perf: eliminate per-message allocations in pub/sub hot path and coalesce outbound writes
Pub/sub 1:1 (16B) improved from 0.18x to 0.50x, fan-out from 0.18x to 0.44x, and JetStream durable fetch from 0.13x to 0.64x vs Go. Key changes: replace .ToArray() copy in SendMessage with pooled buffer handoff, batch multiple small writes into single WriteAsync via 64KB coalesce buffer in write loop, and remove profiling Stopwatch instrumentation from ProcessMessage/StreamManager hot paths.
This commit is contained in:
Joseph Doherty
@@ -0,0 +1,260 @@
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using System.Diagnostics;
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using Microsoft.Extensions.Logging.Abstractions;
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using NATS.Client.Core;
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using NATS.Client.JetStream;
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using NATS.Client.JetStream.Models;
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using NATS.Server.Configuration;
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using NATS.Server.JetStream.Publish;
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using NATS.Server.JetStream.Storage;
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using Xunit.Abstractions;
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using ServerStreamConfig = NATS.Server.JetStream.Models.StreamConfig;
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using ServerStorageType = NATS.Server.JetStream.Models.StorageType;
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using ServerRetentionPolicy = NATS.Server.JetStream.Models.RetentionPolicy;
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namespace NATS.Server.JetStream.Tests.JetStream;
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/// <summary>
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/// Profiling test for the JetStream publish hot path.
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/// </summary>
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public class JetStreamPublishProfileTest(ITestOutputHelper output)
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{
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/// <summary>
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/// FileStore.AppendAsync only — isolates the store layer without StreamManager overhead.
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/// </summary>
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[Fact]
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[Trait("Category", "Profile")]
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public void Profile_FileStore_AppendAsync_Only()
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{
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const int messageCount = 10_000;
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const int payloadSize = 128;
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const string subject = "bench.append.fs";
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var payload = new byte[payloadSize];
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var storeDir = Path.Combine(Path.GetTempPath(), "nats-profile-append-" + Guid.NewGuid().ToString("N")[..8]);
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Directory.CreateDirectory(storeDir);
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try
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{
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var store = new FileStore(new FileStoreOptions { Directory = storeDir, BlockSizeBytes = 256 * 1024 });
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// Warmup
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for (var i = 0; i < 1_000; i++)
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store.AppendAsync(subject, payload, default);
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var sw = Stopwatch.StartNew();
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for (var i = 0; i < messageCount; i++)
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store.AppendAsync(subject, payload, default);
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sw.Stop();
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var msgPerSec = messageCount / sw.Elapsed.TotalSeconds;
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output.WriteLine($"=== FileStore AppendAsync Only ===");
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output.WriteLine($"Messages: {messageCount:N0}, Duration: {sw.Elapsed.TotalMilliseconds:F1} ms");
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output.WriteLine($"Throughput: {msgPerSec:N0} msg/s");
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output.WriteLine($"GC Gen0: {GC.CollectionCount(0)}, Gen1: {GC.CollectionCount(1)}, Gen2: {GC.CollectionCount(2)}");
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store.Dispose();
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}
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finally
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{
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try { Directory.Delete(storeDir, recursive: true); }
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catch { /* best-effort */ }
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}
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}
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/// <summary>
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/// Server-side only: calls StreamManager.Capture directly (no network).
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/// Isolates FileStore vs MemStore performance.
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/// </summary>
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[Fact]
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[Trait("Category", "Profile")]
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public void Profile_FileStore_Publish_ServerSide()
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{
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const int messageCount = 5_000;
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const int payloadSize = 128;
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const string subject = "bench.profile.fs";
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var payload = new byte[payloadSize];
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var storeDir = Path.Combine(Path.GetTempPath(), "nats-profile-fs-" + Guid.NewGuid().ToString("N")[..8]);
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Directory.CreateDirectory(storeDir);
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try
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{
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var streamManager = new StreamManager(storeDir: storeDir);
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var publisher = new JetStreamPublisher(streamManager);
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var config = new ServerStreamConfig
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{
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Name = "PROFILE_FS",
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Subjects = [subject],
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Storage = ServerStorageType.File,
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Retention = ServerRetentionPolicy.Limits,
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MaxMsgs = 10_000_000,
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};
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streamManager.CreateOrUpdate(config);
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// Warmup
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for (var i = 0; i < 500; i++)
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publisher.TryCapture(subject, payload, out _);
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JetStreamProfiler.DumpAndReset();
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var sw = Stopwatch.StartNew();
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for (var i = 0; i < messageCount; i++)
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publisher.TryCapture(subject, payload, out _);
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sw.Stop();
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var msgPerSec = messageCount / sw.Elapsed.TotalSeconds;
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output.WriteLine($"=== FileStore Server-Side Profile ===");
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output.WriteLine($"Messages: {messageCount:N0}, Duration: {sw.Elapsed.TotalMilliseconds:F1} ms");
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output.WriteLine($"Throughput: {msgPerSec:N0} msg/s");
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output.WriteLine("");
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output.WriteLine(JetStreamProfiler.DumpAndReset());
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streamManager.Dispose();
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}
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finally
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{
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try { Directory.Delete(storeDir, recursive: true); }
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catch { /* best-effort */ }
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}
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}
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/// <summary>
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/// Server-side only: MemStore baseline for comparison.
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/// </summary>
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[Fact]
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[Trait("Category", "Profile")]
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public void Profile_MemStore_Publish_ServerSide()
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{
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const int messageCount = 5_000;
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const int payloadSize = 128;
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const string subject = "bench.profile.mem";
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var payload = new byte[payloadSize];
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var streamManager = new StreamManager();
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var publisher = new JetStreamPublisher(streamManager);
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var config = new ServerStreamConfig
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{
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Name = "PROFILE_MEM",
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Subjects = [subject],
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Storage = ServerStorageType.Memory,
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Retention = ServerRetentionPolicy.Limits,
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MaxMsgs = 10_000_000,
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};
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streamManager.CreateOrUpdate(config);
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// Warmup
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for (var i = 0; i < 500; i++)
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publisher.TryCapture(subject, payload, out _);
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JetStreamProfiler.DumpAndReset();
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var sw = Stopwatch.StartNew();
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for (var i = 0; i < messageCount; i++)
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publisher.TryCapture(subject, payload, out _);
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sw.Stop();
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var msgPerSec = messageCount / sw.Elapsed.TotalSeconds;
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output.WriteLine($"=== MemStore Server-Side Profile ===");
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output.WriteLine($"Messages: {messageCount:N0}, Duration: {sw.Elapsed.TotalMilliseconds:F1} ms");
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output.WriteLine($"Throughput: {msgPerSec:N0} msg/s");
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output.WriteLine("");
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output.WriteLine(JetStreamProfiler.DumpAndReset());
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streamManager.Dispose();
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}
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/// <summary>
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/// E2E: in-process NatsServer with real NatsConnection client.
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/// Measures full publish path including network, protocol parsing, ack serialization.
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/// </summary>
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[Fact]
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[Trait("Category", "Profile")]
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public async Task Profile_FileStore_Publish_E2E()
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{
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const int messageCount = 5_000;
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const int payloadSize = 128;
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const int batchSize = 100;
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const string subject = "bench.profile.e2e";
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var payload = new byte[payloadSize];
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var storeDir = Path.Combine(Path.GetTempPath(), "nats-profile-e2e-" + Guid.NewGuid().ToString("N")[..8]);
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Directory.CreateDirectory(storeDir);
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try
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{
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var options = new NatsOptions
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{
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Host = "127.0.0.1",
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Port = 0, // Ephemeral port
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JetStream = new JetStreamOptions
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{
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StoreDir = storeDir,
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MaxMemoryStore = 256 * 1024 * 1024,
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MaxFileStore = 1L * 1024 * 1024 * 1024,
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},
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};
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using var server = new NATS.Server.NatsServer(options, NullLoggerFactory.Instance);
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_ = server.StartAsync(CancellationToken.None);
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await server.WaitForReadyAsync();
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var port = server.Port;
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await using var nats = new NatsConnection(new NatsOpts { Url = $"nats://127.0.0.1:{port}" });
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await nats.ConnectAsync();
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var js = new NatsJSContext(nats);
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var streamName = $"PROFILE_E2E_{Guid.NewGuid():N}"[..24];
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await js.CreateStreamAsync(new StreamConfig(streamName, [subject])
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{
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Storage = StreamConfigStorage.File,
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Retention = StreamConfigRetention.Limits,
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MaxMsgs = 10_000_000,
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});
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// Warmup
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for (var i = 0; i < 500; i++)
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await js.PublishAsync(subject, payload);
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JetStreamProfiler.DumpAndReset();
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// Measurement — fire-and-gather in batches (same as benchmark)
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var sw = Stopwatch.StartNew();
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var tasks = new List<ValueTask<PubAckResponse>>(batchSize);
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for (var i = 0; i < messageCount; i++)
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{
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tasks.Add(js.PublishAsync(subject, payload));
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if (tasks.Count >= batchSize)
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{
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foreach (var t in tasks)
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await t;
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tasks.Clear();
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}
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}
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foreach (var t in tasks)
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await t;
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sw.Stop();
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var msgPerSec = messageCount / sw.Elapsed.TotalSeconds;
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output.WriteLine($"=== FileStore E2E Profile (in-process server) ===");
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output.WriteLine($"Messages: {messageCount:N0}, Duration: {sw.Elapsed.TotalMilliseconds:F1} ms");
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output.WriteLine($"Throughput: {msgPerSec:N0} msg/s");
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output.WriteLine("");
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output.WriteLine(JetStreamProfiler.DumpAndReset());
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await js.DeleteStreamAsync(streamName);
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await server.ShutdownAsync();
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}
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finally
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{
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try { Directory.Delete(storeDir, recursive: true); }
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catch { /* best-effort */ }
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}
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}
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}
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