Cassandra 消息存储

EMQX 3.1 版本后推出强大的规则引擎用于替换插件，建议您前往使用保存数据到 Cassandra规则引擎中创建 保存数据到 Cassandra

配置文件: emqx_backend_cassa.conf

支持配置多台Cassandra服务器连接池:

backend 消息存储规则包括:

自定义 CQL 语句 可用参数包括:

支持 CQL 语句配置:

考虑到用户的需求不同, backend cassandra 自带的函数无法满足用户需求, 用户可根据自己的需求配置 cql 语句

backend.cassa.hook.client.connected.3 = {"action": {"cql": ["insert into conn(clientid) values(${clientid})"]}, "pool": "pool1"}

Cassandra 创建一个 Keyspace

CREATE KEYSPACE mqtt WITH replication = {'class': 'SimpleStrategy', 'replication_factor': '1'}  AND durable_writes = true;
USE mqtt;

导入 Cassandra 表结构

cqlsh -e "SOURCE 'emqx_backend_cassa.cql'"

mqtt.client 存储设备在线状态:

CREATE TABLE mqtt.client (
  clientid text PRIMARY KEY,
  connected timestamp,
  disconnected timestamp,
  node text,
);

查询设备在线状态:

select * from mqtt.client where clientid = ${clientid};

例如 ClientId 为 test 的客户端上线:

例如ClientId为test客户端下线:

select * from mqtt.client where clientid = 'test';
 clientid  | connected                       | disconnected                    | node            | state
-----------+---------------------------------+---------------------------------+-----------------+-------

Cassandra 用户订阅主题表(Sub Table)

mqtt.sub 存储订阅关系:

CREATE TABLE mqtt.sub (
  clientid text,
  topic text,
  qos int,
  PRIMARY KEY (clientid, topic)
);

用户test分别订阅主题test_topic1 test_topic2:

insert into mqtt.sub(clientid, topic, qos) values('test', 'test_topic1', 1);
insert into mqtt.sub(clientid, topic, qos) values('test', 'test_topic2', 2);

某个客户端订阅主题:

select * from mqtt_sub where clientid = ${clientid};

select * from mqtt_sub where clientid = 'test';
 clientid  | topic       | qos
      test | test_topic1 |   1
      test | test_topic2 |   2

Cassandra 发布消息表(Msg Table)

mqtt.msg 存储MQTT消息:

查询某个客户端发布的消息:

select * from mqtt_msg where sender = ${clientid};

查询ClientId为’test’的客户端发布的消息:

 topic | msgid                | arrived                         | payload      | qos | retain | sender
-------+----------------------+---------------------------------+--------------+-----+--------+--------
 hello | 2PguFrHsrzEvIIBdctmb | 2017-02-14 09:07:13.785000+0000 | Hello world! |   1 |      0 |   test
 world | 2PguFrHsrzEvIIBdctmb | 2017-02-14 09:07:13.785000+0000 | Hello world! |   1 |      0 |   test

mqtt.retain 存储 Retain 消息:

CREATE TABLE mqtt.retain (
  topic text PRIMARY KEY,
  msgid text
);

查询 retain 消息:

select * from mqtt_retain where topic = ${topic};

查询 topic 为 ‘t/retain’ 的 retain 消息:

select * from mqtt_retain where topic = 't/retain';
 topic  | msgid
--------+----------------------
 retain | 2PguFrHsrzEvIIBdctmb

Cassandra 接收消息 ack 表(Message Acked Table)

mqtt.acked 存储客户端消息确认:

启用 Cassandra 存储插件