A fully asynchronous Cassandra CQL driver for Scala using Akka IO.
##Highlights:
-
Directly construct objects from results.
-
Completely stateless, no sessions required. Fire any query from anywhere, anytime.
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Load balance between cassandra nodes.
-
Register callbacks for events.
###Connect to cassandra cluster.
Scqla.connect###Import from Scqla object
import Scqla._When you execute a query you get a future which can have a result or an error
ErrorException(error: Error)
where Error is
case class Error(code: Int, e: String)###Create a new keyspace
query("CREATE KEYSPACE demodb WITH REPLICATION = {'class' : 'SimpleStrategy','replication_factor': 1}") onComplete {
case Success =>
case Failure =>
}###Set global keyspace
Note: This only works if you only connect to one node in Cassandra cluster. If that is not the case use full table qualifiers as shown in the examples here.
query("use demodb") onComplete (
case Failure(f) => println(f.error)
case Success =>
)###Create a new table
query("""CREATE TABLE demodb.emp (
empID int,
deptID int,
alive boolean,
id uuid,
first_name varchar,
last_name varchar,
salary double,
age bigint,
PRIMARY KEY (empID, deptID))""") onComplete (
case Failure(f) => println(f.error)
case Success =>
)###Execute prepared queries
prepare("INSERT INTO demodb.emp (empID, deptID, alive, id, first_name, last_name, salary, age) VALUES (?, ?, ?, ?, ?, ?, ?, ?)") onComplete (
case Failure(f) => println(f.error)
case Success(p) => p.execute(104, 15, true, new java.util.UUID(0, 0), "Hot", "Shot", 10000000.0, 98763L)
)###You can directly construct objects from the result.
###Case class list
case class Emp(empId: Int, deptId: Int, alive: Boolean, id: java.util.UUID, first: String, last: String, salary: Double, age: Long)
queryAs[Emp]("select empID, deptID, alive, id, first_name, last_name, salary, age from demodb.emp") onComplete (
case Failure(f) => println(f.error)
case Success(empList) =>
empList.foreach(e => s"First name of employee id ${e.empId} is ${e.first}")
)###Primitives list
queryAs[Int]("select empid from demodb.emp") onComplete (
case Failure(f) => println(f.error)
case Success(idList) => {
idList.foreach(println)
}
)###Strings
queryAs[String]("select first_name from demodb.emp") onComplete (
case Failure(f) => println(f.error)
case Success(nameList) => {
nameList.foreach(println)
}
)###Execute prepared queries and get results
val f = prepare("select empID, deptID, alive, id, first_name, last_name, salary, age from demodb.emp where empid = ? and deptid = ?")
val list = for {
prepared <- f
empList <- prepared.executeGet[Emp](104, 15)
} yield empList
list foreach {
e => println(s"First name of employee id ${e.empId} is ${e.first}")
}###Register a callback for an event
Events.registerDBEvent(CreatedEvent, (a, b) => {
println(s"Hear hear, $a $b have come to be.")
})Events:
abstract class Event
abstract class NodeEvent extends Event
case object NewNodeEvent extends NodeEvent
case object RemovedNodeEvent extends NodeEvent
case object NodeUpEvent extends NodeEvent
case object NodeDownEvent extends NodeEvent
abstract class DBEvent extends Event
case object CreatedEvent extends DBEvent
case object UpdatedEvent extends DBEvent
case object DroppedEvent extends DBEventNodeEvent handlers are of the type Function[InetAddress, Unit]
DBEvent handlers are of the type Function2[String, String, Unit]
###Drop keyspace
query("drop KEYSPACE demodb") onComplete (
case Failure(f) => println(f.error)
case Success => {
//do something
}
)###Configuring thread pool for scqla future execution By default Scqla makes use of the default execution context in scala. However you can specify a manual ExecutionContext config by adding something like this to your application.conf
contexts {
scqla-pool {
fork-join-executor {
parallelism-factor = 1.0
parallelism-max = 4
}
}
}