Socket / FileDescriptor leak for unresolvable hosts

[stephennancekivell]

Hi, using fs2 (v3.1.3) Im seeing this socket & file descriptor leak when opening sockets to domains that dont resolve. eg Network[IO].client(SocketAddress(Host.fromString("nodomain.fs2.io").get, port"80"))

Consider this example

    val printFd: IO[Unit] =
      IO(println(s"fd: ${systemMxBeans.getOpenFileDescriptorCount}"))

    def loop(ttl: Int): IO[Unit] = {
      if (ttl <= 0) IO.unit
      else printFd *> IO.sleep(1.second) *> loop(ttl - 1)
    }

    val network = Network[IO]
    val host =
      "no-domain-here.fs2.io" // leaks file descriptors, doesnt close socket
//    val host = "fs2.io" // doesnt leak

    (0 to 5).toList
      .parTraverseN(5) { i =>
        printFd *>
          network
            .client(SocketAddress(Host.fromString(host).get, port"80"))
            .use { _ =>
              IO(println(s"opening socket $i socket")) *>
                IO.sleep(1.seconds)
            }
            .handleErrorWith { err =>
              IO(println(s"cant connect $i socket $err")) *>
                IO.sleep(1.seconds)
            }
      }
      .flatMap { _ =>
        loop(10)
      }

Outputs ..

fd: 235
fd: 236
fd: 240
fd: 239
fd: 240
cant connect 3 socket java.net.UnknownHostException: no-domain-here.fs2.io
cant connect 4 socket java.net.UnknownHostException: no-domain-here.fs2.io
cant connect 0 socket java.net.UnknownHostException: no-domain-here.fs2.io
cant connect 2 socket java.net.UnknownHostException: no-domain-here.fs2.io
cant connect 1 socket java.net.UnknownHostException: no-domain-here.fs2.io
fd: 241
cant connect 5 socket java.net.UnknownHostException: no-domain-here.fs2.io
fd: 242
fd: 242
fd: 242
fd: 242
fd: 242

With a valid domain the file descriptor count goes down after.

I'll open a PR with a fix.