Jacek Laskowski jaceklaskowski

Rough Notes about CQRS and ES

Once upon a time…

I once took notes (almost sentence by sentence with not much editing) about the architectural design concepts - Command and Query Responsibility Segregation (CQRS) and Event Sourcing (ES) - from a presentation of Greg Young and published it as a gist (with the times when a given sentence was heard).

I then found other summaries of the talk and the gist has since been growing up. See the revisions to know the changes and where they came from (aka the sources).

It seems inevitable to throw Domain Driven Design (DDD) in to the mix.

Designing for API (with Swagger and Scala)

Another API-Blueprint, RAML and Swagger Comparison
- JSON
- Reverb - company behind the project
- API design approach - bottom-up (FIXME what does this mean?)
- API version metadata
- Scala for server and client code possible
- community stats favors...swagger (stackoverflow, github, google search for "swagger rest")
OSCON 2014 - API Ecosystem with Scala, Scalatra, and Swagger at Netflix

From http://www.tinkerpop.com/docs/3.0.0.M1/:

TinkerPop2 and below made a sharp distinction between the various TinkerPop projects: Blueprints, Pipes, Gremlin, Frames, Furnace, and Rexster. With TinkerPop3, all of these projects have been merged and are generally known as Gremlin. Blueprints → Gremlin Structure API : Pipes → GraphTraversal : Frames → Traversal : Furnace → GraphComputer and VertexProgram : Rexster → GremlinServer.

About Cake Pattern

Below are the sources I took notes and hope to learn about Cake Pattern from.

Videos:

From the scaladoc for trait Flow[-In, +Out] (package akka.stream.scaladsl):

A Flow is a set of stream processing steps that has one open input and one open output.

Therefore, Flow[HttpRequest, HttpResponse] is a set of stream processing steps that has one open HttpRequest input and one open HttpResponse output.

It appears that inputs are called Sources and outputs are Sinks. Connecting a Source to a Sink creates a flow graph.

That's pretty much the good ol' Spray.

	lazy val root = Project(
	"sbteclipse",
	file("."),
	aggregate = Seq(sbteclipseCore, sbteclipsePlugin),
	settings = commonSettings ++ Seq(
	publishArtifact := false
	)
	)

	[info] Generating pdf en/sbt-tutorial...
	[error] pandoc: Duplicate link reference `[Using-Plugins]' "source" (line 2418, column 1)
	[error] pandoc: Duplicate link reference `[Full-Def]' "source" (line 2417, column 1)
	[error] pandoc: Duplicate link reference `[Scopes]' "source" (line 2416, column 1)
	[error] pandoc: Duplicate link reference `[Basic-Def]' "source" (line 2415, column 1)
	[error] pandoc: Duplicate link reference `[Using-Plugins]' "source" (line 2166, column 1)
	[error] pandoc: Duplicate link reference `[More-About-Settings]' "source" (line 2165, column 1)
	[error] pandoc: Duplicate link reference `[Basic-Def]' "source" (line 2164, column 1)
	[error] pandoc: Duplicate link reference `[Plugins]' "source" (line 2067, column 1)
	[error] pandoc: Duplicate link reference `[Input-Tasks]' "source" (line 2066, column 1)

	➜ spark git:(master) ./bin/spark-shell --master local --jars /Users/jacek/oss/spark-cassandra-connector/spark-cassandra-connector/target/scala-2.10/spark-cassandra-connector-assembly-1.2.0-SNAPSHOT.jar
	Spark assembly has been built with Hive, including Datanucleus jars on classpath
	Using Spark's default log4j profile: org/apache/spark/log4j-defaults.properties
	14/09/23 22:13:03 INFO SecurityManager: Changing view acls to: jacek
	14/09/23 22:13:03 INFO SecurityManager: Changing modify acls to: jacek
	14/09/23 22:13:03 INFO SecurityManager: SecurityManager: authentication disabled; ui acls disabled; users with view permissions: Set(jacek); users with modify permissions: Set(jacek)
	14/09/23 22:13:03 INFO HttpServer: Starting HTTP Server
	14/09/23 22:13:03 INFO Utils: Successfully started service 'HTTP class server' on port 62525.
	Welcome to
	____ __

	libraryDependencies += "io.reactivex" %% "rxscala" % "0.21.1"

	scalaVersion := "2.11.2"

	initialCommands in console := """
	import rx.lang.scala._
	"""

	// from https://groups.google.com/d/msg/rxjava/GyVmw-ttbDY/qGHSO5EiEugJ
	import rx.lang.scala._
	import scala.concurrent._
	import ExecutionContext.Implicits.global
	import java.util.concurrent.TimeUnit

	println(s"Current thread: ${Thread.currentThread.getName()}") // run-main-1

	def timeConsumingComputation() = {
	TimeUnit.SECONDS.sleep(2)