Basic usage help

EventStoreDB
#1

Hi

So… I have am trying to wrap my head around GES again!

I have a solution that has 2 consol apps in.

The first - mainly taken from the repository test project:

https://gist.github.com/wayne-o/e1d6daf85b9525364f5f

this creates an aggregate, raises some events and saves it. All good so far. I have some streams with names like:

testAggregate-623b55e410c74eb2b2874198c462c36c

The second is the subscriber:

https://gist.github.com/wayne-o/686aa4207c43abb692bf

I want this to listen for events coming out of the eventstore so that i can pretend to update a readmodel or two.

My understanding is that to do this I would subscribe to a stream.

Issue is SubscribeToAll yields an access denied error

SubscribeToStream wants the name of a stream…

which is troublesome as the stream names being created are agregateName-Id - so there appears to be a stream per aggregate instance? Can’t I just subscribe to all testAggregate or is there a way to subscibe to the events themselves?

Can anyone advice me on what my next steps should be?

I want to subscribe to all WoftamEvents so that I can update the WoftamReadModel or whatever I call it…

#2

Hi Wayne,

You can use the credentials ‘admin’ and ‘changeit’ to subscribe to all (either in the defaults or on the subscription call)

James

#3

By default $all (subscribe to all) is a system stream which requires system level privs. There are controllable defaults see Default ACLs here https://github.com/EventStore/EventStore/wiki/Access-Control-Lists. The default is that you should have admin access.

As such just provide credentials of your admin user (or change the default).

Cheers,

Greg

#4

bah beat me

#5

HAHA!!

You’re doing ok on the Turing test btw - almost had me convinced :wink:

#6

OK - brilliant

I can see my events are coming into the subscriber.

I now have a RecordedEvent coming into my read model

How do I get the data out of this so that i can decide what to do?

Do I deserialize the byte[] .Data?

#7

How did you serialize them? :slight_smile:

If using the repository example I believe it uses json

#8

Ok - cool - so the byte[] in Data will be JSON?

#9

I believe so without reviewing the exact code you are using. From an Event Store perspective its just a byte [] and that is decided by you (though we recommend json :))

#10

OK - so that’s cool and the gang…

Now I want to dial into another type of event - the wikiWikiWahJustHappenedEvent - in one place and then wikiWikiWahDidntJustHappen in another place…

How do I go about doing that?

Should I deserialize the events in a single place and route by convention or is there a better way to do it?

w://

#11

It depends - you could subscribe to $et-wikiWikiWahJustHappenedEvent etc and pass different handlers or you could dispatch yourself

#12

Out of curiosity, by “wikiWikiWahDidntJustHappen”, do you mean “received 5 ‘minutepassed events’ without receiving a wikiWikiWahJustHappenedEvent”? Or something else…

#13

It’s just another event. Absolutely no real world usage.

#14

OK so I have the following:

connection.SubscribeToStream("$et-wikiWikiWahJustHappened", false,

(subscription, @event) => Console.WriteLine(“recieved!!” + @event.OriginalEvent.EventId),

(subscription, reason, arg3) => { }, new UserCredentials(“admin”, “changeit”));

but when I run the event producing console app nothing happens this side anymore?

what is the $et- part? are there any docs for this?

#15

–run-projections=all from the command line

#16

You have to run with --run-projections=all and enable the bytype projection in the admin ui

#17

Thanks guys!

And thanks for being patient with me.

:slight_smile:

#18

No worries. To help you along a bit, the internal projection that does the $et streams is the equivalent of:

fromAll().

when({

$any : function(s,e) { linkTo(e.eventType, e); }

})

This makes a stream per event type which is quite useful in many scenarios as subscribers are interested in event type regardless of stream the event came into.

Cheers,

Greg