1. 前言
按照我自己设计的物联网框架，对于MQTT集群中的所有消息，是要持久化到磁盘的，这里采用一个消息队列中间件Kafka作为数据缓冲，缓冲结果存到数据仓库中，以供后续作为数据分析。由于MQTT集群中的消息都是比较分散的，所以使用Kafka来聚合、采集消息。
2. 下载&编译&安装
Kafka依赖ZooKeeper
在这里下载 http://mirrors.shuosc.org/apache/zookeeper/zookeeper-3.4.11/zookeeper-3.4.11.tar.gz
http://mirrors.shuosc.org/apache/kafka/1.0.0/kafka-1.0.0-src.tgz
http://mirror.bit.edu.cn/apache/kafka/1.0.0/kafka_2.12-1.0.0.tgz
学习的话， 可以参考这个文档 http://orchome.com/kafka/index
配置使用过程可以参考官网的 http://kafka.apache.org/quickstart http://zookeeper.apache.org/doc/current/zookeeperStarted.html ，有些资料因为版本升级的原因，已经不是以前的那种启动方式了。https://cwiki.apache.org/confluence/display/KAFKA/Clients
3. 启动Zookeeper
1 cp ./conf/zoo_sample.cfg ./conf/zoo.cfg 2 ./bin/zkServer.sh start
上图，就表示启动单机模式。
./bin/zkCli.sh -server 127.0.0.1:2181 进行连接
然后进入命令行模式，可以慢慢玩了
单击模式就没有什么要配置的。最多修改zoo.cfg中的dataDir文件
ZooKeeper启动replicated模式，集群模式
zoo.cfg 增加服务器集群信息
1 server.1=172.16.20.229:2888:3888 2 server.2=172.16.23.203:2888:3888 3 server.3=172.16.23.204:2888:3888
1 ./bin/zkServer.sh start-foreground #启动
注意在echo “1” > %dataDir%/myid 对于每个服务器都要创建一个myid文件
启动都是会有一些奇奇怪怪的问题，上网找资料就可以了。
一般第一台ZooKeeper启动是会有Connection refused 出错，这个是正常的，后面的两台还没有启动，不过后面也一个一个启动了。
如果过程中，有一个断开了，然后修改数据，然后这个断开的又连上了，那么ZooKeeper集群内部会镜像diff
1 2017-12-28 16:30:38,570 [myid:3] - INFO [QuorumPeer[myid=3]/0.0.0.0:2181:Learner@332] - Getting a diff from the leader 0x100000005
然后就用客户端A
1 ./bin/zkCli.sh -server 172.16.20.229:2181 2 ls / 3 create /zk_test my_data 4 ls /
然后用客户端B
1 ./bin/zkCli.sh -server 172.16.23.203:2181 2 ls / 3 get /zk_test 4 ls /
可以看到ZooKeeper信息在内部进行了共享
具体可以参考这篇博客 http://www.cnblogs.com/sunddenly/p/4018459.html
4. 启动 Kafka
由于kafka以来ZooKeeper，所以有了上面一步的ZooKeeper了解。
实际中，可以直接下载kafka的二进制包，直接使用，http://mirror.bit.edu.cn/apache/kafka/1.0.0/kafka_2.12-1.0.0.tgz
启动Zookeeper
1 ./bin/zookeeper-server-start.sh config/zookeeper.properties
启动Kafka
1 ./bin/kafka-server-start.sh config/server.properties
创建主题
1 ./bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic test
查看主题
1 ./bin/kafka-topics.sh --list --zookeeper localhost:2181
发送消息
1 ./bin/kafka-console-producer.sh --broker-list localhost:9092 --topic test
消费消息
1 ./bin/kafka-console-consumer.sh --zookeeper localhost:2181 --topic test --from-beginning
5. Erlang 连接 kafka
主要参考这个 https://github.com/msdevanms/emqttd_plugin_kafka_bridge
增加依赖 https://github.com/helpshift/ekaf.git
首先在Makefile增加
1 DEPS = eredis ecpool clique ekaf 2 dep_ekaf = git https://github.com/helpshift/ekaf master
然后在rebar.config 增加
1 {ekaf, “.*”, {git, “https://github.com/helpshift/ekaf”, “master”}}
在etc/emq_plugin_wunaozai.conf 中增加
1 ## kafka config 2 wunaozai.msg.kafka.server = 127.0.0.1:9092 3 wunaozai.msg.kafka.topic = test
在priv/emq_plugin_wunaozai.schema 中增加
1 %% wunaozai.msg.kafka.server = 127.0.0.1:9092 2 { 3 mapping, 4 "wunaozai.msg.kafka.server", 5 "emq_plugin_wunaozai.kafka", 6 [ 7 {default, {"127.0.0.1", 9092}}, 8 {datatype, [integer, ip, string]} 9 ] 10 }. 11 12 %% wunaozai.msg.kafka.topic = test 13 { 14 mapping, 15 "wunaozai.msg.kafka.topic", 16 "emq_plugin_wunaozai.kafka", 17 [ 18 {default, "test"}, 19 {datatype, string}, 20 hidden 21 ] 22 }. 23 24 %% translation 25 { 26 translation, 27 "emq_plugin_wunaozai.kafka", 28 fun(Conf) -> 29 {RHost, RPort} = case cuttlefish:conf_get("wunaozai.msg.kafka.server", Conf) of 30 {Ip, Port} -> {Ip, Port}; 31 S -> case string:tokens(S, ":") of 32 [Domain] -> {Domain, 9092}; 33 [Domain, Port] -> {Domain, list_to_integer(Port)} 34 end 35 end, 36 Topic = cuttlefish:conf_get("wunaozai.msg.kafka.topic", Conf), 37 [ 38 {host, RHost}, 39 {port, RPort}, 40 {topic, Topic} 41 ] 42 end 43 }.
6. 数据发往Kafka
接下来，由于功能基本上是基于EMQ框架的Hook钩子设计，在EMQ接收到客户端上下线、主题订阅或消息发布确认时，触发钩子顺序执行回调函数，所以大部分功能在 src/emq_plugin_wunaozai.erl 文件进行修改。
1 -module(emq_plugin_wunaozai). 2 3 -include("emq_plugin_wunaozai.hrl"). 4 5 -include_lib("emqttd/include/emqttd.hrl"). 6 7 -export([load/1, unload/0]). 8 9 %% Hooks functions 10 11 -export([on_client_connected/3, on_client_disconnected/3]). 12 13 -export([on_client_subscribe/4, on_client_unsubscribe/4]). 14 15 -export([on_session_created/3, on_session_subscribed/4, on_session_unsubscribed/4, on_session_terminated/4]). 16 17 -export([on_message_publish/2, on_message_delivered/4, on_message_acked/4]). 18 19 %% Called when the plugin application start 20 load(Env) -> 21 ekaf_init([Env]), 22 emqttd:hook('client.connected', fun ?MODULE:on_client_connected/3, [Env]), 23 emqttd:hook('client.disconnected', fun ?MODULE:on_client_disconnected/3, [Env]), 24 emqttd:hook('client.subscribe', fun ?MODULE:on_client_subscribe/4, [Env]), 25 emqttd:hook('client.unsubscribe', fun ?MODULE:on_client_unsubscribe/4, [Env]), 26 emqttd:hook('session.created', fun ?MODULE:on_session_created/3, [Env]), 27 emqttd:hook('session.subscribed', fun ?MODULE:on_session_subscribed/4, [Env]), 28 emqttd:hook('session.unsubscribed', fun ?MODULE:on_session_unsubscribed/4, [Env]), 29 emqttd:hook('session.terminated', fun ?MODULE:on_session_terminated/4, [Env]), 30 emqttd:hook('message.publish', fun ?MODULE:on_message_publish/2, [Env]), 31 emqttd:hook('message.delivered', fun ?MODULE:on_message_delivered/4, [Env]), 32 emqttd:hook('message.acked', fun ?MODULE:on_message_acked/4, [Env]), 33 io:format("start wunaozai Test Reload.~n", []). 34 35 on_client_connected(ConnAck, Client = #mqtt_client{client_id = ClientId}, _Env) -> 36 io:format("client ~s connected, connack: ~w~n", [ClientId, ConnAck]), 37 ekaf_send(<<"connected">>, ClientId, {}, _Env), 38 {ok, Client}. 39 40 on_client_disconnected(Reason, _Client = #mqtt_client{client_id = ClientId}, _Env) -> 41 io:format("client ~s disconnected, reason: ~w~n", [ClientId, Reason]), 42 ekaf_send(<<"disconnected">>, ClientId, {}, _Env), 43 ok. 44 45 on_client_subscribe(ClientId, Username, TopicTable, _Env) -> 46 io:format("client(~s/~s) will subscribe: ~p~n", [Username, ClientId, TopicTable]), 47 {ok, TopicTable}. 48 49 on_client_unsubscribe(ClientId, Username, TopicTable, _Env) -> 50 io:format("client(~s/~s) unsubscribe ~p~n", [ClientId, Username, TopicTable]), 51 {ok, TopicTable}. 52 53 on_session_created(ClientId, Username, _Env) -> 54 io:format("session(~s/~s) created.", [ClientId, Username]). 55 56 on_session_subscribed(ClientId, Username, {Topic, Opts}, _Env) -> 57 io:format("session(~s/~s) subscribed: ~p~n", [Username, ClientId, {Topic, Opts}]), 58 ekaf_send(<<"subscribed">>, ClientId, {Topic, Opts}, _Env), 59 {ok, {Topic, Opts}}. 60 61 on_session_unsubscribed(ClientId, Username, {Topic, Opts}, _Env) -> 62 io:format("session(~s/~s) unsubscribed: ~p~n", [Username, ClientId, {Topic, Opts}]), 63 ekaf_send(<<"unsubscribed">>, ClientId, {Topic, Opts}, _Env), 64 ok. 65 66 on_session_terminated(ClientId, Username, Reason, _Env) -> 67 io:format("session(~s/~s) terminated: ~p.~n", [ClientId, Username, Reason]), 68 stop. 69 70 %% transform message and return 71 on_message_publish(Message = #mqtt_message{topic = <<"$SYS/", _/binary>>}, _Env) -> 72 {ok, Message}; 73 on_message_publish(Message, _Env) -> 74 io:format("publish ~s~n", [emqttd_message:format(Message)]), 75 ekaf_send(<<"public">>, {}, Message, _Env), 76 {ok, Message}. 77 78 on_message_delivered(ClientId, Username, Message, _Env) -> 79 io:format("delivered to client(~s/~s): ~s~n", [Username, ClientId, emqttd_message:format(Message)]), 80 {ok, Message}. 81 82 on_message_acked(ClientId, Username, Message, _Env) -> 83 io:format("client(~s/~s) acked: ~s~n", [Username, ClientId, emqttd_message:format(Message)]), 84 {ok, Message}. 85 86 %% Called when the plugin application stop 87 unload() -> 88 emqttd:unhook('client.connected', fun ?MODULE:on_client_connected/3), 89 emqttd:unhook('client.disconnected', fun ?MODULE:on_client_disconnected/3), 90 emqttd:unhook('client.subscribe', fun ?MODULE:on_client_subscribe/4), 91 emqttd:unhook('client.unsubscribe', fun ?MODULE:on_client_unsubscribe/4), 92 emqttd:unhook('session.created', fun ?MODULE:on_session_created/3), 93 emqttd:unhook('session.subscribed', fun ?MODULE:on_session_subscribed/4), 94 emqttd:unhook('session.unsubscribed', fun ?MODULE:on_session_unsubscribed/4), 95 emqttd:unhook('session.terminated', fun ?MODULE:on_session_terminated/4), 96 emqttd:unhook('message.publish', fun ?MODULE:on_message_publish/2), 97 emqttd:unhook('message.delivered', fun ?MODULE:on_message_delivered/4), 98 emqttd:unhook('message.acked', fun ?MODULE:on_message_acked/4). 99 100 %% ==================== ekaf_init STA.===============================%% 101 ekaf_init(_Env) -> 102 % clique 方式读取配置文件 103 Env = application:get_env(?APP, kafka), 104 {ok, Kafka} = Env, 105 Host = proplists:get_value(host, Kafka), 106 Port = proplists:get_value(port, Kafka), 107 Broker = {Host, Port}, 108 Topic = proplists:get_value(topic, Kafka), 109 io:format("~w ~w ~w ~n", [Host, Port, Topic]), 110 111 % init kafka 112 application:set_env(ekaf, ekaf_partition_strategy, strict_round_robin), 113 application:set_env(ekaf, ekaf_bootstrap_broker, Broker), 114 application:set_env(ekaf, ekaf_bootstrap_topics, list_to_binary(Topic)), 115 %application:set_env(ekaf, ekaf_bootstrap_broker, {"127.0.0.1", 9092}), 116 %application:set_env(ekaf, ekaf_bootstrap_topics, <<"test">>), 117 118 %io:format("Init ekaf with ~s:~b~n", [Host, Port]), 119 %%ekaf:produce_async_batched(<<"test">>, list_to_binary(Json)), 120 ok. 121 %% ==================== ekaf_init END.===============================%% 122 123 124 %% ==================== ekaf_send STA.===============================%% 125 ekaf_send(Type, ClientId, {}, _Env) -> 126 Json = mochijson2:encode([ 127 {type, Type}, 128 {client_id, ClientId}, 129 {message, {}}, 130 {cluster_node, node()}, 131 {ts, emqttd_time:now_ms()} 132 ]), 133 ekaf_send_sync(Json); 134 ekaf_send(Type, ClientId, {Reason}, _Env) -> 135 Json = mochijson2:encode([ 136 {type, Type}, 137 {client_id, ClientId}, 138 {cluster_node, node()}, 139 {message, Reason}, 140 {ts, emqttd_time:now_ms()} 141 ]), 142 ekaf_send_sync(Json); 143 ekaf_send(Type, ClientId, {Topic, Opts}, _Env) -> 144 Json = mochijson2:encode([ 145 {type, Type}, 146 {client_id, ClientId}, 147 {cluster_node, node()}, 148 {message, [ 149 {topic, Topic}, 150 {opts, Opts} 151 ]}, 152 {ts, emqttd_time:now_ms()} 153 ]), 154 ekaf_send_sync(Json); 155 ekaf_send(Type, _, Message, _Env) -> 156 Id = Message#mqtt_message.id, 157 From = Message#mqtt_message.from, %需要登录和不需要登录这里的返回值是不一样的 158 Topic = Message#mqtt_message.topic, 159 Payload = Message#mqtt_message.payload, 160 Qos = Message#mqtt_message.qos, 161 Dup = Message#mqtt_message.dup, 162 Retain = Message#mqtt_message.retain, 163 Timestamp = Message#mqtt_message.timestamp, 164 165 ClientId = c(From), 166 Username = u(From), 167 168 Json = mochijson2:encode([ 169 {type, Type}, 170 {client_id, ClientId}, 171 {message, [ 172 {username, Username}, 173 {topic, Topic}, 174 {payload, Payload}, 175 {qos, i(Qos)}, 176 {dup, i(Dup)}, 177 {retain, i(Retain)} 178 ]}, 179 {cluster_node, node()}, 180 {ts, emqttd_time:now_ms()} 181 ]), 182 ekaf_send_sync(Json). 183 184 ekaf_send_async(Msg) -> 185 Topic = ekaf_get_topic(), 186 ekaf_send_async(Topic, Msg). 187 ekaf_send_async(Topic, Msg) -> 188 ekaf:produce_async_batched(list_to_binary(Topic), list_to_binary(Msg)). 189 ekaf_send_sync(Msg) -> 190 Topic = ekaf_get_topic(), 191 ekaf_send_sync(Topic, Msg). 192 ekaf_send_sync(Topic, Msg) -> 193 ekaf:produce_sync_batched(list_to_binary(Topic), list_to_binary(Msg)). 194 195 i(true) -> 1; 196 i(false) -> 0; 197 i(I) when is_integer(I) -> I. 198 c({ClientId, Username}) -> ClientId; 199 c(From) -> From. 200 u({ClientId, Username}) -> Username; 201 u(From) -> From. 202 %% ==================== ekaf_send END.===============================%% 203 204 205 %% ==================== ekaf_set_host STA.===============================%% 206 ekaf_set_host(Host) -> 207 ekaf_set_host(Host, 9092). 208 ekaf_set_host(Host, Port) -> 209 Broker = {Host, Port}, 210 application:set_env(ekaf, ekaf_bootstrap_broker, Broker), 211 io:format("reset ekaf Broker ~s:~b ~n", [Host, Port]), 212 ok. 213 %% ==================== ekaf_set_host END.===============================%% 214 215 %% ==================== ekaf_set_topic STA.===============================%% 216 ekaf_set_topic(Topic) -> 217 application:set_env(ekaf, ekaf_bootstrap_topics, list_to_binary(Topic)), 218 ok. 219 ekaf_get_topic() -> 220 Env = application:get_env(?APP, kafka), 221 {ok, Kafka} = Env, 222 Topic = proplists:get_value(topic, Kafka), 223 Topic. 224 %% ==================== ekaf_set_topic END.===============================%%
上面是所有源代码，下面对其进行简单说明
ekaf_init 函数，主要对配置文件的读取和解析并存放到application的环境变量中
ekaf_send 函数，主要是封装成对应的JSON数据，然后发到Kafka中
ekaf_send_async 函数，主要是异步发送JSON数据，不确保发往Kafka的顺序与Kafka消费者的接收时的顺序
ekaf_send_sync 函数，是同步发送JSON数据，确保按照顺序发往kafka与Kafka消费者有序接收数据
ekaf_set_host 函数，设置kafka的域名与端口
ekaf_set_topic 函数，设置发往kafka时的主题
ekaf_get_topic 函数，获取当前主题
load函数增加ekaf_init调用
剩下的在每个钩子回调中调用 ekaf_send函数
7. 测试
（1）启动Zookeeper ./bin/zookeeper-server-start.sh config/zookeeper.properties
（2）启动Kafka ./bin/kafka-server-start.sh config/server.properties
（3）启动消费者 ./bin/kafka-console-consumer.sh --zookeeper localhost:2181 --topic test --from-beginning
（4）启动一个生产者 ./bin/kafka-console-producer.sh --broker-list localhost:9092 --topic test
（5）启动EMQ ./_rel/emqttd/bin/emqttd console
（6）打开MQTT客户端并连接、订阅、发布等操作
（7）可以在消费者界面上看到获取到的信息
8. 插件源码
最后给出本次插件开发的所有源码
https://files.cnblogs.com/files/wunaozai/emq_plugin_wunaozai.zip
