Does anyone use ElasticSearch for building read model in CQRS approach? I have some questions related to such solution:
Where the authoritative repository for your domain event is located is an implementation detail. For example, you could store serialized versions on S3 or CouchDB or any other number of storage implementations. The easiest if you re just getting started is a relational database.
Typically people use event handlers that understand the business intent behind each message and can then properly denormalize the message into the read model structure appropriate for the needs of your views.
If the view model is ever corrupted or perhaps you have a bug in a view model handler, there are a few simple steps to follow after fixing the bug:
Temporarily enqueue the flow of events arriving from the domain--these are the typical messages that are being published as your domain is doing work. We still want these messages, but not just yet. This could be done by turning off any message bus or not connecting to your queuing infrastructure if you use one.
Read all events from event storage. As each event is received (this can be done through a simple DB query), run each message through the appropriate message handler. Make sure that you keep track of the last 10,000 (or so) identifiers for all messages processed.
Now reconnect to your queues and start processing normally. If the identifier for the message has been seen, drop the message. Otherwise, process it normally.
The reason for tracking identifiers is to avoid a race condition where you re getting all events from the event store but the same message is coming across through the message queue.
Another technique that s highly related, but involves keeping track of all message identifiers can be found here: http://blog.jonathanoliver.com/2011/03/removing-2pc-two-phase-commit.html
I have a fairly simple domain model involving a list of Facility aggregate roots. Given that I m using CQRS and an event-bus to handle events raised from the domain, how could you handle validation ...
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We are trying out CQRS. We have a validation situation where a CustomerService (domain service) needs to know whether or not a Customer exists. Customers are unique by their email address. Our ...
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