PollyMediatR

Polly v8 resilience pipelines for MediatR — add retry, timeout, circuit-breaker, rate-limiting, hedging and chaos engineering to any MediatR request handler with a single line of registration. No changes to handler code required.

services.AddPollyMediatR(pipeline =>
    pipeline
        .AddRetry(new RetryStrategyOptions
        {
            MaxRetryAttempts = 3,
            Delay = TimeSpan.FromMilliseconds(200),
            ShouldHandle = new PredicateBuilder().Handle<Exception>(),
        })
        .AddTimeout(TimeSpan.FromSeconds(5)));

Every IRequest<T> handler is now automatically wrapped with retry + timeout — zero changes to existing handlers.

---

Why PollyMediatR?

MediatR's IPipelineBehavior<TRequest, TResponse> is the natural place to apply cross-cutting resilience concerns, but wiring it up with Polly v8 requires boilerplate. PollyMediatR does the wiring for you.

Without PollyMediatR	With PollyMediatR
Write a custom IPipelineBehavior per pipeline	One AddPollyMediatR(...) call
Manually inject ResiliencePipeline into each behavior	Pipeline registered & injected automatically
Duplicate retry/timeout logic across query & command handlers	Single pipeline applied to all handlers
Must update handlers to apply new resilience policies	Zero changes to existing handlers

---

Installation

dotnet add package PollyMediatR

Targets net6.0, net8.0, and net9.0.

Dependencies: Polly.Core 8.*, MediatR 12.*, Microsoft.Extensions.DependencyInjection.Abstractions 8.*

---

Quick start

1. Register with an inline builder (recommended)

using Polly.Retry;
using PollyMediatR;

services.AddPollyMediatR(pipeline =>
    pipeline.AddRetry(new RetryStrategyOptions
    {
        MaxRetryAttempts = 3,
        Delay = TimeSpan.FromMilliseconds(200),
        BackoffType = DelayBackoffType.Exponential,
        ShouldHandle = new PredicateBuilder().Handle<Exception>(),
    }));

2. Register with a pre-built pipeline

var pipeline = new ResiliencePipelineBuilder()
    .AddRetry(new RetryStrategyOptions { ... })
    .AddTimeout(TimeSpan.FromSeconds(10))
    .Build();

services.AddPollyMediatR(pipeline);

3. Use normally with MediatR — nothing changes

// Handler — no Polly code needed
public class GetOrderHandler : IRequestHandler<GetOrderQuery, Order>
{
    public async Task<Order> Handle(GetOrderQuery request, CancellationToken ct)
    {
        return await _db.Orders.FindAsync(request.Id, ct); // retried automatically
    }
}

// At the call site — identical to normal MediatR usage
var order = await mediator.Send(new GetOrderQuery(id));

---

ASP.NET Core example

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddMediatR(cfg =>
    cfg.RegisterServicesFromAssemblyContaining<Program>());

builder.Services.AddPollyMediatR(pipeline =>
    pipeline
        .AddRetry(new RetryStrategyOptions
        {
            MaxRetryAttempts = 3,
            Delay = TimeSpan.FromMilliseconds(100),
            BackoffType = DelayBackoffType.Exponential,
            ShouldHandle = new PredicateBuilder()
                .Handle<HttpRequestException>()
                .Handle<TimeoutException>(),
        })
        .AddTimeout(TimeSpan.FromSeconds(30))
        .AddCircuitBreaker(new CircuitBreakerStrategyOptions
        {
            FailureRatio = 0.5,
            MinimumThroughput = 10,
            SamplingDuration = TimeSpan.FromSeconds(30),
            BreakDuration = TimeSpan.FromSeconds(15),
        }));

---

Pipeline order

Polly strategies are applied outer-to-inner (left-to-right). The recommended order is:

[Timeout] → [Retry] → [Circuit Breaker] → [Handler]

pipeline
    .AddTimeout(TimeSpan.FromSeconds(10))    // 1. Overall deadline
    .AddRetry(retryOptions)                  // 2. Retry on failure
    .AddCircuitBreaker(cbOptions)            // 3. Open circuit if overloaded

---

Combining with chaos engineering (PollyChaos)

Use PollyChaos to harden your handlers in test/staging:

services.AddPollyMediatR(pipeline =>
    pipeline
        .AddRetry(retryOptions)
        .AddChaosFault(injectionRate: 0.1)); // inject faults 10% of the time

---

Related Packages

Package	Downloads	Description
PollyHealthChecks		ASP.NET Core health checks for Polly v8 circuit breakers — expose circuit-breaker state (Closed, HalfOpen, Open, Isolated) as /health endpoint responses
PollyOpenTelemetry		OpenTelemetry instrumentation for Polly v8 resilience pipelines
PollyBackoff		Backoff delay strategies for Polly v8 resilience pipelines
PollyGrpc		Polly v8 resilience interceptor for gRPC
PollyEFCore		Polly v8 resilience pipelines for Entity Framework Core — wrap every EF Core query and SaveChanges with retry, timeout and circuit-breaker via a single AddPollyResilience() call
PollyRabbitMQ		Polly v8 resilience for RabbitMQ.Client v7+ — retry, circuit-breaker, and timeout for IChannel operations, with built-in RabbitMqTransientErrors predicate covering AlreadyClosedException, BrokerUnreachableException, OperationInterruptedException, and ConnectFailureException
PollyMailKit		Polly v8 resilience pipelines for MailKit — retry, timeout, and circuit-breaker for SmtpClient.SendAsync and any MailKit SMTP operation
PollyMassTransit		Polly v8 resilience pipelines for MassTransit — retry, timeout, and circuit-breaker for IBus.Publish and ISendEndpointProvider.Send
PollyOpenAI		Polly v8 resilience for OpenAI and Azure OpenAI API calls
PollyAzureEventHub		Polly v8 resilience pipelines for Azure Event Hubs — retry, timeout, and circuit-breaker for EventHubProducerClient and EventHubConsumerClient
PollySignalR		Polly v8 reconnect policy for SignalR
PollyElasticsearch		Polly v8 resilience pipelines for Elastic.Clients.Elasticsearch 8+ — retry, timeout, and circuit-breaker for any Elasticsearch operation, plus a built-in ElasticTransientErrors predicate covering rate limiting (429), service unavailability (503), gateway timeouts (504), and connection failures
PollyHangfire		Polly v8 resilience pipelines for Hangfire — retry, timeout, and circuit-breaker for IBackgroundJobClient.Enqueue and Schedule
PollySendGrid		Polly v8 resilience pipelines for SendGrid — retry, timeout, and circuit-breaker for ISendGridClient.SendEmailAsync
PollyAzureKeyVault		Polly v8 resilience pipelines for Azure Key Vault — retry, timeout, and circuit-breaker for SecretClient, KeyClient, and CertificateClient
PollyAzureQueueStorage		Polly v8 resilience pipelines for Azure Queue Storage — retry, timeout, and circuit-breaker for Azure.Storage.Queues QueueClient
PollyRedis		Polly v8 resilience for StackExchange.Redis
PollyAzureServiceBus		Polly v8 resilience for Azure Service Bus — retry, circuit breaker, and timeout for sending and receiving messages
PollyKafka		Polly v8 resilience for Confluent.Kafka — retry, circuit breaker, and timeout for producers and consumers
PollyAzureTableStorage		Polly v8 resilience pipelines for Azure Table Storage — retry, timeout, and circuit-breaker for Azure.Data.Tables TableClient
PollyCaching		A caching resilience strategy for Polly v8 pipelines
PollyChaos		Chaos engineering and fault-injection resilience strategies for Polly v8 pipelines
PollyBulkhead		Bulkhead isolation strategy for Polly v8 resilience pipelines

💼 Need .NET consulting?

The author of this package is available for consulting on Polly v8 resilience, Azure cloud architecture, and clean .NET design.

→ solidqualitysolutions.com · LinkedIn

License

MIT