rabbitmq_binding breaks idempotency if arguments is not empty

[oneoneonepig]

SUMMARY

When a binding is created, it will calculate the properties_key based on the routing_key and arguments:

# pseudo code
if len(arguments) == 0 and routing_key == "":
  properties_key = "~"
else if len(arguments) == 0 and routing_key != "":
  properties_key = routing_key
else if len(arguments) > 0:
  properties_key = f"{routing_key}~{hash(arguments)}"

The actual hash() algorithm will be mentioned later

When rabbitmq_binding checks if the resource exists, it invokes the following request:

# https://github.com/ansible-collections/community.rabbitmq/blob/146b006de99112e1abb5c2be0c4f2bcc8d6c3a5f/plugins/modules/rabbitmq_binding.py#L114-L123

        self.props = urllib_parse.quote(self.routing_key) if self.routing_key != '' else '~'
        self.base_url = '{0}://{1}:{2}/api/bindings'.format(self.login_protocol,
                                                            self.login_host,
                                                            self.login_port)
        self.url = '{0}/{1}/e/{2}/{3}/{4}/{5}'.format(self.base_url,
                                                      urllib_parse.quote(self.vhost, safe=''),
                                                      urllib_parse.quote(self.name, safe=''),
                                                      self.destination_type,
                                                      urllib_parse.quote(self.destination, safe=''),
                                                      self.props)

The logic does not consider arguments. As a result, bindings with arguments will not have idempotency and will introduce some incorrect behavior.

The check uses the HTTP API /api/bindings/vhost/e/exchange/q/queue/props, which describes as below:

An individual binding between an exchange and a queue. The props part of the URI is a "name" for the binding composed of its routing key and a hash of its arguments. props is the field named "properties_key" from a bindings listing response.

The following snippet describes the actual hash algorithm:

%% https://github.com/rabbitmq/rabbitmq-server/blob/70047f52453c37d8f3fa185807c8f574dd95ef71/deps/rabbitmq_management_agent/src/rabbit_mgmt_format.erl#L412-L424
binding(#binding{source      = S,
                 key         = Key,
                 destination = D,
                 args        = Args}) ->
    format(
      [{source,           S},
       {destination,      D#resource.name},
       {destination_type, D#resource.kind},
       {routing_key,      Key},
       {arguments,        Args},
       {properties_key, pack_binding_props(Key, Args)}],
      {fun format_binding/1, false}).

%% https://github.com/rabbitmq/rabbitmq-server/blob/70047f52453c37d8f3fa185807c8f574dd95ef71/deps/rabbitmq_management_agent/src/rabbit_mgmt_format.erl#L336-L342
pack_binding_props(<<"">>, []) ->
    <<"~">>;
pack_binding_props(Key, []) ->
    list_to_binary(quote_binding(Key));
pack_binding_props(Key, Args) ->
    ArgsEnc = args_hash(Args),
    list_to_binary(quote_binding(Key) ++ "~" ++ quote_binding(ArgsEnc)).

%% https://github.com/rabbitmq/rabbitmq-server/blob/70047f52453c37d8f3fa185807c8f574dd95ef71/deps/rabbitmq_management_agent/src/rabbit_mgmt_format.erl#L605-L606
args_hash(Args) ->
    list_to_binary(rabbit_misc:base64url(<<(erlang:phash2(Args, 1 bsl 32)):32>>)).

%% https://github.com/rabbitmq/rabbitmq-server/blob/70047f52453c37d8f3fa185807c8f574dd95ef71/deps/rabbit_common/src/rabbit_misc.erl#L1120-L1125
base64url(In) ->
    lists:reverse(lists:foldl(fun ($\+, Acc) -> [$\- | Acc];
                                  ($\/, Acc) -> [$\_ | Acc];
                                  ($\=, Acc) -> Acc;
                                  (Chr, Acc) -> [Chr | Acc]
                              end, [], base64:encode_to_string(In))).

I do not write Erlang, let me know if I am grabbing the wrong blocks

Suggested fixes:

1. Instead of using self.http_check_states.get(self.api_result.status_code, False), retrieve all bindings via /api/bindings/vhost/e/exchange/q/queue and check if the resource exists,
2. Use the same method to create the properties_key and place it in URL when invoking /api/bindings/vhost/e/exchange/q/queue/props

ISSUE TYPE

• Bug Report

COMPONENT NAME

community.rabbitmq.rabbitmq_binding

ANSIBLE VERSION

ansible [core 2.15.3]
  config file = /var/user/ansible/ansible.cfg
  configured module search path = ['/home/jeffrey/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/jeffrey/.local/lib/python3.10/site-packages/ansible
  ansible collection location = /home/jeffrey/.ansible/collections
  executable location = /home/jeffrey/.local/bin/ansible
  python version = 3.10.12 (main, Jun 11 2023, 05:26:28) [GCC 11.4.0] (/usr/bin/python3)
  jinja version = 3.0.3
  libyaml = True

COLLECTION VERSION

# /home/jeffrey/.ansible/collections/ansible_collections
Collection         Version
------------------ -------
community.rabbitmq 1.2.3

CONFIGURATION

Omitted

OS / ENVIRONMENT

OS: Ubuntu 22.04.3 LTS
Kernel: 5.15.0-76-generic
RabbitMQ: 3.9.13-1ubuntu0.22.04.1 (current latest release with Ubuntu 22.04)

STEPS TO REPRODUCE

Run the following tasks at least once:

    - name: Bind queue to exchange rk/ arg/
      community.rabbitmq.rabbitmq_binding:
        name: xexchange
        destination: xqueue
        type: queue
        routing_key: ""
    - name: Bind queue to exchange rk/aaa arg/AAA
      community.rabbitmq.rabbitmq_binding:
        name: xexchange
        destination: xqueue
        type: queue
        routing_key: "aaa"
        arguments:
          type: "AAA"
    - name: Bind queue to exchange rk/bbb arg/
      community.rabbitmq.rabbitmq_binding:
        name: xexchange
        destination: xqueue
        type: queue
        routing_key: "bbb"
    - name: Bind queue to exchange rk/# arg/CCC
      community.rabbitmq.rabbitmq_binding:
        name: xexchange
        destination: xqueue
        type: queue
        arguments:
          type: "CCC"
    - name: Bind queue to exchange rk/ arg/DDD
      community.rabbitmq.rabbitmq_binding:
        name: xexchange
        destination: xqueue
        type: queue
        routing_key: ""
        arguments:
          type: "DDD"

EXPECTED RESULTS

After the first run, all consecutive runs should report ok: [...] instead of changed: [...]

ACTUAL RESULTS

TASK [Bind queue to exchange rk/ arg/] *************************************************
ok: [lab1]

TASK [Bind queue to exchange rk/aaa arg/AAA] *******************************************
changed: [lab1]

TASK [Bind queue to exchange rk/bbb arg/] **********************************************
ok: [lab1]

TASK [Bind queue to exchange rk/# arg/CCC] *********************************************
changed: [lab1]

TASK [Bind queue to exchange rk/ arg/DDD] **********************************************
ok: [lab1]

case	routing_key	arguments	idempotency	properties_key
1			ok	finds "~", and it is "~"
2	aaa	type:AAA	changed	finds "aaa", but actually "aaa~xxxx"
3	bbb		ok	finds "bbb", and it is "bbb"
4	#	type:CCC	changed	finds "#", and actually "#~xxxx", similar to case 2
5		type:DDD	ok (wrong!)	finds "~", found "~", but actually matches the binding created by case 1

Invoke the HTTP API and see the properties_key:
curl -u guest -s http://localhost:15672/api/bindings/%2F/e/xexchange/q/xqueue | jq

[
  {
    "source": "xexchange",
    "vhost": "/",
    "destination": "xqueue",
    "destination_type": "queue",
    "routing_key": "",
    "arguments": {},
    "properties_key": "~"
  },
  {
    "source": "xexchange",
    "vhost": "/",
    "destination": "xqueue",
    "destination_type": "queue",
    "routing_key": "",
    "arguments": {
      "type": "DDD"
    },
    "properties_key": "~7V4gwQ"
  },
  {
    "source": "xexchange",
    "vhost": "/",
    "destination": "xqueue",
    "destination_type": "queue",
    "routing_key": "#",
    "arguments": {
      "type": "CCC"
    },
    "properties_key": "%23~fF974A"
  },
  {
    "source": "xexchange",
    "vhost": "/",
    "destination": "xqueue",
    "destination_type": "queue",
    "routing_key": "aaa",
    "arguments": {
      "type": "AAA"
    },
    "properties_key": "aaa~yG2vtw"
  },
  {
    "source": "xexchange",
    "vhost": "/",
    "destination": "xqueue",
    "destination_type": "queue",
    "routing_key": "bbb",
    "arguments": {},
    "properties_key": "bbb"
  }
]