clusterPorts = new int[3];
    private readonly int[] _monitorPorts = new int[3];
    private readonly string[] _configs = new string[3];

    public async Task InitializeAsync()
    {
        // Pre-allocate all ports upfront so they can be reused across kill/restart
        for (var i = 0; i < 3; i++)
        {
            _clientPorts[i] = NatsServerProcess.AllocateFreePort();
            _clusterPorts[i] = NatsServerProcess.AllocateFreePort();
            _monitorPorts[i] = NatsServerProcess.AllocateFreePort();
        }

        var routes = $"""
            nats-route://127.0.0.1:{_clusterPorts[0]}
            nats-route://127.0.0.1:{_clusterPorts[1]}
            nats-route://127.0.0.1:{_clusterPorts[2]}
            """;

        for (var i = 0; i < 3; i++)
        {
            _configs[i] = $$"""
                server_name: node{{i + 1}}
                cluster {
                    name: e2e-cluster
                    listen: 127.0.0.1:{{_clusterPorts[i]}}
                    pool_size: 1
                    routes: [
                        {{routes}}
                    ]
                }
                """;

            _servers[i] = new NatsServerProcess(
                _clientPorts[i],
                extraArgs: ["-DV"],
                configContent: _configs[i],
                enableMonitoring: true,
                monitorPort: _monitorPorts[i]);
        }

        await Task.WhenAll(_servers.Select(s => s!.StartAsync()));

        await WaitForFullMeshAsync();
    }

    /// <summary>
    /// Kills the server at the given index (0–2) by disposing it.
    /// </summary>
    public async Task KillNode(int index)
    {
        if (_servers[index] is { } server)
        {
            await server.DisposeAsync();
            _servers[index] = null;
        }
    }

    /// <summary>
    /// Restarts the server at the given index on its originally allocated ports.
    /// </summary>
    public async Task RestartNode(int index)
    {
        // Dispose any existing process first (idempotent)
        if (_servers[index] is not null)
            await KillNode(index);

        _servers[index] = new NatsServerProcess(
            _clientPorts[index],
            extraArgs: ["-DV"],
            configContent: _configs[index],
            enableMonitoring: true,
            monitorPort: _monitorPorts[index]);

        await _servers[index]!.StartAsync();
    }

    /// <summary>
    /// Polls /routez on all alive nodes until each reports NumRoutes >= expectedRoutes.
    /// Times out after 30 seconds.
    /// </summary>
    public async Task WaitForFullMeshAsync(int expectedRoutes = 2)
    {
        using var http = new HttpClient();
        using var timeout = new CancellationTokenSource(TimeSpan.FromSeconds(30));
        using var timer = new PeriodicTimer(TimeSpan.FromMilliseconds(200));

        while (await timer.WaitForNextTickAsync(timeout.Token).ConfigureAwait(false))
        {
            var allConnected = true;

            for (var i = 0; i < 3; i++)
            {
                // Skip killed nodes
                if (_servers[i] is null)
                    continue;

                try
                {
                    var routez = await http.GetFromJsonAsync<Routez>(
                        $"http://127.0.0.1:{_monitorPorts[i]}/routez",
                        timeout.Token);

                    if (routez?.NumRoutes < expectedRoutes)
                    {
                        allConnected = false;
                        break;
                    }
                }
                catch
                {
                    allConnected = false;
                    break;
                }
            }

            if (allConnected)
                return;
        }

        throw new TimeoutException($"Cluster did not reach {expectedRoutes} routes per node within 30s.");
    }

    /// <summary>
    /// Creates a NatsConnection pointed at the given node index (0–2).
    /// </summary>
    public NatsConnection CreateClient(int index = 0)
        => new(new NatsOpts { Url = $"nats://127.0.0.1:{_clientPorts[index]}" });

    /// <summary>
    /// Returns the captured stdout/stderr output from the server at the given index.
    /// </summary>
    public string GetServerOutput(int index)
        => _servers[index]?.Output ?? string.Empty;

    public async Task DisposeAsync()
    {
        var disposeTasks = _servers
            .Where(s => s is not null)
            .Select(s => s!.DisposeAsync().AsTask());

        await Task.WhenAll(disposeTasks);
    }

    private sealed class Routez
    {
        [JsonPropertyName("num_routes")]
        public int NumRoutes { get; init; }
    }
}

[CollectionDefinition("E2E-ThreeNodeCluster")]
public class ThreeNodeClusterCollection : ICollectionFixture<ThreeNodeClusterFixture>;