Virtual CQRS ES and Event Modeling Workshop | ADAPTECH | Your Chance to Learn CQRS, Event Sourcing and Event Modeling from the industry pioneers

MateuszNaKodach commented 3 years ago

https://www.adaptechgroup.com/virtual-workshop/

https://www.adaptechgroup.com/virtual-workshop-signup/

VIDEOS:

OAuth2 Event Modeling in Go, Part 2: Process Manager https://www.youtube.com/watch?v=_iSiz_JBGGM&ab_channel=CodeIsMyCraft
https://www.youtube.com/watch?v=bayngCRM7j0
Panel and closing: https://www.bigmarker.com/adaptech-group1/Panel-and-Closing?bmid=046eebc6a6c3

MIRO:

Questions

Event Sourcing

replay events - external system? / bad logic - how to fix?
handling events from external system - how? Translate to domain command etc? - Q&A: Projections. How to keep encapsulation and loosely coupling while updating projections? I want to expose outside my Bounded Context only certain events (not all domain events) in order do not to couple to my domain events and be able to, for example, enhance events and send only (for example) summary like OrderPlaced(IntegrationEvent) which all data needed for other BCs. So I've made mapping from Domain Events to Integration Events (going outside BC - doesn't matter if those are microservices or its modular monolith). And it works for Write Side, but what if on Query Side I want to update projections for every domain event. Now it looks like I need to expose those Domain Events (maybe mapped 1:1 to Integration Events) and the coupling may increase (events are now visible outside of the BC and I loose encapsulation, which I previously tried to keep introducing IntegrationEvents).
Where should i publish domain events/ I have a repository implementation which save events from aggregate. But what about publishing? If i do it in repo its fine because only infra knows about them, but publishing is hidden there. On the other hand -> publishing from app layer shows that im using it.
How to you keep rules - exceptions / either monad
how to deal with changing in streams / aggregate boundaries and events

- Versioning of Events is one thing, but how to versioning Business Logic. For example, we have Event - OrderPlaced. Since the beginning we have been giving 5 customer points, but business change their mind and now we want to give 10 for the same actions (the same event?). Do we use Policy Pattern in this case or something else?

CQRS

Security & Permissions. Maybe do you have some solution for efficient permissions handling with Event Sourcing & Projections?

- Security & Permissions (2/2). More about DDD & CQRS than EventSourcing. Write Side: I've heard many times that permissions are not a domain concern. Imagine a collaborative domain (like Google Docs) where I can give permission to do something to whomever I want. It's easy to reject a command if for example your role is not able to do that. But what about command which rejection depends on domain model state (only assigned users can edit this doc)?

- Security & Permissions. (1/2) Do you have some nice solution how to use Event Sourcing while limiting what user can see? For example I want to have dynamic permissions (not role-based). It's easy to create projections for each role, but what if - for example - this user 1 can read field A from projection P, and user 2 can read field B from projection P.

EVENT MODELING - It’s nice to hear such things and after they stay in our minds. But it’s so difficult to repeat such things as you to others. Are you going to write about this topic (replacing DDD / C4 / meetings) with Event Modeling :) ?

how to split system for slices to implementation? In not complex cases it's easy. But how do you do that with estimations? For example when one view relay on many events etc. ? It's not easy to split for COMMAND->EVENT->VIEW.
Could you show more complex with examples / rules?
Event Storming Process / Design - is it useful? Politicy is nice for see where is decisions, where are moving parts of business. But as far as i see business people have very difficulty with understanding. Where are those parts in EventModeling? The UI / Processor part? Could we say it it politics (reacts on events and dispatch commands).
Alternatives?
Can we mark on Event Modeling which serivce prepare read model?
How to know granuality of events?
Excel / JIRA managers VS Event Modeling. How to keep benefits of EM (slices, estimations) and do not repeat work, while you have to use JIRA etc. in your Company?
How do you implement - what do you recommend for slices - Serverless functions / Microservices / Monolith?
How not to dig into alternavties. How to focus on main path and do not left somethng important.
I know thath event modeling shows sequence. So what do you recommend to show logic like: review code UNTIL 2 people accpt it. It looks like something like loop. Repeat?
What are the most useful questions to discover more?
How to work with UX Designers? They have many propositions of their own workshops (Design Studio, User Journey Map). If I can choose one workshop (business people have limited time) how to encourage them we should (or not?) run Event Modeling session instead of others.
As I see people have problem with understand why view need to go to processor (why not events). How to explain it to non-technical people.

TESTING

How to test CQRS / with Domain Model system and how not to repeat.
For example - domain model i can test -> that method invocation result in event
On App level - tests looks very similar.
On Infra Level -> cases te same, but interactions with external dependencies and events differ. I feel like repeat. How to test CQRS if i cannot query for state?

DOMAIN-DRIVEN DESIGN

Why in most books Repository is Domain.

oNote Yes templates would be nice. But what about... "extending notation on the fly" like in Event Storming. Sometimes we need to do something unusual. I'm always aware of that something which should help, can limit us in some cases. It would be nice if the oNote won't respond with "it's not possible, system doesn't allow to do that "like in state offices. How is it planned to be flexible and useful as well?

EVENT SOTRE

One for whole or per BC? If per BC how to create projections from different BCs?

MateuszNaKodach commented 3 years ago

Event-Centric Thinking Lowering complexity. Sometimes published events differ from state.

Q&A

MateuszNaKodach commented 3 years ago

Greg uzywa ES kiedy ludzie z biznesu sa bardzo zainteresowani. Jest duzo systemow gdzie CRUD jest OK. Jak to jest tylko updejt data.

MateuszNaKodach commented 3 years ago

Event Sourcing Event Sourcing jest jak księgowość.

Questions:

MateuszNaKodach commented 3 years ago

Event Modeling

MateuszNaKodach commented 3 years ago

Event Modeling Tooling

MateuszNaKodach commented 3 years ago

DB better than Kafka as EventStore (indexes - id of event / aggregate type / )

Kafka does not have

MateuszNaKodach commented 3 years ago

Event Sourcing and Machine Learning

Christian Johansen 11:23:53 pm
So you feed the data with historical temperature Data

Shamresh Khan 11:24:34 pm
The first roomtemperatureview was made of from a number of views but the following views were not. Should they be and if not, where do those following views get the information?

Steven Elliott 11:25:50 pm
right. so, in this example, gathering some historic weather data, we can use it to augment our data when we rebuild our readmodels during a catchup of all events stored in the EventStore db

Christian Johansen 11:28:33 pm
Would like to see how do you bind the azure function event handlers with event store events

Christian Johansen 11:29:27 pm
Do you use Azure event grid at all ?

Steven Elliott 11:30:14 pm
I personally do not have experience with event grid, I understand it can be quite powerful especially when working with IoT and massive firehoses of data

Steven Elliott 11:31:34 pm
I apologize here for simulating a ton of historical data

Steven Elliott 11:33:20 pm
Main point I'm trying to display is how you can generate new datasets to utilize information you originally overlooked

Christian Johansen 11:34:05 pm
Makes sense

Rob Hale 11:36:44 pm
The problem I've encountered with event grid and event hub is that there are limits to the number of events that can be sent. IMHO, events within a domain should be handled within the domain. Cloud services and there limitations should be avoided for command and event handling

Rob Hale 11:37:47 pm
The limits are very high, but you're better publishing events and command internally. They are to critical to your system to trust to an external service

Christian Johansen 11:38:17 pm
@Rob Hale Probalby makes sense. MAybe use it for integration events to other Bounded contexts

Jonathan Swieboda 11:39:25 pm
Sorry just ran to the bathroom - what is this UI?

Rob Hale 11:39:47 pm
Exactly, I wouldn't have an issue using service bus to send things between domain. For example, send an event from ordering to purchasing. But within ordering, I should handle all event processing internally to keep control over issues like eventual consistency

Steven Elliott 11:39:50 pm
This is Azure Machine Learning Studio. It's pretty slick.

Steven Elliott 11:40:28 pm
Doesn't really allow for a lot of customizations, but you can quickly build up a model. Microsoft loves their gui's

MateuszNaKodach commented 3 years ago

Event Sourcing and Machine Learning (Steven Elliott) Lookup tables - how to rebuild projections. OK Lookups have timestamps.

MateuszNaKodach commented 3 years ago

Testing Event Sourcing Systems

Ludzie testujac biora gettery i settery obiektow domenowych i wszystkie sprawdzaja. A przeciez nie spradzasz np. zmieniajac adresu czy zmienilo Ci sie imie. W tym przykladzie wyrkyjesz cos innego.

Kto testuje nasze testy? Nikt, biznes - dostaje wydrukowane i mowi czy to tak działa. Główna wartosc to czytanie testów, a nie ich pisanie.

MateuszNaKodach commented 3 years ago

Polyglot Development & Finding Sub-System Boundaries Możesz zatrudniać Juniorów - proste zadanie do wykonania - kawałek. Najwyżej się przepisze. Inny język? Junior vs doswiadczenie w innym jezyku. Możesz kogos zatrudnić.

MateuszNaKodach commented 3 years ago

State Machines and Types of Storage