Allow for port to be configured as a string

[akoutmos]

This is a quality of life change for configuring connections to RabbitMQ. If the port is provided as a string (which is often the time if the port is configured via an environment variable), a cryptic Erlang authentication error if returned back and it makes it difficult to root cause that the problem was merely a type issue (string vs integer). Attaching the error below when this occurs.

The proposed change is something that is also done in Phoenix for similar reasons: https://github.com/phoenixframework/phoenix/blob/b53813bf3e612077c887f4241a3ff82b41ae9a3f/lib/phoenix/endpoint/cowboy2_adapter.ex#L124-L125

I have also added some README changes to make contributing to amqp a bit easier :).

=ERROR REPORT==== 31-Jan-2020::09:34:08.524654 ===
** Generic server <0.241.0> terminating
** Last message in was connect
** When Server state == {<0.240.0>,
                         {amqp_params_network,<<"guest">>,
                             <<"V3ihvPxvBUBPNWzQ37AA6/iZvMYi8yQd25lHVFO+ru5o64ZrBSJV0jFkyL/KsuEw">>,
                             <<"/">>,"localhost",<<"5672">>,0,0,10,50000,none,
                             [fun amqp_auth_mechanisms:plain/3,
                              fun amqp_auth_mechanisms:amqplain/3],
                             [],[]}}
** Reason for termination ==
** {function_clause,
       [{amqp_gen_connection,terminate,
            [{function_clause,
                 [{inet_tcp,getserv,
                      [<<"5672">>],
                      [{file,"inet_tcp.erl"},{line,55}]},
                  {gen_tcp,connect1,4,[{file,"gen_tcp.erl"},{line,176}]},
                  {gen_tcp,connect,4,[{file,"gen_tcp.erl"},{line,163}]},
                  {amqp_network_connection,do_connect,4,
                      [{file,
                           "~/amqp/deps/amqp_client/src/amqp_network_connection.erl"},
                       {line,132}]},
                  {amqp_gen_connection,handle_call,3,
                      [{file,
                           "~/amqp/deps/amqp_client/src/amqp_gen_connection.erl"},
                       {line,174}]},
                  {gen_server,try_handle_call,4,
                      [{file,"gen_server.erl"},{line,661}]},
                  {gen_server,handle_msg,6,
                      [{file,"gen_server.erl"},{line,690}]},
                  {proc_lib,init_p_do_apply,3,
                      [{file,"proc_lib.erl"},{line,249}]}]},
             {<0.240.0>,
              {amqp_params_network,<<"guest">>,
                  <<"V3ihvPxvBUBPNWzQ37AA6/iZvMYi8yQd25lHVFO+ru5o64ZrBSJV0jFkyL/KsuEw">>,
                  <<"/">>,"localhost",<<"5672">>,0,0,10,50000,none,
                  [fun amqp_auth_mechanisms:plain/3,
                   fun amqp_auth_mechanisms:amqplain/3],
                  [],[]}}],
            [{file,
                 "~/amqp/deps/amqp_client/src/amqp_gen_connection.erl"},
             {line,242}]},
        {gen_server,try_terminate,3,[{file,"gen_server.erl"},{line,673}]},
        {gen_server,terminate,10,[{file,"gen_server.erl"},{line,858}]},
        {proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,249}]}]}
** Client <0.238.0> stacktrace
** [{gen,do_call,4,[{file,"gen.erl"},{line,167}]},
    {gen_server,call,3,[{file,"gen_server.erl"},{line,219}]},
    {'Elixir.AMQP.Connection',do_open,2,
                              [{file,"lib/amqp/connection.ex"},{line,207}]},
    {'Elixir.ConnectionTest','test open connection with host as binary',1,
                             [{file,"test/connection_test.exs"},{line,12}]},
    {'Elixir.ExUnit.Runner',exec_test,1,
                            [{file,"lib/ex_unit/runner.ex"},{line,355}]},
    {timer,tc,1,[{file,"timer.erl"},{line,166}]},
    {'Elixir.ExUnit.Runner','-spawn_test_monitor/4-fun-1-',4,
                            [{file,"lib/ex_unit/runner.ex"},{line,306}]}]

=CRASH REPORT==== 31-Jan-2020::09:34:08.526813 ===
  crasher:
    initial call: amqp_gen_connection:init/1
    pid: <0.241.0>
    registered_name: []
    exception error: no function clause matching
                     amqp_gen_connection:terminate({function_clause,
                                                    [{inet_tcp,getserv,
                                                      [<<"5672">>],
                                                      [{file,"inet_tcp.erl"},
                                                       {line,55}]},
                                                     {gen_tcp,connect1,4,
                                                      [{file,"gen_tcp.erl"},
                                                       {line,176}]},
                                                     {gen_tcp,connect,4,
                                                      [{file,"gen_tcp.erl"},
                                                       {line,163}]},
                                                     {amqp_network_connection,
                                                      do_connect,4,
                                                      [{file,
                                                        "~/amqp/deps/amqp_client/src/amqp_network_connection.erl"},
                                                       {line,132}]},
                                                     {amqp_gen_connection,
                                                      handle_call,3,
                                                      [{file,
                                                        "~/amqp/deps/amqp_client/src/amqp_gen_connection.erl"},
                                                       {line,174}]},
                                                     {gen_server,
                                                      try_handle_call,4,
                                                      [{file,"gen_server.erl"},
                                                       {line,661}]},
                                                     {gen_server,handle_msg,
                                                      6,
                                                      [{file,"gen_server.erl"},
                                                       {line,690}]},
                                                     {proc_lib,
                                                      init_p_do_apply,3,
                                                      [{file,"proc_lib.erl"},
                                                       {line,249}]}]},
                                                   {<0.240.0>,
                                                    {amqp_params_network,
                                                     <<"guest">>,
                                                     <<"V3ihvPxvBUBPNWzQ37AA6/iZvMYi8yQd25lHVFO+ru5o64ZrBSJV0jFkyL/KsuEw">>,
                                                     <<"/">>,"localhost",
                                                     <<"5672">>,0,0,10,50000,
                                                     none,
                                                     [fun amqp_auth_mechanisms:plain/3,
                                                      fun amqp_auth_mechanisms:amqplain/3],
                                                     [],[]}}) (~amqp/deps/amqp_client/src/amqp_gen_connection.erl, line 242)
      in function  gen_server:try_terminate/3 (gen_server.erl, line 673)
      in call from gen_server:terminate/10 (gen_server.erl, line 858)
    ancestors: [<0.239.0>,amqp_sup,<0.211.0>]
    message_queue_len: 0
    messages: []
    links: [<0.239.0>]
    dictionary: []
    trap_exit: true
    status: running
    heap_size: 6772
    stack_size: 27
    reductions: 21699
  neighbours:

[akoutmos]

Any thoughts or input on this PR? Just a friendly bump :)

[ono]

Nice work. I think it makes sense but we might want to be consistent on all integer parameters. It is confusing to do the conversion that only for the port parameter. Can you apply the change to other integer parameters for the function too?

I like to keep the documentation tidy so let's trim as either a string or an integer bit. I still like to encourage users to pass integer here and the expected type is obvious from the default value.

Can you also do README change on a separate PR 🙏? And leave * for a bullet list item? I rather like to change - to * then we can be consistent on the repo. Docker bit is a good tip 👍

[akoutmos]

@ono Thanks for the feedback! I went ahead and added the integer normalize functionality to the other integer options like you suggested and also removed the README changes as I can make those in a separate PR.

Let me know if you have any additional comments. Thanks!

[ono]

Sorry for my slow response - I have been bit busy this week. Looking good at glance. I will take a closer look this weekend and merge if there is no issue. Thanks!

[akoutmos]

Thanks @ono! Have a nice weekend :)

[ono]

@akoutmos Merged and released 1.4.1. Thanks!