Comments (5)
I do it by intent. Idea is that aggregate could be restored to actual state reading event log. In my case
If i persit data and smth happens i have 2 options
1 - data is not written. i got failure and do not reduce state (thus not damaging buisness-data and not starting any effects)
2 - data is writen and i have error in aggregation function. even if it fails (saying it's not bug in aggregation logic but within infrastructure) next time i read evelt log i restore to consistent state
but if i switch to "effect-first" - i easy get to situation when aggregation was reduced (and launched long-running effects) but no data was added to datastore
from zio-event-sourcing.
As it is, if you call persist for events which are not valid according to the reducer, it will first persist the event to the event journal, then it will try to modify the aggregate, and then update the ref with the new aggregate if it was a success. But at this point you have stored the events in the journal, even though they were not valid.
However, if you first had reduced the event it would fail and no event would be persisted.
What you are doing now is persist -> reduce -> update ref, but if you switch it around you would have reduce -> persist -> update ref. The latter would mean no incorrectly persisted events.
from zio-event-sourcing.
i see your idea but filtering must happen on read side. all incoming data should be saved. but when reducing you could skip any "unwanted" data you want.
in EventSourcing you could have more than one aggregate build using same event log and different aggregates could count different events as "unwanted".
method you speaking about was made to have a little optimization in most-used case when there is only one aggregate type and aggregate is kept for a long time (i'm not quite sure if i need to keep it or not - cause you just made a mistake i was thinking about when created this method).
from zio-event-sourcing.
But if the event can't be reduced, then you can never reduce that aggregate as you will always read an invalid event after you have stored it? If I have an event Created that is not supposed to be possible to reduce twice for the same aggregate, but is stored twice in the journal, how do you solve this?
from zio-event-sourcing.
But if the event can't be reduced
- don't get this. I could always filter-out unneeded events. But if i have this events in event log i'm able to build some analytics aggregations on this "corrupted" data
from zio-event-sourcing.
Related Issues (5)
Recommend Projects
-
React
A declarative, efficient, and flexible JavaScript library for building user interfaces.
-
Vue.js
🖖 Vue.js is a progressive, incrementally-adoptable JavaScript framework for building UI on the web.
-
Typescript
TypeScript is a superset of JavaScript that compiles to clean JavaScript output.
-
TensorFlow
An Open Source Machine Learning Framework for Everyone
-
Django
The Web framework for perfectionists with deadlines.
-
Laravel
A PHP framework for web artisans
-
D3
Bring data to life with SVG, Canvas and HTML. 📊📈🎉
-
Recommend Topics
-
javascript
JavaScript (JS) is a lightweight interpreted programming language with first-class functions.
-
web
Some thing interesting about web. New door for the world.
-
server
A server is a program made to process requests and deliver data to clients.
-
Machine learning
Machine learning is a way of modeling and interpreting data that allows a piece of software to respond intelligently.
-
Visualization
Some thing interesting about visualization, use data art
-
Game
Some thing interesting about game, make everyone happy.
Recommend Org
-
Facebook
We are working to build community through open source technology. NB: members must have two-factor auth.
-
Microsoft
Open source projects and samples from Microsoft.
-
Google
Google ❤️ Open Source for everyone.
-
Alibaba
Alibaba Open Source for everyone
-
D3
Data-Driven Documents codes.
-
Tencent
China tencent open source team.
from zio-event-sourcing.