1.現象
2021-06-24 14:30:06.667 WARN 93 --- [ task-725] com.zaxxer.hikari.pool.PoolBase : HikariPool-6 - Failed to validate connection com.mysql.jdbc.JDBC4Connection@2a681385 (No operations allowed after connection closed.). Possibly consider using a shorter maxLifetime value.
2.查看mysql server的配置
show variables like '%timeout%';

其中,interactive_timeout 和 wait_timeout 設置的不合理。
3.HikaiConfig的默認參數設置

4.總結
當連接池的參數idleTimeout或maxLifetime大於數據庫的interactive_timeout或wait_timeout時,連接池里的連接沒過期,但數據庫那邊已經過期了,就會出現上面的錯誤。
推薦配置
spring:
datasource:
hikari:
connection-timeout: 10000
validation-timeout: 3000
idle-timeout: 60000
login-timeout: 5
max-lifetime: 60000
maximum-pool-size: 10
minimum-idle: 5
read-only: false
