VIP Query Store

CHALLENGES

#1 Message order

Example:

IShopItemQuantityChanged

{ Quantity: 15, PublishedTime: 2013-05-20 04:31 }

{ Quantity: 10, PublishedTime: 2013-05-20 04:30 }

{
  Quantity: 5

  MetaInfo: {
    Version: 1
    FieldChanges: {
      Quantity: 2013-05-20 04:30 
    }
  }
}

{ Quantity: 15, PublishedTime: 2013-05-20 04:31 }

{
  Quantity: 15

  MetaInfo: {
    Version: 2
    FieldChanges: {
      Quantity: 2013-06-07 04:31 
    }
  }
}

QuantityUpdated Value: 10 PublishedTime: 2013-06-07 04:30

{
  Quantity: 15

  MetaInfo: {
    Version: 2
    FieldChanges: {
      Quantity: 2013-06-07 04:31 
    }
  }
}

ChallEnges

#2 Update message before create

Example:

CreateAuction PublishedTime: 2013-06-27 04:30 UpdateDescription PublishedTime: 2013-06-27 04:33

Challenges

#3 Messages can be received more than once

IItemAdditionalDescriptionAdded: {
   Description: "Addendum 1",
   PublishedTime: 2013-06-27 04:30,
   MessageId: "FBCE65B5-8392-45AB-884C-BC24910B5BFE"
}

IItemAdditionalDescriptionAdded: {
   Description: "Addendum 1",
   PublishedTime: 2013-06-27 04:30
   MessageId: "FBCE65B5-8392-45AB-884C-BC24910B5BFE"
}

Same message received twice or different?

{  
  AdditionalDescriptions: [
    "Addendum 1"
  ],
  MetaInfo: {
    Version: 2
    FieldChanges: {
      ..
    },
    HandledMessages: [
      "348C6FF1-CEE7-4031-9C39-A72C3DE95E67"
    ]
  }
}

IItemAdditionalDescriptionAdded: {
   Description: "Addendum 1",
   PublishedTime: 2013-06-27 04:30
   MessageId: "FBCE65B5-8392-45AB-884C-BC24910B5BFE"
}

Can now detect that message was already handled!

Concurrency

Concurrent write to same document

 {  
  ......
  MetaInfo: {
    Version: 2
    FieldChanges: {
      ..
    },
    HandledMessages: [
      ...
    ]
  }
}

var query = Query.And(
  Query.EQ(x => x.ItemId, id),
  Query.EQ(x => x.MetaInfo.Version, ViewModel.MetaInfo.Version) ←
);

Initializer

Requirements

Create initial state
Add missing (new) properties
Correct state (if a bug is identified)

Initializer

Reads data from master data

Creates init command messages that are sent to denormalizer

Advantages

Init commands are handled as any message update

Uses the same update pipeline and concurrent write protection

Can be run at the same time as normal messages are handled

Can be executed multiple times without having to clear mongo store.