adamw

run("caveat 1") {
  val someEffect = IO.shift(ec1) *> printThread
  printThread *> someEffect *> printThread
}

/*
Outputs:

-- caveat 1 --
main

adamw

printThread *> printThread

adamw

run("Eval on") {
  printThread *> cs1.evalOn(ec2)(printThread) *> printThread
}

/*
Outputs:

-- Eval on --
main
ec2-1-1945604815

adamw

val cs1 = IO.contextShift(ec1)
val cs2 = IO.contextShift(ec2)

def run(name: String)(th: IO[_]): Unit = {
  println(s"-- $name --")
  th.unsafeRunSync()
  println()
}

run("Shift") {

adamw

val printThread = IO { println(Thread.currentThread().getName) }

adamw

val ec1 = ExecutionContext.fromExecutor(Executors.newCachedThreadPool(
  new NamedThreadFactory("ec1", true)))
val ec2 = ExecutionContext.fromExecutor(Executors.newCachedThreadPool(
  new NamedThreadFactory("ec2", true)))
val ec3 = Executors.newCachedThreadPool(new NamedThreadFactory("ec3", true))

adamw

implicit val backend: SttpBackend[Id, Nothing] = 
  new LoggingSttpBackend[Id, Nothing](HttpURLConnectionBackend())
 
request.send()

adamw

class LoggingSttpBackend[R[_], S](delegate: SttpBackend[R, S]) 
  extends SttpBackend[R, S] with StrictLogging {
    
  override def send[T](request: Request[T, S]): R[Response[T]] = {
    responseMonad.map(responseMonad.handleError(delegate.send(request)) {
      case e: Exception =>
        logger.error(
          s"Exception when sending request: $request.\n" +
            s"To reproduce, run: ${request.toCurl}",
          e

adamw

class LoggingSttpBackend[R[_], S](delegate: SttpBackend[R, S]) 
  extends SttpBackend[R, S] with StrictLogging {
    
  override def send[T](request: Request[T, S]): R[Response[T]] = {
    responseMonad.map(responseMonad.handleError(delegate.send(request)) {
      case e: Exception =>
        logger.error(
          s"Exception when sending request: $request.\n" +
            s"To reproduce, run: ${request.toCurl}",
          e

adamw

println(request.toCurl)

/*
Outputs:

curl -L --max-redirs 32 -X POST 
  -H "Content-Type: application/json; charset=utf-8" -H "X-Auth: 123" 
  --data '{"name":"Mary","age":52}' 
  "http://httpbin.org/post"
*/