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POWhat is causing EventStore to throw ConcurrencyException so easily?
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  1. POWhat is causing EventStore to throw ConcurrencyException so easily?
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    copied!<p>Using <a href="http://github.com/joliver/EventStore" rel="nofollow">JOliver EventStore</a> 3.0, and just getting started with simple samples.</p> <p>I have a simple pub/sub CQRS implementation using NServiceBus. A client sends commands on the bus, a domain server recieves and processes the commands and stores events to the eventstore, which are then published on the bus by the eventstore's dispatcher. a read-model server then subscribes to those events to update the read-model. Nothing fancy, pretty much by-the-book.</p> <p>It is working, but just in simple tests I am getting lots of concurrency exceptions (intermittantly) on the domain server when the event is stored to the EventStore. It properly retries, but sometimes it hits the 5 retry limit and the command ends up on the error queue.</p> <p>Where could I start investigating to see what is causing the concurrency exception? I remove the dispatcher and just focus on storing events and it has the same issue.</p> <p>I'm using RavenDB for persistence of my EventStore. I'm not doing anything fancy, just this:</p> <pre class="lang-cs prettyprint-override"><code>using (var stream = eventStore.OpenStream(entityId, 0, int.MaxValue)) { stream.Add(new EventMessage { Body = myEvent }); stream.CommitChanges(Guid.NewGuid()); } </code></pre> <p>The stack trace for the exception looks like this:</p> <blockquote> <p>2012-03-17 18:34:01,166 [Worker.14] WARN NServiceBus.Unicast.UnicastBus [(null)] &lt;(null)> - EmployeeCommandHandler failed handling message. EventStore.ConcurrencyException: Exception of type 'EventStore.ConcurrencyException' was thrown. at EventStore.OptimisticPipelineHook.PreCommit(Commit attempt) in c:\Code\public\EventStore\src\proj\EventStore.Core\OptimisticPipelineHook.cs:line 55 at EventStore.OptimisticEventStore.Commit(Commit attempt) in c:\Code\public\EventStore\src\proj\EventStore.Core\OptimisticEventStore.cs:line 90 at EventStore.OptimisticEventStream.PersistChanges(Guid commitId) in c:\Code\public\EventStore\src\proj\EventStore.Core\OptimisticEventStream.cs:line 168 at EventStore.OptimisticEventStream.CommitChanges(Guid commitId) in c:\Code\public\EventStore\src\proj\EventStore.Core\OptimisticEventStream.cs:line 149 at CQRSTest3.Domain.Extensions.StoreEvent(IStoreEvents eventStore, Guid entityId, Object evt) in C:\dev\test\CQRSTest3\CQRSTest3.Domain\Extensions.cs:line 13 at CQRSTest3.Domain.ComandHandlers.EmployeeCommandHandler.Handle(ChangeEmployeeSalary message) in C:\dev\test\CQRSTest3\CQRSTest3.Domain\ComandHandlers\Emplo yeeCommandHandler.cs:line 55</p> </blockquote>
 

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