Set Up Example Project and Configure Build
Full sources for all Cloudflow example applications can be found in the
examples folder of the
A typical Cloudflow application uses the organization shown below. We will implement the example in Scala.
In a convenient location, such as
my-cloudflow-examplecreate the following directory structure:
|-project |--cloudflow-plugins.sbt |-src |---main |-----avro |-----blueprint |-----resources |-----scala |-------sensordata |-build.sbt
As we move through the process, the leaf level directories of the above tree will contain the following:
project/cloudflow-plugins.sbt : contains the Cloudflow
sbtplugin name and version.
avro : the avro schema of the domain objects
blueprint : the blueprint of the application in a file named
scala : the source code of the application under the package name
build.sbt : the sbt build script
From the top-level directory, initialize
git(after adding files you will commit them):
sbtplugin assumes that your project is version-managed using
git. It will use
git commitinformation to generate dynamic versioning for the Docker images it produces. If the project doesn’t have an initialized git index with at least one commit, some commands will fail with a
not a git repositoryerror.
Cloudflow provides sbt plugins for the supported runtimes, Akka, Spark and Flink. The plugins speed up development by adding the necessary dependencies and abstracting much of the boilerplate necessary to build a complete application. You can use multiple runtimes in the same application, provided that each runtime is defined in its own sub-project.
In this example, we use the
CloudflowAkkaPlugin that provides the building blocks for developing a Cloudflow application with Akka Streams.
In addition to the backend-specific plugin, we need to add the
CloudflowApplicationPlugin that provides the image-building and local-running capabilities to the project.
build.sbtfile with the following contents and save it in at the same level as your
import sbt._ import sbt.Keys._ //tag::local-conf lazy val sensorData = (project in file(".")) .enablePlugins(CloudflowApplicationPlugin, CloudflowAkkaPlugin, ScalafmtPlugin) .settings( scalaVersion := "2.12.11", runLocalConfigFile := Some("src/main/resources/local.conf"), (1) runLocalLog4jConfigFile := Some("src/main/resources/log4j.xml"), (2) scalafmtOnCompile := true, name := "sensor-data-scala", //end::local-conf libraryDependencies ++= Seq( "com.lightbend.akka" %% "akka-stream-alpakka-file" % "1.1.2", "com.typesafe.akka" %% "akka-http-spray-json" % "10.1.12", "ch.qos.logback" % "logback-classic" % "1.2.3", "com.typesafe.akka" %% "akka-http-testkit" % "10.1.12" % "test", "org.scalatest" %% "scalatest" % "3.0.8" % "test" ), organization := "com.lightbend.cloudflow", headerLicense := Some(HeaderLicense.ALv2("(C) 2016-2020", "Lightbend Inc. <https://www.lightbend.com>")), crossScalaVersions := Vector(scalaVersion.value), scalacOptions ++= Seq( "-encoding", "UTF-8", "-target:jvm-1.8", "-Xlog-reflective-calls", "-Xlint", "-Ywarn-unused", "-Ywarn-unused-import", "-deprecation", "-feature", "-language:_", "-unchecked" ), scalacOptions in (Compile, console) --= Seq("-Ywarn-unused", "-Ywarn-unused-import"), scalacOptions in (Test, console) := (scalacOptions in (Compile, console)).value )
The script is a standard Scala sbt build file—with the addition of the Cloudflow plugin for Akka Streams, the Cloudflow application plugin, and also the Scalafmt plugin that we suggest to keep the style consistent in the application (optional).
Create the file
project/cloudflow-plugins.sbtand add the Cloudflow plugin dependency in it:
addSbtPlugin("com.lightbend.cloudflow" % "sbt-cloudflow" % "2.1.0-SNAPSHOT")
Now, let’s define the Avro schema.