mixpanel's documentation says that
tracker.track(user_id, 'Sent Message')
which requires a user_id to be the source of the event.
What do I do if the user isn't logged it or the event just happens without the user interaction? for example, a redirect caused by some dynamic data
is there a way to track event (with the ruby api) that isn't matched to a user?
It is possible to track an event without a distinct_id (aka user_id) at the API level, but it's not a good idea because this event will not be usable in any report except "Segmentation" with the "Total" parameter (i.e. it will be useless in Segmentation+Unique, Retention, and Funnel reports). At that point, it's likely better to just not send anything, since it can never be attributed to a user.
If you're really just looking for counts of an event, you can simply generate a UUID. Don't default to -1, null, or another catchall as this can have unintended consequences.
Related
I am implementing an example of spring-boot and axon. I have two events
(deposit and withdraw account balance). I want to know is there any way to get the state of the Account Aggregate by a given date ?
I want to get not just the final state, but to replay events in a range of dates.
I think I can help with this.
In the context of Axon Framework, you can start a replay of events by telling a given TrackingEventProcessor to 'reset' it's Tokens. By the way, the current description on this in the Reference Guide can be found here.
These TrackingTokens are the objects which know how far a given TrackingEventProcessor is in terms of handling events from the Event Stream. Thus resetting/adjusting these TrackingTokens is what will issue a Replay of events.
Knowing all these, the second step is to look at the methods the TrackingEventProcessor provides to 'reset tokens', which is threefold:
TrackingEventProcessor#resetTokens()
TrackingEventProcessor#resetTokens(Function<StreamableMessageSource, TrackingToken>)
TrackingEventProcessor#resetTokens(TrackingToken)
Option one will reset your tokens to the beginning of the event stream, which will thus replay everything.
Option two and three however give you the opportunity to provide a TrackingToken.
Thus, you could provide a TrackingToken starting from several points on the Event Stream. So, how do you go about to creating such a TrackingToken at a specific point in time? To that end, you should take a look at the StreamableMessageSource interface, which has the following operations:
StreamableMessageSource#createTailToken()
StreamableMessageSource#createHeadToken()
StreamableMessageSource#createTokenAt(Instant)
StreamableMessageSource#createTokenSince(Duration)
Option 1 is what's used to create a token at the start of the stream, whilst 2 will create a token at the head of the stream.
Option 3 and 4 will however allow you to create a token at a specific point in time, thus allowing you to replay all the events since the defined instance up to now.
There is one caveat in this scenario however. You're asking to replay an Aggregate. From Axon's perspective by default the Aggregate is the Command Model in a CQRS set up, thus dealing with Commands going in to your system. In the majority of the applications, you want Commands (e.g. the requests to change something) to occur on the current state of the application. As such, the Repository provided to retrieve an Aggregate does not allow specifying a point in time.
The above described solution in regards to replaying is thus solely tied to Query Model creation, as the TrackingEventProcessor is part of the Event Handling side in your application most often used to create views. This idea also ties in with your questions, that you want to know the "state of the Account Aggregate" at a given point in time. That's not a command, but a query, as you have 'a request for data' instead of 'the request to change state'.
Hope this helps you out #Safe!
While user registration process in my domain several actions occur: user created (with email/password or with linked social network account), user login is done.
I have (see) two options how to register the events:
One UserRegistred event (which contains all the info, password hashes, external social accounts)
Multiple events UserCreated, UserPasswordSet, UserExternalAccountLinked, UserLoggedIn
Events from second option (UserPasswordSet, UserExternalAccountLinked, UserLoggedIn) may appear on their own later while performing corresponded operations.
I understand that question and options may be subjective, but I would like hear opinions of experienced ES/DDD users about the issue.
I don't claim to be experienced, but I think it's simpler output multiple events rather than having a complex simple event.
The pros are:
Simplicity - projections (including the aggregate itself) and other event handlers don't need to understand a complex UserRegistered event as well as the fine grained events
Less churn on the event schemas - e.g. if you change details of your authentication events, fewer event types will need to change (since there's no UserRegistered event to change)
Clarity - the events better capture the sequence of state changes involved in user registration
I can think of a minor con:
Non-atomic registration. It's likely projections could handle a single user registered event and atomically create the read model in a state that the client can immediately query. If you have multiple events, the read model might handle them one by one, meaning the user may be temporarily in a half-registered state, that you might not want to handle in your clients.
This can be avoided by having your read projection consume all available events and make its update in a single transaction, so that the sequence of events causes only a single transaction commit, and hence you never see a half-registered user. This is more efficient in any case, but might not be that simple, depending on your read store.
Alternatively, you can automatically filter out half-registered users when querying the service
I'm developing small CQRS+ES framework and develop applications with it. In my system, I should log some action of the client and use it for analytics, statistics and maybe in the future do something in domain with it. For example, client (on web) download some resource(s) and I need save date, time, type (download, partial,...), from region or country (maybe IP), etc. after that in some view client can see count of download or some complex report. I'm not sure how to implement this feather.
First solution creates analytic context and some aggregate, in each client action send some command like IncreaseDownloadCounter(resourced) them handle the command and raise domain event's and updating view, but in this scenario first download occurred and after that, I send command so this is not really command and on other side version conflict increase.
The second solution is raising event, from client side and update the view model base on it, but in this type of handling my event not store in event store because it's not raise by command and never change any domain context. If is store it in event store, no aggregate to handle it after fetch for some other use.
Third solution is raising event, from client side and I store it on other database may be for each type of event have special table, but in this manner of event handle I have multiple event storage with different schema and difficult on recreating view models and trace events for recreating contexts states so in future if I add some domain for use this type of event's it's difficult to use events.
What is the best approach and solution for this scenario?
First solution creates analytic context and some aggregate
Unquestionably the wrong answer; the event has already happened, so it is too late for the domain model to complain.
What you have is a stream of events. Putting them in the same event store that you use for your aggregate event streams is fine. Putting them in a separate store is also fine. So you are going to need some other constraint to make a good choice.
Typically, reads vastly outnumber writes, so one concern might be that these events are going to saturate the domain store. That might push you towards storing these events separately from your data model (prior art: we typically keep the business data in our persistent book of record, but the sequence of http requests received by the server is typically written instead to a log...)
If you are supporting an operational view, push on the requirement that the state be recovered after a restart. You might be able to get by with building your view off of an in memory model of the event counts, and use something more practical for the representations of the events.
Thanks for your complete answer, so I should create something like the ES schema without some field (aggregate name or type, version, etc.) and collect client event in that repository, some offline process read and update read model or create command to do something on domain space.
Something like that, yes. If the view for the client doesn't actually require any validation by your model at all, then building the read model from the externally provided events is fine.
Are you recommending save some claim or authorization token of the user and sender app for validation in another process?
Maybe, maybe not. The token describes the authority of the event; our own event handler is the authority for the command(s) that is/are derived from the events. It's an interesting question that probably requires more context -- I'd suggest you open a new question on that point.
How do I tell mixpanel the userID of my logged on user?
Do I need to call mixpanel.people.identify() everytime my user logs in, or only the first time that I'm creating them on mixpanel?
If only the first time, how does mixpanel know who to associate events to?
Also, once I have identified the person, will all events be tracable to that person, or do I need to call people.set() explicitly to track a generic event separately from a user-specific event?
You should call mixpanel.people.identify() every time a user logs in. You can even call it every time a page loads in a logged in state if you want.
identify sets some data in a cookie about what distinct_id the library should use when sending people data.
If you have called mixpanel.identify with the same distinct_id as mixpanel.people.identify, events that you send (with mixpanel.track) will show up under the user's profile on the Customers tab. In order for the user to show up at all, though, you will need to call mixpanel.people.set (or .add) at least once.
EDIT: mixpanel.people.identify is no longer necessary; you can just call mixpanel.identify and it will set both.
This should be easy to follow, but after some reading I still can find an answer.
So, say that the user needs to change his mobile number, to accomplished that, we might have a command as: ChangedUserMobileNumber
holding the new number. The domain responsible for handling the command will perform the change in the aggregate and publish an event: UserMobilePhoneChanged
There is a subscriber for that event in another domain, which also holds the user mobile number in its aggregate but according to our software architect, events can not old any data so what we end up is rather stupid to say the least:
The Domain 1, receives the command to update the mobile number, the number is updated and one event is published, also, because the event cannot hold data, the command handler in the Domain 1 issues yet another command which is sent to Domain 2. The subscriber of that event lives in Domain 2 too, we then have a Saga to handle both the event and the command.
In terms of implementation we are using NServiceBus, so we have this saga to handle these message and in it we have this line of code, where the entity.IsMobilePhoneUpdated field stored in a saga entity is changed when the event is handeled.
bool isReady = (entity.IsMobilePhoneUpdated && entity.MobilePhoneNumber != null);
Effectively the Saga is started by both the command and the event raised in the Domain 1, and until this condition is met, the saga is kept alive.
If it was up to me, I would be sending the mobile number in the event itself, I just want to get a few other opinions on this.
Thanks
I'm not sure how a UserMobilePhoneChanged event could be useful in any way unless it contained the new phone number. User asks to change a number, the event shoots out that it has. Should be very simple indeed. Why does your architect say that events shouldn't contain any information?
In the first event based system i've designed events also had no data. I also did enforce that rule. At the time that sounded like a clever decision. After a while i realised that it was dumb, and i was making a lot of workarounds because of it. Also this caused a lot of querying form the event subscribers, even for trivial data. I had no problem changing this "rule" after i realised i'm doing it wrong.
Events should have all the data required to make them meaningful. Also they should only have the data that makes sense for that event. ( No point in having the user address in a ChangePhoneNumber message )
If your architect imposes such a restriction, it's not going to be easy to develop a CQRS system. How are the read models updated? Since the events have no data then you either query something to get the data ( the write side ? ) of find some way of sending a command to the read model ( then what's the point of publishing events? ). To fix your problem you should try to have a professional discussion with this architect, preferably including other tech heads and without offending anybody try to get him to relax this constraint.
On argument you could use is Event Sourcing. Event Sourcing is complementary to CQRS and would not make sense without events that have data. Even more when using event sourcing, the only data you have is the data stored in the events. Even if you don't actually implement event sourcing you can use it's existence as a reason for events to have data.
There is little point in finding a technical solution to a people problem.