Dennis van der Stelt
all your batch jobs are belong to us
Dennis van der Stelt
Software Architect
http://dennis.bloggingabout.net/
Particular Software engineer
death of the batch job
@dvdstelt
#nservicebus
Dennis van der Stelt
AGENDA
Dennis van der Stelt
NServiceBusIn Particular
Dennis van der Stelt
NServiceBus
It’s not like WCF, which does RPC
But closes to WCF than to BizTalk
Dennis van der Stelt
BUS TOPOLOGY
Dennis van der Stelt
MessagingWhat is it and why do I need it?
reduce
coupling
Dennis van der Stelt
SpatialTemporalPlatform
coupling aspects
Dennis van der Stelt
PLATFORM
Also known as ‘interoperability’
http, json, xml, xsd, etc…
Dennis van der Stelt
TEMPORAL
Store Front End Shipping Service
Dennis van der Stelt
TEMPORAL
Store Front End Shipping ServiceShipping Service
Dennis van der Stelt
TEMPORAL
Store Front End Shipping ServiceOrder Queue
Dennis van der Stelt
TEMPORAL
Store Front End Shipping ServiceOrder Queue
Dennis van der Stelt
TEMPORAL
Store Front End Shipping ServiceOrder Queue
Dennis van der Stelt
Messaging
Reduces spatial coupling
XML/JSON for platform coupling
Asynchronous for temporal coupling
demo
Messaging using WCF
Dennis van der Stelt
PERFORMANCE
RPC versus Messaging
Dennis van der Stelt
NServiceBus SagasA pattern by relation database community
Dennis van der Stelt
demo
NServiceBus Sagas
Dennis van der Stelt
Sagas Recap“What have you done” – Within Temptation
Dennis van der Stelt
HANDLING MESSAGES
Behavior like normal message handlers
class MySaga : IHandleMessages<MyMessage>{public void Handle(MyMessage message){…
}}
Dennis van der Stelt
STARTING SAGAS
Extends the default IHandleMessages<T>
class MySaga : IAmStartedByMessages<MyMessage>{public void Handle(MyMessage message){…
}}
Dennis van der Stelt
STORING STATE
Extends the default IHandleMessages<T>
class MySaga : Saga<MySagaData>,IAmStartedByMessages<MyMessage>
{public void Handle(MyMessage message){this.Saga.Data.MyStateProperty = Message.MyProperty;
}}
Dennis van der Stelt
CORRELATING MESSAGES TO SAGA INSTANCE
class MySaga : Saga<MySagaData>,IAmStartedByMessages<MyMessage>
{protected override void ConfigureHowToFindSaga(SagaPropertyMapper<MySagaData> mapper){mapper.ConfigureMapping<MyMessage>(m => m.MyProperty).ToSaga(s => s.MyStateProperty);
}
public void Handle(MyMessage message){this.Saga.Data.MyStateProperty = Message.MyProperty;
}}
Dennis van der Stelt
REQUESTING TIMEOUTS
Reminders to the Saga itself
class MySaga : Saga<MySagaData>,IAmStartedByMessages<MyMessage>,IHandleTimeouts<MyTimeout>
{public void Handle(MyMessage message){this.Saga.Data.MyStateProperty = Message.MyProperty;RequestTimeout<MyTimeout>(TimeSpan.FromSeconds(10));
}
public void Timeout(MyTimeout state){…
}}
Dennis van der Stelt
SENDING MESSAGES
Reminders to the Saga itself
class MySaga : Saga<MySagaData>,IAmStartedByMessages<MyMessage>
{public void Handle(MyMessage message){this.Saga.Data.MyStateProperty = Message.MyProperty;
this.Bus.Send(new MyCommand());this.Bus.Publish(new MyEvent());
}}
Dennis van der Stelt
SAGA STATE
Memento
class MySagaData : IContainSagaData{public virtual Guid Id { get; set; }public virtual string Originator { get; set; }public virtual string OriginalMessageId { get; set; }
[Unique]public virtual Guid MySagaId { get; set; }
}
ALTER TABLE [dbo].[MySagaData] ADD UNIQUE NONCLUSTERED ([MySagaId] ASC) ON [PRIMARY]
Dennis van der Stelt
SAGA STATE
Memento
class MySagaData : IContainSagaData{public virtual Guid Id { get; set; }public virtual string Originator { get; set; }public virtual string OriginalMessageId { get; set; }
[Unique]public virtual Guid MySagaId { get; set; }
public virtual IList<Product> Products { get; set; }}
public class Product{public virtual Guid ProductId { get; set; }
}
Dennis van der Stelt
SAGA STATE
Memento
class MySagaData : IContainSagaData{public virtual Guid Id { get; set; }public virtual string Originator { get; set; }public virtual string OriginalMessageId { get; set; }
[Unique]public virtual Guid MySagaId { get; set; }
public virtual IList<Product> Products { get; set; }}
public class Product{public virtual Guid ProductId MyUniqueId { get; set; }
}
Dennis van der Stelt
Death to the batch jobBecause we don’t want to depend on operations ;-)
Dennis van der Stelt
Dennis van der Stelt
scheduled tasks
Your CEO had insomnia and was using the system in the middle of the night. The batch job failed somewhere in
the middle of updating 74 million records…
You need to figure out which row it failed on (how?), why it failed, correct the issue, then start the job again from where it left off, because if you have to start from the beginning, it won't get done before peak hours in
the morning.
because that sounds better than batch job
Dennis van der Stelt
BATCH JOB
All customers that ordered $5000 in the last year, get preferred status
DateTime cutoff = DateTime.Today.AddDays(-365);
foreach(var customer in customers){var orderTotal = customer.Orders.Where(o => o.OrderDate > cutoff).Sum(order => order.OrderValue);
customer.Prefered = orderTotal > 5000;}
Dennis van der Stelt
Tromsø, Norway
Dennis van der Stelt
what if
we can see things before they happen?
Dennis van der Stelt
customer preferred status
Dev: Let's say Steve orders something for $100. At what point does that amount no longer count toward Steve's preferred status?
BA: That's easy, after 365 days!
Dennis van der Stelt
-$300-$100
+$300
DURABLE TIMEOUTS
Our way to predict the future
2015 2016
+$100
Dennis van der Stelt
DURABLE TIMEOUTS
public void Handle(OrderPlaced message){
if(this.Data.CustomerId == 0)this.Data.CustomerId = message.CustomerId;
this.Data.RunningTotal += message.Amount;this.RequestTimeout<OrderExpired>(TimeSpan.FromDays(365),
timeout => timeout.Amount = message.Amount);
CheckForPreferredStatusChange();}
public void Handle(OrderExpired message){
this.Data.RunningTotal -= message.Amount;CheckForPreferredStatusChange();
}
Dennis van der Stelt
DURABLE TIMEOUTS
private void CheckForPreferredStatusChange(){
if(this.Data.PreferredStatus == false && this.Data.RunningTotal >= 5000){
this.Bus.Publish<CustomerHasBecomePreferred>(evt => evt.CustomerId = this.Data.CustomerId);
}else if(this.Data.PreferredStatus == true && this.Data.RunningTotal < 5000){
this.Bus.Publish<CustomerHasBecomeNonPreferred(evt => evt.CustomerId = this.Data.CustomerId);
}}
Dennis van der Stelt
Best PracticesThe silver bullets?
Dennis van der Stelt
Rule #1 : Don’t query data
Never ever, ever, ever query data
- From the saga to another data source
- Owned by saga with a 3rd party tool
Dennis van der Stelt
Business eventsTimeoutsStarting sagas
out of order
Dennis van der Stelt
ASYNCHRONOUS COMMUNICATION
Order of message delivery
OrderAccepted
OrderAccepted
OrderBilled
Dennis van der Stelt
ASYNCHRONOUS COMMUNICATION
Order of message delivery
OrderAccepted
OrderAccepted
OrderBilled
Dennis van der Stelt
ASYNCHRONOUS COMMUNICATION
Order of message delivery
OrderAccepted
OrderAccepted
OrderBilled
OrderCancelled
How to solve?
race conditions do not exist
Dennis van der Stelt
STARTING SAGAS
What business events can start a Saga?
class MySaga : Saga<MySagaData>,IAmStartedByMessages<MyMessage>,IAmStartedByMessages<YourMessage>,IAmStartedByMessages<AnotherMesssage>
{public void Handle(MyMessage message){…
if (VerifyState())MarkAsComplete();
}}
Dennis van der Stelt
404 ON SAGAS
What if the Saga was already MarkedAsComplete
public class SagaNotFoundHandler : IHandleSagaNotFound{
IBus bus;
public SagaNotFoundHandler(IBus bus){
this.bus = bus;}
public void Handle(object message){
bus.Reply(new SagaDisappearedMessage());}
}
Dennis van der Stelt
AUTO CORRELATION
Avoids the need for mapping responses
class MySaga : Saga<MySagaData>,IAmStartedByMessages<MyMessage>,IHandleMessages<Response>
{protected override void ConfigureHowToFindSaga(SagaPropertyMapper<MySagaData> mapper){mapper.ConfigureMapping<MyMessage>(m => m.MyProperty).ToSaga(s => s.MyStateProperty);// Mapping for Respose not needed!
}}
public class RequestHandler : IHandleMessages<Request> {public void Handle(Request message) {Bus.Reply(new Response());
}}
Dennis van der Stelt
AUTO CORRELATION
Avoids the need for mapping responses
class MySaga : Saga<MySagaData>,IAmStartedByMessages<MyMessage>,IHandleMessages<MyTimeout>
{public void Timeout(MyTimeout state){if (state.RasiedAtUtc == …
}}
public class MyTimeout{public DateTime RaisedAtUtc { get; set; } = DateTime.UtcNow;
}
Can be a POCO
No `virtual` as it’s serialized to string format
Dennis van der Stelt
CONCURRENCY
[LockMode(LockModes.Read)]class ShoppingCartSagaData : IContainSagaData{…
[RowVersion]public virtual int RowVersion { get; set; }
[Unique]public virtual Guid CartId { get; set; }
}
Dennis van der Stelt
CONCURRENCY
DELETE FROM ShoppingCartSagaDataWHERE Id = '1C669378-3508-4A20-8EFD-A5C60168893E'AND Originator is null AND OriginalMessageId = 'd6436b7-eb17-4de5-8b92-a5c60168888c'AND CartId = '49784AF0-0854-4FF9-B8CD-E57CC8EE6CFC‘AND …AND …AND …
DELETE FROM ShoppingCartSagaDataWHERE Id = '1C669378-3508-4A20-8EFD-A5C60168893E'AND RowVersion = 1
Sagas is business agility
http://bit.ly/nlnsbug