scalar

Value Members

1. package lang

   

   Contains Scala side adapters for implicits conversion.

2. package pimps

   

   Contains Scala "Pimp" implementations for main Ignite entities.

3. object scalar extends ScalarConversions

   

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   Overview

   scalar is the main object that encapsulates Scalar DSL. It includes global functions on "scalar" keyword, helper converters as well as necessary implicit conversions. scalar also mimics many methods in Ignite class from Java side.

   The idea behind Scalar DSL - zero additional logic and only conversions implemented using Scala "Pimp" pattern. Note that most of the Scalar DSL development happened on Java side of Ignite 3.0 product line - Java APIs had to be adjusted quite significantly to support natural adaptation of functional APIs. That basically means that all functional logic must be available on Java side and Scalar only provides conversions from Scala language constructs to Java constructs. Note that currently Ignite supports Scala 2.8 and up only.

   This design approach ensures that Java side does not starve and usage paradigm is mostly the same between Java and Scala - yet with full power of Scala behind. In other words, Scalar only adds Scala specifics, but not greatly altering semantics of how Ignite APIs work. Most of the time the code in Scalar can be written in Java in almost the same number of lines.

   Suffix '$' In Names

   Symbol $ is used in names when they conflict with the names in the base Java class that Scala pimp is shadowing or with Java package name that your Scala code is importing. Instead of giving two different names to the same function we've decided to simply mark Scala's side method with $ suffix.

   Importing

   Scalar needs to be imported in a proper way so that necessary objects and implicit conversions got available in the scope:

   import org.apache.ignite.scalar._
   import scalar._
   

   This way you import object scalar as well as all methods declared or inherited in that object as well.

   Examples

   Here are few short examples of how Scalar can be used to program routine distributed task. All examples below use default Ignite configuration and default grid. All these examples take an implicit advantage of auto-discovery and failover, load balancing and collision resolution, zero deployment and many other underlying technologies in the Ignite - while remaining absolutely distilled to the core domain logic.

   This code snippet prints out full topology:

   scalar {
       grid$ foreach (n => println("Node: " + n.id8))
   }
   

   The obligatory example - cloud enabled Hello World!. It splits the phrase into multiple words and prints each word on a separate grid node:

   scalar {
       grid$ *< (SPREAD, (for (w <- "Hello World!".split(" ")) yield () => println(w)))
   }
   

   This example broadcasts message to all nodes:

   scalar {
       grid$ *< (BROADCAST, () => println("Broadcasting!!!"))
   }
   

   This example "greets" remote nodes only (note usage of Java-side closure):

   scalar {
       val me = grid$.localNode.id
       grid$.remoteProjection() *< (BROADCAST, F.println("Greetings from: " + me))
   }
   

   Next example creates a function that calculates lengths of the string using MapReduce type of processing by splitting the input string into multiple substrings, calculating each substring length on the remote node and aggregating results for the final length of the original string:

   def count(msg: String) =
       grid$ @< (SPREAD, for (w <- msg.split(" ")) yield () => w.length, (s: Seq[Int]) => s.sum)
   

   This example shows a simple example of how Scalar can be used to work with in-memory data grid:

   scalar {
       val t = cache$[Symbol, Double]("partitioned")
       t += ('symbol -> 2.0)
       t -= ('symbol)
   }