revert(bridge-mqtt): remove the mqtt_sub resource

We have several reasons to remove this feature:

1. The design does not make sense. A rule engine resource should
not have an impact on the system's messages directly after it is created.
This mqtt_sub actually conflicts with any design concept of the rules engine.

2. The implementation is incorrect. mqtt_sub uses a client pool to establish
a subscription relationship to an MQTT Broker. This causes a message to be
sent repeatedly to EMQ X. Unless a shared subscription is used,
or a Pool Size of 1 is configured.

3. The emqx-bridge-mqtt supports all the features of mqtt_sub.

This feature introduced by https://github.com/emqx/emqx-bridge-mqtt/pull/78.
And it released to v4.2.0 (NOT WORK), v4.2.1-v4.2.7 (FIXED)

apps/emqx_bridge_mqtt/src/emqx_bridge_mqtt_actions.erl

@@ -39,7 +39,6 @@
         ]).
 
 -define(RESOURCE_TYPE_MQTT, 'bridge_mqtt').
--define(RESOURCE_TYPE_MQTT_SUB, 'bridge_mqtt_sub').
 -define(RESOURCE_TYPE_RPC, 'bridge_rpc').
 
 -define(RESOURCE_CONFIG_SPEC_MQTT, #{
@@ -111,7 +110,7 @@
                        zh => <<"桥接挂载点"/utf8>>},
             description => #{
                 en => <<"MountPoint for bridge topic:<br/>"
-                        "Example: The topic of messages sent to `topic1` on local node"
+                        "Example: The topic of messages sent to `topic1` on local node "
                         "will be transformed to `bridge/aws/${node}/topic1`">>,
                 zh => <<"桥接主题的挂载点:<br/>"
                         "示例: 本地节点向 `topic1` 发消息，远程桥接节点的主题"
@@ -126,8 +125,8 @@
             enum => [<<"on">>, <<"off">>],
             title => #{en => <<"Disk Cache">>,
                        zh => <<"磁盘缓存"/utf8>>},
-            description => #{en => <<"The flag which determines whether messages"
-                                     "can be cached on local disk when bridge is"
+            description => #{en => <<"The flag which determines whether messages "
+                                     "can be cached on local disk when bridge is "
                                      "disconnected">>,
                              zh => <<"当桥接断开时用于控制是否将消息缓存到本地磁"
                                      "盘队列上"/utf8>>}
@@ -244,181 +243,6 @@
         }
     }).
 
--define(RESOURCE_CONFIG_SPEC_MQTT_SUB, #{
-        address => #{
-            order => 1,
-            type => string,
-            required => true,
-            default => <<"127.0.0.1:1883">>,
-            title => #{en => <<" Broker Address">>,
-                       zh => <<"远程 broker 地址"/utf8>>},
-            description => #{en => <<"The MQTT Remote Address">>,
-                             zh => <<"远程 MQTT Broker 的地址"/utf8>>}
-        },
-        pool_size => #{
-            order => 2,
-            type => number,
-            required => true,
-            default => 8,
-            title => #{en => <<"Pool Size">>,
-                       zh => <<"连接池大小"/utf8>>},
-            description => #{en => <<"MQTT Connection Pool Size">>,
-                             zh => <<"连接池大小"/utf8>>}
-        },
-        clientid => #{
-            order => 3,
-            type => string,
-            required => true,
-            default => <<"client">>,
-            title => #{en => <<"ClientId">>,
-                       zh => <<"客户端 Id"/utf8>>},
-            description => #{en => <<"ClientId for connecting to remote MQTT broker">>,
-                             zh => <<"连接远程 Broker 的 ClientId"/utf8>>}
-        },
-        append => #{
-            order => 4,
-            type => boolean,
-            required => true,
-            default => true,
-            title => #{en => <<"Append GUID">>,
-                       zh => <<"附加 GUID"/utf8>>},
-            description => #{en => <<"Append GUID to MQTT ClientId?">>,
-                             zh => <<"是否将GUID附加到 MQTT ClientId 后"/utf8>>}
-        },
-        username => #{
-            order => 5,
-            type => string,
-            required => false,
-            default => <<"">>,
-            title => #{en => <<"Username">>, zh => <<"用户名"/utf8>>},
-            description => #{en => <<"Username for connecting to remote MQTT Broker">>,
-                             zh => <<"连接远程 Broker 的用户名"/utf8>>}
-        },
-        password => #{
-            order => 6,
-            type => password,
-            required => false,
-            default => <<"">>,
-            title => #{en => <<"Password">>,
-                       zh => <<"密码"/utf8>>},
-            description => #{en => <<"Password for connecting to remote MQTT Broker">>,
-                             zh => <<"连接远程 Broker 的密码"/utf8>>}
-        },
-        subscription_opts => #{
-            order => 7,
-            type => array,
-            items => #{
-                type => object,
-                schema => #{
-                    topic => #{
-                        order => 1,
-                        type => string,
-                        default => <<>>,
-                        title => #{en => <<"MQTT Topic">>,
-                                    zh => <<"MQTT 主题"/utf8>>},
-                        description => #{en => <<"MQTT Topic">>,
-                                        zh => <<"MQTT 主题"/utf8>>}
-                    },
-                    qos => #{
-                        order => 2,
-                        type => number,
-                        enum => [0, 1, 2],
-                        default => 0,
-                        title => #{en => <<"MQTT Topic QoS">>,
-                                    zh => <<"MQTT 服务质量"/utf8>>},
-                        description => #{en => <<"MQTT Topic QoS">>,
-                                        zh => <<"MQTT 服务质量"/utf8>>}
-                    }
-                }
-            },
-            default => [],
-            title => #{en => <<"Subscription Opts">>,
-                        zh => <<"订阅选项"/utf8>>},
-            description => #{en => <<"Subscription Opts">>,
-                            zh => <<"订阅选项"/utf8>>}
-        },
-        proto_ver => #{
-            order => 8,
-            type => string,
-            required => false,
-            default => <<"mqttv4">>,
-            enum => [<<"mqttv3">>, <<"mqttv4">>, <<"mqttv5">>],
-            title => #{en => <<"Protocol Version">>,
-                       zh => <<"协议版本"/utf8>>},
-            description => #{en => <<"MQTTT Protocol version">>,
-                             zh => <<"MQTT 协议版本"/utf8>>}
-        },
-        keepalive => #{
-            order => 9,
-            type => string,
-            required => false,
-            default => <<"60s">> ,
-            title => #{en => <<"Keepalive">>,
-                       zh => <<"心跳间隔"/utf8>>},
-            description => #{en => <<"Keepalive">>,
-                             zh => <<"心跳间隔"/utf8>>}
-        },
-        reconnect_interval => #{
-            order => 10,
-            type => string,
-            required => false,
-            default => <<"30s">>,
-            title => #{en => <<"Reconnect Interval">>,
-                       zh => <<"重连间隔"/utf8>>},
-            description => #{en => <<"Reconnect interval of bridge">>,
-                             zh => <<"重连间隔"/utf8>>}
-        },
-        ssl => #{
-            order => 11,
-            type => boolean,
-            default => false,
-            title => #{en => <<"Bridge SSL">>,
-                       zh => <<"Bridge SSL"/utf8>>},
-            description => #{en => <<"Switch which used to enable ssl connection of the bridge">>,
-                             zh => <<"是否启用 Bridge SSL 连接"/utf8>>}
-        },
-        cacertfile => #{
-            order => 12,
-            type => file,
-            required => false,
-            default => <<"etc/certs/cacert.pem">>,
-            title => #{en => <<"CA certificates">>,
-                       zh => <<"CA 证书"/utf8>>},
-            description => #{en => <<"The file path of the CA certificates">>,
-                             zh => <<"CA 证书路径"/utf8>>}
-        },
-        certfile => #{
-            order => 13,
-            type => file,
-            required => false,
-            default => <<"etc/certs/client-cert.pem">>,
-            title => #{en => <<"SSL Certfile">>,
-                       zh => <<"SSL 客户端证书"/utf8>>},
-            description => #{en => <<"The file path of the client certfile">>,
-                             zh => <<"客户端证书路径"/utf8>>}
-        },
-        keyfile => #{
-            order => 14,
-            type => file,
-            required => false,
-            default => <<"etc/certs/client-key.pem">>,
-            title => #{en => <<"SSL Keyfile">>,
-                       zh => <<"SSL 密钥文件"/utf8>>},
-            description => #{en => <<"The file path of the client keyfile">>,
-                             zh => <<"客户端密钥路径"/utf8>>}
-        },
-        ciphers => #{
-            order => 15,
-            type => string,
-            required => false,
-            default => <<"ECDHE-ECDSA-AES256-GCM-SHA384,ECDHE-RSA-AES256-GCM-SHA384">>,
-            title => #{en => <<"SSL Ciphers">>,
-                       zh => <<"SSL 加密算法"/utf8>>},
-            description => #{en => <<"SSL Ciphers">>,
-                             zh => <<"SSL 加密算法"/utf8>>}
-        }
-    }).
-
 -define(RESOURCE_CONFIG_SPEC_RPC, #{
         address => #{
             order => 1,
@@ -438,7 +262,7 @@
             title => #{en => <<"Bridge MountPoint">>,
                        zh => <<"桥接挂载点"/utf8>>},
             description => #{en => <<"MountPoint for bridge topic<br/>"
-                                     "Example: The topic of messages sent to `topic1` on local node"
+                                     "Example: The topic of messages sent to `topic1` on local node "
                                      "will be transformed to `bridge/aws/${node}/topic1`">>,
                              zh => <<"桥接主题的挂载点<br/>"
                                      "示例: 本地节点向 `topic1` 发消息，远程桥接节点的主题"
@@ -482,8 +306,8 @@
             enum => [<<"on">>, <<"off">>],
             title => #{en => <<"Disk Cache">>,
                        zh => <<"磁盘缓存"/utf8>>},
-            description => #{en => <<"The flag which determines whether messages"
-                                     "can be cached on local disk when bridge is"
+            description => #{en => <<"The flag which determines whether messages "
+                                     "can be cached on local disk when bridge is "
                                      "disconnected">>,
                              zh => <<"当桥接断开时用于控制是否将消息缓存到本地磁"
                                      "盘队列上"/utf8>>}
@@ -508,15 +332,6 @@
         description => #{en => <<"MQTT Message Bridge">>, zh => <<"MQTT 消息桥接"/utf8>>}
     }).
 
--resource_type(#{
-        name => ?RESOURCE_TYPE_MQTT_SUB,
-        create => on_resource_create,
-        status => on_get_resource_status,
-        destroy => on_resource_destroy,
-        params => ?RESOURCE_CONFIG_SPEC_MQTT_SUB,
-        title => #{en => <<"MQTT Subscribe">>, zh => <<"MQTT Subscribe"/utf8>>},
-        description => #{en => <<"MQTT Subscribe">>, zh => <<"MQTT 订阅消息"/utf8>>}
-    }).
 
 -resource_type(#{
         name => ?RESOURCE_TYPE_RPC,
@@ -542,7 +357,8 @@
                         default => <<"">>,
                         title => #{en => <<"Forward Topic">>,
                                    zh => <<"转发消息主题"/utf8>>},
-                        description => #{en => <<"The topic used when forwarding the message. Defaults to the topic of the bridge message if not provided.">>,
+                        description => #{en => <<"The topic used when forwarding the message. "
+                                                 "Defaults to the topic of the bridge message if not provided.">>,
                                          zh => <<"转发消息时使用的主题。如果未提供，则默认为桥接消息的主题。"/utf8>>}
                     },
                     payload_tmpl => #{
@@ -553,8 +369,11 @@
                         default => <<"">>,
                         title => #{en => <<"Payload Template">>,
                                    zh => <<"消息内容模板"/utf8>>},
-                        description => #{en => <<"The payload template, variable interpolation is supported. If using empty template (default), then the payload will be all the available vars in JSON format">>,
-                                         zh => <<"消息内容模板，支持变量。若使用空模板（默认），消息内容为 JSON 格式的所有字段"/utf8>>}
+                        description => #{en => <<"The payload template, variable interpolation is supported. "
+                                                 "If using empty template (default), then the payload will be "
+                                                 "all the available vars in JSON format">>,
+                                         zh => <<"消息内容模板，支持变量。"
+                                                 "若使用空模板（默认），消息内容为 JSON 格式的所有字段"/utf8>>}
                     }
         },
         title => #{en => <<"Data bridge to MQTT Broker">>,
@@ -731,12 +550,6 @@ options(Options, PoolName, ResId) ->
                   {connect_module, emqx_bridge_rpc},
                   {batch_size, Get(<<"batch_size">>)}];
              false ->
-                 Subscriptions = format_subscriptions(GetD(<<"subscription_opts">>, [])),
-                 Subscriptions1 = case Get(<<"topic">>) of
-                     undefined -> Subscriptions;
-                     Topic ->
-                         [{subscriptions, [{Topic, Get(<<"qos">>)}]} | Subscriptions]
-                 end,
                  [{address, binary_to_list(Address)},
                   {bridge_mode, GetD(<<"bridge_mode">>, true)},
                   {clean_start, true},
@@ -748,8 +561,7 @@ options(Options, PoolName, ResId) ->
                   {password, str(Get(<<"password">>))},
                   {proto_ver, mqtt_ver(Get(<<"proto_ver">>))},
                   {retry_interval, cuttlefish_duration:parse(str(GetD(<<"retry_interval">>, "30s")), s)}
-                  | maybe_ssl(Options, Get(<<"ssl">>), ResId)
-                 ] ++ Subscriptions1
+                  | maybe_ssl(Options, Get(<<"ssl">>), ResId)]
          end.
 
 maybe_ssl(_Options, false, _ResId) ->
@@ -765,8 +577,3 @@ mqtt_ver(ProtoVer) ->
        <<"mqttv5">> -> v5;
        _ -> v4
    end.
-
-format_subscriptions(SubOpts) ->
-    lists:map(fun(Sub) ->
-        {maps:get(<<"topic">>, Sub), maps:get(<<"qos">>, Sub)}
-    end, SubOpts).