EasyNetQ.PollyHandlerRunner

An extension for EasyNetQ which allows you to execute message handlers within a Polly policy.

Examples

Retry messages 3 times before failing...

var policy = Policy
    .Handle<Exception>()
    .Retry(3);

var bus = RabbitHutch.CreateBus("host=localhost;username=guest;password=guest",
    registrar => registrar.UseMessageHandlerPolicy(policy));

---

Retry MySql deadlocks only...

var policy = Policy
    .Handle<MySqlException>(error => error.Number == 1213) // 1213 = deadlock
    .RetryForever();

var bus = RabbitHutch.CreateBus("host=localhost;username=guest;password=guest",
    registrar => registrar.UseMessageHandlerPolicy(policy));

---

Retry messages 5 times with an exponential backoff between attempts...

var policy = Policy
    .Handle<Exception>()
    .WaitAndRetry(5, attempt => TimeSpan.FromSeconds(Math.Pow(2, attempt)));

var bus = RabbitHutch.CreateBus("host=localhost;username=guest;password=guest",
    registrar => registrar.UseMessageHandlerPolicy(policy));

---

Set 5 second timeout for all message processing...

var policy = Policy.Timeout(TimeSpan.FromSeconds(5));

var bus = RabbitHutch.CreateBus("host=localhost;username=guest;password=guest",
    registrar => registrar.UseMessageHandlerPolicy(policy));

---

Combine policies...

var deadlockRetryPolicy = Policy
    .Handle<MySqlException>(error => error.Number == 1213)
    .Retry(3);

var timeoutPolicy = Policy
    .Timeout(TimeSpan.FromSeconds(10));

var combinedPolicy = Policy.Wrap(deadlockRetryPolicy, timeoutPolicy);

var bus = RabbitHutch.CreateBus("host=localhost;username=guest;password=guest",
    registrar => registrar.UseMessageHandlerPolicy(combinedPolicy));

---

Circuit breaker...

IBus bus;
ISubscriptionResult subscription;

Action establishSubscription = () => {
    subscription = bus.Subscribe<MyMessage>(message => Console.Log(message.ToString()));
};

Action<Exception, TimeSpan> onBreak = (exception, timespan) => subscription.Dispose();
Action onReset = () => establishSubscription();

// Trip the circuit breaker for 1 minute after 3 consecutive failures...
var circuitBreaker = Policy
    .Handle<Exception>()
    .CircuitBreaker(3, TimeSpan.FromMinutes(1), onBreak, onReset);

bus = RabbitHutch.CreateBus("host=localhost;username=guest;password=guest",
    registrar => registrar.UseMessageHandlerPolicy(circuitBreaker));

establishSubscription();

See Polly-Samples for more examples.