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perf: Phase 1 JetStream async file publish optimizations

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- Add cached state properties (LastSeq, MessageCount, TotalBytes, FirstSeq)
  to IStreamStore/FileStore/MemStore — eliminates GetStateAsync on publish path
- Add Capture(StreamHandle, ...) overload to StreamManager — eliminates
  double FindBySubject lookup (once in JetStreamPublisher, once in Capture)
- Remove _messageIndexes dictionary from FileStore write path — all lookups
  now use _messages directly, saving ~48B allocation per message
- Add JetStreamPubAckFormatter for hand-rolled UTF-8 success ack formatting —
  avoids JsonSerializer overhead on the hot publish path
- Switch flush loop to exponential backoff (1→2→4→8ms) matching Go server
This commit is contained in:
Joseph Doherty
2026-03-13 15:09:21 -04:00
parent 82cc3ec841
commit 7404ecdb0e
7 changed files with 106 additions and 30 deletions
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34
src/NATS.Server/JetStream/Storage/FileStore.cs
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@@ -28,7 +28,8 @@ public sealed class FileStore : IStreamStore, IAsyncDisposable, IDisposable
// In-memory cache: keyed by sequence number. This is the primary data structure
// for reads and queries. The blocks are the on-disk persistence layer.
private readonly Dictionary<ulong, StoredMessage> _messages = new();
private readonly Dictionary<ulong, StoredMessageIndex> _messageIndexes = new();
// _messageIndexes removed — all lookups now use _messages directly to avoid
// per-message StoredMessageIndex allocation on the write path.
private readonly Dictionary<string, ulong> _lastSequenceBySubject = new(StringComparer.Ordinal);
// Block-based storage: the active (writable) block and sealed blocks.
@@ -89,6 +90,12 @@ public sealed class FileStore : IStreamStore, IAsyncDisposable, IDisposable
public int BlockCount => _blocks.Count;
public bool UsedIndexManifestOnStartup { get; private set; }
// IStreamStore cached state properties — O(1), maintained incrementally.
public ulong LastSeq => _last;
public ulong MessageCount => _messageCount;
public ulong TotalBytes => _totalBytes;
ulong IStreamStore.FirstSeq => _messageCount == 0 ? (_first > 0 ? _first : 0UL) : _firstSeq;
public FileStore(FileStoreOptions options)
{
_options = options;
@@ -266,7 +273,6 @@ public sealed class FileStore : IStreamStore, IAsyncDisposable, IDisposable
public ValueTask RestoreSnapshotAsync(ReadOnlyMemory<byte> snapshot, CancellationToken ct)
{
_messages.Clear();
_messageIndexes.Clear();
_lastSequenceBySubject.Clear();
_last = 0;
_messageCount = 0;
@@ -415,7 +421,6 @@ public sealed class FileStore : IStreamStore, IAsyncDisposable, IDisposable
{
var count = (ulong)_messages.Count;
_messages.Clear();
_messageIndexes.Clear();
_lastSequenceBySubject.Clear();
_generation++;
_last = 0;
@@ -542,7 +547,6 @@ public sealed class FileStore : IStreamStore, IAsyncDisposable, IDisposable
{
// Truncate to nothing.
_messages.Clear();
_messageIndexes.Clear();
_lastSequenceBySubject.Clear();
_generation++;
_last = 0;
@@ -845,7 +849,6 @@ public sealed class FileStore : IStreamStore, IAsyncDisposable, IDisposable
private void TrackMessage(StoredMessage message)
{
_messages[message.Sequence] = message;
_messageIndexes[message.Sequence] = message.ToIndex();
_lastSequenceBySubject[message.Subject] = message.Sequence;
_messageCount++;
_totalBytes += (ulong)(message.RawHeaders.Length + message.Payload.Length);
@@ -861,8 +864,6 @@ public sealed class FileStore : IStreamStore, IAsyncDisposable, IDisposable
{
if (!_messages.Remove(sequence, out var message))
return false;
_messageIndexes.Remove(sequence);
_messageCount--;
_totalBytes -= (ulong)(message.RawHeaders.Length + message.Payload.Length);
UpdateLastSequenceForSubject(message.Subject, sequence);
@@ -890,7 +891,7 @@ public sealed class FileStore : IStreamStore, IAsyncDisposable, IDisposable
private void AdvanceFirstSequence(ulong start)
{
var candidate = start;
while (!_messageIndexes.ContainsKey(candidate) && candidate <= _last)
while (!_messages.ContainsKey(candidate) && candidate <= _last)
candidate++;
if (candidate <= _last)
@@ -911,7 +912,7 @@ public sealed class FileStore : IStreamStore, IAsyncDisposable, IDisposable
for (var seq = startExclusive - 1; ; seq--)
{
if (_messageIndexes.ContainsKey(seq))
if (_messages.ContainsKey(seq))
return seq;
if (seq == 0)
@@ -926,7 +927,7 @@ public sealed class FileStore : IStreamStore, IAsyncDisposable, IDisposable
for (var seq = removedSequence - 1; ; seq--)
{
if (_messageIndexes.TryGetValue(seq, out var candidate) && string.Equals(candidate.Subject, subject, StringComparison.Ordinal))
if (_messages.TryGetValue(seq, out var candidate) && string.Equals(candidate.Subject, subject, StringComparison.Ordinal))
{
_lastSequenceBySubject[subject] = seq;
return;
@@ -941,7 +942,6 @@ public sealed class FileStore : IStreamStore, IAsyncDisposable, IDisposable
private void RebuildIndexesFromMessages()
{
_messageIndexes.Clear();
_lastSequenceBySubject.Clear();
_messageCount = 0;
_totalBytes = 0;
@@ -2317,12 +2317,16 @@ public sealed class FileStore : IStreamStore, IAsyncDisposable, IDisposable
if (block is null)
continue;
var waited = 0;
while (block.PendingWriteSize < CoalesceMinimum && waited < MaxFlushWaitMs)
// Go-style exponential backoff: 1→2→4→8ms (vs linear 1ms × 8).
var waitMs = 1;
var totalWaited = 0;
while (block.PendingWriteSize < CoalesceMinimum && totalWaited < MaxFlushWaitMs)
{
try { await Task.Delay(1, ct); }
var delay = Math.Min(waitMs, MaxFlushWaitMs - totalWaited);
try { await Task.Delay(delay, ct); }
catch (OperationCanceledException) { break; }
waited++;
totalWaited += delay;
waitMs *= 2;
}
block.FlushPending();