Optionally disable sequence numbers using optimistic locking (etags) #362
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mumby0168
commented
Nov 2, 2023
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mumby0168
commented
- 1. Introduces a new way to sequence events without optimistic locking
- 2. Adds the ability to use in memory testing for events
- 3. Adds the ability to test change feed projections using an in-memory implementation
- 4. Shows how the in-memory library can be used with functional tests via a sample
- document non-sequenced option along with the aggregate root settings with the config option
- document how the in-memory testing works
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| namespace Microsoft.Azure.CosmosEventSourcing.Options; | ||
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| public class CosmosEventSourcingOptions |
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We'll need triple slash for these public APIs.
| IEventStore<TEventItem> where TEventItem : EventItem | ||
| { | ||
| private readonly IOptionsMonitor<CosmosEventSourcingOptions> _optionsMonitor = optionsMonitor; |
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This field isn't needed, you can access the optionsMonitor anywhere within the partial class. These are primary constructors.
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ahhh that makes sense now, I'll update this cheers!
| @@ -22,9 +22,12 @@ internal partial class DefaultEventStore<TEventItem> | |||
| return; | |||
| } | |||
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| if (eventItems.Count(x => x.EventName is nameof(AtomicEvent)) is not 1) | |||
| if(_optionsMonitor.CurrentValue.IsSequenceNumberingDisabled is false) | |||
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| if(_optionsMonitor.CurrentValue.IsSequenceNumberingDisabled is false) | |
| if (optionsMonitor.CurrentValue.IsSequenceNumberingDisabled is false) |
| typeof(TEventItem), | ||
| aggregateRoot.AtomicEvent, | ||
| partitionKey) as TEventItem); | ||
| if(_optionsMonitor.CurrentValue.IsSequenceNumberingDisabled is false) |
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| if(_optionsMonitor.CurrentValue.IsSequenceNumberingDisabled is false) | |
| if (optionsMonitor.CurrentValue.IsSequenceNumberingDisabled is false) |
| switch (domainEvent) | ||
| { | ||
| case ReplayableEvent: | ||
| ReplayedEvents++; |
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Any race condition concerns with multiple threads calling apply at the same time, and reads of the ReplayedEvents?
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Yes there will be, kind of a long story to this change, I plan to update the docs alongside this as well. But in short, the sequence number and the strong consistency provided by the atomic event is great in a single region scenario.
However, when we have been assessing the ability to enable multi region writes where traffic would be load balanced across two regions both writing to there local cosmos db data store, we could not guarantee that this sequence number remains in sync and in some use cases for event sourcing it doesn't really matter. The plan here is to handle simultaneous writes, as long as that event is valid at the point in time we are going to let it go ahead.
This diagram is covering our use case, but I am still fleshing out all the details of whether this is 100% suitable via some POCs.
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I'm good with it if you are, let's 
| y is EventItemPartitionKeyAttribute)) | ||
| .ToList(); | ||
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| switch (partitionKeyProperties.Count) |
| @@ -36,4 +39,41 @@ eventItem.DomainEvent switch | |||
| null => null, | |||
| _ => throw new ArgumentOutOfRangeException() | |||
| }; | |||
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| public static TAggregateRoot Replay<TAggregateRoot, TEventItem>(this IEnumerable<TEventItem> events) | |||
| where TEventItem : EventItem | |||
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| where TEventItem : EventItem | |
| where TEventItem : EventItem |
| public static IEnumerable<TEventItem> SetCorrelationId<TEventItem>( | ||
| this IEnumerable<TEventItem> eventItems, | ||
| IContextService contextService) | ||
| where TEventItem : EventItem |
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| where TEventItem : EventItem | |
| where TEventItem : EventItem |
