I’m following a video tutorial. The moment where the author exits the process by Process.exit(pid, :because) it works out. But I’m running into a bit of a snag. I tried to retype everything twice, then I tried to run the author’s code on my machine. The author mix’s file had version of elixir 1.9 and mine was 1.8.1, so I thought it might be it. After updating and running the author’s code I had the same exception.
defmodule HttpServer do
require Logger # because Logger built in part with macros
@port 8000
@http_options [active: false, packet: :http_bin, reuseaddr: true]
def start_link() do
spawn_link(HttpServer, :init, [])
end
def init() do
Process.flag(:trap_exit, true)
start_listener()
|> supervise()
end
def supervise(socket) do
receive do
{:EXIT, pid, reason} ->
Logger.error("Listener process (#{inspect(pid)}) Crashed. #{reason}")
:gen_tcp.close(socket)
start_listener()
|> supervise()
end
end
def start_listener() do
{:ok, socket} = :gen_tcp.listen(@port, @http_options)
IO.inspect socket, label: "START_LISTENER SOCKET :: :"
pid = spawn_link(HttpServer, :accept, [socket])
Logger.info("Listener started #{inspect(pid)}")
socket
end
def accept(socket) do
IO.inspect socket, label: "ACCEPT SOCKET :: :"
{:ok, client} = :gen_tcp.accept(socket)
IO.inspect client, label: "CLIENT :: :: :"
pid = spawn(HttpServer, :handle, [client])
:ok = :gen_tcp.controlling_process(client, pid)
accept(socket)
end
def handle(client) do
Logger.info("Servicing a new request on pid #{inspect(self())}")
body = "Hello from Elixir #{inspect(self())}"
:gen_tcp.send(client, view(body))
:gen_tcp.close(client)
end
def view(body) do
[
"HTTP/1.1 200\n",
"Content-Type: text/html\n",
"Content-Length: ",
"#{byte_size(body)}",
"\n\n",
body
]
end
end
- I start the server
- Then I make a few requests with curl. The server works fine and handle the requests in the way it is supposed to.
- Then I run Process.exit(pid, :because)
- The server logs the message as it should
19:41:45.997 [error] Listener process (#PID<0.144.0>) Crashed. because - But then it’s supposed to restart and it doesn’t.
I understand that I can handle the error by pattern matching in the start_listener() function, but I did exactly as the author of the video and for him everything works out fine.
iex(1)> HttpServer.start_link
#PID<0.146.0>
iex(2)>
19:41:11.828 [info] Listener started #PID<0.147.0>
19:41:27.829 [info] Servicing new request on pid #PID<0.149.0>
nil
iex(3)> Process.exit(pid(0,146,0), :because)
true
iex(4)>
19:41:45.997 [error] Listener process (#PID<0.144.0>) Crashed. because
19:41:45.997 [info] Listener started #PID<0.152.0>
19:41:45.997 [error] Process #PID<0.147.0> raised an exception
** (MatchError) no match of right hand side value: {:error, :closed}
(http_server 0.1.0) lib/http_server.ex:36: HttpServer.accept/1
** (EXIT from #PID<0.144.0>) shell process exited with reason: an exception was raised:
** (Protocol.UndefinedError) protocol String.Chars not implemented for {{:badmatch, {:error, :closed}}, [{HttpServer, :accept, 1, [file: 'lib/http_server.ex', line: 36]}]} of type Tuple. This protocol is implemented for the following type(s): Date, Integer, List, Atom, BitString, NaiveDateTime, DateTime, URI, Version, Version.Requirement, Time, Float
(elixir 1.12.3) lib/string/chars.ex:3: String.Chars.impl_for!/1
(elixir 1.12.3) lib/string/chars.ex:22: String.Chars.to_string/1
(http_server 0.1.0) lib/http_server.ex:27: HttpServer.supervise/1
iex(4)>
19:41:46.003 [error] Process #PID<0.146.0> raised an exception
** (Protocol.UndefinedError) protocol String.Chars not implemented for {{:badmatch, {:error, :closed}}, [{HttpServer, :accept, 1, [file: 'lib/http_server.ex', line: 36]}]} of type Tuple. This protocol is implemented for the following type(s): Date, Integer, List, Atom, BitString, NaiveDateTime, DateTime, URI, Version, Version.Requirement, Time, Float
(elixir 1.12.3) lib/string/chars.ex:3: String.Chars.impl_for!/1
(elixir 1.12.3) lib/string/chars.ex:22: String.Chars.to_string/1
(http_server 0.1.0) lib/http_server.ex:27: HttpServer.supervise/1
Interactive Elixir (1.12.3) - press Ctrl+C to exit (type h() ENTER for help)
P.S. I first put the code on gist.github, but then thought it might be okay to post the full code here.
