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Fix keyset pagination with monotonic UUIDv7-like task IDs (#1215)

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: eiriktsarpalis <2813363+eiriktsarpalis@users.noreply.github.com>
Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>
Co-authored-by: Stephen Toub <stoub@microsoft.com>
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Copilot 2026-01-30 17:09:24 -05:00 • committed by GitHub
commit e47f88419c
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2 changed files with 247 additions and 25 deletions
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2
src/ModelContextProtocol.Core/ModelContextProtocol.Core.csproj
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@ -7,7 +7,6 @@
<PackageId>ModelContextProtocol.Core</PackageId>
<Description>Core .NET SDK for the Model Context Protocol (MCP)</Description>
<PackageReadmeFile>README.md</PackageReadmeFile>
<AllowUnsafeBlocks>True</AllowUnsafeBlocks>
<!-- Suppress the experimental tasks warning -->
<NoWarn>$(NoWarn);MCPEXP001</NoWarn>
</PropertyGroup>
@ -19,6 +18,7 @@
<PropertyGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
<!-- CS0436: Allow ObsoleteAttribute to be redefined internally -->
<NoWarn>$(NoWarn);CS0436</NoWarn>
<AllowUnsafeBlocks>true</AllowUnsafeBlocks>
</PropertyGroup>
<ItemGroup>

79
src/ModelContextProtocol.Core/Server/InMemoryMcpTaskStore.cs
View file

@ -3,7 +3,11 @@ using System.Collections.Concurrent;
using System.Diagnostics.CodeAnalysis;
using System.Text.Json;
#if MCP_TEST_TIME_PROVIDER
namespace ModelContextProtocol.Tests.Internal;
#else
namespace ModelContextProtocol;
#endif
/// <summary>
/// Provides an in-memory implementation of <see cref="IMcpTaskStore"/> for development and testing.
@ -35,6 +39,9 @@ public sealed class InMemoryMcpTaskStore : IMcpTaskStore, IDisposable
private readonly int _pageSize;
private readonly int? _maxTasks;
private readonly int? _maxTasksPerSession;
#if MCP_TEST_TIME_PROVIDER
private readonly TimeProvider _timeProvider;
#endif
/// <summary>
/// Initializes a new instance of the <see cref="InMemoryMcpTaskStore"/> class.
@ -120,6 +127,9 @@ public sealed class InMemoryMcpTaskStore : IMcpTaskStore, IDisposable
_pageSize = pageSize;
_maxTasks = maxTasks;
_maxTasksPerSession = maxTasksPerSession;
#if MCP_TEST_TIME_PROVIDER
_timeProvider = TimeProvider.System;
#endif
cleanupInterval ??= TimeSpan.FromMinutes(1);
if (cleanupInterval.Value != Timeout.InfiniteTimeSpan)
@ -128,6 +138,26 @@ public sealed class InMemoryMcpTaskStore : IMcpTaskStore, IDisposable
}
}
#if MCP_TEST_TIME_PROVIDER
/// <summary>
/// Initializes a new instance of the <see cref="InMemoryMcpTaskStore"/> class with a custom time provider.
/// This constructor is only available for testing purposes.
/// </summary>
internal InMemoryMcpTaskStore(
TimeSpan? defaultTtl,
TimeSpan? maxTtl,
TimeSpan? pollInterval,
TimeSpan? cleanupInterval,
int pageSize,
int? maxTasks,
int? maxTasksPerSession,
TimeProvider timeProvider)
: this(defaultTtl, maxTtl, pollInterval, cleanupInterval, pageSize, maxTasks, maxTasksPerSession)
{
_timeProvider = timeProvider ?? TimeProvider.System;
}
#endif
/// <inheritdoc/>
public Task<McpTask> CreateTaskAsync(
McpTaskMetadata taskParams,
@ -155,7 +185,7 @@ public sealed class InMemoryMcpTaskStore : IMcpTaskStore, IDisposable
}
var taskId = GenerateTaskId();
var now = DateTimeOffset.UtcNow;
var now = GetUtcNow();
// Determine TTL: use requested, fall back to default, respect max limit
var ttl = taskParams.TimeToLive ?? _defaultTtl;
@ -242,7 +272,7 @@ public sealed class InMemoryMcpTaskStore : IMcpTaskStore, IDisposable
var updatedEntry = new TaskEntry(entry)
{
Status = status,
LastUpdatedAt = DateTimeOffset.UtcNow,
LastUpdatedAt = GetUtcNow(),
StoredResult = result
};
@ -303,7 +333,7 @@ public sealed class InMemoryMcpTaskStore : IMcpTaskStore, IDisposable
{
Status = status,
StatusMessage = statusMessage,
LastUpdatedAt = DateTimeOffset.UtcNow,
LastUpdatedAt = GetUtcNow(),
};
if (_tasks.TryUpdate(taskId, updatedEntry, entry))
@ -321,32 +351,22 @@ public sealed class InMemoryMcpTaskStore : IMcpTaskStore, IDisposable
string? sessionId = null,
CancellationToken cancellationToken = default)
{
// Parse cursor: format is "CreatedAt|TaskId" for keyset pagination
(DateTimeOffset, string)? parsedCursor = null;
if (cursor != null)
{
var parts = cursor.Split('|');
if (parts.Length == 2 &&
DateTimeOffset.TryParse(parts[0], out var parsedDate))
{
parsedCursor = (parsedDate, parts[1]);
}
}
// Stream enumeration - filter by session, exclude expired, apply keyset pagination
var query = _tasks.Values
.Where(e => sessionId == null || e.SessionId == sessionId)
.Where(e => !IsExpired(e));
// Apply keyset filter if cursor provided: (CreatedAt, TaskId) > cursor
if (parsedCursor is { } parsedCursorValue)
// Apply keyset filter if cursor provided: TaskId > cursor
// UUID v7 task IDs are monotonically increasing and inherently time-ordered
if (cursor != null)
{
query = query.Where(e => (e.CreatedAt, e.TaskId).CompareTo(parsedCursorValue) > 0);
query = query.Where(e => string.CompareOrdinal(e.TaskId, cursor) > 0);
}
// Order by (CreatedAt, TaskId) for stable, deterministic pagination
// Order by TaskId for stable, deterministic pagination
// UUID v7 task IDs sort chronologically due to embedded timestamp
var page = query
.OrderBy(e => (e.CreatedAt, e.TaskId))
.OrderBy(e => e.TaskId, StringComparer.Ordinal)
.Take(_pageSize + 1) // Take one extra to check if there's a next page
.Select(e => e.ToMcpTask())
.ToList();
@ -356,7 +376,7 @@ public sealed class InMemoryMcpTaskStore : IMcpTaskStore, IDisposable
if (page.Count > _pageSize)
{
var lastItemInPage = page[_pageSize - 1]; // Last item we'll actually return
nextCursor = $"{lastItemInPage.CreatedAt:O}|{lastItemInPage.TaskId}";
nextCursor = lastItemInPage.TaskId;
page.RemoveAt(_pageSize); // Remove the extra item
}
else
@ -397,7 +417,7 @@ public sealed class InMemoryMcpTaskStore : IMcpTaskStore, IDisposable
var updatedEntry = new TaskEntry(entry)
{
Status = McpTaskStatus.Cancelled,
LastUpdatedAt = DateTimeOffset.UtcNow,
LastUpdatedAt = GetUtcNow(),
};
if (_tasks.TryUpdate(taskId, updatedEntry, entry))
@ -417,12 +437,23 @@ public sealed class InMemoryMcpTaskStore : IMcpTaskStore, IDisposable
_cleanupTimer?.Dispose();
}
private static string GenerateTaskId() => Guid.NewGuid().ToString("N");
private string GenerateTaskId() =>
IdHelpers.CreateMonotonicId(GetUtcNow());
private static bool IsTerminalStatus(McpTaskStatus status) =>
status is McpTaskStatus.Completed or McpTaskStatus.Failed or McpTaskStatus.Cancelled;
#if MCP_TEST_TIME_PROVIDER
private DateTimeOffset GetUtcNow() => _timeProvider.GetUtcNow();
#else
private static DateTimeOffset GetUtcNow() => DateTimeOffset.UtcNow;
#endif
#if MCP_TEST_TIME_PROVIDER
private bool IsExpired(TaskEntry entry)
#else
private static bool IsExpired(TaskEntry entry)
#endif
{
if (entry.TimeToLive == null)
{
@ -430,7 +461,7 @@ public sealed class InMemoryMcpTaskStore : IMcpTaskStore, IDisposable
}
var expirationTime = entry.CreatedAt + entry.TimeToLive.Value;
return DateTimeOffset.UtcNow >= expirationTime;
return GetUtcNow() >= expirationTime;
}
private void CleanupExpiredTasks(object? state)