Play Framework: "too many connections" database error - postgresql

Question

Play Framework 2.6, Postgresql. Jooq as db access library.
When running test, I'm getting
org.postgresql.util.PSQLException: FATAL: sorry, too many clients
already
Here is a helper class which provides jooq's dsl context:
#Singleton
class Db #Inject() (val db: Database, system: ActorSystem) {
val databaseContext: ExecutionContext = system.dispatchers.lookup("contexts.database")
def query[A](block: DSLContext => A): Future[A] = Future {
db.withConnection { connection: Connection =>
val dsl = DSL.using(connection, SQLDialect.POSTGRES_9_4)
block(dsl)
}
}(databaseContext)
def withTransaction[A](block: DSLContext => A): Future[A] = Future {
db.withTransaction { connection: Connection =>
val dsl: DSLContext = DSL.using(connection, SQLDialect.POSTGRES_9_4)
block(dsl)
}
}(databaseContext)
}
I use this helper class in repositories like this:
db.query { dsl =>
val records = dsl
.selectFrom(USERS)
.where(...)
...
}
}
application.conf
db.default.driver="org.postgresql.Driver"
db.default.url="jdbc:postgresql://localhost/postgres?user=postgres"
...
contexts {
database {
executor = "thread-pool-executor"
throughput = 1
thread-pool-executor {
fixed-pool-size = 9
}
}
}
...
build.sbt
...
libraryDependencies += jdbc
libraryDependencies += "org.jooq" % "jooq" % "3.10.5"
libraryDependencies += "org.jooq" % "jooq-codegen-maven" % "3.10.5"
libraryDependencies += "org.jooq" % "jooq-meta" % "3.10.5"
libraryDependencies += "org.postgresql" % "postgresql" % "42.1.4"
...
And base trait for all my tests for any case:
class BaseFeatureSpec extends FeatureSpec
with GivenWhenThen
with GuiceOneServerPerSuite
with Matchers
with WsScalaTestClient
with BeforeAndAfterEach
with MockitoSugar {
override def fakeApplication(): Application =
new GuiceApplicationBuilder()
.overrides(bind[EmailService].to(classOf[EmailServiceStub]))
.build()
def config: Configuration = fakeApplication().configuration
def actorSystem: ActorSystem = fakeApplication().actorSystem
val db: Db = app.injector.instanceOf[Db]
val wsClient: WSClient = app.injector.instanceOf[WSClient]
val myPublicAddress = s"localhost:$port"
private val injector = fakeApplication().injector
def truncateDbOnEachRun = true
override protected def beforeEach(): Unit = {
if (truncateDbOnEachRun) {
truncateDb
}
}
protected def truncateDb = {
await(db.withTransaction { dsl =>
... truncate all dbs...
})
}
}
max_connections of my postgresql instance is 100.
What I noticed is that when running test, I see that pool is created multiple times almost before each test:
[info] application - Creating Pool for datasource 'default'
[info] application - Creating Pool for datasource 'default'
[info] application - Creating Pool for datasource 'default'
[info] application - Creating Pool for datasource 'default'
And after I'm getting too many connections error.
Please help.

Answer 1

Look like you use a dispatcher with default type, try to add type = PinnedDispatcher, which is used for io type dispatcher, as follow.
thread-pool-executor {
...
type = PinnedDispatcher
}
And you can find details from
https://doc.akka.io/docs/akka/2.5/dispatchers.html

Answer 2

I'v found the issue:
override def fakeApplication(): Application =
new GuiceApplicationBuilder()
.overrides(bind[EmailService].to(classOf[EmailServiceStub]))
.build()
Creates new application instance (because it is method) each time I access to it like app.injector.instanceOf[Db], so that's why I have so many application - Creating Pool for datasource 'default' logs.
I've replaced def with val
override val fakeApplication(): Application =
new GuiceApplicationBuilder()
.overrides(bind[EmailService].to(classOf[EmailServiceStub]))
.build()
And it works fine.