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Thanks Il giorno ven 19 mag 2017 alle ore 18:39 xprt64 <xpr...@gmail.com> ha scritto: > So, there is hope to standardize this :) > > This would be good for the PHP community as the efforts would be split in > implementing the main components of the architecture like the EventStore > and the CommandDispatcher. > > The EventStore that I use is done in MongoDB but some greater minds than > me (and there are many, that is the power of the community) could implement > something that is faster, more scalable, more robust, more tested, more > whatever. > > The CommandDispatcher could be implemented as a RabbitMQ queue and many > decorators implemented (like validators, pipe middlewares etc). > > 2017-05-19 19:31 GMT+03:00 Rivera, John <rive...@buffalo.edu>: > >> Regarding an AggregateCommand extending Command, that is ironically >> enough exactly how I did it (albeit with a slightly different name) :) >> >> John >> >> On May 19, 2017, at 12:26 PM, xprt64 <xpr...@gmail.com> wrote: >> >> DDD has many patterns, some are at the strategic level and some are the >> tactical level. Aggregates are at the tactical level are are the building >> blocks of DDD. Aggregates ensure that the application is in consistent >> state at all times. >> >> Regarding your example, DDD could come into play by defining a FileImport >> aggregate that yields (raises, returns, whatever; I use the super-nice >> yield feature of PHP) FileUploaded event or throws an FileIsInvalid >> exception. You could raise two events if the failed validation is an >> important aspect of the business that you want to capture, otherwise I >> would choose to just throw an exception. >> >> Anyway, I think I get your point in the first reply: there is a need to >> send commands to something other than an Aggregate/Entity, like a >> application service, and I agree with you. So, my Command propose should in >> fact be a AggregateCommand that inherits from (the now simpler) Command >> and adds the getAggregateId method. >> >> >> >> 2017-05-19 18:07 GMT+03:00 Rivera, John <rive...@buffalo.edu>: >> >>> Hello — >>> >>> Let me give you an example. >>> >>> We have a requirement: an user uploads a file. This file is to be ETL’d >>> into the database. But before being uploaded, the file needs to be >>> validated. And this validation needs to be user-friendly, so the user can >>> fix the file (we use a custom file format for file uploads). If all goes >>> well, the file is to be ETL’d into the staging database. >>> >>> So I have a command that validates, and uploads, the file. It raises >>> (actually, returns) two possible events: files uploaded, or validation >>> failed. The validation failed event triggers the compilation of the errors >>> into a user-friendly to be returned as a response. The file uploaded event >>> triggers the ETL process which grabs the file, performs ETL, and loads it >>> directly into the staging database. >>> >>> Where did DDD come into play here? >>> >>> John >>> >>> On May 19, 2017, at 10:43 AM, xprt64 <xpr...@gmail.com> wrote: >>> >>> Hi, thanks for the feedback, it's nice to see that other are thinking >>> about CQRS in PHP :) >>> >>> > ... you’re assuming that we would use DDD as the domain .. >>> >>> I assumed DDD as the approach, not the "domain". The domain is the >>> business domain and probably any (complex enough) domain would work (we are >>> not talking about CRUD implementations, we are assuming that the problem >>> CQRS is trying to solve is not solvable by CRUD). I assumed DDD because it >>> is one of the nicest approaches used to solve complex domains and CQRS is >>> one of the DDD implementations. >>> >>> 2017-05-19 16:38 GMT+03:00 Rivera, John <rive...@buffalo.edu>: >>> >>>> Hello! >>>> >>>> Thanks for bringing this topic up — I’m a big fan of CQRS/ES! >>>> >>>> But I’ll begin with a caveat — I do not believe it’s suitable to a PSR. >>>> That is my opinion, and I am definitely open to debate. >>>> >>>> Continuing with the assumption that I was convinced that it’s a worthy >>>> PSR… I think your interfaces are definitely excessive. Here’s my minimum >>>> requirements for a working CQRS application: >>>> >>>> Interface Command {} >>>> >>>> interface Query {} >>>> >>>> interface Event {} >>>> >>>> interface Mediator >>>> { >>>> public function send(Command $command): void; >>>> public function request(Query $query): mixed; >>>> public function raise(Event $event): void; >>>> } >>>> >>>> That’s it. >>>> >>>> You’re probably asking ‘wait a minute, what about the CommandHandler >>>> and EventHandler?” — we could have interfaces for each, as follows: >>>> >>>> interface CommandHandler >>>> { >>>> public function __invoke(Command $command): Event; >>>> } >>>> >>>> interface EventHandler >>>> { >>>> public function __invoke(Event $event): void; >>>> } >>>> >>>> However, I eliminated those interfaces in my application because >>>> without them, I can write in the concrete Command object as a type hint >>>> instead of being forced to do a ‘if ($command instanceof ConcreteCommand) { >>>> … }”. Requiring the handlers to be invokable is sufficient. Perhaps someday >>>> we’ll get generics in PHP… >>>> >>>> Another typical way of defining the Handler interfaces is to replace >>>> __invoke(…) with handle(…), but I liked the elegance of working with >>>> invokable classes in the Mediator, and that I could enforce an sort of >>>> ‘interface’ without defining one. >>>> >>>> One more thing — requiring that the Command interface has a >>>> getAggregateId() method is a no-no — you’re assuming that we would use DDD >>>> as the domain. Don’t assume this — in fact, I’m not using DDD in my >>>> application at all, only CQRS/ES. >>>> >>>> Your Subscriber stuff seems intriguing, however — I’ll take a closer >>>> look at your application to see how they work. >>>> >>>> Thanks for bringing up the topic — I hope this will lead to a >>>> illuminating debate! >>>> John >>>> >>>> On May 19, 2017, at 2:53 AM, Constantin Galbenu <xpr...@gmail.com> >>>> wrote: >>>> >>>> What do you think about introducing some standards regarding CQRS and >>>> Event sourcing? >>>> >>>> I have a working/in production web based CRM application that uses one >>>> of my micro-frameworks <https://github.com/xprt64/cqrs-es> . It uses >>>> the command handler style described on cqrs.nu, where command handlers >>>> are aggregate methods. The aggregate is identified by the ID (extracted >>>> from Command) and class (manually/automatically subscribed). >>>> >>>> The normal flow is this (the flow implemented by my >>>> DefaultCommandDispatcher): >>>> - the client code (i.e. a REST endpoint) creates a new Command and it >>>> sends the command to the CommandDispatcher >>>> - the CommandDispatcher identifies the aggregate class (using >>>> CommandSubscriber) and ID (using Command::getAggregateId) then >>>> creates a new aggregate instance >>>> - it rehydrates the aggregate from the event store (by loading all the >>>> prior events and applying them to the aggregate instance) >>>> - it calls the aggregate's command method (identified by using >>>> CommandSubscriber) and collects the yielded events (also it applies >>>> them onto the aggregate itself, one by one, at collect time - a kind of >>>> reactive aggregate); >>>> - it persists the collected events to the EventStore, FutureEventsStore >>>> or ScheduledCommandStore depending on the yielded message type >>>> - it notifies the event handlers using EventDispatcher >>>> - it discards the aggregate >>>> >>>> The aggregate should not inherit from anything and nothing should be >>>> injected into it. It should remain pure, side effect free. Any side effect >>>> should be observed by its yielded events. >>>> >>>> I like this style because it reduces a lot of code duplication found in >>>> the other style (command handler being in the Application layer) where >>>> almost every command handler looks the same: it loads the Events from the >>>> store using a Repository, it factories a new Aggregate, it rehydrates the >>>> Aggregate (by applying the events to the Aggregate), it calls a method on >>>> the aggregate, it collects the events, it persists the events and then >>>> notify all subscribers (event handlers). In cqrs.nu's style this >>>> entire algorithm can be extracted in a CommandDispatcher. >>>> >>>> So, I propose (at least) the following interfaces (in the namespace >>>> Cqrs) >>>> >>>> //events >>>> >>>> interface Event; >>>> >>>> >>>> interface EventDispatcher; >>>> >>>> >>>> interface EventSubscriber; >>>> >>>> >>>> interface MetadataFactory; >>>> >>>> >>>> interface EventStore; >>>> >>>> >>>> interface AggregateEventStream extends EventStream; >>>> >>>> >>>> interface EventStream extends \IteratorAggregate; >>>> >>>> >>>> interface EventStreamGroupedByCommit extends EventStream; >>>> >>>> >>>> //commands >>>> >>>> >>>> interface Command; >>>> >>>> >>>> interface CommandDispatcher; //can be decorated by a >>>> CommandDispatcherWithCommandValidation >>>> >>>> >>>> interface CommandSubscriber; >>>> >>>> >>>> interface MetadataWrapper; >>>> >>>> >>>> interface CommandValidatorSubscriber; //used by >>>> CommandDispatcherWithCommandValidation >>>> >>>> >>>> //scheduling >>>> >>>> >>>> interface FutureEventsStore >>>> >>>> >>>> interface ScheduledCommand extends Command, ScheduledMessage; >>>> >>>> >>>> interface ScheduledEvent extends ScheduledMessage >>>> >>>> >>>> interface ScheduledMessage extends IdentifiedMessage; >>>> >>>> >>>> interface IdentifiedMessage; >>>> >>>> >>>> interface CommandScheduler; >>>> >>>> >>>> interface ScheduledCommandStore; >>>> >>>> >>>> //read models and sagas (process managers) >>>> >>>> >>>> interface ReadModelInterface; >>>> >>>> >>>> interface SagaEventTrackerRepository; >>>> >>>> >>>> >>>> I know that there are a lot of interfaces, but in fact, in a working >>>> application, more interfaces are needed. >>>> >>>> In order for this to work, the minimal requirements from the code in >>>> the Domain layer is the Command interface (for its getAggregateId >>>> method). The Event interface should be used only to detect event >>>> handlers by reflection. So, the domain code remains (almost) pure. >>>> >>>> I have a todo <https://github.com/xprt64/todosample-cqrs-es> example >>>> on github if you want to learn more. >>>> >>>> I know that my question mixes the proposed standard with my >>>> implementation but I don't know how to start the discussion otherwise. >>>> >>>> So, what do you think? >>>> >>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "PHP Framework Interoperability Group" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to php-fig+unsubscr...@googlegroups.com. >>>> To post to this group, send email to php-fig@googlegroups.com. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/php-fig/0c9a062b-4f1b-4f3c-85d3-433a93fdb234%40googlegroups.com >>>> <https://groups.google.com/d/msgid/php-fig/0c9a062b-4f1b-4f3c-85d3-433a93fdb234%40googlegroups.com?utm_medium=email&utm_source=footer> >>>> . >>>> For more options, visit https://groups.google.com/d/optout. >>>> >>>> >>>> >>>> -- >>>> You received this message because you are subscribed to a topic in the >>>> Google Groups "PHP Framework Interoperability Group" group. >>>> To unsubscribe from this topic, visit >>>> https://groups.google.com/d/topic/php-fig/78LIU6d7mic/unsubscribe. >>>> To unsubscribe from this group and all its topics, send an email to >>>> php-fig+unsubscr...@googlegroups.com. >>>> To post to this group, send email to php-fig@googlegroups.com. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/php-fig/2E629BBA-3015-4A4C-AA47-E85DC1539E64%40buffalo.edu >>>> <https://groups.google.com/d/msgid/php-fig/2E629BBA-3015-4A4C-AA47-E85DC1539E64%40buffalo.edu?utm_medium=email&utm_source=footer>. >>>> >>>> >>>> For more options, visit https://groups.google.com/d/optout. >>>> >>> >>> >>> >>> -- >>> Best regards, >>> Constantin Galbenu, >>> Tel: +40728247366 <0728%20247%20366> >>> Skype: xprt64 >>> Twitter: @gicagalbenu <https://twitter.com/gicagalbenu> >>> Github: https://github.com/xprt64 >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "PHP Framework Interoperability Group" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to php-fig+unsubscr...@googlegroups.com. >>> To post to this group, send email to php-fig@googlegroups.com. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/php-fig/CABEUsAe24OaPQRQrKwHiYHfpzEJGG71S4o%3DeHBxPcK-A9-rvfw%40mail.gmail.com >>> <https://groups.google.com/d/msgid/php-fig/CABEUsAe24OaPQRQrKwHiYHfpzEJGG71S4o%3DeHBxPcK-A9-rvfw%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >>> For more options, visit https://groups.google.com/d/optout. >>> >>> >>> >>> -- >>> You received this message because you are subscribed to a topic in the >>> Google Groups "PHP Framework Interoperability Group" group. >>> To unsubscribe from this topic, visit >>> https://groups.google.com/d/topic/php-fig/78LIU6d7mic/unsubscribe. >>> To unsubscribe from this group and all its topics, send an email to >>> php-fig+unsubscr...@googlegroups.com. >>> To post to this group, send email to php-fig@googlegroups.com. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/php-fig/C3FB5291-3FE4-4639-AC19-F4A616A2C0BB%40buffalo.edu >>> <https://groups.google.com/d/msgid/php-fig/C3FB5291-3FE4-4639-AC19-F4A616A2C0BB%40buffalo.edu?utm_medium=email&utm_source=footer>. >>> >>> >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> >> >> -- >> Best regards, >> Constantin Galbenu, >> Tel: +40728247366 <0728%20247%20366> >> Skype: xprt64 >> Twitter: @gicagalbenu <https://twitter.com/gicagalbenu> >> Github: https://github.com/xprt64 >> >> -- >> You received this message because you are subscribed to the Google Groups >> "PHP Framework Interoperability Group" group. >> To unsubscribe from this group 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