saintprubyconf2018

CRDT:

https://github.com/bind-disney/spbrubyconf-2108-crdt-example

react data stores (sets are stored in vesrions vector) (vesrions vector, changes vector)
so the max index of value wins in the case of this structures

merge fucntion is applyied when  the replication starts

merge function has access to the index and merge state (vectors)

real world apps: systems which use riak, akka systems (have crdt under the hood)

from version 4.0 of redis it uses crdt 

RUBOCOP:

a brief history: jonas054 issue on emacs support 
ripper is on github

state of unity release 0.8
- new features(formatters, conf options, better performance)
- checkout cache functionality code
- pattern matching

curernt status of rubocop:
- metrics: 100
- style: disabled
- limit cops 
- different configs for different directories
- inherit configuration files
- ruboop layout feature

GRANITE
toptal dev over rails

emacs check it out 

Rubocop future: 

v1.0

- remove rails 
- api for extensions
- moving to rubocop HQ (all is there)
- mry for rubocop
- new site of docs

emacsredux.com

EVENTS, EVENTS, EVENTS:

Event sourcing, DDD, CQRS

When some work on events need to before, after states

Event sourcing:
- events
- event storming (DDD)
- event strore (kafka, redis)
- immutable events

e.g new database with current state

pros:
- easier to communicate with domain experts
- time traveling
- restore a system
- logging out of the box
- work with events
- experemental data structures
- persistance 
- easier to add instance for service
- any language 
cons:
 - hard to understand and complicated abstraction
 - not popular in ruby and bad tooling
 - developers need deprogramming
 - hard to get state
 - hard to understand chain
 - another arch types of DB style
 - async world
 - versions compatibility
 - evenual consistency 
 - updatding and deleting events

rails event store gem
sequent gem on github.com

karafka - kafka impl on ruby, it works only with kafka

hanami gem for microservices

ideas of event sourcing:

1) sync way of microservices

0ne service know about another

2) events

a lot of inforamation for event

Last part: CQRS (the most interesting part)

databases for reading and for writing

DDD: 
Eriv Evans, pragprog DD modeling , Martin on Oreily

Q: cleaning cache>loose time travel
A: recalculate all the staff
 
Q: about message bus and events on microservices
A: comparing with message bus, cache database is not need cause u can recalculate staff 

Q: message bus is a transitional arcitecture?
A: yes, and event sourcing is like a git

event-sourcing is like message bus and uses a store concept and the evalutioning the message bus
  
Q: Database full of events and if it is large?
A: Store last month e.g, or combine events with information 

Q: e.g remove user information due to GDPR 
A: user gets notification, so the data removed in combined events

TESTING WITH PETRI NETS

Approach for testins

Build a solution in Toptal on top of this approach (not oss)

1. unsufficiency of usual test

AAA (setup, execute, verify)

common mistakes over constraits in DB (delete user which has some relations :note e.g)

State combinations:
1. Write more tests?
2. Randomize test data?
3. not cool …

Mode-bases testins
1.Create mode of the system
Graphwlker (Spotify, Java and Python)
model -> test selections -> test execotions ->
Problem: finite-state machine (quite big models and complex in cocncurrency)
A big picture on that, and a waste of time
2 …

Petri nets
places store tokens -(arcs)> transitions -> 

tokens for things in Petri nets

Based on tokens you can model complex things 
Heisenbug 2018

RHIZOME
1. Reproducible tests using seed
2. Parallelize like ny other test framework
3. General purpose framework

rspec/ rhizome (1000 loc/100loc)
Time to write tests decreasing

where also it is used: a lot of facilities 
discover about Reset arc, Inhibitor arc

merging subnets gives mutable tokens (token can be colored)

can put algorithms layes on perti nets

TRAILBLAZER WAY

Life of a rails developer

BPMN diagrams