I have written this slick DAO and its unit test in specs2.
My code has race conditions. When I run the same tests, I get different outputs.
The race conditions exist even though in both the functions I do Await.result(future, Duration.Inf)
DAO
package com.example
import slick.backend.DatabasePublisher
import slick.driver.H2Driver.api._
import scala.concurrent.ExecutionContext.Implicits.global
import slick.jdbc.meta._
import scala.concurrent._
import ExecutionContext.Implicits.global
import scala.concurrent.duration._
case class Person(id: Int, firstname: String, lastname: String)
class People(tag: Tag) extends Table[Person](tag, "PEOPLE") {
def id = column[Int]("PERSON_ID", O.PrimaryKey)
def firstname = column[String]("PERSON_FIRST_NAME")
def lastname = column[String]("PERSON_LAST_NAME")
def * = (id, firstname, lastname) <> (Person.tupled, Person.unapply _)
}
object PersonDAO {
private def createList(numRows: Int) : List[Person] = {
def recFunc(counter: Int, result: List[Person]) : List[Person] = {
counter match {
case x if x <= numRows => recFunc(counter + 1, Person(counter, "test" + counter, "user" + counter) :: result)
case _ => result
}
}
recFunc(1, List[Person]())
}
val db = Database.forConfig("test1")
val people = TableQuery[People]
def createAndPopulate(numRows: Int) = {
val action1 = people.schema.create
val action2 = people ++= Seq(createList(numRows) : _* )
val combined = db.run(action1 andThen action2)
val future1 = combined.map { result =>
result map {x =>
println(s"number of rows inserted $x")
x
}
}
Await.result(future1, Duration.Inf).getOrElse(0)
}
def printAll() = {
val a = people.result
val b = db.run(a)
val y = b map { result =>
result map {x => x}
}
val z = Await.result(y, Duration.Inf)
println(z)
println(z.length)
z
}
}
Unit Test
import org.specs2.mutable._
import com.example._
class HelloSpec extends Specification {
"This usecase " should {
"should insert rows " in {
val x = PersonDAO.createAndPopulate(100)
x === 100
}
}
"This usecase " should {
"return 100 rows" in {
val x = PersonDAO.printAll()
val y = PersonDAO.printAll()
y.length === 100
}
}
}
When I run this same code using activator test I see 2 different types of outputs on different runs
sometimes the code gets exception
number of rows inserted 100 [info] HelloSpec [info] [info] This usecase should [info] + should insert rows [info] [info] This usecase should [info] ! return 100 rows [error] JdbcSQLException: : Table PEOPLE not found; SQL statement: [error] select x2."PERSON_ID", x2."PERSON_FIRST_NAME", x2."PERSON_LAST_NAME" from "PEOPLE" x2 [42S02-60] (Message.java:84) [error] org.h2.message.Message.getSQLException(Message.java:84) [error] org.h2.message.Message.getSQLException(Message.java:88) [error] org.h2.message.Message.getSQLException(Message.java:66)
Sometimes the 1st function call returns 0 rows and the 2nd function call returns 100 values
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder". SLF4J: Defaulting to no-operation (NOP) logger implementation SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details. number of rows inserted 100 Vector() 0 Vector(Person(100,test100,user100), Person(99,test99,user99), Person(98,test98,user98), Person(97,test97,user97), Person(96,test96,user96), Person(95,test95,user95), Person(94,test94,user94), Person(93,test93,user93), Person(92,test92,user92), Person(91,test91,user91), Person(90,test90,user90), Person(89,test89,user89), Person(88,test88,user88), Person(87,test87,user87), Person
I don't understand why does my code have these race conditions because I block on future in each method.
