Hi all,
I've recently been working on some projects involving qpid-proton (C++
and Python variants) and rabbitmq servers and there are a couple of
issues I've observed, could anybody comment on these?
Environment
-----------
I'm running Debian jessie / stable with the qpid-proton packages from
the Debian backports repository[1], currently version 0.14.0-4~bpo8+1
and rabbitmq[2] version 3.3.5-1.1+deb8u1
When I install the rabbitmq-server package on a host, I run these
commands to enable AMQP 1.0 support:
apt-get install rabbitmq-server
rabbitmq-plugins enable rabbitmq_amqp1_0
systemctl restart rabbitmq-server
I've also tried installing a config file /etc/rabbitmq/rabbitmq.config
although if I understand correctly, it is not needed and in fact the
package doesn't install it there by default.
Sending to RabbitMQ with qpid-proton python
-------------------------------------------
I started with the simple_send.py[3] example and trimmed it down to send
a single string and then stop:
def on_sendable(self, event):
if self.msg_body is not None:
print("on_sendable !")
print ("sending : %s" % (self.msg_body,))
msg = Message(body=self.msg_body)
event.sender.send(msg)
self.msg_body = None
I found that the connection to RabbitMQ would be dropped and an error
would appear in the RabbitMQ log. I tried changing the body type to a
dict containing a string, e.g. {'my_body':'foo'} and then it would
successfully pass the message to RabbitMQ but then the receiver would
complain that it was a map and not a string.
I found that the problem could be fixed by adding "inferred=True" to the
Message constructor:
msg = Message(body=self.msg_body, inferred=True)
Below is a complete example of the error from the RabbitMQ log when
inferred=True is not present, the body in this case was the string "foo"
Receiving from RabbitMQ with qpid-proton C++
--------------------------------------------
I looked at the receive example simple_recv.cpp[4] and other examples
and noticed code like this being used to access the message body as
std::string:
proton::get<std::string>(m.body())
However, that didn't work for me, it threw a conversion_error exception
"unexpected type, want: string got: binary" complaining that the body
was binary. I had to use something like this to convert my message body
to a std::string:
proton::binary __b = proton::get<proton::binary>(m.body());
std::string _s = (std::string)__b;
If I send a string from Python, should it appear as binary in the
receiver? What is the suggested way to write a receiver that can handle
any arbitrary message that started as a string and may arrive in some
other format, especially if the message broker or client is changed at
some arbitrary time in the future?
I also observed similar issues receiving messages that had been sent
into RabbitMQ by Kamailio's kazoo module[5], it is linked with the
librabbitmq client library.
Regards,
Daniel
1. https://packages.qa.debian.org/q/qpid-proton.html
2. https://packages.qa.debian.org/r/rabbitmq-server.html
3.
https://qpid.apache.org/releases/qpid-proton-0.17.0/proton/python/examples/simple_send.py.html
4.
https://qpid.apache.org/releases/qpid-proton-0.17.0/proton/cpp/examples/simple_recv.cpp.html
5. http://www.kamailio.org/docs/modules/4.4.x/modules/kazoo.html
Error from RabbitMQ log:
=INFO REPORT====
accepting AMQP connection <0.891.0> (127.0.0.1:48410 -> 127.0.0.1:5672)
=ERROR REPORT====
** Generic server <0.897.0> terminating
** Last message in was {'$gen_cast',
{frame,
{{'v1_0.transfer',
{uint,0},
{uint,0},
{binary,<<"1">>},
{uint,0},
false,false,undefined,undefined,undefined,
undefined,undefined},
<<0,83,112,208,0,0,0,11,0,0,0,5,66,80,4,64,66,
82,0,0,83,115,208,0,0,0,34,0,0,0,13,64,64,
64,64,64,64,64,64,131,0,0,0,0,0,0,0,0,131,0,
0,0,0,0,0,0,0,64,82,0,64,0,83,119,160,3,102,
111,111>>},
<0.891.0>}}
** When Server state == {state,<0.900.0>,<0.906.0>,unlimited,<0.891.0>,
<0.896.0>,
{[],[]},
{session,0,2147483647,2147483647,0,65535,65535,0,
65535,65535,1,0,
{0,nil},
{0,nil}}}
** Reason for termination ==
** {function_clause,
[{rabbit_amqp1_0_framing,fill_from_binary,
[{'v1_0.amqp_value',undefined},<<"foo">>],
[{file,"rabbitmq-amqp1.0/src/rabbit_amqp1_0_framing.erl"},
{line,56}]},
{rabbit_amqp1_0_message,decode_section,1,
[{file,"rabbitmq-amqp1.0/src/rabbit_amqp1_0_message.erl"},
{line,122}]},
{rabbit_amqp1_0_message,assemble,4,
[{file,"rabbitmq-amqp1.0/src/rabbit_amqp1_0_message.erl"},
{line,62}]},
{rabbit_amqp1_0_message,assemble,1,
[{file,"rabbitmq-amqp1.0/src/rabbit_amqp1_0_message.erl"},
{line,30}]},
{rabbit_amqp1_0_incoming_link,transfer,4,
[{file,"rabbitmq-amqp1.0/src/rabbit_amqp1_0_incoming_link.erl"},
{line,148}]},
{rabbit_amqp1_0_session_process,handle_control,2,
[{file,"rabbitmq-amqp1.0/src/rabbit_amqp1_0_session_process.erl"},
{line,214}]},
{rabbit_amqp1_0_session_process,handle_cast,2,
[{file,"rabbitmq-amqp1.0/src/rabbit_amqp1_0_session_process.erl"},
{line,134}]},
{gen_server2,handle_msg,2,
[{file,"src/gen_server2.erl"},{line,1022}]}]}
=ERROR REPORT====
closing AMQP connection <0.891.0> (127.0.0.1:48410 -> 127.0.0.1:5672):
{handshake_error,running,<0.897.0>,
{{symbol,"amqp:internal-error"},
"Session error: ~p~n~p~n",
[function_clause,
[{rabbit_amqp1_0_framing,fill_from_binary,
[{'v1_0.amqp_value',undefined},<<"foo">>],
[{file,"rabbitmq-amqp1.0/src/rabbit_amqp1_0_framing.erl"},
{line,56}]},
{rabbit_amqp1_0_message,decode_section,1,
[{file,"rabbitmq-amqp1.0/src/rabbit_amqp1_0_message.erl"},
{line,122}]},
{rabbit_amqp1_0_message,assemble,4,
[{file,"rabbitmq-amqp1.0/src/rabbit_amqp1_0_message.erl"},
{line,62}]},
{rabbit_amqp1_0_message,assemble,1,
[{file,"rabbitmq-amqp1.0/src/rabbit_amqp1_0_message.erl"},
{line,30}]},
{rabbit_amqp1_0_incoming_link,transfer,4,
[{file,"rabbitmq-amqp1.0/src/rabbit_amqp1_0_incoming_link.erl"},
{line,148}]},
{rabbit_amqp1_0_session_process,handle_control,2,
[{file,"rabbitmq-amqp1.0/src/rabbit_amqp1_0_session_process.erl"},
{line,214}]},
{rabbit_amqp1_0_session_process,handle_cast,2,
[{file,"rabbitmq-amqp1.0/src/rabbit_amqp1_0_session_process.erl"},
{line,134}]},
{gen_server2,handle_msg,2,
[{file,"src/gen_server2.erl"},{line,1022}]}]]}}
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