使用 ProxySQL 实现读写分离和副本健康检查

命令

-- On MySQL (source): monitor user
CREATE USER 'proxysql_mon'@'%' IDENTIFIED BY 'M0n#itor2024';
GRANT USAGE, REPLICATION CLIENT ON *.* TO 'proxysql_mon'@'%';

-- ProxySQL admin: mysql -u admin -p -h 127.0.0.1 -P 6032
UPDATE global_variables SET variable_value = 'proxysql_mon' WHERE variable_name = 'mysql-monitor_username';
UPDATE global_variables SET variable_value = 'M0n#itor2024' WHERE variable_name = 'mysql-monitor_password';
LOAD MYSQL VARIABLES TO RUNTIME; SAVE MYSQL VARIABLES TO DISK;
INSERT INTO mysql_replication_hostgroups (writer_hostgroup, reader_hostgroup, check_type, comment) VALUES (10, 20, 'read_only', 'shop');
INSERT INTO mysql_servers (hostgroup_id, hostname, port, max_replication_lag) VALUES (10, 'db1', 3306, 0), (20, 'db2', 3306, 30), (20, 'db3', 3306, 30);
LOAD MYSQL SERVERS TO RUNTIME; SAVE MYSQL SERVERS TO DISK;
INSERT INTO mysql_users (username, password, default_hostgroup, transaction_persistent) VALUES ('app', 'App#Pass2024', 10, 1);
LOAD MYSQL USERS TO RUNTIME; SAVE MYSQL USERS TO DISK;
INSERT INTO mysql_query_rules (rule_id, active, match_digest, destination_hostgroup, apply) VALUES (100, 1, '^SELECT .* FOR (UPDATE|SHARE)', 10, 1), (200, 1, '^SELECT ', 20, 1);
LOAD MYSQL QUERY RULES TO RUNTIME; SAVE MYSQL QUERY RULES TO DISK;

-- Verify
SELECT hostgroup_id, hostname, status FROM runtime_mysql_servers;
SELECT hostgroup, srv_host, status, ConnUsed, Queries, Latency_us FROM stats_mysql_connection_pool;
SELECT hostgroup, substr(digest_text, 1, 60) AS digest, count_star, sum_time / 1000 AS sum_ms FROM stats_mysql_query_digest ORDER BY sum_time DESC LIMIT 10;

作用

根据 read_only 标志自动管理 writer（10）和 reader（20）主机组；将 SELECT 路由到副本，将加锁读和写入路由到源；临时移除超过 max_replication_lag 的副本（SHUNNED）。

适用场景

用于在不修改应用的情况下分散异步复制拓扑中的读负载；用于连接池以及按查询的路由/缓存/防火墙。

注意

配置分为 3 层（MEMORY → RUNTIME → DISK）：不执行 LOAD ... TO RUNTIME 则什么都不会改变，不执行 SAVE ... TO DISK 则重启后会丢失。read_only 检查要求副本上 super_read_only=ON；否则副本会被移入 writer 主机组。将每个 SELECT 都发送到副本会因延迟导致写后读错误；基于 stats_mysql_query_digest 只为重型/报表查询编写规则更安全。管理接口是 SQLite：不存在 LEFT() 等 MySQL 函数，请使用 substr()。请修改默认的 admin:admin 账户（admin-admin_credentials）。