STREAMS API in Garnet #1131

ramananeesh · 2025-03-23T23:42:06Z

Adds support for STREAMS in Garnet.

Index Structure

Uses an in-memory B+tree (B-tree) index that has the following features:

Fast insertions through the tail leaf node of the index, taking advantage of sorted data input.
Maximizes leaf occupancy, taking advantage of sorted data input.
Uses tombstones for deletes.
Supports forward and reverse range scans.

Supported Operations in API

The following operations are currently supported:

XADD - add using auto-generated id and user-defined id. Does not currently support [NOMKSTREAM], [MAXLEN], [MINID] and [threshold]
XLEN
XRANGE
XDEL

STREAMID

Stream ID is a 128-bit ID for an entry in the Stream that is of a format ts-seq where ts is generally the timestamp and seq is the sequence number.

STREAM

The Stream Object that consists of an instance to its B-tree index and a Tsavorite log instance for persistence. Every entry added to a Stream is first inserted into the Tsavorite log that returns the added address. This address is added as the value to the index using the STREAMID as key.

StreamManager

A container/wrapper that holds all Streams in the server in a dictionary.

SessionStreamCache

A local cache of Streams added by the client for faster access. Currently capped at capacity and uses a simple FIFO policy for the initial version. Can be extended to support other eviction strategies (preferably LRU).

…/streams

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badrishc · 2025-03-24T02:33:31Z

Directory.Build.props

@@ -12,7 +12,7 @@
    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
    <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
    <GenerateDocumentationFile>true</GenerateDocumentationFile>
-	  <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+	  <TreatWarningsAsErrors>false</TreatWarningsAsErrors>


revert this change

PaulusParssinen

First thanks for contributing!

I see the PR is marked as draft, but there's misunderstanding about the nature of Unsafe.AsPointer I want to help with as early as possible: It's use is always a mistake and unnecessary. Embrace Span<T> and normal struct usage as much as possible. I left few preliminary comments.

PaulusParssinen · 2025-03-24T06:37:23Z

libs/server/BTreeIndex/BTree.cs

+            byte[] keyBytes = new byte[BTreeNode.KEY_SIZE];
+            Buffer.MemoryCopy(leaf->GetKey(0), Unsafe.AsPointer(ref keyBytes[0]), BTreeNode.KEY_SIZE, BTreeNode.KEY_SIZE);


Unsafe.AsPointer is the single most dangerous method in the entire .NET. Using it here and elsewhere is certainly a mistake and unnecessary.

update: This is great example of GC hole. GC is free to move keyBytes to entirely different location after Unsafe.AsPointer call (yes, GC can occur between Unsafe.AsPointer call and Buffer.MemoryCopy). We could trigger this pretty consistently with GC stress.

Embrace (ReadOnly)Span<T> here and elsewhere! Here this heap copy would look like:

Suggested change

byte[] keyBytes = new byte[BTreeNode.KEY_SIZE];

Buffer.MemoryCopy(leaf->GetKey(0), Unsafe.AsPointer(ref keyBytes[0]), BTreeNode.KEY_SIZE, BTreeNode.KEY_SIZE);

byte[] keyBytes = new ReadOnlySpan<byte>(leaf->GetKey(0), BTreeNode.KEY_SIZE).ToArray();

Thanks for the suggestion! I have fixed this in the latest commit.

PaulusParssinen · 2025-03-24T06:41:20Z

libs/server/BTreeIndex/BTree.cs

+        {
+            bufferPool = new SectorAlignedBufferPool(1, BTreeNode.PAGE_SIZE);
+            // var memoryBlock = bufferPool.Get(BTreeNode.PAGE_SIZE);
+            var memoryBlock = (IntPtr*)Marshal.AllocHGlobal(BTreeNode.PAGE_SIZE).ToPointer();


Marshal.AllocHGlobal is considered legacy API nowadays. We have thinner "malloc" wrappers available as NativeMemory.Alloc today.

If we need aligned native allocations for the B-Tree page, we can use NativeMemory.AlignedAlloc. Just be very careful to free whatever native memory is allocated, on dispose.

PaulusParssinen · 2025-03-24T06:50:40Z

libs/server/BTreeIndex/BTree.cs

+                return default;
+            }
+            byte[] keyBytes = new byte[BTreeNode.KEY_SIZE];
+            Buffer.MemoryCopy(leaf->GetKey(leaf->info->count - 1), Unsafe.AsPointer(ref keyBytes[0]), BTreeNode.KEY_SIZE, BTreeNode.KEY_SIZE);


ditto, GC hole.

fixed in latest commit.

PaulusParssinen · 2025-03-24T06:56:53Z

libs/server/Stream/StreamID.cs

+                throw new ArgumentException("idBytes must be 16 bytes");
+            }
+
+            Buffer.MemoryCopy((byte*)Unsafe.AsPointer(ref inputBytes[0]), (byte*)Unsafe.AsPointer(ref idBytes[0]), 16, 16);


GC Hole with Unsafe.AsPointer usage here. I won't add comments for all of the Unsafe.AsPointer uses, ~~almost~~ certainly, every single one of them is unnecessary. All of them need to go.

fixed in latest commit.

PaulusParssinen · 2025-03-24T07:38:00Z

libs/server/Resp/ByteArrayComparer.cs

-        private ByteArrayComparer() { }
+        public ByteArrayComparer() { }


Revert. Use the .Instance above.

prvyk · 2025-03-24T08:22:56Z

Two nits:

FLUSHDB/FLUSHALL should clear the sequence number.
Return value is bulk string, not simple string.

…lloc instead of Marshal.AllocHGlobal

badrishc · 2025-03-28T20:52:05Z

Run dotnet format at the command line to get rid of formatting errors.

badrishc · 2025-03-28T20:54:56Z

libs/common/RespWriteUtils.cs

@@ -186,6 +186,23 @@ public static bool TryWriteSimpleString(ReadOnlySpan<byte> simpleString, ref byt
            return true;
        }

+        /// <summary>


remove commented code.

badrishc · 2025-03-28T20:56:06Z

libs/server/Servers/ServerOptions.cs

@@ -99,6 +99,10 @@ public class ServerOptions
        /// </summary>
        public bool SkipRDBRestoreChecksumValidation = false;

+        public string StreamPageSize = "4m";


Move these to GarnetServerOptions.cs and add comments.

badrishc · 2025-03-28T20:58:12Z

libs/server/Stream/SessionStreamCache.cs

+
+namespace Garnet.server
+{
+    internal struct SessionStreamCache


Can we make this a class, I don't think perf will be impacted that much? Please try it.

badrishc · 2025-03-28T21:00:34Z

libs/server/Resp/RespServerSession.cs

@@ -249,6 +254,10 @@ public RespServerSession(
                if (this.networkSender.GetMaxSizeSettings?.MaxOutputSize < sizeof(int))
                    this.networkSender.GetMaxSizeSettings.MaxOutputSize = sizeof(int);
            }
+
+            // grab stream manager from storeWrapper
+            this.streamManager = storeWrapper.streamManager;


We need a flag to enable streams --streams and leave it disabled by default. Similar to --lua which enables Lua. If not enabled, we should not incur the overhead of creating stream manager or session stream cache at all. Or any other objects or statics related to streams feature.

ramananeesh added 23 commits March 9, 2025 18:28

Streams API Work in progress

75f20bd

Streams - sector aligned bufferpool for index work in progress

73b3f20

sector aligned bufferpool integration works

b4723ec

testing code wip

1068e53

bug fixed

53e204b

fixed major bug in btree

c64785a

updates

9a6099e

fixed memory alloc by reverting to Marshal.AllocHGlobal

edaa741

code cleanup

7710e56

delete passes

0129aca

Merge branch 'main' of github.com:ramananeesh/garnet into ramananeesh…

fab86a8

…/streams

tying up the streams API

1be22c6

added command to RespCommandsInfo

d8a41f4

basic test with XADD and XLEN works

70f3bac

added XRANGE and XDEL - basic tests work

460d88f

fixed bug with stream id parsing/encode/decode

579bd6e

added ACL Tests

40af237

added RespStreamTests

83acdc7

minor cleanup

5444205

added cleaner command strings for incorrect arguments

5cab8b7

cleanup; removed TRIM code

d3551d8

cleanup; added more documentation about node structure

dcd33b9

more cleanup

8003334

badrishc reviewed Mar 24, 2025

View reviewed changes

PaulusParssinen suggested changes Mar 24, 2025

View reviewed changes

PaulusParssinen reviewed Mar 24, 2025

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ramananeesh added 2 commits March 27, 2025 10:46

reverted visibility change to ByteArrayComparer to instead use .Instance

5f92120

removed most of Unsafe.AsPointer() instances from BTree code

ede575d

ramananeesh added 3 commits March 27, 2025 23:15

swapped out memory allocation for B-tree to use NativeMemory.AlignedA…

6e4f239

…lloc instead of Marshal.AllocHGlobal

cleanup; removed unused imports + commented out code.

ce15667

bug fix - mismatch in allocates v/s deallocates for B-tree

e66d113

badrishc reviewed Mar 28, 2025

View reviewed changes

TalZaccai self-requested a review March 28, 2025 20:57

badrishc reviewed Mar 28, 2025

View reviewed changes

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STREAMS API in Garnet #1131

STREAMS API in Garnet #1131

ramananeesh commented Mar 23, 2025

microsoft-github-policy-service bot commented Mar 23, 2025

Contribution License Agreement

badrishc Mar 24, 2025

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badrishc Mar 28, 2025 •

edited

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		byte[] keyBytes = new byte[BTreeNode.KEY_SIZE];
		Buffer.MemoryCopy(leaf->GetKey(0), Unsafe.AsPointer(ref keyBytes[0]), BTreeNode.KEY_SIZE, BTreeNode.KEY_SIZE);

	byte[] keyBytes = new byte[BTreeNode.KEY_SIZE];
	Buffer.MemoryCopy(leaf->GetKey(0), Unsafe.AsPointer(ref keyBytes[0]), BTreeNode.KEY_SIZE, BTreeNode.KEY_SIZE);
	byte[] keyBytes = new ReadOnlySpan<byte>(leaf->GetKey(0), BTreeNode.KEY_SIZE).ToArray();

		private ByteArrayComparer() { }
		public ByteArrayComparer() { }

STREAMS API in Garnet #1131

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STREAMS API in Garnet #1131

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ramananeesh commented Mar 23, 2025

Index Structure

Supported Operations in API

STREAMID

STREAM

StreamManager

SessionStreamCache

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