MySQL Backend

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After EMQX version 3.1, a powerful rule engine is introduced to replace plug-ins. It is recommended that you use it. See Save data to MySQL to setup Save data to MySQL in rule engine.

Config file: emqx_backend_mysql.conf

Configure MySQL Server

Connection pool of multiple MySQL servers is supported:

  1. ## Mysql Server
  2. backend.mysql.pool1.server = 127.0.0.1:3306
  4. ## Mysql Pool Size
  5. backend.mysql.pool1.pool_size = 8
  7. ## Mysql Username
  8. backend.mysql.pool1.user = root
  10. ## Mysql Password
  11. backend.mysql.pool1.password = public
  13. ## Mysql Database
  14. backend.mysql.pool1.database = mqtt
  16. ## Max number of fetch offline messages. Without count limit if infinity
  17. ## backend.mysql.max_returned_count = 500
  19. ## Time Range. Without time limit if infinity
  20. ## d - day
  21. ## h - hour
  22. ## m - minute
  23. ## s - second
  24. ## backend.mysql.time_range = 2h

Configure MySQL Persistence Hooks

  1. ## Client Connected Record
  2. backend.mysql.hook.client.connected.1    = {"action": {"function": "on_client_connected"}, "pool": "pool1"}
  4. ## Subscribe Lookup Record
  5. backend.mysql.hook.client.connected.2    = {"action": {"function": "on_subscribe_lookup"}, "pool": "pool1"}
  7. ## Client DisConnected Record
  8. backend.mysql.hook.client.disconnected.1 = {"action": {"function": "on_client_disconnected"}, "pool": "pool1"}
  10. ## Lookup Unread Message QOS > 0
  11. backend.mysql.hook.session.subscribed.1  = {"topic": "#", "action": {"function": "on_message_fetch"}, "pool": "pool1"}
  13. ## Lookup Retain Message
  14. backend.mysql.hook.session.subscribed.2  = {"topic": "#", "action": {"function": "on_retain_lookup"}, "pool": "pool1"}
  16. ## Store Publish Message  QOS > 0
  17. backend.mysql.hook.message.publish.1     = {"topic": "#", "action": {"function": "on_message_publish"}, "pool": "pool1"}
  19. ## Store Retain Message
  20. backend.mysql.hook.message.publish.2     = {"topic": "#", "action": {"function": "on_message_retain"}, "pool": "pool1"}
  22. ## Delete Retain Message
  23. backend.mysql.hook.message.publish.3     = {"topic": "#", "action": {"function": "on_retain_delete"}, "pool": "pool1"}
  25. ## Store Ack
  26. backend.mysql.hook.message.acked.1       = {"topic": "#", "action": {"function": "on_message_acked"}, "pool": "pool1"}
  28. ## Get offline messages
  29. ### "offline_opts": Get configuration for offline messages
  30. ### max_returned_count: Maximum number of offline messages get at a time
  31. ### time_range: Get only messages in the current time range
  32. ## backend.mysql.hook.session.subscribed.1  = {"topic": "#", "action": {"function": "on_message_fetch"}, "offline_opts": {"max_returned_count": 500, "time_range": "2h"}, "pool": "pool1"}
  34. ## If you need to store Qos0 messages, you can enable the following configuration
  35. ## Tip: When the following configuration is enabled, 'on_message_fetch' needs to be disabled, otherwise qos1, qos2 messages will be stored twice
  36. ## backend.mysql.hook.message.publish.4     = {"topic": "#", "action": {"function": "on_message_store"}, "pool": "pool1"}

Description of MySQL Persistence Hooks

hooktopicactionDescription
client.connectedon_client_connectedStore client connected state
client.connectedon_subscribe_lookupSubscribed topics
client.disconnectedon_client_disconnectedStore client disconnected state
session.subscribed#on_message_fetchFetch offline messages
session.subscribed#on_retain_lookupLookup retained messages
message.publish#on_message_publishStore published messages
message.publish#on_message_retainStore retained messages
message.publish#on_retain_deleteDelete retained messages
message.acked#on_message_ackedProcess ACK

SQL Parameters Description

hookParametersExample (${name} represents available parameter)
client.connectedclientidinsert into conn(clientid) values(${clientid})
client.disconnectedclientidinsert into disconn(clientid) values(${clientid})
session.subscribedclientid, topic, qosinsert into sub(topic, qos) values(${topic}, ${qos})
session.unsubscribedclientid, topicdelete from sub where topic = ${topic}
message.publishmsgid, topic, payload, qos, clientidinsert into msg(msgid, topic) values(${msgid}, ${topic})
message.ackedmsgid, topic, clientidinsert into ack(msgid, topic) values(${msgid}, ${topic})
message.deliveredmsgid, topic, clientidinsert into delivered(msgid, topic) values(${msgid}, ${topic})

Configure ‘action’ with SQL

MySQL backend supports SQL in ‘action’:

  1. ## After a client is connected to the EMQX server, it executes a SQL command (multiple SQL commands also supported)
  2. backend.mysql.hook.client.connected.3 = {"action": {"sql": ["insert into conn(clientid) values(${clientid})"]}, "pool": "pool1"}

Create MySQL DB

  1. create database mqtt;

Import MySQL DB & Table Schema

  1. mysql -u root -p mqtt < etc/sql/emqx_backend_mysql.sql

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DB name is free of choice

MySQL Client Connection Table

mqtt_client stores client connection states:

  1. DROP TABLE IF EXISTS `mqtt_client`;
  2. CREATE TABLE `mqtt_client` (
  3.   `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  4.   `clientid` varchar(64) DEFAULT NULL,
  5.   `state` varchar(3) DEFAULT NULL,
  6.   `node` varchar(100) DEFAULT NULL,
  7.   `online_at` datetime DEFAULT NULL,
  8.   `offline_at` datetime DEFAULT NULL,
  9.   `created` timestamp NULL DEFAULT CURRENT_TIMESTAMP,
  10.   PRIMARY KEY (`id`),
  11.   KEY `mqtt_client_idx` (`clientid`),
  12.   UNIQUE KEY `mqtt_client_key` (`clientid`)
  13. ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Query the client connection state:

  1. select * from mqtt_client where clientid = ${clientid};

If client ‘test’ is online:

  1. select * from mqtt_client where clientid = "test";
  3. +----+----------+-------+----------------+---------------------+---------------------+---------------------+
  4. | id | clientid | state | node           | online_at           | offline_at          | created             |
  5. +----+----------+-------+----------------+---------------------+---------------------+---------------------+
  6.    |  1 | test     | 1     | emqx@127.0.0.1 | 2016-11-15 09:40:40 | NULL                | 2016-12-24 09:40:22 |
  7. +----+----------+-------+----------------+---------------------+---------------------+---------------------+
  8. 1 rows in set (0.00 sec)

If client ‘test’ is offline:

  1. select * from mqtt_client where clientid = "test";
  3. +----+----------+-------+----------------+---------------------+---------------------+---------------------+
  4. | id | clientid | state | node           | online_at           | offline_at          | created             |
  5. +----+----------+-------+----------------+---------------------+---------------------+---------------------+
  6. |  1 | test     | 0     | emqx@127.0.0.1 | 2016-11-15 09:40:40 | 2016-11-15 09:46:10 | 2016-12-24 09:40:22 |
  7. +----+----------+-------+----------------+---------------------+---------------------+---------------------+
  8. 1 rows in set (0.00 sec)

MySQL Subscription Table

mqtt_sub table stores MQTT subscriptions of clients:

  1. DROP TABLE IF EXISTS `mqtt_sub`;
  2. CREATE TABLE `mqtt_sub` (
  3.   `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  4.   `clientid` varchar(64) DEFAULT NULL,
  5.   `topic` varchar(255) DEFAULT NULL,
  6.   `qos` int(3) DEFAULT NULL,
  7.   `created` timestamp NULL DEFAULT CURRENT_TIMESTAMP,
  8.   PRIMARY KEY (`id`),
  9.   KEY `mqtt_sub_idx` (`clientid`,`topic`(255),`qos`),
  10.   UNIQUE KEY `mqtt_sub_key` (`clientid`,`topic`)
  11. ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

E.g., client ‘test’ subscribes to ‘test_topic1’ and ‘test_topic2’:

  1. insert into mqtt_sub(clientid, topic, qos) values("test", "test_topic1", 1);
  2. insert into mqtt_sub(clientid, topic, qos) values("test", "test_topic2", 2);

Query subscription of a client:

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

E.g., query the Subscription of client ‘test’:

  1. select * from mqtt_sub where clientid = "test";
  3. +----+--------------+-------------+------+---------------------+
  4. | id | clientId     | topic       | qos  | created             |
  5. +----+--------------+-------------+------+---------------------+
  6. |  1 | test         | test_topic1 |    1 | 2016-12-24 17:09:05 |
  7. |  2 | test         | test_topic2 |    2 | 2016-12-24 17:12:51 |
  8. +----+--------------+-------------+------+---------------------+
  9. 2 rows in set (0.00 sec)

MySQL Message Table

mqtt_msg stores MQTT messages:

  1. DROP TABLE IF EXISTS `mqtt_msg`;
  2. CREATE TABLE `mqtt_msg` (
  3.   `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  4.   `msgid` varchar(100) DEFAULT NULL,
  5.   `topic` varchar(1024) NOT NULL,
  6.   `sender` varchar(1024) DEFAULT NULL,
  7.   `node` varchar(60) DEFAULT NULL,
  8.   `qos` int(11) NOT NULL DEFAULT '0',
  9.   `retain` tinyint(2) DEFAULT NULL,
  10.   `payload` blob,
  11.   `arrived` datetime NOT NULL,
  12.   PRIMARY KEY (`id`)
  13. ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Query messages published by a client:

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

Query messages published by client ‘test’:

  1. select * from mqtt_msg where sender = "test";
  3. +----+-------------------------------+----------+--------+------+-----+--------+---------+---------------------+
  4. | id | msgid                         | topic    | sender | node | qos | retain | payload | arrived             |
  5. +----+-------------------------------+----------+--------+------+-----+--------+---------+---------------------+
  6. | 1  | 53F98F80F66017005000004A60003 | hello    | test   | NULL |   1 |      0 | hello   | 2016-12-24 17:25:12 |
  7. | 2  | 53F98F9FE42AD7005000004A60004 | world    | test   | NULL |   1 |      0 | world   | 2016-12-24 17:25:45 |
  8. +----+-------------------------------+----------+--------+------+-----+--------+---------+---------------------+
  9. 2 rows in set (0.00 sec)

MySQL Retained Message Table

mqtt_retain stores retained messages:

  1. DROP TABLE IF EXISTS `mqtt_retain`;
  2. CREATE TABLE `mqtt_retain` (
  3.   `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  4.   `topic` varchar(200) DEFAULT NULL,
  5.   `msgid` varchar(60) DEFAULT NULL,
  6.   `sender` varchar(100) DEFAULT NULL,
  7.   `node` varchar(100) DEFAULT NULL,
  8.   `qos` int(2) DEFAULT NULL,
  9.   `payload` blob,
  10.   `arrived` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  11.   PRIMARY KEY (`id`),
  12.   UNIQUE KEY `mqtt_retain_key` (`topic`)
  13. ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Query retained messages:

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

Query retained messages with topic ‘retain’:

  1. select * from mqtt_retain where topic = "retain";
  1. +----+----------+-------------------------------+---------+------+------+---------+---------------------+
  2. | id | topic    | msgid                         | sender  | node | qos  | payload | arrived             |
  3. +----+----------+-------------------------------+---------+------+------+---------+---------------------+
  4. |  1 | retain   | 53F33F7E4741E7007000004B70001 | test    | NULL |    1 | www     | 2016-12-24 16:55:18 |
  5. +----+----------+-------------------------------+---------+------+------+---------+---------------------+
  7. >    1 rows in set (0.00 sec)

MySQL Acknowledgement Table

mqtt_acked stores acknowledgements from the clients:

  1. DROP TABLE IF EXISTS `mqtt_acked`;
  2. CREATE TABLE `mqtt_acked` (
  3.   `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  4.   `clientid` varchar(200) DEFAULT NULL,
  5.   `topic` varchar(200) DEFAULT NULL,
  6.   `mid` int(200) DEFAULT NULL,
  7.   `created` timestamp NULL DEFAULT NULL,
  8.   PRIMARY KEY (`id`),
  9.   UNIQUE KEY `mqtt_acked_key` (`clientid`,`topic`)
  10. ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Enable MySQL Backend

  1. ./bin/emqx_ctl plugins load emqx_backend_mysql