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hello a little bit nervous and this is


where I need to check this clicker I


think all works and I want to say it's


really complicated conference because I


was on three different after parties on


the last three days and it was hard but


I hope we did it and I'm happy that


today's last party and the city is


really nice because when I walk around


the city I found this one and I can say


it's looked like previous of two parties


and usually I manage her were also of


hashtag on Twitter and I found that the


dog can drink a beer so hello Roscoe


Furby it's my first time in pond and


before I come here I know only two


things about Poland the first one it's a


lot of great ideas and engineers here


I'm working a lot with drive system and


ROM and usually a little blog post from


our concea and the second one the


Poland's it's a place with some nice


games I really love this game full of


this game - Wow awesome


so and what I what I studied now as the


first and the most important part it's a


pure gear in Russia we have Apple many a


pair I give is me awesome and vareniki


is a pure guru skier and I tried


yesterday was on Tantra gear it was


yesterday yeah oh no it was two days ago


no I know it was yesterday


and it was funny because usually in


Russia we have a really small - raggy


it's like something like this but


yesterday it was something like this and


it's nice and also I found the best


implementation of state mission thanks


for this conference it's look like this


[Music]


just five lines of court and I have


everything so also I found the is


popular here I checked on dogs and found


that we have six talks about even


sourcing or maybe mentions to and


sourcing but unfortunately memes is not


popular because I found only three dogs


ship with sound routes and names and one


more important thing it's after load


it's still good


and of course are some people and


community I'm happy to be here and thank


you everyone my name is Anton I'm from


Moscow I'm Russian developer and usually


you can meet with me when everyone say


Konami so okay I'm software developer


and the hippo it's American startup


open-source even released economic or


developer I try to make some products


and also technical consultant I love


stickers you can check my laptop and you


will see that I really love stickers and


if you want to talk with me we can talk


on some different terms for example


about coffee and I am really happy to


see it's obvious it's the first


conference where I can drink coffee a


lot because it's a great coffee some


beer and I'm happy to see a lot of craft


beer here some psychology and I have


Nintendo's wish we can play if you want


but when I come to Moscow and also I


love drawing and rest for my


presentations that's where we can talk


about it and all images here it's drawed


by me and so and also a lot of bad


stories and when I preparing to this


presentation the first time I tried to


make a story and when I did it I


expected that I'll be like this guy I'll


create a cool story about something here


and although ok but I fortunately


reality was different


and


I go to health I got to help from my


friend it's awesome friend and his name


is Jia Jie and he's quiet and really


loved ask some questions since this why


he helped me a lot and it's a flower but


anyway to do talk about events events in


school I draw this event and events


everywhere like state machines but


events too and sometimes we need to


catch these events and do something with


it and the first example I really love


this example I imagine it a few days ago


ask some people and it's a good for


example digits in okay one more question


who know what is it and who use it


awesome


so each committin get it's something


which was happening for example we have


a repository with a list of comets and


each commit contain description and some


changes for example I found the commit


from my friend and he described what


happen it and create a sample load which


will update a state the next example


it's a list of items which usually


delete it or edit for example it's


useful for order scenario commerce some


activity I did when someone tried to say


what happened before and what will do


with it and my favorite example who


deleted not deleted data


I mean who have this field in database


ok I think you understand my problem I


and I fortunately in programming we


usually work increase the current state


of application I mean we have web


applications and in our web applications


our actions in controllers it's some


events which says that something


happened


and our dating database it's a current


state and always so yeah sometimes ask a


questions and I don't know how to answer


on this question because he asked what


will happen with it and I think if we


will do this stuff we will get something


like this and what the general idea is


the general idea it's stored in your


persistence layer it can be anything


what happened instead of current state


of your application and after that you


can get state a state of your


application anytime anywhere without any


problems and the first question where we


need to store all the stuff and usually


in some ecosystems is call it event


storage it can be anything like Oracle


MongoDB Kafka to make anything possibly


has radius if you want an in-memory and


we have some rules about it the first


rule event was happened the second one


it's immutable objects I mean you can't


delete or update event and what does


mean when you put some when you have a


rest or it's like a list for example and


you put something in through table can't


create you can't update this event you


need to create one more event which will


update a state for your application and


that's why you need to put only a valid


data into events and for example you


have this situation you have user web


application some store and user creative


and from real world you need to validate


it and say ok I can store it and user


roles ok or you need to say sorry it's


wrong data I can do it the next


important stuff it's because we have


immutable system with immutable data we


can't update it or maybe rename


something or delete something we need to


think about data evolution and what is


mean for example we have a story


and you have a small start-up and e27


sourcing like general architecture for


some parts of your system and you store


some information about users and you


store first name and for example it's


Anton but so but after some time for


example some years someone from


management say hey we don't know we


don't need to store our first name we


need to store full name and in this case


we'll go to problem but because we can


break application and how we can do it


we can use optional fuels binary data


structures with different versions and


also we can find more in this book I'll


show this book five times on my talk I


think because it's a really great book


about data how to work with data and


cells etc also you can find some


information about data by this and


others interesting stuff so we can store


some events and we don't have the


current state how we can get a state


from our list of events we need to


calculate it every time using events


which we get now and usually it's called


projections and it looks like this it's


a function will which take three


different parts three different


arguments the first one it's a function


usually it's like a block which we used


in mob function and Ruby method or each


as the second one it's events and


initial state and as you can see we can


so it's a it's a perfect peel function


because when you put events an initial


state here will always get on you state


every time it will be same and how how


it works usually we have events store we


put something new


about user for example and his name and


after that she understands that we need


to update this name to something else


and we updates name and we start we have


a list of events we don't have a current


stage we don't know that user have a new


name but we know what happened to his


user on this time and we start from


empty initial state and we go by events


go go go take name in Sandton take a new


event that name was updated update the


name in our current state and return a


new state and of course this looks slow


and the problem here we compile current


state every time and it's hard if our


application lives two years maybe ten


years it will be extremely slow and I


know again I'm Syria he really loves


some questions and I didn't know how to


answer it again but how we can fix this


problem with faster calculating stem


state the first idea is streams and for


explain what is it I I drove this party


bus it's a two different party bus where


you can take some ice cream and for


example we have a system which say us


how to sell some ice cream to children's


maybe not children's we have a list of


events and for calculating how many ice


creams with so result in the first bus


we need to calculate all events for all


bus party bus and can get a state for


one maybe or all buses in our system and


instead of this we can say event for bus


one have a stream bus one and all events


which related to second bus will have a


stream bus to and after that when we get


events we can say please give me a rest


for specific stream in my case it's a


bus number one and instead of all


streams we will get only related to


stream and


- boss events and after that instead of


calculating 6 or maybe 10 events we will


calculate only 3 and the second bus you


can use it to you can take events so for


second bus two and one positive side you


can process less events and it will be a


little bit faster for example an


e-commerce system when you work with


orders I'm not sure that order can make


more than a thousand four two thousand


events for only one order usually it's


around 10 maybe 20 or maybe more but


it's violating you obstruction you need


to think about streams and how to work


and process with it you need to update


you events start to work with it and the


second idea how to improve the situation


we can use snapshot for current data


state what is mean our project function


is superior function will take function


events and state and it can be empty


state or can be state from previous day


for example and again we have a user we


have a web store we have application and


use your put event to event store we


take all events I'm sorry I forgot s


here I will take all events in our


application calculate estate put the


state into cash and after search and


stand of recalculate state again in


again where you can use cash and send it


to user and for this you can use any


databases like my sequel


Redis again Oracle Cassandra and the


interesting idea here our cache database


is not a source of true and we can set


up any state here and we can use a


different databases for different


functions for example we can use


relation database for search for example


and index


and index patient on our web application


but when user click on show action will


use the comment orientated database with


full object of physicians and such


researcher and instead of calling a lot


of drawings we just send just one and


it's all so let's talk about real world


where it can be useful I found some part


of the systems where it can be useful


first of all its e-commerce system when


you have orders and you work with orders


it's something which happen you need to


make advance you need to add or maybe


delete some items in the cells etc


Shekau flow is really important stuff


because you work with money and I don't


like to lose some money and with the


rent sourcing you can calculate state


and check what happen I'm sorry


so also it's a good idea to use events


or synchronous systems where you need to


version control for example Google Docs


who use Google Docs instead of updating


concurrent the commands you can create


someone updated and edit something else


or deleted some something and calculate


a state for current moment for all users


or if you need to check a history like


indeed you can just go back by history


and see what happened so and also some


demands depend on events usually it's a


tracking system for example if your life


if you like cube or sport or something


like this you can create it you need to


create a system which will store what


happened when someone play to dot our


cares go you can use event sourcing for


stores these events and process it and


calculate the state every time and after


that for example show shown in real time


what happened before and no I don't


think the tree alex is a good idea


because you need to understand that when


sourcing can avenge our energy check


sure it's the same because they have


event in the name as it's all


but they use events in different ways in


event sourcing system you say that ever


happened and I'll store it and we'll use


in future in event-driven and it's


actually usually something happened and


usually your queue or something else say


okay I'll say it everyone's something


was happened and yeah my blockchain is a


good solution to here I don't know so


some good parts about event sourcing


it's easy to communicate is the main


experts because instead of creating


connections you can create the main


related event and understand the order


if order was check out you might check


out flow for the stuff also you will get


a login code from the box because you


have a list of event you can check what


happened time-traveling restore state if


you a drop Postgres like github you can


easily take current state for current


moment and just restore the system


without any and troubles and streams in


a search et cetera


also it will not to work with tables you


work with events and changes and what


happens in your system it's little bit


different and you need to change your


mind for this and in this case you can


use experimental data structures for


displaying information maybe store this


information and you can easily change


[Music]


sketch database implementation and of


course even sourcing contained a lot of


problems I think it's more than positive


size was the first problem it's really


hard to understand the stuff because you


need to change your mind from our saving


and updating current state to work


increase state in different way it's


another popular in Ruby now but after


Roscoe Furby I don't think so so and


developers need the programming they


need to spend more time understanding


time for in time for new developer


before before starting can distance what


happened here and new feature will be


increase decrease and so the next


problem it's really hard to get state so


if you have a simple crude application


sometimes it's really hard to get a


state for this application you need to


understand all chains for grants for


example have created one event this


event will create other events and as a


etc it can be a really big graph and it


will be hard to understand it's another


type of architecture you need two


different database structure you need to


think about versions and versions


compatibility about data evolutions is


more about distribution problems it's


really hard to updating and deleting


events and I'll talk about it later and


some advising topics maybe it will be


interesting how to display data as soon


as possible for example we have orders


someone create events that orders added


something to order for example item and


I know two solutions for this


the first one is instead of displaying


that you can cheat user how it looks


like I have a client you have web


application and events store clients say


okay I want to add something to my order


you will data state and after that you


put event and return success result and


client will show what user added on the


on client side


I mean user don't need to take


information about new item because he


has it in a client it's like


opportunistically right so the second


solution is WebSockets and long pooling


but here I know one really terrible


problem it's how to make an order of


events for example you web application


second law application one application


put event to


second port I went to one store but we


have a net splitting the first


application and what happened is the


situation and I want to say hello


distributed systems are a little of it


because it's challenged usually and the


more you can find here because it's more


about distributed system and data and


also here if you can travel in time you


can go back and listen it again but the


second topic how to delete an user


related data for example if in Europe


and someone say ask you to delete


everything about him and I found two


ways to do it three ways the first way


it's reactive why to end it was


described by Martin Fowler


unfortunately I I don't read it this way


I can't explain it now but maybe later


the second one it was from NJ he told me


that they encrypted data and after that


you can just lose a key for decrypting


this stuff and the last wave was about


Kafka you can just explore some stuff


but it's not true way but you can do it


sometimes too so how to use seven


sources in Caen rubia so we have a


simple way in Ruby is the gems the first


one it's a real civil store who uses


German production the second one it's


this one and you can check a lot of


interesting information and also an


entire project which has more features


and more information so but also we also


have brave way we can build this stuff


myself and for example you can use Kafka


7 storage and use Kafka craft code was


developed by this guy who know him


and usually when I talked to him he told


me that Kafka's great


the second way we build hanami events


hanami events it's it won't drive and


transport layer just for this event


versions and types you can create a type


of event it's just a pops up and also we


have our connections with all global


stage what is mean you need to you can


create instance of each stuff myself and


after that so now we have only three


adapters it's a memory to two memory


adapters one for sync and synchronous


way in one for radius you can easily


change it by changing instance of your


aryans and also we use dragon trainers


that's why we can easily register a new


one adapter


I know folk he created Google pops up


stuff based on random events and you can


just register a new stuff and after that


use it and in this way you don't need to


load all adapters on your memory every


time instead of this you just take


adapter and take all data around it into


memory so broadcasters subscriber and


yes sourcing looks cool and the common


question how I can be created and for


examples some user add something to cart


I hope I made right example you have for


hanami for example who use hanami in


production oh I found you so you know


what is it much better


okay so we have action in hanami we have


action and separate classes which method


call and in this class we use terrible


logic like you check repository and


after that you create a new item and


repository or create copy of this item


and after that are called some analytic


stuff like Cygnet or something like this


and the first step you need to some


stuff from ddd it's ren storming you


need to detect important business


in the system in your system not in our


code in system in general and in my case


we can create two different events first


one is item added and the second one


it's a corporate item item added and so


we need to apply restore at that store


it's look like this we just put it here


and after that we will refactor it but


now we have a problem how to validate


item was it created or not


I mean how we can implement this line of


code and we need to calculate State for


understand can be adding you item or we


need to add a copy of item for this we


can use so what's the first we need to


take events for specific stream in my


case it's order ID in your case it can


be anything after that you'll get a list


of events and you can use projections


for for calculate state for items in my


order usually projections in dotnet and


if sharp looks like this in other


libraries it can be something else but


general idea


you take event you take event and you


can you take a state and after that you


always return a state and after that you


check type of event do some stuff you


can check type of all the event and make


other stuff and instead of calling


repository you take state you can check


can be at this stuff and the soul and


after this we just set a new events and


so so but we have a problem we have one


terrible analytics call and for this we


can use subscribers it's not about


events or sync in general but we can do


it for example we can create some


subscribers and detect what happened


with our item it was added it was a


mobile channel such etc and creates some


stuff and analytics logic around just


around this and in our case new course


will look like this and the last step


which moves a steerable logic to other


place for example to model so what's the


profit


of this I'm sorry it's it's a profit


it's our profit it's not a profit of


this it's just profit so and some small


chip we can use it once or think like


only one small part of our system for


example don't create a resourcing system


for users or some other stuff but


created for orders or maybe a game or


something like this and what next and


the next is Sega oh I'm sorry it's the


saga


it's a sucker pattern who know what is


it Wow awesome so it's a business


transaction for example you try to order


order Hotel on the booking it's a long


way and I found this image high so it's


about how to order a business trip and


these funny situations that you need to


process all the stuff and if you fail on


one of the step you need to roll back


and the interesting stuffs that saga


it's state machine you can implement it


it by state machine so what's the next


next it's sqs it's about you have read


model right model and work with it and


also i really suggest suggest looking


outside the review world because you can


find a really interesting github project


its OS almond ddd awesome ddd and if you


check it here I try to find something


about Ruby and as you can see I found


nothing in all this project so this is


why sometimes I'm looking to some


implementations and for example I have a


repository you can check it I trying to


understand how F sharp guys might even


sourcing can build something similar in


rubia take some ideas from this


implementation to my presentation and


the next step its DDD who know what is


it and I think Georgie know what is it -


so we we can use the ddr4 store business


for detect what kind of events we can


store


we can split system by domains and make


it easily and of course how suggest this


book I remember that I when I read this


book the first time my facebook was like


this I'll say if you like f-sharp


language and calm dotnet you can read


this book it's good book too and also


usually if you think that even sourcing


it's more about a synchronous way you


need to understand her distributed


systems and problems and I'll suggest


this book again I'll suggest this book


again and some conclusions it's just


small conclusions sometimes even based


architecture convene and sometimes not


it's not a silver bullet it's just idea


how to process your state of your


application


eversource ink is simplest conception


because for example we use git every day


and for us it's simple when you use it -


or maybe here three years but when some


junior developers will come to new


project and never tried it before


he will get some troubles and that's why


this conception it reduce a lot of


practical problems data evolution


ordering kindness etc and of course


events or sink is really expensive and


expensive with money expensive in


understanding and developers and etc etc


and I think it's the most important part


events or sync is not about distributed


seems systems and it's not about how to


communicate with different micro


services it's about only state and I


think even sourcing could be a trend in


the future in the Ruby world and if you


don't trust me I made this slide and


thank you this hole


[Applause]


hi there thanks for my stock I have more


like an unknowing to what to what she


said because you presented how to comply


the right to be forgotten when you have


an event sourcing system and you've


mentioned that you can just encrypt the


data and just lost your keys and once


I've heard from one lawyer that it's


also not a good approach because it is


very possible that in the future the


computer performance will increase like


let's say quantum computers or something


like that that it will be even possible


to the crypto those data so it's still


not sufficient way to to handle the


right to be forgotten yeah I agree


but if quantum computers will decrease


anything will get more problems raises


and deleted user but anyways it's good I


agree just the comments the blockchain


guys had another idea to do it they have


the same problem you can modify


blockchain inside and they actually do


it in banking systems in production in


Poland so I believe it's is correct you


store the payload separately from the


blockchain so you can store fingerprints


in your events to be sure that payload


is immutable and you can always delete


the payload and if you find the event


you just just say sorry is deleted good


ideator


I think I need to check your chain for


better understanding sister


hey nice dog thank you so my question is


I know when you want to have a current


state you make a snapshot right and so


what about the searching how would you


search for like I know and most


attractive items when you need to


process like millions of events to get


the real table it's a good question


you can create anything you can


calculate state and make a super slow


system every time you can try to catch


this stuff and try to find something by


in difficut


for example you have elastic search put


all the stuff into elastic search every


time updated and use elastic search only


for searching and after that you'll take


some information and after that you can


for example get stayed for example you


you try to search some orders you have a


lot of orders you need to find something


you need to find some order buy


something you will find this from


elastic search take stream idea and


after that take list of events and


process state current state or something


like this I'm not sure that's right way


but it's a just idea from my brain now


two questions really one is that you


said that event sourcing systems would


be more expensive do you think that is


the case also in the long run but like


is it a it's short term it's more


expensive but in the long run maybe it's


less and then also how do you think we


could get that cost down I'm obviously a


big proponent of building systems this


way but how do we make that lower cost


okay I understand the question so the


first part I think if you're small


startup and you try to find some money


and to the next round or something like


this you can live without it because


really you need to spend more time for


building horizon


usual crude you just need to prototype


and take and check any features to


understanding will it make can you make


some money with this new feature or not


and in this case it can be slow to use


events or sync and I think that company


which switch to the stuff they know that


it will be they notice problems and


usually say ok we know these problems we


know how much we will pay for this


but we can pay for this and in future it


will be better for us and usually is


funniest funny stuff about even sourcing


I know some folks one of this is my it's


my friend from Russia he work with Java


before and I explained all the stuff for


preparing the presentation and he told


me oh it's call it event source and we


use the same thing but you don't know


what is it and usually I think some


developers for example if you work


increase not not iterating to you


working creates a tracking system it


track what happened on a game for


example you're working a similar way you


store events and try to work with it and


I think in some parts it will be costs a


lot but you can pay for this but in


other parts it will be cost a lot and


you don't need to pay for this it's like


a blockchain you can use it everywhere


but I here sure that you need to use it


and the second question how to how to


make it less costs I think it's a


problem in in two maybe three different


ways the first one it's learning they


love what are can see do with it they


made a lot of blog posts they made


workshops conference and talk about it


and for example if


you don't know what is it and start


working crazy at the time before you're


understanding what what happened in the


system and first Fisher you'll be less


or I will be more eyes than developer


who know what is it and teaching can


it's a good idea to decrease cost for


sourcing also I think it's a good


tooling too because sometimes you need


to spend a lot of time for debug the


system and understand what happened and


this why I think to link it's a good


idea to decrease the cost - and I don't


know any I think I need to think more


about it transfers the question and


other questions thank you thank you


[Applause]