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Safe, async-first parallel operators with bounded concurrency, retries, cancellation, and streaming backpressure for I/O-heavy workloads.

📚 Read the Full Documentation

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📦 Packages

Released

Rivulet.Core

Safe, async-first parallel operators with bounded concurrency, retries, and backpressure for I/O-heavy workloads. Docs

Key Features:

• Bounded Concurrency - Control max parallel operations with backpressure
• Adaptive Concurrency - Auto-scale workers based on latency and success rate (AIMD algorithm)
• Retry Policies - Automatic retries with exponential backoff for transient errors
• Circuit Breaker - Prevent cascading failures with automatic service protection
• Rate Limiting - Token bucket algorithm for controlling operation rates
• Error Handling Modes - FailFast, CollectAndContinue, or BestEffort
• Streaming Support - Process results incrementally via IAsyncEnumerable<T>
• Ordered Output - Maintain input sequence order when needed
• Runtime Metrics - Built-in monitoring via EventCounters and custom callbacks
• Progress Reporting - Periodic snapshots with throughput, ETA, and percent-complete
• Cancellation - Full CancellationToken support throughout
• Lifecycle Hooks - OnStart, OnComplete, OnRetry, OnError, OnThrottle, OnDrain callbacks
• Fallback Values - Supply default results for failed items instead of throwing
• Per-Item Timeouts - Enforce timeouts for individual operations
• Works with both IEnumerable<T> and IAsyncEnumerable<T>

Rivulet.Diagnostics

Enterprise observability for Rivulet.Core with EventListener wrappers, metric aggregators, and health check integration. Docs

Key Features:

• EventListener Wrappers: Console, File, and Structured JSON logging
• Metrics Aggregation: Time-window based metric aggregation with statistics
• Prometheus Export: Export metrics in Prometheus text format
• Health Check Integration: Microsoft.Extensions.Diagnostics.HealthChecks support
• Fluent Builder API: Easy configuration with DiagnosticsBuilder

Rivulet.Diagnostics.OpenTelemetry

OpenTelemetry integration for Rivulet.Core providing distributed tracing, metrics export, and comprehensive observability. Docs

Key Features:

• Distributed Tracing: Automatic activity creation with parent-child relationships
• Metrics Export: Bridge EventCounters to OpenTelemetry Meters
• Retry Tracking: Record retry attempts as activity events
• Circuit Breaker Events: Track circuit state changes in traces
• Adaptive Concurrency: Monitor concurrency adjustments
• Error Correlation: Link errors with retry attempts and transient classification

Rivulet.Hosting

Integration package for using Rivulet with Microsoft.Extensions.Hosting, ASP.NET Core, and the .NET Generic Host. Docs

Key Features:

• Dependency Injection integration
• Configuration binding for ParallelOptionsRivulet
• Base classes for parallel background services
• Health checks for monitoring parallel operations
• Support for ASP.NET Core and Worker Services

Rivulet.Testing

Testing utilities for Rivulet parallel operations including deterministic schedulers, virtual time, fake channels, and chaos injection. Docs

Key Features:

• VirtualTimeProvider: Control time in tests without actual delays
• FakeChannel: Testable channel implementation with operation tracking
• ChaosInjector: Inject failures and delays for resilience testing
• ConcurrencyAsserter: Assert and verify concurrency behavior

Rivulet.Http

Parallel HTTP operations with automatic retries, resilient downloads, and HttpClientFactory integration. Docs

Key Features:

• HttpClientFactory integration
• Connection pooling awareness
• Transient error handling (timeouts, 5xx responses)
• Bounded concurrency to avoid overwhelming servers
• Progress reporting for downloads

Rivulet.IO

Parallel file and directory operations with bounded concurrency, resilience, and streaming support for efficient I/O processing. Docs

Key Features:

• Safe concurrent file access
• Directory tree processing
• File pattern matching (glob patterns)
• Progress reporting
• Atomic write operations

Rivulet.Sql

Safe parallel SQL operations with connection pooling awareness and bulk operations. Docs

Key Features:

• Works with any ADO.NET provider
• Connection pooling awareness
• Transaction support
• Parameterized queries
• Respects database connection pool limits

Rivulet.Sql.SqlServer

SQL Server-specific optimizations for Rivulet.Sql including SqlBulkCopy integration for 10-100x faster bulk inserts. Docs

Key Features:

• SqlBulkCopy Integration: Ultra-high performance bulk inserts (50,000+ rows/sec)
• Parallel Bulk Operations: Process multiple batches in parallel
• Automatic Column Mapping: Maps DataTable columns to SQL Server table columns
• Custom Column Mappings: Support for explicit source-to-destination column mappings
• DataReader Support: Bulk insert from IDataReader sources
• Configurable Batching: Control batch size and timeout settings

Rivulet.Sql.PostgreSql

PostgreSQL-specific optimizations for Rivulet.Sql including COPY command integration for 10-100x faster bulk inserts. Docs

Key Features:

• COPY Command Integration: Ultra-high performance bulk inserts using COPY
• Multiple Formats: Binary, CSV, and text formats supported
• Parallel Operations: Process multiple batches in parallel
• Streaming Import: Efficient memory usage with streaming
• Custom Delimiters: Support for CSV with custom delimiters
• Header Support: Handle CSV files with headers

Rivulet.Sql.MySql

MySQL-specific optimizations for Rivulet.Sql using MySqlBulkLoader (LOAD DATA LOCAL INFILE) for 10-100x faster bulk inserts. Docs

Key Features:

• MySqlBulkLoader: LOAD DATA LOCAL INFILE for maximum performance
• File-based Loading: Direct file import support
• Parallel Operations: Process multiple batches in parallel
• Custom Delimiters: Support for any field separator
• Automatic Column Mapping: Maps columns automatically

Rivulet.Polly

Integration between Rivulet parallel processing and Polly resilience policies. Docs

Key Features:

• Use Polly policies with Rivulet - Apply any Polly policy to parallel operations
• Convert Rivulet to Polly - Use Rivulet configuration as standalone Polly policies
• Advanced resilience patterns - Hedging, result-based retry, and more
• Battle-tested - Built on Polly's production-proven resilience library

Rivulet.Pipeline

Multi-stage pipeline composition for Rivulet with fluent API, per-stage concurrency, backpressure management between stages, and streaming support. Docs

Key Features:

• Fluent Builder API - Type-safe pipeline construction with IntelliSense support
• Per-Stage Concurrency - Different parallelism levels for each processing stage
• Backpressure Management - Automatic flow control between stages using channels
• Streaming & Buffered Modes - Memory-efficient streaming or materialized results
• Full Rivulet.Core Integration - Retries, circuit breakers, rate limiting, metrics

Rivulet.Csv

Parallel CSV parsing and writing with CsvHelper integration, bounded concurrency, and batching support for high-throughput data processing. Docs

Key Features:

• CsvHelper integration for robust CSV parsing
• Multi-type operations (2-5 generic type parameters)
• Memory-efficient streaming with IAsyncEnumerable
• Per-file CSV configuration (delimiters, culture, class maps)
• Progress tracking and lifecycle callbacks
• Error handling modes (FailFast, CollectAndContinue, BestEffort)
• Circuit breaker and retry support
• Ordered and unordered output options

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🚀 Features

• Async-first (ValueTask), works with IEnumerable<T> and IAsyncEnumerable<T>
• Bounded concurrency with backpressure (Channels)
• Retry policy with transient detection and configurable backoff strategies (Exponential, ExponentialJitter, DecorrelatedJitter, Linear, LinearJitter)
• Per-item timeouts, cancellation, lifecycle hooks
• Flexible error modes: FailFast, CollectAndContinue, BestEffort
• Ordered output mode for sequence-sensitive operations

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🚦 Quick Start

var results = await urls.SelectParallelAsync(
    async (url, ct) =>
    {
        using var resp = await http.GetAsync(url, ct);
        resp.EnsureSuccessStatusCode();
        return (url, (int)resp.StatusCode);
    },
    new ParallelOptionsRivulet {
        MaxDegreeOfParallelism = 32,
        MaxRetries = 3,
        IsTransient = ex => ex is HttpRequestException or TaskCanceledException,
        ErrorMode = ErrorMode.CollectAndContinue
    });

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📖 Core Features

Streaming Results

await foreach (var r in source.SelectParallelStreamAsync(
    async (x, ct) => await ComputeAsync(x, ct),
    new ParallelOptionsRivulet { MaxDegreeOfParallelism = 16 }))
{
    // consume incrementally
}

Ordered Output

Maintain input order when sequence matters:

// Results returned in same order as input, despite parallel processing
var results = await items.SelectParallelAsync(
    async (item, ct) => await ProcessAsync(item, ct),
    new ParallelOptionsRivulet
    {
        MaxDegreeOfParallelism = 32,
        OrderedOutput = true  // Ensures results match input order
    });

// Streaming with ordered output
await foreach (var result in source.SelectParallelStreamAsync(
    async (x, ct) => await TransformAsync(x, ct),
    new ParallelOptionsRivulet { OrderedOutput = true }))
{
    // Results arrive in input order
}

Backoff Strategies

Choose from multiple backoff strategies to optimize retry behavior:

// Exponential backoff with jitter - recommended for rate-limited APIs
// Reduces thundering herd by randomizing retry delays
var results = await requests.SelectParallelAsync(
    async (req, ct) => await apiClient.SendAsync(req, ct),
    new ParallelOptionsRivulet
    {
        MaxRetries = 4,
        BaseDelay = TimeSpan.FromMilliseconds(100),
        BackoffStrategy = BackoffStrategy.ExponentialJitter,  // Random(0, BaseDelay * 2^attempt)
        IsTransient = ex => ex is HttpRequestException
    });

// Decorrelated jitter - best for preventing synchronization across multiple clients
var results = await tasks.SelectParallelAsync(
    async (task, ct) => await ProcessAsync(task, ct),
    new ParallelOptionsRivulet
    {
        MaxRetries = 3,
        BackoffStrategy = BackoffStrategy.DecorrelatedJitter,  // Random based on previous delay
        IsTransient = ex => ex is TimeoutException
    });

// Linear backoff - gentler, predictable increase
var results = await items.SelectParallelAsync(
    async (item, ct) => await SaveAsync(item, ct),
    new ParallelOptionsRivulet
    {
        MaxRetries = 5,
        BaseDelay = TimeSpan.FromSeconds(1),
        BackoffStrategy = BackoffStrategy.Linear,  // BaseDelay * attempt
        IsTransient = ex => ex is InvalidOperationException
    });

Available strategies:

• Exponential (default): BaseDelay * 2^(attempt-1) - Predictable exponential growth
• ExponentialJitter: Random(0, BaseDelay * 2^(attempt-1)) - Reduces thundering herd
• DecorrelatedJitter: Random(BaseDelay, PreviousDelay * 3) - Prevents client synchronization
• Linear: BaseDelay * attempt - Gentler, linear growth
• LinearJitter: Random(0, BaseDelay * attempt) - Linear with randomization

Progress Reporting

Track progress with real-time metrics for long-running operations:

// Monitor ETL job progress with ETA
var records = await database.GetRecordsAsync().SelectParallelAsync(
    async (record, ct) => await TransformAndLoadAsync(record, ct),
    new ParallelOptionsRivulet
    {
        MaxDegreeOfParallelism = 20,
        Progress = new ProgressOptions
        {
            ReportInterval = TimeSpan.FromSeconds(5),
            OnProgress = progress =>
            {
                Console.WriteLine($"Progress: {progress.ItemsCompleted}/{progress.TotalItems}");
                Console.WriteLine($"Rate: {progress.ItemsPerSecond:F1} items/sec");
                Console.WriteLine($"ETA: {progress.EstimatedTimeRemaining}");
                Console.WriteLine($"Errors: {progress.ErrorCount}");
                return ValueTask.CompletedTask;
            }
        }
    });

// Streaming progress (total unknown)
await foreach (var result in stream.SelectParallelStreamAsync(
    async (item, ct) => await ProcessAsync(item, ct),
    new ParallelOptionsRivulet
    {
        Progress = new ProgressOptions
        {
            ReportInterval = TimeSpan.FromSeconds(10),
            OnProgress = progress =>
            {
                // No ETA or percent for streams - total is unknown
                Console.WriteLine($"Processed: {progress.ItemsCompleted}");
                Console.WriteLine($"Rate: {progress.ItemsPerSecond:F1} items/sec");
                return ValueTask.CompletedTask;
            }
        }
    }))
{
    // Process results as they arrive
}

Progress metrics:

• ItemsStarted: Total items that began processing
• ItemsCompleted: Successfully completed items
• TotalItems: Total count (known for arrays/lists, null for streams)
• ErrorCount: Failed items across all retries
• Elapsed: Time since operation started
• ItemsPerSecond: Processing rate
• EstimatedTimeRemaining: ETA (when total is known)
• PercentComplete: 0-100% (when total is known)

Batching Operations

Process items in batches for bulk operations like database inserts, batch API calls, or file operations:

// Bulk database inserts - batch 100 records at a time
var results = await records.BatchParallelAsync(
    batchSize: 100,
    async (batch, ct) =>
    {
        // Insert entire batch in a single database call
        await db.BulkInsertAsync(batch, ct);
        return batch.Count;
    },
    new ParallelOptionsRivulet
    {
        MaxDegreeOfParallelism = 4, // Process 4 batches in parallel
        MaxRetries = 3,
        IsTransient = ex => ex is SqlException
    });

// Batch API calls with timeout - flush partial batches after delay
var apiResults = await items.BatchParallelAsync(
    batchSize: 50,
    async (batch, ct) =>
    {
        // Call API with batch of items
        return await apiClient.ProcessBatchAsync(batch, ct);
    },
    batchTimeout: TimeSpan.FromSeconds(2) // Flush batch after 2 seconds even if not full
);

// Streaming batches from async source
await foreach (var result in dataStream.BatchParallelStreamAsync(
    batchSize: 100,
    async (batch, ct) =>
    {
        await ProcessBatchAsync(batch, ct);
        return batch.Count;
    },
    new ParallelOptionsRivulet
    {
        MaxDegreeOfParallelism = 8,
        OrderedOutput = true, // Maintain batch order
        Progress = new ProgressOptions
        {
            ReportInterval = TimeSpan.FromSeconds(5),
            OnProgress = progress =>
            {
                Console.WriteLine($"Batches processed: {progress.ItemsCompleted}");
                return ValueTask.CompletedTask;
            }
        }
    }))
{
    // Process batch results as they complete
    Console.WriteLine($"Batch completed with {result} items");
}

Key Features:

• Size-based batching: Groups items into batches of specified size
• Timeout-based flushing: Optional timeout to flush incomplete batches (async streams only)
• Parallel batch processing: Process multiple batches concurrently with bounded parallelism
• All existing features: Works with retries, error handling, progress tracking, ordered output
• Efficient for bulk operations: Reduces API calls, database round-trips, and I/O overhead

Use Cases:

• Bulk database inserts/updates/deletes
• Batch API calls to external services
• File processing in chunks
• Message queue batch processing
• ETL pipelines with staged operations

Runtime Metrics & EventCounters

Monitor parallel operations with built-in metrics via .NET EventCounters and optional callbacks for custom monitoring systems:

// Zero-cost monitoring with EventCounters (always enabled)
// Monitor with: dotnet-counters monitor --process-id <PID> --counters Rivulet.Core
var results = await items.SelectParallelAsync(ProcessAsync, options);

// Custom metrics callback for Prometheus, DataDog, Application Insights
var options = new ParallelOptionsRivulet
{
    MaxDegreeOfParallelism = 32,
    Metrics = new MetricsOptions
    {
        SampleInterval = TimeSpan.FromSeconds(10),
        OnMetricsSample = async snapshot =>
        {
            // Export to your monitoring system
            await prometheus.RecordMetrics(new
            {
                active_workers = snapshot.ActiveWorkers,
                items_completed = snapshot.ItemsCompleted,
                throughput = snapshot.ItemsPerSecond,
                error_rate = snapshot.ErrorRate,
                total_retries = snapshot.TotalRetries
            });
        }
    }
};

var results = await urls.SelectParallelAsync(
    async (url, ct) => await httpClient.GetAsync(url, ct),
    options);

Available Metrics:

• ActiveWorkers: Current number of active worker tasks
• QueueDepth: Items waiting in the input channel queue
• ItemsStarted: Total items that began processing
• ItemsCompleted: Total items completed successfully
• TotalRetries: Cumulative retry attempts across all items
• TotalFailures: Total failed items (after all retries)
• ThrottleEvents: Backpressure events when queue is full
• ItemsPerSecond: Current throughput rate
• ErrorRate: Failure rate (TotalFailures / ItemsStarted)
• Elapsed: Time since operation started

EventCounters (zero-cost monitoring):

# Monitor in real-time with dotnet-counters
dotnet-counters monitor --process-id <PID> --counters Rivulet.Core

# Available counters:
# - items-started
# - items-completed
# - total-retries
# - total-failures
# - throttle-events
# - drain-events

Key Features:

• Zero-cost when not monitored: EventCounters have minimal overhead
• Thread-safe: Uses lock-free Interlocked operations
• Callback isolation: Exceptions in callbacks don't break operations
• Integrates with all operators: SelectParallelAsync, SelectParallelStreamAsync, ForEachParallelAsync, BatchParallel*

Use Cases:

• Production monitoring and alerting
• Performance tuning and capacity planning
• Debugging throughput issues
• SLA compliance verification
• Auto-scaling triggers

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🔧 Advanced Features

Rate Limiting with Token Bucket

Control the maximum rate of operations using the token bucket algorithm, perfect for respecting API rate limits or smoothing traffic bursts:

// Limit to 100 requests/sec with burst capacity of 200
var results = await apiUrls.SelectParallelAsync(
    async (url, ct) => await httpClient.GetAsync(url, ct),
    new ParallelOptionsRivulet
    {
        MaxDegreeOfParallelism = 32,
        RateLimit = new RateLimitOptions
        {
            TokensPerSecond = 100,  // Sustained rate
            BurstCapacity = 200     // Allow brief bursts
        }
    });

// Heavy operations consume more tokens
var results = await heavyTasks.SelectParallelAsync(
    async (task, ct) => await ProcessHeavyAsync(task, ct),
    new ParallelOptionsRivulet
    {
        RateLimit = new RateLimitOptions
        {
            TokensPerSecond = 50,
            BurstCapacity = 50,
            TokensPerOperation = 5  // Each operation costs 5 tokens
        }
    });

Key Features:

• Token bucket algorithm: Allows controlled bursts while maintaining average rate
• Configurable rates: Set tokens per second and burst capacity
• Weighted operations: Different operations can consume different token amounts
• Works with all operators: SelectParallel*, ForEachParallel*, BatchParallel*
• Combines with retries: Rate limiting applies to retry attempts too

Use Cases:

• Respect API rate limits (e.g., 1000 requests/hour)
• Smooth traffic bursts to downstream services
• Prevent resource exhaustion
• Control database connection usage
• Implement fair resource sharing

Circuit Breaker

Protect your application from cascading failures when a downstream service is unhealthy. The circuit breaker monitors for failures and automatically fails fast when a threshold is reached, giving the failing service time to recover.

// Protect against a flaky API - open after 5 consecutive failures
var results = await urls.SelectParallelAsync(
    async (url, ct) => await httpClient.GetAsync(url, ct),
    new ParallelOptionsRivulet
    {
        MaxDegreeOfParallelism = 32,
        CircuitBreaker = new CircuitBreakerOptions
        {
            FailureThreshold = 5,                      // Open after 5 consecutive failures
            SuccessThreshold = 2,                       // Close after 2 consecutive successes in HalfOpen
            OpenTimeout = TimeSpan.FromSeconds(30),     // Test recovery after 30 seconds
            OnStateChange = async (from, to) =>
            {
                Console.WriteLine($"Circuit {from} → {to}");
                await LogCircuitStateChangeAsync(from, to);
            }
        }
    });

// Time-based failure tracking (percentage within window)
var results = await requests.SelectParallelAsync(
    async (req, ct) => await apiClient.SendAsync(req, ct),
    new ParallelOptionsRivulet
    {
        CircuitBreaker = new CircuitBreakerOptions
        {
            FailureThreshold = 10,                          // Open if 10 failures occur...
            SamplingDuration = TimeSpan.FromSeconds(60),     // ...within 60 seconds
            OpenTimeout = TimeSpan.FromMinutes(5)
        }
    });

Circuit States:

• Closed: Normal operation. Operations execute normally. Failures are tracked.
• Open: Failure threshold exceeded. Operations fail immediately with CircuitBreakerOpenException without executing. Prevents cascading failures.
• HalfOpen: After OpenTimeout expires, circuit allows limited operations to test recovery. Success transitions to Closed. Failure transitions back to Open.

Key Features:

• Fail-fast protection: Prevents overwhelming failing services
• Automatic recovery testing: Transitions to HalfOpen after timeout to probe health
• Flexible failure tracking: Consecutive failures or time-window based (with SamplingDuration)
• State change callbacks: Monitor circuit transitions for alerting/logging
• Works with all operators: SelectParallel*, ForEachParallel*, BatchParallel*

Use Cases:

• Protecting downstream microservices from overload
• Preventing cascading failures in distributed systems
• Graceful degradation when dependencies are unhealthy
• Reducing latency by failing fast instead of waiting for timeouts

Adaptive Concurrency

Automatically adjust parallelism based on real-time performance metrics. Instead of using a fixed MaxDegreeOfParallelism, adaptive concurrency dynamically scales workers up when performance is good and scales down when latency increases or errors occur.

// Auto-scale between 1-32 workers based on latency and success rate
var results = await urls.SelectParallelAsync(
    async (url, ct) => await httpClient.GetAsync(url, ct),
    new ParallelOptionsRivulet
    {
        AdaptiveConcurrency = new AdaptiveConcurrencyOptions
        {
            MinConcurrency = 1,                             // Lower bound
            MaxConcurrency = 32,                            // Upper bound
            InitialConcurrency = 8,                         // Starting point (optional)
            TargetLatency = TimeSpan.FromMilliseconds(100), // Target p50 latency
            MinSuccessRate = 0.95,                          // 95% success rate threshold
            SampleInterval = TimeSpan.FromSeconds(1),       // How often to adjust
            OnConcurrencyChange = async (old, @new) =>
            {
                Console.WriteLine($"Concurrency: {old} → {@new}");
                await metricsClient.RecordGaugeAsync("concurrency", @new);
            }
        }
    });

// Different adjustment strategies
var results = await tasks.SelectParallelAsync(
    async (task, ct) => await ProcessAsync(task, ct),
    new ParallelOptionsRivulet
    {
        AdaptiveConcurrency = new AdaptiveConcurrencyOptions
        {
            MinConcurrency = 2,
            MaxConcurrency = 64,
            IncreaseStrategy = AdaptiveConcurrencyStrategy.Aggressive, // Faster increase
            DecreaseStrategy = AdaptiveConcurrencyStrategy.Gradual,    // Slower decrease
            MinSuccessRate = 0.90
        }
    });

How It Works: Uses AIMD (Additive Increase Multiplicative Decrease) algorithm similar to TCP congestion control:

• Increase: When success rate is high and latency is acceptable, add workers gradually (AIMD: +1, Aggressive: +10%)
• Decrease: When latency exceeds target or success rate drops, reduce workers sharply (AIMD/Aggressive: -50%, Gradual: -25%)
• Samples performance every SampleInterval and adjusts within [MinConcurrency, MaxConcurrency] bounds

Adjustment Strategies:

• AIMD (default): Additive Increase (+1), Multiplicative Decrease (-50%) - Like TCP
• Aggressive: Faster increase (+10%), same decrease (-50%) - For rapidly changing workloads
• Gradual: Same increase (+1), gentler decrease (-25%) - For stable workloads

Key Features:

• Self-tuning: Automatically finds optimal concurrency for current load
• Latency-aware: Reduces workers when operations are too slow
• Error-aware: Scales down when success rate drops below threshold
• Bounded: Always stays within configured min/max limits
• Observable: Callbacks for monitoring concurrency changes
• Works with all operators: SelectParallel*, ForEachParallel*, BatchParallel*

Use Cases:

• Variable load scenarios where optimal concurrency changes over time
• Auto-scaling to match downstream service capacity
• Preventing overload when downstream services slow down
• Maximizing throughput without manual tuning
• Handling unpredictable workload patterns

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📚 Documentation

• Full Documentation
• Contributing Guide
• Roadmap
• Security Policy
• Code of Conduct
• Benchmarks

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📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

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🙏 Acknowledgments

Built with ❤️ using:

• .NET 8.0 and .NET 9.0
• System.Threading.Channels for backpressure
• xUnit for testing
• BenchmarkDotNet for performance validation