优势 #

  1. 基于Mysql实现持久化存储和集群,运维成本低
  2. 数据可靠性高,默认支持集群,mqtt broker无状态,可横向扩展

劣势 #

  1. 性能较低,必要时,需要优化DB及相关的处理
  2. 基于DB的集群实现方式:为poll的集群实现方式,每隔一段时间,mqtt broker节点从消息事件表中拉取相应的事件进行处理(处理session,分发节点消息等) 事件处理会有一定延时。

集群实现详解 #

以client1发送消息,client2消费消息为例:

  1. client1连接jmqtt brokerA; client2连接jmqtt brokerB
  2. client1发送消息到brokerA,brokerA收到消息后以事件的形式将数据存储到DB的事件表中
  3. brokerB内部会定时获取DB中的未处理的事件,进行处理,brokerB拉取到该事件后,判断到是分发消息事件。
  4. brokerB将事件转换为消息分发给brokerB上连接的client,这里为client2

mysql相关配置 #

# 这里需要采用集群2的方式
clusterMode = 2
# 每次最多从事件表中拉取未处理的10条
maxPollEventNum = 10 
# 若每次拉取不满,则等待10ms再拉取,防止一直请求DB
pollWaitInterval = 10
# DB数据源配置
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/jmqtt?characterEncoding=utf8&autoReconnect=true&failOverReadOnly=false&maxReconnects=10&useSSL=false
username=root
password=CallmeZ2013

初始化sql #

这里为最初的表结构,后续更新可能不及时,具体请查看jmqtt源码中/jmqtt/jmqtt-broker/resources/conf下的jmqtt.sql

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for jmqtt_event
-- ----------------------------
DROP TABLE IF EXISTS `jmqtt_event`;
CREATE TABLE `jmqtt_event` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键:也是集群节点批量拉消息的offset',
`content` text NOT NULL COMMENT '消息体',
`gmt_create` bigint(20) NOT NULL COMMENT '创建时间',
`jmqtt_ip` varchar(24) NOT NULL COMMENT 'jmqtt服务器ip,发送该消息到集群中的broker ip',
`event_code` int(4) NOT NULL COMMENT '事件码',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='jmqtt 集群事件转发表:由发送端将消息发送到该表中,其他节点批量拉取该表中的事件进行处理';

-- ----------------------------
-- Table structure for jmqtt_inflow_message
-- ----------------------------
DROP TABLE IF EXISTS `jmqtt_inflow_message`;
CREATE TABLE `jmqtt_inflow_message` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键id',
`client_id` varchar(64) NOT NULL COMMENT '设备id',
`msg_id` int(11) NOT NULL COMMENT '消息id',
`content` text NOT NULL COMMENT '消息体内容',
`gmt_create` bigint(20) NOT NULL COMMENT '消息保存时间(对应消息接收时间)',
PRIMARY KEY (`id`),
UNIQUE KEY `uqe_client_id_msg_id` (`client_id`,`msg_id`) USING BTREE,
KEY `idx_client_id` (`client_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='入栈消息表';

-- ----------------------------
-- Table structure for jmqtt_offline_message
-- ----------------------------
DROP TABLE IF EXISTS `jmqtt_offline_message`;
CREATE TABLE `jmqtt_offline_message` (
  `id` bigint(20) AUTO_INCREMENT NOT NULL,
`client_id` varchar(64) NOT NULL COMMENT '客户端id',
`content` text NOT NULL COMMENT '消息体',
`gmt_create` bigint(20) NOT NULL COMMENT '创建时间',
PRIMARY KEY (`id`),
KEY `idx_client_id` (`client_id`),
KEY `idx_gmt_create` (`gmt_create`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='离线消息表';

-- ----------------------------
-- Table structure for jmqtt_outflow_message
-- ----------------------------
DROP TABLE IF EXISTS `jmqtt_outflow_message`;
CREATE TABLE `jmqtt_outflow_message` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键',
`client_id` varchar(64) NOT NULL COMMENT '目标客户端id',
`msg_id` int(11) NOT NULL COMMENT '消息id',
`content` text NOT NULL COMMENT '消息内容',
`gmt_create` bigint(20) NOT NULL COMMENT '消息缓存时间',
PRIMARY KEY (`id`),
UNIQUE KEY `uqe_client_id_msg_id` (`msg_id`,`client_id`) USING BTREE,
KEY `idx_client_id` (`client_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='出栈消息表';

-- ----------------------------
-- Table structure for jmqtt_outflow_sec_message
-- ----------------------------
DROP TABLE IF EXISTS `jmqtt_outflow_sec_message`;
CREATE TABLE `jmqtt_outflow_sec_message` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键',
`client_id` varchar(64) NOT NULL COMMENT '目标客户端id',
`msg_id` int(11) NOT NULL COMMENT '消息id',
`gmt_create` bigint(20) NOT NULL COMMENT '消息缓存时间',
PRIMARY KEY (`id`),
UNIQUE KEY `uqe_client_id_msg_id` (`msg_id`,`client_id`) USING BTREE,
KEY `idx_client_id` (`client_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='发送qos2消息后的第二阶段的消息缓存表:接收pubRec后保留clientId,msgId等报文。设备重连时候进行重发';

-- ----------------------------
-- Table structure for jmqtt_retain_message
-- ----------------------------
DROP TABLE IF EXISTS `jmqtt_retain_message`;
CREATE TABLE `jmqtt_retain_message` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键',
`topic` varchar(128) NOT NULL COMMENT '所属topic',
`content` text NOT NULL COMMENT '消息体',
PRIMARY KEY (`id`),
UNIQUE KEY `uqe_topic` (`topic`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='保留消息表';

-- ----------------------------
-- Table structure for jmqtt_session
-- ----------------------------
DROP TABLE IF EXISTS `jmqtt_session`;
CREATE TABLE `jmqtt_session` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键',
`client_id` varchar(64) NOT NULL COMMENT '客户端id',
`state` varchar(12) NOT NULL COMMENT '状态:ONLINE,OFFLINE两种',
`offline_time` bigint(20) DEFAULT NULL COMMENT 'OFFLINE状态时对应的离线时间戳(只有cleanStart为0时候离线才有该数据)',
PRIMARY KEY (`id`),
UNIQUE KEY `uqe_client_id` (`client_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='客户端会话状态';

-- ----------------------------
-- Table structure for jmqtt_subscription
-- ----------------------------
DROP TABLE IF EXISTS `jmqtt_subscription`;
CREATE TABLE `jmqtt_subscription` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键',
`client_id` varchar(64) NOT NULL COMMENT '客户端id',
`topic` varchar(128) NOT NULL COMMENT '订阅的topic',
`qos` tinyint(4) NOT NULL COMMENT '对应的qos',
PRIMARY KEY (`id`),
KEY `idx_client_id` (`client_id`),
KEY `idx_topic` (`topic`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='客户端订阅关系';

-- ----------------------------
-- Table structure for jmqtt_will_message
-- ----------------------------
DROP TABLE IF EXISTS `jmqtt_will_message`;
CREATE TABLE `jmqtt_will_message` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
`client_id` varchar(64) NOT NULL COMMENT '客户端id',
`content` text NOT NULL COMMENT '消息体',
`gmt_create` bigint(20) NOT NULL COMMENT '创建时间',
PRIMARY KEY (`id`),
UNIQUE KEY `uqe_client_id` (`client_id`) USING BTREE
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='遗嘱消息表';

SET FOREIGN_KEY_CHECKS = 1;

上次更新: 2/9/2021, 4:44:28 PM