Inconsistent "Host header required for HTTP/1.1 request" error

Hello 😃

Using version 0.20.0-M7, but also happens on 0.19.0.

import cats.effect.{ContextShift, IO}
import org.http4s.Uri
import org.http4s.client.blaze.BlazeClientBuilder

import scala.concurrent.ExecutionContext.Implicits.global


object IssueBad extends App {
  private implicit val cs: ContextShift[IO] = IO.contextShift(global)

  val uri: Uri = Uri().withPath(s"http://localhost:8080")

  BlazeClientBuilder[IO](global).resource.use { client =>
    client.expect[String](uri)
  }.unsafeRunSync()
}

This fails for me with:

Exception in thread "main" java.lang.IllegalArgumentException: Host header required for HTTP/1.1 request
	at org.http4s.client.blaze.Http1Connection.validateRequest(Http1Connection.scala:329)
	at org.http4s.client.blaze.Http1Connection.executeRequest(Http1Connection.scala:124)
	at org.http4s.client.blaze.Http1Connection.$anonfun$runRequest$1(Http1Connection.scala:103)
	at cats.effect.internals.IORunLoop$.liftedTree1$1(IORunLoop.scala:95)
	at cats.effect.internals.IORunLoop$.cats$effect$internals$IORunLoop$$loop(IORunLoop.scala:95)
	at cats.effect.internals.IORunLoop$RestartCallback.signal(IORunLoop.scala:351)
	at cats.effect.internals.IORunLoop$RestartCallback.apply(IORunLoop.scala:372)
	at cats.effect.internals.IORunLoop$RestartCallback.apply(IORunLoop.scala:312)
	at cats.effect.internals.Callback$AsyncIdempotentCallback.run(Callback.scala:127)
	at cats.effect.internals.Trampoline.cats$effect$internals$Trampoline$$immediateLoop(Trampoline.scala:70)
	at cats.effect.internals.Trampoline.startLoop(Trampoline.scala:36)
	at cats.effect.internals.TrampolineEC$JVMTrampoline.super$startLoop(TrampolineEC.scala:93)
	at cats.effect.internals.TrampolineEC$JVMTrampoline.$anonfun$startLoop$1(TrampolineEC.scala:93)
	at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at scala.concurrent.BlockContext$.withBlockContext(BlockContext.scala:81)
	at cats.effect.internals.TrampolineEC$JVMTrampoline.startLoop(TrampolineEC.scala:93)
	at cats.effect.internals.Trampoline.execute(Trampoline.scala:43)
	at cats.effect.internals.TrampolineEC.execute(TrampolineEC.scala:44)
	at cats.effect.internals.Callback$AsyncIdempotentCallback.apply(Callback.scala:133)
	at cats.effect.internals.Callback$AsyncIdempotentCallback.apply(Callback.scala:120)
	at cats.effect.concurrent.Deferred$ConcurrentDeferred.$anonfun$unsafeRegister$1(Deferred.scala:205)
	at cats.effect.concurrent.Deferred$ConcurrentDeferred.$anonfun$unsafeRegister$1$adapted(Deferred.scala:205)
	at cats.effect.concurrent.Deferred$ConcurrentDeferred.$anonfun$notifyReadersLoop$1(Deferred.scala:241)
	at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at cats.effect.internals.IORunLoop$.cats$effect$internals$IORunLoop$$loop(IORunLoop.scala:87)
	at cats.effect.internals.IORunLoop$RestartCallback.signal(IORunLoop.scala:351)
	at cats.effect.internals.IORunLoop$RestartCallback.apply(IORunLoop.scala:372)
	at cats.effect.internals.IORunLoop$RestartCallback.apply(IORunLoop.scala:312)
	at cats.effect.internals.IOShift$Tick.run(IOShift.scala:36)
	at java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1402)
	at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
	at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
	at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
	at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)

I can fix it just by turning the Uri into a String:

import cats.effect.{ContextShift, IO}
import org.http4s.Uri
import org.http4s.client.blaze.BlazeClientBuilder

import scala.concurrent.ExecutionContext.Implicits.global


object IssueOK extends App {
  private implicit val cs: ContextShift[IO] = IO.contextShift(global)

  val uriString: String = Uri().withPath("http://localhost:8080").toString()

  BlazeClientBuilder[IO](global).resource.use { client =>
    client.expect[String](uriString)
  }.unsafeRunSync()
}

It also fails, since I don’t have anything running at localhost:8080, but this error is expected.

Exception in thread "main" java.net.ConnectException: Connection refused
	at sun.nio.ch.UnixAsynchronousSocketChannelImpl.checkConnect(Native Method)
	at sun.nio.ch.UnixAsynchronousSocketChannelImpl.finishConnect(UnixAsynchronousSocketChannelImpl.java:252)
	at sun.nio.ch.UnixAsynchronousSocketChannelImpl.finish(UnixAsynchronousSocketChannelImpl.java:198)
	at sun.nio.ch.UnixAsynchronousSocketChannelImpl.onEvent(UnixAsynchronousSocketChannelImpl.java:213)
	at sun.nio.ch.EPollPort$EventHandlerTask.run(EPollPort.java:293)
	at java.lang.Thread.run(Thread.java:748)

I would expect that both pieces of code to have the same behavior.

[rossabaker]

The problem is that Uri.withPath assumes the entire thing is a path, rather than noting that part of it should be the scheme and authority. URI as a case class is tempting, but it allows this trap.

For some prior art, java.net.URI does not have setters on the individual components. You have to reparse the entire String. That’s not efficient when constructing a String, but does neatly work around this issue.

[kevinmeredith]

Thanks, Ross, for the explanation. So the following seem to me to be possible courses of action:

1. Take java.net.URI’s approach, which means re-parsing the entire String
2. Validate the input to Uri#withPath
3. Leave it as-is

1 would be a breaking change since withPath, along with maybe other methods, would be deleted. 2 would be a breaking change, I think, since it’d, I assume, change the return type of Uri#withPath to be an Option[Uri] or Either[?, Uri]?

What are your thoughts, Ross?