prooph/improoph

Support chat for http://getprooph.org/ - official announcement: https://www.sasaprolic.com/2018/08/the-future-of-prooph-components.html

Bradley Weston

@bweston92

however as I am now getting more and more contexts I think the eventstore will probably restrict me a little bit

and think the following might be better

Fritz Gerneth

@fritz-gerneth

i.e. add a publisher in between to off-load work from the ES to a queue

I've been playing with this a bit myself, mostly because mysql does not support subscriptions

the two major things to take care of here are:

how can you detect gaps in your stream (i.e. ensure messages are consumed in order, not every queue guarantees this)
how can you get access to historic events (i.e. when you create a new projection and want to / need to start from the very beginning of a stream)

so I was/am aiming for a hybrid approach, use event store to get up to date, then stay up to date with pubsub

Bradley Weston

@bweston92

so them 2 issues you've explained, I have thought about both with no real solution other then write tooling

Fritz Gerneth

@fritz-gerneth

nothing there out of the box, yes

Bradley Weston

@bweston92

event order can be determined by aggregate identifiers and versions and if there is a missed event send it away for a while until it gets it, if not then report an error I suppose? but then when replaying would use a lot of resources to handle this

and the second one would be to send directly to a subscription from all the stream sources it cares about

Fritz Gerneth

@fritz-gerneth

tbh.. I gave up on this after a while.. I had ideas how to handle all these, but the effort wasn't just worth it

Bradley Weston

@bweston92

is the trade off worth it :'(

just about to say that yeah

but the more I get eventstore to do the slower and harder it will get

Fritz Gerneth

@fritz-gerneth

do you think this or measured this?

Bradley Weston

@bweston92

bit of both, eventstore when having lots of running projections aggregating different streams becomes slow

Fritz Gerneth

@fritz-gerneth

we have about 100 projections running and we still can scale the ES (aws rds instance)

but then I don't know the eventstore.org :)

you can still start splitting them up, but have read models on ES directly

from the graph you're doing both at the same time?

Bradley Weston

@bweston92

ES has the projections that aggregate streams, the resulting streams from that aggregation a projection that writes it to a local read model uses a persistent subscription on the result stream

Fritz Gerneth

@fritz-gerneth

we did delegate this in a query-bus instead

Bradley Weston

@bweston92

the query bus would only read from the local projection

Fritz Gerneth

@fritz-gerneth

do they need to?

Bradley Weston

@bweston92

yes, because that is where the data is formatted for each api endpoint response type

Fritz Gerneth

@fritz-gerneth

formatted = stored I assume?

Bradley Weston

@bweston92

stored in the way the consumers of that endpoint will want it

@prolic / @codeliner you have any thoughts on this?

Fritz Gerneth

@fritz-gerneth

all in all it sounds like an issue scaling the eventstore to more projections though

Bradley Weston

@bweston92

yes, but also means I don't have to use event sourcing for everything either :| for smaller stuff I could just just an outbox that pushes it onto a message broker

Fritz Gerneth

@fritz-gerneth

that's the part where we use the MQ, for anything that doesn't need to be replayed in the future :)

Bradley Weston

@bweston92

but what if some of your projections consume both an event stream that can be replayed and a standard MQ?

Fritz Gerneth

@fritz-gerneth

for us, they don't, one is a projection updating a read model, the other a standaline event listener

Bradley Weston

@bweston92

for example a customer is event sourced but how many times they've clicked a link isn't. The projection is total clicks by a customer. Customer created event (from event sourced) inserts with 0 clicks then clicks from the MQ increment that

Fritz Gerneth

@fritz-gerneth

that'll introduce some serious concurrency pain :)

Bradley Weston

@bweston92

so what would the solution be?

store the events locally?

Fritz Gerneth

@fritz-gerneth

use only one of it I guess

Bradley Weston

@bweston92

the events from the MQ store them in a local event store?

just imagining all the backup and restoration to put in place and test

Fritz Gerneth

@fritz-gerneth

that sounds like you're trying to re-invent ES-replication then (read-instances)

Bradley Weston

@bweston92

doing what I suggested would end up doing that yeah, just trying to think of a way round it all

Fritz Gerneth

@fritz-gerneth

I'd probably try to solve this issue on the ES side, with read-replicas on their side

or split up into different ES instances

Bradley Weston

@bweston92

ok, thanks

MtK

@kochen

Hey all, long time!
I'm designing a small quiz application that has a known structure: Categories, Series & Questions. Categories have 1 or more Series. Series has 1 or more Questions. You could start any Category or multiple and in any order (1, 4, 2, 3), but the Series inside the [started] Category are linear, as well as the Question inside the Series.
Again, for simplicity, we have a known structure.

This logic needs to be kept a bit abstract, in order to allow different "types" of quiz (i.e a single linear series of questions, with other hierarchy or something more complex like "if you answer A your next question is 5").
Scoring rules (for correct or incorrect answers and/or bonus for completion) might change for each instantiated Quiz.

For each user participating in the quiz, we need to store his state/progress including scoring his answers.
We need to be able to mark events such as:

Answer Submitted
Answer Marked as Correct & Answer Marked as Incorrect to be able to provide the right feedback as the appropriate Score Granted
Series Marked as Completed
Category Marked as Completed

What is important here is to be able to determine at any moment the "next question" in each series as well as the states of each series (and the next available) & categories.

What I'm struggling a bit with is the modelling of the aggregates here - where would an answer be submitted to, who would the calculate the score (better yet, aggregate the scores) and how to maintain user-progress within the quiz.
For example: Would it make sense to have an QuizState aggregate that gets created when a new Quiz is started by a certain User and is responsible for all the above events? looks a bit too much responsibility, but I can't figure out how to properly split it...

Zacharias

@netiul

Any time soon my first event sourced app goes live 🎉 (Based on event engine). Quite a journey it was, so much new stuff learned, still so much to discover too.

Sascha-Oliver Prolic

@prolic

Congrats @netiul

Greg Szczotka

@greg606

Hello, I have legacy Symfony PSB + PEStore + PESourcing app, in AggregateRoot I have this:

        $this->recordThat(
            BookingWasSettledPartly::into(
                $this->bookingId,
                $newBookingId,
            )
        );

        return $newBooking;

$newBooking is added correctly but this event BookingWasSettledPartly is not, it used to work with older version but now it's not.
What is essential to make it work in this config (PSB+PES+PES)?

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